CN110847929B - Tunnel portal section pre-reinforcing and excavating construction method based on partition blasting - Google Patents
Tunnel portal section pre-reinforcing and excavating construction method based on partition blasting Download PDFInfo
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- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/003—Linings or provisions thereon, specially adapted for traffic tunnels, e.g. with built-in cleaning devices
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- E—FIXED CONSTRUCTIONS
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- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/02—Improving by compacting
- E02D3/10—Improving by compacting by watering, draining, de-aerating or blasting, e.g. by installing sand or wick drains
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
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- E02D5/46—Concrete or concrete-like piles cast in position ; Apparatus for making same making in situ by forcing bonding agents into gravel fillings or the soil
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- E—FIXED CONSTRUCTIONS
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- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
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- E21D11/04—Lining with building materials
- E21D11/10—Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor
- E21D11/105—Transport or application of concrete specially adapted for the lining of tunnels or galleries ; Backfilling the space between main building element and the surrounding rock, e.g. with concrete
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/14—Lining predominantly with metal
- E21D11/15—Plate linings; Laggings, i.e. linings designed for holding back formation material or for transmitting the load to main supporting members
- E21D11/152—Laggings made of grids or nettings
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/14—Lining predominantly with metal
- E21D11/18—Arch members ; Network made of arch members ; Ring elements; Polygon elements; Polygon elements inside arches
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/38—Waterproofing; Heat insulating; Soundproofing; Electric insulating
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D20/00—Setting anchoring-bolts
- E21D20/003—Machines for drilling anchor holes and setting anchor bolts
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D21/00—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection
- E21D21/0026—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection characterised by constructional features of the bolts
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
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- E21D9/006—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries by making use of blasting methods
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Abstract
The invention discloses a tunnel portal section pre-reinforcing and excavating construction method based on partition blasting, which comprises the following steps of: firstly, dewatering and pre-reinforcing; secondly, pre-reinforcing the ground surface: reinforcing the earth surface of the backfill segment in the tunnel portal section by adopting a cement soil mixing pile; thirdly, tunnel excavation construction: excavation construction is carried out by dividing a plurality of excavation sections from back to front, and the process is as follows: measuring and setting out, drilling and blasting construction, upper hole body excavation, middle hole body excavation and lower hole body excavation. The invention has reasonable design, simple construction and good use effect, reduces the underground water level through precipitation pre-reinforcement, effectively reinforces the surrounding rock, performs surface pre-reinforcement on the backfill segment by using the cement soil mixing pile, and performs the partition blasting excavation by adopting a three-step synchronous excavation mode, thereby ensuring the safety and reliability of the tunnel excavation process and the stability of the tunnel structure.
Description
Technical Field
The invention belongs to the technical field of tunnel construction, and particularly relates to a tunnel portal section pre-reinforcing and excavating construction method based on partition blasting.
Background
In the construction process of railway and highway tunnel engineering, the construction is greatly influenced and difficult due to the limitation and influence of geological conditions. In the tunnel construction process, various different rock stratum combinations are often encountered, for example, the conditions of weak and uneven surrounding rocks, shallow buried bias landform, soil and stone mixed geology and the like emerge endlessly. When a tunnel penetrating through a soil-rock mixed stratum (also called soil-rock interface geology or soil-rock boundary stratum) is excavated and supported, the tunnel is mainly treated by methods such as advanced pipe shed grouting support, advanced horizontal jet grouting pile reinforcement, excavation footage control and the like at home at present so as to prevent collapse or deformation in the tunnel construction process.
Loess refers to yellow silt deposit which is carried by wind during the quaternary period in geological times. The loess collapsibility coefficient (also called collapsibility coefficient) is a mechanical parameter for evaluating collapsibility of loess, and refers to the ratio of the height difference of a soil sample before and after soaking to the original height of the soil sample under a certain pressure. The loess collapsibility coefficient is an important index for evaluating the collapsibility of loess, and can be directly measured by experiments. Loess is classified into collapsible loess and non-collapsible loess according to the difference in the coefficient of collapse of loess. Through geological exploration, the types of loess in the loess stratum are more, and the loess stratum is divided into sandy loess (also called sand loess), cohesive loess (also called cohesive loess or cohesive loess) and the like according to the material quality, wherein the sandy loess refers to the loess with higher fine sand particle content generally more than 30% and the loess is the loess-shaped soil in essence, and the cohesive loess refers to the loess with fine sand content less than 15%, clay content more than 25% and the loess is the loess-shaped soil in essence; the loess is divided into new loess and old loess according to geological age, wherein the old loess is loess belonging to early and middle updated ages in the geological age and generally has no collapsibility, the new loess is loess later than the old loess, the new loess is loose in structure and generally has collapsibility, and the new loess is mostly distributed on the old loess.
The loess stratum has the geological characteristics of porosity, vertical joint development, strong water permeability, subsidence and the like. In a soil-rock boundary stratum in a loess area, loess is arranged at the upper part of a tunnel excavation section, rocks are arranged at the lower part of the tunnel excavation section, the height fluctuation of a soil-rock interface (also called a soil-rock interface) is linearly changed, the upper soil body mainly comprises silty clay or viscous old loess, and the lower part of the upper soil body is a strongly weathered or weakly weathered mudstone sandstone interbed; underground water exists in rock soil in the form of interstitial water and fracture water, the water distribution is uneven, and mudstone kaolinite swelling soil may exist in the construction area where the tunnel is located. When actually carrying out tunnel construction, tunnel excavation construction in the soil and stone boundary stratum mainly has following problem: firstly, the hardness of rock soil is not uniform, and the upper soil layer is easy to collapse due to blasting of the weathered rock stratum at the lower part, so that the damage to constructors is caused; secondly, the underground water enrichment area further softens the earth-rock boundary stratum, so that the deformation of surrounding rocks is serious; and thirdly, the expansive soil expands when meeting water to cause primary support deformation and cracking, and the deformation structure of the primary support arch centering is damaged to lose the support capability under severe conditions. Especially when the deep-buried tunnel which is positioned in the earth-rock boundary stratum and the covering layer of the upper part of the tunnel is 2.5 times larger than the tunnel span (namely the tunnel excavation width) is constructed, the buried depth of the deep-buried tunnel is large, and when the tunnel excavation section is larger than 100m2In time, the rock soil layer on the periphery of the hole body deforms greatly, and the excavation construction difficulty is very high. Because the high-bottom fluctuation of the earth-rock interface (namely the earth-rock interface) exists on the upper step, the middle step or the lower step, the most adverse condition is that the earth-rock interface is positioned on the upper step, and the blasting area is closest to the arch crown and the tunnel face during blasting, which most easily causes the arch crownCollapse of the top and palm surfaces.
From the above, the earth-rock boundary stratum is a special geological condition with uneven hardness and soil-rock transition, and has a more special formation mechanism. When a tunnel is constructed under the geological condition of the earth-rock boundary, besides different lithology and distribution of strata at the earth-rock boundary, factors such as further softening action of a ground water enrichment area on the earth-rock boundary strata, shallow burying and bias voltage of the tunnel and the like often exist, surrounding rocks are deformed, and stress is also unbalanced. Once reasonable supporting measures corresponding to the actual construction are not adopted or the excavation method is not proper, the serious consequences that the support in front of the tunnel face is deformed and even collapsed are probably caused.
The construction of the tunnel opening section is difficult and key in tunnel construction, and the stability of the slope body of the tunnel opening is related to whether the tunnel can smoothly enter the tunnel and the construction in the tunnel is developed. The tunnel portal section is generally positioned in a slope body which is seriously eroded by surface water and developed by weathered cracks, and the tunnel burial depth of the portal section is usually shallow, so that a bearing arch is difficult to form on the soil body on the upper part of the structure, and the stability is poor. The main problems in the construction of the loess tunnel portal section include ground surface cracking above the portal, portal side slope damage and cave collapse (also called as pit). Through analysis, the surface of the earth above the hole is cracked due to a plurality of reasons, and the tunnel hole and the shallow tunnel buried section are easy to generate large disturbance on the overlying soil body in the construction process, so that the soil body sinks and cracks, and finally cracks are generated on the surface of the earth; in addition, under the infiltration and soaking effects of irrigation water and rainwater, the water content of the soil body is increased, the pressure on the upper part of the tunnel is obviously increased, and the soil body on the upper part of the tunnel forms a wedge-shaped funnel along the fracture surface. And the loosening load of the upper earthing soil basically acts on the primary support, when the inverted arch is not immediately followed and the primary support is not closed to form a ring in time, a closed stress structure cannot be formed, so that the bearing capacity is insufficient, the ground surface and the vault are sunk, and cracks are generated. In addition, the loess tunnel foundation bearing capacity is insufficient, so that the tunnel arch springing sinks to generate cracks. If cracks appear in the construction process, the crack extension section and the cave are backfilled and compacted firstly.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a tunnel portal section pre-reinforcing and excavation construction method based on zone blasting, which is reasonable in design, simple and convenient in construction and good in use effect.
In order to solve the technical problems, the invention adopts the technical scheme that: a tunnel portal section pre-reinforcing and excavating construction method based on partition blasting is characterized by comprising the following steps: the section of the tunnel portal is a cross section of more than 100m2The tunnel section is positioned in the earth-rock boundary stratum, the rear end of the constructed tunnel portal section is a tunnel portal, and the length of the tunnel portal section is 70-100 m; the soil-rock boundary stratum comprises a loess stratum and a rock stratum below the loess stratum, and an interface between the loess stratum and the rock stratum is a soil-rock interface; the tunnel cave of the tunnel cave mouth section under construction is divided into an upper cave body, a middle cave body and a lower cave body from top to bottom, wherein the upper cave body is formed by performing upper step excavation on the tunnel cave mouth section under construction from back to front, the middle cave body is formed by performing middle step excavation on the tunnel cave mouth section under construction from back to front, the lower cave body is formed by performing lower step excavation on the tunnel cave mouth section under construction from back to front, the earth and stone interface is positioned in the upper cave body, and the upper cave body and the middle cave body form the upper cave body;
a backfill soil layer exists in a construction area where a tunnel portal section to be constructed is located, the backfill soil layer is formed after backfilling cracks or caves existing on the ground surface of a construction area to be treated, and the backfill soil layer is a loess layer; the construction area to be processed is a construction area where a tunnel portal section is located; the tunnel section with the backfill soil layer in the tunnel portal section is a backfill section;
when the pre-reinforcing and excavating construction is carried out on the tunnel portal section, the method comprises the following steps:
firstly, dewatering and pre-reinforcing: two rows of precipitation wells are constructed in a construction area where the tunnel portal section is located, precipitation is synchronously performed on the construction area where the tunnel portal section is located through the two rows of precipitation wells, and the underground water level of the construction area where the tunnel portal section is located is reduced to be below the excavation contour line of the tunnel portal section;
two rows of the dewatering wells are respectively arranged on the left side and the right side of the tunnel portal section under construction, each row of the dewatering wells comprises a plurality of dewatering wells which are arranged from back to front along the longitudinal extension direction of the tunnel, a plurality of the dewatering wells 3-2 in each row of the dewatering wells are uniformly arranged, and the dewatering wells in the two rows of the dewatering wells are arranged in a staggered manner;
step two, pre-reinforcing the earth surface: reinforcing the earth surface of the backfill segment in the tunnel portal section by adopting a cement soil mixing pile, and obtaining a mixing pile reinforcing structure;
the stirring pile reinforcing structure is arranged along the longitudinal extension direction of the tunnel of the backfill segment, and the longitudinal length of the stirring pile reinforcing structure is the same as that of the backfill segment; the width of the stirring pile reinforcing structure is larger than the excavation width of the backfill segment; the tunnel buried depth of the backfill segment is 12 m-15 m, the stirring pile reinforcing structure is formed by reinforcing a loess stratum in the region where the backfill segment is located by adopting a plurality of cement stirring piles, the plurality of cement stirring piles are distributed in a quincunx shape, the plurality of cement stirring piles are uniformly distributed and vertically distributed, and the bottom of each cement stirring pile is supported on a rock stratum; the distance L0 between two adjacent cement soil mixing piles is 70-80 cm, and the pile bodies of the two adjacent cement soil mixing piles are meshed with each other; many the structure and the size of cement mixing pile are all the same, the height of cement mixing pile is the same with mixing pile reinforced structure's vertical height, cement mixing pile is cylinder pile and its stake footpath
Wherein d0 > L0;
step three, tunnel excavation construction: after the ground surface pre-reinforcement is completed in the second step, excavating construction is carried out on the tunnel portal section under construction;
when the excavation construction is carried out on the tunnel portal section, the excavation construction is carried out on the tunnel portal section by a plurality of excavation sections from back to front along the longitudinal extension direction of the tunnel, and the excavation construction methods of all the excavation sections are the same; when any excavation segment of the tunnel portal section under construction is excavated, the process is as follows:
step 301, measurement and paying-off: respectively measuring and paying off the excavation contour lines of the upper hole body, the middle hole body and the lower hole body on the current construction excavation surface, and simultaneously respectively measuring and paying off the number of blastholes to be arranged and the arrangement positions of the blastholes on the excavation surfaces of the upper hole body, the middle hole body and the lower hole body in the current construction excavation segment; the current construction excavation surface is the excavation surface of the current construction excavation segment;
the blasting excavation surface of the upper cavity body is divided into a left upper blasting area and a right upper blasting area positioned on the right side of the left upper blasting area, and the blasting excavation surface of the upper cavity body is positioned below the earth-rock interface; the blasting excavation surface of the middle hole body is divided into a left blasting area, a middle blasting area and a right blasting area from left to right, and the left blasting area and the right blasting area are symmetrically distributed on the left side and the right side of the middle blasting area;
the medium explosion area is a cutting area and is provided with four groups of cutting holes, and each group of cutting holes comprises a plurality of cutting holes distributed on the same vertical surface from top to bottom; the four groups of the cutting holes comprise a left group of inner cutting holes and a right group of outer cutting holes which are symmetrically distributed, and the two groups of the inner cutting holes are positioned between the two groups of the outer cutting holes; the inner side cutting holes and the outer side cutting holes are arranged in a staggered manner;
a plurality of peripheral eyes are arranged on the left side of the left upper explosion area, the right side of the right upper explosion area, the left side of the left explosion area and the right side of the right explosion area from top to bottom;
three rows of auxiliary eyes are distributed on the left explosion area and the right explosion area from left to right, and each row of auxiliary eyes on the left explosion area and the right explosion area comprises a plurality of auxiliary eyes distributed on the same vertical plane from top to bottom; the upper left explosion area and the upper right explosion area are uniformly provided with an upper row of auxiliary holes and a lower row of auxiliary holes, and each row of auxiliary holes on the upper left explosion area and the upper right explosion area comprises a plurality of auxiliary holes arranged from left to right;
the blasting excavation surface of the upper hole body is divided into 5 blasting areas, and the 5 blasting areas are a left upper blasting area, a right upper blasting area, a left blasting area, a middle blasting area and a right blasting area respectively; the left explosion area and the right explosion area in the 5 explosion areas are detonated simultaneously, the left upper explosion area and the right upper explosion area are detonated simultaneously, and the middle explosion area, the right explosion area and the right upper explosion area are detonated in sequence from first to last;
the cutting holes, the peripheral holes and the auxiliary holes are blast holes;
step 302, drilling and blasting construction: according to the arrangement positions of the blastholes obtained by measuring and setting out in the step 301, drilling all the blastholes on the current construction excavation surface by adopting drilling equipment, respectively charging the blastholes formed by drilling, and detonating for blasting after charging is completed;
step 303, excavating an upper hole body: excavating the upper cavity of the currently constructed excavation segment from back to front along the longitudinal extension direction of the tunnel;
excavating the loess stratum in the upper cavity from back to front when the upper cavity of the currently constructed excavation segment is excavated from back to front; in the process of excavating the loess stratum in the upper cave from back to front, a ballast conveying vehicle is adopted to convey the crushed stones generated after the inner explosion of the upper cave to the outer side of the tunnel cave mouth section to be constructed from back to front so as to finish the excavating construction process of the upper cave body;
step 304, excavating a middle hole body: excavating the middle cavity body of the currently constructed excavation segment from back to front along the longitudinal extension direction of the tunnel;
when the middle tunnel body of the current constructed excavation section is excavated from back to front, the slag conveying vehicle is adopted to convey slag stones generated after the internal explosion of the middle tunnel body from back to front to the outer side of the tunnel portal section under construction, and the excavation construction process of the middle tunnel body is completed;
step 305, excavating a lower cavity: excavating the lower cavity of the currently constructed excavation segment from back to front along the longitudinal extension direction of the tunnel to finish the excavation construction process of one excavation segment;
when the lower tunnel body of the currently constructed excavation section is excavated from back to front, the slag conveying vehicle is adopted to convey slag stones generated after the inner explosion of the lower tunnel body from back to front to the outer side of the tunnel portal section under construction, so that the excavation construction process of the lower tunnel body is completed, and the tunnel portal formed by construction is obtained;
step 306, excavating construction of the next excavation segment: excavating the next excavation section of the tunnel portal section according to the construction process from the step 301 to the step 305;
and 307, repeating the step 306 for multiple times until all excavation construction processes of the tunnel portal section are completed.
The tunnel portal section pre-reinforcing and excavating construction method based on the partition blasting is characterized by comprising the following steps: in step 301, each group of the inner cutting holes comprises two cutting holes, and each group of the outer cutting holes comprises three cutting holes;
each column of the auxiliary eyes on the left burst area and the right burst area comprises 3 or 4 auxiliary eyes;
each row of the auxiliary eyes on the left upper explosion area and the right upper explosion area comprises 4 auxiliary eyes.
The tunnel portal section pre-reinforcing and excavating construction method based on the partition blasting is characterized by comprising the following steps: in step 301, the section positions of the two groups of detonators for the inner undermining eye blasting are both 1 section, the section positions of one group of detonators for the outer undermining eye blasting close to a right blasting area are both 3 sections, and the section positions of one group of detonators for the outer undermining eye blasting close to a left blasting area are both 5 sections;
the three rows of the detonators for auxiliary eye blasting on the left blasting area are respectively 3 sections, 5 sections and 7 sections from right to left, and the three rows of the detonators for auxiliary eye blasting on the right blasting area are respectively 3 sections, 5 sections and 7 sections from left to right;
the section positions of all detonators for blasting of peripheral holes on the left blasting area and the right blasting area are 9 sections;
the detonators with the upper section of the middle explosion area being 5 sections are connected with the detonators for blasting blastholes on the left explosion area through detonating tubes, and the detonators with the upper section of the middle explosion area being 3 sections are connected with the detonators for blasting blastholes on the right explosion area through detonating tubes;
the detonators with the upper section position of the left blasting area being 5 sections are connected with the detonators for blasting of each blasthole on the left blasting area through detonating tubes, and the detonators with the upper section position of the right blasting area being 5 sections are connected with the detonators for blasting of each blasthole on the right blasting area through detonating tubes.
The tunnel portal section pre-reinforcing and excavating construction method based on the partition blasting is characterized by comprising the following steps: excavating the loess stratum in the upper cavity by adopting an excavator in the step 303 from back to front;
before adopting the excavator to excavate, firstly install a scarifier on excavator's grab bucket and pass through the scarifier loosens the soil to the internal loess stratum in upper portion hole, will again the scarifier is demolishd and is adopted the excavator excavates the internal loess stratum in upper portion hole.
The tunnel portal section pre-reinforcing and excavating construction method based on the partition blasting is characterized by comprising the following steps: the tunnel primary supporting structure of the tunnel hole is divided into an arch wall primary supporting structure for carrying out primary supporting on an arch wall of the tunnel hole and a primary supporting inverted arch for carrying out primary supporting on the bottom of the tunnel hole;
the tunnel primary support structure comprises a full-section support structure for performing full-section support on a tunnel hole, an arch wall net-jet support structure for performing primary support on an arch wall of the tunnel hole and an inverted arch primary support structure for performing primary support on the bottom of the tunnel hole; the full-section supporting structure comprises a plurality of full-section supporting frames which are arranged from back to front along the longitudinal extension direction of the tunnel, the two adjacent full-section supporting frames at the front and the back are fixedly connected into a whole through a plurality of longitudinal connecting reinforcing steel bars, the longitudinal connecting reinforcing steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal connecting reinforcing steel bars are arranged along the contour line of the full-section supporting frames; a plurality of full-section support frames in the full-section support structure are uniformly distributed, the distance between two adjacent full-section support frames in the front and the back is L, and the value range of L is 0.5-0.8 m;
the shape of the full-section support frame is the same as the shape of the cross section of the tunnel hole, each full-section support frame is formed by splicing an arch wall support arch frame for supporting an arch wall of the tunnel hole and a tunnel inverted arch support frame for supporting the bottom of the tunnel hole, the tunnel inverted arch support frame is positioned right below the arch wall support arch frame, the arch wall support arch frame and the tunnel inverted arch support frame are positioned on the same tunnel cross section, and the tunnel inverted arch support frame and the arch wall support arch frame form a closed full-section support frame; the inverted arch primary support structure is an inverted arch concrete injection layer injected at the bottom of the tunnel, and the tunnel inverted arch support is fixed in the inverted arch concrete injection layer;
the arch wall mesh-spraying supporting structure and all arch wall steel arch frames in the full-section supporting structure form an arch wall primary supporting structure, and the inverted arch primary supporting structure and all tunnel inverted arch frames in the full-section supporting structure form a primary supporting inverted arch;
the arch wall supporting arch comprises an upper arch located in an upper tunnel body, two middle side brackets symmetrically arranged below the left side and the right side of the upper arch and located in the middle tunnel body, and two lower side brackets symmetrically arranged below the left side and the right side of the upper arch and located in the lower tunnel body, wherein the tunnel inverted arch bracket is located in the lower tunnel body; each middle side bracket is connected between the upper end of one lower side bracket and one end of the upper arch frame; the left end of the tunnel inverted arch support is fixedly connected with the bottom of one lower side support, and the right end of the tunnel inverted arch support is fixedly connected with the bottom of the other lower side support;
after the excavation of the upper hole body of the currently constructed excavation section is finished in the step 303, installing an upper arch frame in the excavated and formed upper hole body from back to front; simultaneously, in step 304, excavating the middle hole body of the currently constructed excavation segment from back to front;
in step 304, after the excavation of the middle hole body of the currently constructed excavation section is finished, respectively installing middle side supports on the left side and the right side of the excavated and formed middle hole body from back to front, and firmly connecting each middle side support with an upper arch frame positioned above the middle side support into a whole; simultaneously, step 305 is carried out, and the lower cavity of the currently constructed excavation segment is excavated from back to front;
step 305, after the excavation of the lower cavity of the currently constructed excavation section is finished, respectively installing lower side supports on the left side and the right side of the excavated and formed lower cavity from back to front, and enabling each lower side support to be fixedly connected with a middle side support above the lower side support into a whole; simultaneously, by back forward at lower part cave body bottom installation tunnel invert support and make the tunnel invert support of installing and the lower part collateral branch frame fastening connection of lower part cave body left and right sides installation as an organic whole, obtain to erect and accomplish full section support frame, and through the multichannel longitudinal joint reinforcing bar is adjacent two around with full section support frame fastening connection is as an organic whole.
The tunnel portal section pre-reinforcing and excavating construction method based on the partition blasting is characterized by comprising the following steps: a tunnel secondary lining is arranged on the inner side of the tunnel primary supporting structure, the tunnel primary supporting structure and the tunnel secondary lining are full-section supporting structures for supporting a tunnel hole in a full-section mode, and the tunnel secondary lining is a reinforced concrete lining;
the tunnel secondary lining is divided into an arch wall secondary lining for supporting an arch wall of the tunnel hole and an inverted arch secondary lining for supporting the bottom of the tunnel hole; the inverted arch secondary lining is positioned above a primary supporting inverted arch, an inverted arch backfill layer is arranged on the inverted arch secondary lining, the upper surface of the inverted arch secondary lining is a horizontal plane, the bottoms of the left side and the right side of the arch wall secondary lining are horizontal planes, the arch wall secondary lining is supported on the inverted arch secondary lining and cast into a whole, and the inverted arch backfill layer is a concrete filling layer;
in the third step, in the process of excavating the tunnel portal section to be constructed, constructing the secondary lining of the tunnel from back to front on the inner side of the primary tunnel supporting structure which is constructed and formed;
when the tunnel secondary lining is constructed from back to front, the inverted arch secondary lining is constructed on the constructed primary support inverted arch from back to front, and the inverted arch secondary lining formed by construction is obtained; in the process of constructing the secondary lining of the inverted arch from back to front, constructing the secondary lining of the arch wall on the constructed secondary lining of the inverted arch from back to front, and connecting the constructed secondary lining of the arch wall and the secondary lining of the inverted arch positioned below the constructed secondary lining of the inverted arch into a whole to obtain the constructed secondary lining of the tunnel;
and in the third step, in the construction process of the inverted arch secondary lining from back to front, constructing an inverted arch backfill layer on the constructed inverted arch secondary lining from back to front along the longitudinal extension direction of the tunnel.
The tunnel portal section pre-reinforcing and excavating construction method based on the partition blasting is characterized by comprising the following steps: a reinforcing sleeve arch is arranged on the inner side of the primary supporting structure of the tunnel;
the tunnel primary supporting structure and the reinforcing sleeve arch are full-section supporting structures for supporting a tunnel hole in a full-section mode, and the tunnel primary supporting structure and the reinforcing sleeve arch positioned on the inner side of the tunnel primary supporting structure form a reinforced primary supporting structure;
the reinforced arch comprises a plurality of arch units, the arch units are identical in structure and are arranged from back to front along the longitudinal extension direction of the tunnel, an isolation layer is arranged between each arch unit and the primary tunnel supporting structure, the isolation layer is a full-section isolation layer formed by non-woven fabrics paved between the arch units and the primary tunnel supporting structure, and the cross section of the isolation layer is identical to that of the tunnel;
each arch sheathing unit comprises M section steel arch frames which are arranged from back to front along the longitudinal extension direction of the tunnel and an inner side concrete spraying layer formed by concrete sprayed on the isolation layer, the thickness of the inner side concrete spraying layer is not less than 25cm, the M section steel arch frames are uniformly arranged, and the distance between two adjacent front and back section steel arch frames is 0.8-1.2M; each structural steel arch is a full-section support for full-section supporting of a tunnel hole, M structural steel arches are fixed in the inner side concrete injection layer, the shape of each structural steel arch is the same as the shape of the cross section of the tunnel hole, wherein M is a positive integer and is more than or equal to 4; m steel arch frames in each arch sheathing unit are fixedly connected into a whole through a plurality of longitudinal steel bars, the longitudinal steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal steel bars are arranged along the contour line of the steel arch frames; each structural steel arch comprises an arch wall structural steel support for supporting an arch wall of a tunnel hole and an inverted arch structural steel support for supporting the bottom of the tunnel hole, the inverted arch structural steel support is positioned under the arch wall structural steel support, the arch wall structural steel support and the inverted arch structural steel support are both arch supports, the left end of the inverted arch structural steel support is fixedly connected with the bottom of the left end of the arch wall structural steel support, and the right end of the inverted arch structural steel support is fixedly connected with the bottom of the right end of the arch wall structural steel support;
in the step 304, in the process of excavating the lower cavity from back to front, the reinforcing sleeve arch is constructed on the inner side of the constructed primary tunnel supporting structure from back to front along the longitudinal extension direction of the tunnel, so that the reinforced primary support structure formed by construction is obtained;
when the reinforcing sleeve arch is constructed from back to front, a plurality of sleeve arch units in the reinforcing sleeve arch are constructed from back to front respectively, and the construction methods of the plurality of sleeve arch units are the same; the tunnel primary supporting structure section with the arch sheathing units distributed on the inner side in the tunnel primary supporting structure is a primary supporting section to be reinforced;
when any one of the set arch units in the reinforced set arch is constructed, the process is as follows:
d1, paving an isolation layer: paving a layer of isolation layer on the inner wall of the primary support section to be enhanced outside the currently constructed arch sheathing unit from back to front;
step D2, installing the profile steel arch frame: in the process of laying an isolation layer from back to front in the step D1, respectively installing M steel arches of the currently constructed arch sheathing unit in the primary support section to be enhanced from back to front in the step 301, enabling each steel arch to stand on the inner side of the isolation layer in the step D1, and enabling the isolation layer in the step D1 to be padded between the installed M steel arches and the inner wall of the primary support section to be enhanced;
step D3, longitudinal steel bar installation: d2, after M steel arches are installed, firmly connecting M steel arches into a whole through a plurality of longitudinal steel bars;
step D4, concrete spraying: spraying concrete on the isolating layer in the step D1 from back to front to form an inner concrete spraying layer, fixing M steel arches in the step D2 and a plurality of longitudinal steel bars in the step D3 in the inner concrete spraying layer, and padding the isolating layer between the primary support section to be reinforced and the inner concrete spraying layer in the step D1.
The tunnel portal section pre-reinforcing and excavating construction method based on the partition blasting is characterized by comprising the following steps: after the concrete is sprayed in the step D4, radial grouting reinforcement is needed to be carried out on the arch wall of the primary support section to be reinforced in the step D1, and a radial grouting reinforcement structure is obtained;
the upper hole body and the middle hole body form an upper tunnel body, and the radial grouting reinforcement structure is positioned on the outer side of the upper tunnel body;
the radial grouting reinforcement structure is formed by grouting and reinforcing soil outside the tunnel upper hole body through a plurality of rows of radial grouting holes, the plurality of rows of radial grouting holes are arranged from back to front along the extending direction of the tunnel, each row of radial grouting holes comprises a plurality of radial grouting holes which are arranged on the section of the same tunnel from left to right along the excavation contour line of the tunnel upper hole body, each radial grouting hole is a drill hole which is drilled into the soil from the inside to the outside of the tunnel upper hole body, a plurality of radial grouting holes in each row of radial grouting holes are uniformly arranged, and the radial grouting holes in the front and back adjacent two rows of radial grouting holes are arranged in a staggered manner; the length of the radial grouting hole is not less than 3 m;
each row of radial grouting holes are located between two front and rear adjacent full-section supporting frames, and each row of radial grouting holes are located between two front and rear adjacent profile steel arches;
and D1, when the arch wall of the primary support section to be reinforced is reinforced by radial grouting, the arch wall is reinforced by grouting from back to front through a plurality of rows of radial grouting holes.
The tunnel portal section pre-reinforcing and excavating construction method based on the partition blasting is characterized by comprising the following steps: in the radial grouting reinforcement process of the arch wall of the primary support section to be reinforced in the step D1, arch changing is carried out on an arch section needing to be subjected to arch changing in the tunnel portal section to be constructed;
the arch section to be changed is formed by connecting an intrusion limit section and two extension sections which are respectively positioned at the front side and the rear side of the intrusion limit section, and the primary supporting structure of the arch section to be changed is the reinforced primary supporting structure; the limit invasion section is a tunnel section of the reinforced primary support structure in the constructed tunnel portal section, and the two extension sections are adjacent to and communicated with the limit invasion section in the constructed tunnel portal section; the length of each of the two extension sections is not less than 3L;
and when the arch of the section needing to be changed, which needs to be changed, of the tunnel portal section to be constructed is changed, the reinforced primary support structure in the section needing to be changed is dismantled, and primary support construction is synchronously carried out on the section needing to be changed in the dismantling process, so that the primary support structure of the tunnel after being changed is obtained.
The tunnel portal section pre-reinforcing and excavating construction method based on the partition blasting is characterized by comprising the following steps: the surrounding rock level of the tunnel hole is V level or VI level, and the length of each excavation section is 2L.
Compared with the prior art, the invention has the following advantages:
1. the method has the advantages of simple steps, reasonable design, simple and convenient construction and lower input cost. Firstly, lowering the underground water level of the earth-rock boundary stratum through precipitation pre-reinforcement, and simultaneously effectively reinforcing surrounding rocks, so that the problems of water inrush and collapse of a tunnel face in the tunnel excavation process are avoided; the areas such as cracks, caves and the like existing at the tunnel portal section are backfilled firstly, and then the cement soil mixing piles are utilized for ground surface pre-reinforcement, so that the pre-reinforcement effect can be further improved, the safety of tunnel construction is ensured, and the stability of the tunnel structure can be ensured.
2. The invention adopts a partition blasting mode to respectively divide an upper blasting area in the upper step and a middle blasting area on the middle step into blasting areas and limit the arrangement position of each blast hole in each blasting area, thereby effectively preventing the tunnel face collapse or the vault collapse caused by large vibration generated by blasting when the large-section primary explosive loading is excessive and ensuring the safety and reliability of the tunnel excavation process.
3. The upper and middle bench blasting excavation adopts the partition blasting, the blasting area is divided reasonably, the number and the position of blastholes are designed reasonably, the construction is simple and convenient, the partition delay blasting is realized by limiting the section position and the detonation network of the blasting cap in each blasthole, the upper blasting area positioned in the upper bench is the blasting area of delay detonation after the blastholes in the middle blasting area are detonated, so the upper blasting area in the upper bench is the pressure blasting area, the vibration generated in the blasting process of the middle blasting area is suppressed and restrained, and the damage of the vibration generated in the blasting process to the tunnel face and the vault is further reduced; the middle blasting area is divided into a left blasting area, a middle blasting area and a right blasting area from left to right, the middle blasting area is a cut-out area, the cut-out holes are changed from traditional 8 holes to 10 holes in the middle blasting area, and the total explosive loading of the traditional cut-out holes is further reduced and decomposed, so that the vibration generated in the blasting process can be effectively reduced; meanwhile, the outer slotted holes on the left side and the right side in the middle explosion area are detonated first and then, the left explosion area and the right explosion area are auxiliary areas, and the left explosion area and the right explosion area are detonated first and then, so that the middle explosion area, the left explosion area and the right explosion area adopt an asymmetric detonation mode, and the vibration generated in the blasting process can be further reduced.
4. The lower blasting area is farthest away from the arch crown and the tunnel face of the upper hole body, so that the influence of blasting vibration is minimum, and the rock and soil generated in the blasting process of the lower blasting area can be suppressed and restrained by the upper blasting area and the rock and soil generated in the middle blasting, so that the vibration generated in the blasting process can be effectively reduced.
5. The reinforced primary support structure has reasonable design, simple and convenient construction and good use effect, the reinforced sleeve arch is adopted to reinforce the primary support structure of the tunnel and form the reinforced primary support structure, the primary support effect of the tunnel can be effectively realized, and the primary support deformation of the deeply-buried loess tunnel is effectively controlled; meanwhile, an isolation layer is arranged between the reinforcing sleeve arch and the primary supporting structure of the tunnel, so that the deformation of the soil body outside the reinforcing sleeve arch can be further controlled; and the reinforcing sleeve arch adopts a plurality of sleeve arch units to reinforce the tunnel primary support structure in a sectional mode, so that the construction is simple and convenient, the reinforced primary support structure formed by construction has certain self-adaptive capacity, the deformation condition of the soil body on the periphery of the tunnel can be effectively adapted, and the deformation resistance of the reinforced primary support structure is effectively reduced.
6. The full-section support frame can support the tunnel hole in a full-section manner, the support is stable and reliable, the full-section support frame is formed by assembling an arch wall support arch frame and a tunnel inverted arch frame, the arch wall support arch frame is formed by assembling an upper arch frame, two middle side supports and two lower side supports, the assembly can be simply and conveniently carried out when the tunnel is actually excavated, the requirement of supporting the section of the tunnel hole in blocks is met, the primary support of the upper hole body is not influenced by the primary support construction in the middle hole body and the lower hole body, the primary support of the middle hole body is not influenced by the primary support construction in the lower hole body, the primary support of the upper hole body and the primary support of the middle hole body are constructed immediately after the excavation is finished, so that the support is timely and stable, the tunnel hole is not completely excavated at the moment, and the support stability of the primary support structure in the upper hole body and the middle hole body of the tunnel is further ensured, and the preliminary bracing process in tunnel upper portion cavern body and the middle part cavern body is changeed in going on, and it is more powerful to strut simultaneously, more is favorable to tunnel construction safety.
7. And the anchoring system is adopted to fix the surrounding rock of the tunnel in a full section manner, so that the primary support stability is further improved. And moreover, the anchoring system and the full-section support frame are connected into a whole, the overall stability is further improved, and meanwhile, the construction is simple and convenient.
8. The advance support adopts advance little pipe slip casting supporting construction, and the construction is simple and convenient and the efficiency of construction is high, can effectively ensure the advance support intensity and the effect of strutting in big section tunnel, can effectively restrict loess tunnel hunch portion deformation. The adopted advanced small conduit grouting supporting structure is reasonable in design, simple and convenient to construct and good in using effect, effectively reinforces the arch part of the tunnel and forms a stable arch wall bearing ring, can effectively improve the self-stabilizing capacity of rock strata on the periphery of a tunnel body, can effectively save construction cost and save construction period, and meanwhile, construction equipment is simple, and the preliminary bracing construction is timely carried out after the tunnel entering construction, and the working procedures are closely linked. Moreover, the disturbance to the soil layers on the peripheral sides in the supporting process is small, the construction cost is low, the problems that the arch part of the tunnel is easy to deform and settle under the influence of horizontal pressure generated after the tunnel is excavated can be effectively solved, and the arch part of the tunnel can be stably supported.
9. The reinforcing cover arch structure that adopts reasonable in design just strengthens tunnel primary support structure sectional type through a plurality of cover arch units, and not only the construction is simple and convenient to form the full section supporting construction of a transition nature between tunnel primary support structure and tunnel secondary lining structure, can warp tunnel primary support structure and effectively cushion and correct, thereby can tunnel hole overall structure more firm, and tunnel deformation control effect is better.
10. The tunnel forepoling structure for forepoling the tunnel arch part of the tunnel portal section under construction and the reinforced primary support structure for full-section support of the tunnel portal effectively control the deformation of the large-section tunnel, and can effectively improve the stability of the earth-rock boundary tunnel.
11. The adopted radial grouting reinforcement structure has reasonable design, simple and convenient construction and good use effect, and can further supplement the combined supporting effect of the reinforced primary support structure; and when the reinforced primary support structure invades the secondary lining of the tunnel and needs to be arched, the stability of the tunnel hole in the arch changing process can be effectively improved, and safety accidents are avoided.
12. The construction is simple and convenient, the use effect is good, and the stability of the excavated molded tunnel is ensured by adopting a three-step synchronous excavation mode and carrying out regional blasting; reinforcing the primary tunnel supporting structure by adopting a reinforcing sleeve arch and forming a reinforced primary support structure, so that the primary tunnel supporting effect can be effectively achieved, and the primary supporting deformation of the earth-rock boundary tunnel can be effectively controlled; meanwhile, an isolation layer is arranged between the reinforcing sleeve arch and the primary supporting structure of the tunnel, so that the deformation of the soil body outside the reinforcing sleeve arch can be further controlled; and the reinforcing sleeve arch adopts a plurality of sleeve arch units to reinforce the tunnel primary support structure in a sectional mode, so that the construction is simple and convenient, the reinforced primary support structure formed by construction has certain self-adaptive capacity, the deformation condition of the soil body on the periphery of the tunnel can be effectively adapted, and the deformation resistance of the reinforced primary support structure is effectively reduced. In addition, the full-section support frame structure tunnel is adopted for layered supporting, and an anchoring system is adopted for integrally reinforcing the outer side of the tunnel, so that the structural stability of the large-section tunnel is ensured, and the construction safety is ensured; simultaneously, the excavation in-process carries out the purpose that the concrete sprays through wet blasting manipulator, can effectively accelerate the construction progress to enable the preliminary bracing to seal the cyclization fast, further ensure the tunnel structure steadiness, the construction is simple, and construction speed is fast, and the work progress is safe, reliable. According to the above contents, the adopted supporting method has the characteristics of safety, reliability, high degree of mechanization, high construction speed, low labor intensity, advanced construction period, cost saving and the like through a three-step construction method, and the lower step and the primary support of the inverted arch are constructed simultaneously according to the geological characteristics of soil and stones in the loess stratum, so that the short time of sealing and looping can be ensured, the overlarge deformation of surrounding rocks can be prevented, and the construction safety can be ensured; in addition, the construction method is simplified, the interference among all the procedures is prevented, the mechanized construction can be met to the maximum extent, the labor intensity is reduced, the space full-section flow construction is adopted, the construction efficiency can be improved, and the engineering cost is reduced. In addition, the temporary inverted arch is cancelled, so that the engineering cost is reduced, and the safety risk in the process of dismantling the temporary inverted arch is avoided.
13. The tunnel excavation construction speed is high, the construction period can be effectively ensured, the excavation process of V-level or VI-level surrounding rock large-section tunnels can be effectively accelerated, and the safety and reliability of the construction process can be ensured.
14. The upper surface of the secondary lining inverted arch is adjusted to be a horizontal plane, the interface between the inverted arch secondary lining and the inverted arch filling layer is adjusted to be the horizontal plane, the construction is simple and convenient, the construction efficiency is high, the inverted arch filling layer and the inverted arch secondary lining can be poured simultaneously, the construction process of the inverted arch secondary lining and the inverted arch filling layer can be greatly simplified, the concrete of the inverted arch secondary lining and the inverted arch filling layer cannot be mixed into a whole, the construction quality of the inverted arch secondary lining and the inverted arch filling layer can be effectively ensured, and the problems that the construction quality of the inverted arch secondary lining and the inverted arch filling layer cannot be ensured and the like due to different concrete grades are avoided. Meanwhile, the upper surface of the inverted arch secondary lining is a horizontal plane, the arc shape of the inverted arch secondary lining is not required to be guaranteed in the concrete pouring process, an arc-shaped template is not required to be adopted, the pouring is convenient to carry out by a large margin, the pouring is simple and convenient, and the construction quality of the inverted arch secondary lining is easy to guarantee.
15. The tunnel secondary lining is reasonable in structure, the tunnel secondary lining is formed by connecting an inverted arch secondary lining and an arch wall secondary lining, and the middle arc part inside the inverted arch secondary lining is optimized to be a horizontal plane. The inverted arch secondary lining after optimizing makes tunnel inverted arch structure's rigidity whole promote by a wide margin to need not to install the arc template in the construction, concrete vibration is simple and convenient and the quality of vibrating is easily controlled, and inverted arch secondary lining's external dimension and construction quality change in the control, and can improve tunnel inverted arch's efficiency of construction by a wide margin, tunnel secondary lining's seal time shortens greatly to do not have the interference of arc template to make inverted arch concrete easily vibrate, concrete quality promotes greatly. Simultaneously, will have two lining arch wall lining now and two low side wall to be connected and constitute whole lining cutting (promptly arch wall secondary lining) and construct to adopt two lining platform trucks to construct arch wall secondary lining, once construction shaping can further improve tunnel secondary lining's efficiency of construction, accelerate tunnel secondary lining seal time shortens tunnel secondary lining's seal ring time, further improves the structural stability of the tunnel entrance to a cave section of being under construction, can effectively reduce simultaneously construction joint among the tunnel secondary lining makes tunnel secondary lining's wholeness stronger, and whole atress effect is better. And the tunnel secondary lining structure has reasonable design, simple construction method and easy control of construction quality, thereby greatly reducing the construction cost, saving the construction period and ensuring the construction safety.
16. The dewatering pre-consolidation effect is good, the dewatering construction period is short, and the dewatering process is safe and reliable, dewatering wells are distributed on the left side and the right side of the tunnel portal section in a staggered manner, the underground water level of the soil-stone boundary stratum where the tunnel is located is reduced to the lower side of the tunnel through the dewatering wells, and the purpose that no water or a small amount of water seeps in the tunnel when the tunnel is excavated is achieved; meanwhile, after loess formation pore water and rock stratum fracture water are discharged through the dewatering well, the pore and the fracture of the rock soil of the soil and stone boundary formation where the tunnel is located are reduced or even closed under the action of the dead weight, the purpose of secondary soil body consolidation is achieved, the self bearing capacity and the stability of the rock soil can be effectively improved, and the purpose of self-stabilization of surrounding rock of tunnel excavation is achieved. Compared with other existing soil body reinforcing methods, the surface cement mixing pile reinforcing method can only reinforce soil bodies and is not suitable for rock strata, the sleeve valve pipe grouting reinforcing method is influenced by underground rock-soil cracks, the grouting amount is large in frequent deviation and large in cost estimation deviation, the in-tunnel curtain grouting reinforcing method is large in interference on in-tunnel construction, the construction progress is slow, and the cost is high, when the water reducing wells are adopted for dewatering, water pumping (namely dewatering) is started 15 days before tunnel excavation, the underground water level can be timely reduced, and after 7 dewatering wells are used for dewatering simultaneously, the water inflow amount in the tunnel is obviously reduced, the palm is water-free or water seepage is occasionally caused, and surrounding rocks are stable; the sprayed concrete on the surface of the primary support can be sprayed to be flat and compact due to the fact that the vault is anhydrous; the water accumulation in the tunnel is less, and the phenomenon of water seepage or small amount of water seepage is generated when the primary inverted arch is excavated.
17. The adopted ground surface pre-reinforcement method is simple, the construction is simple and convenient, the design is reasonable, the reinforcement effect is good, the investment construction cost is low, the cement soil mixing piles are constructed according to the conventional construction method, the stratum of the region where the backfill segments are located is integrally reinforced through the plurality of mutually meshed cement soil mixing piles, the construction efficiency is high, and the required construction period is short. And, adopt cement soil mixing pile to consolidate the back to loess tunnel earth's surface in advance, consolidate the loose soil body in tunnel hole top in advance, practiced thrift the time of carrying out the pipe shed method construction in the hole, avoided the problem of tunnel hole body week side soil body soft down hard simultaneously, make tunnel hole structure more stable, improve and add the reinforcement effect in advance, ensure construction safety.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a block diagram of the process flow of the present invention.
Fig. 2 is a schematic cross-sectional structure diagram of the primary tunnel supporting structure, the secondary tunnel lining and the cover arch of the invention.
Fig. 3 is a schematic longitudinal section structure view of the preliminary tunnel supporting structure of the present invention.
FIG. 4 is a schematic view of the construction state of the wet-spraying manipulator of the present invention.
Fig. 5 is a schematic cross-sectional structure diagram of the radial grouting reinforcement structure of the invention.
Fig. 6 is a schematic longitudinal section structure diagram of the radial grouting reinforcement structure of the invention.
Fig. 7 is a schematic diagram of the arrangement positions of blastholes on the upper blasting area and the middle blasting area.
Fig. 8 is a schematic diagram of the arrangement position of blastholes on the lower blasting area.
Figure 9 is a schematic diagram of the initiation network of the upper and middle blast zones of the present invention.
Fig. 10 is a schematic plan view showing the arrangement positions of the slitting holes, the peripheral holes and the auxiliary holes in the blasting region according to the present invention.
Fig. 11 is a schematic plan layout position diagram of two rows of dewatering wells according to the invention.
FIG. 12 is a schematic diagram of the arrangement of the vertical sections of two rows of dewatering wells according to the present invention.
FIG. 13 is a schematic diagram of the cross-sectional layout of two rows of dewatering wells according to the present invention.
FIG. 14 is a schematic structural view of the dewatering well of the present invention.
Fig. 15 is a schematic view illustrating a reinforcing state of the mixing pile reinforcing structure according to the present invention.
Fig. 16 is a schematic view showing the engagement state of the soil-cement mixing pile in the mixing pile reinforcing structure according to the present invention.
Fig. 17 is a schematic structural view of a front mold plate according to the present invention.
Description of reference numerals:
1, tunnel boring; 1-upper cavity; 1-11-upper left blast zone;
1-12-upper right blast zone; 1-2-a middle hole body; 1-21-left blast zone;
1-22-a medium explosion zone; 1-23-right blast zone; 1-3-lower cavity;
1-4-cutting holes; 1-5-peripheral eye; 1-6-auxiliary eye;
2-tunnel inverted arch support; 2-1-upper arch centering;
3-a loess stratum; 3-1-bottom filter material filling layer; 3-2-dewatering well;
3-pumping equipment; 3-4-a water pumping pipe; 3-5-wellbore;
3-6-a settling tube; 3-7-a strainer; 3-8-a filter material filling layer;
3-9-clay blocking layer; 3-10-filter screen; 4-a rock formation;
5-middle side support; 6-lower side support; 7-backfilling a soil layer at the bottom of the tunnel;
8, locking a pin anchor pipe; 9-middle locking leg anchor tube; 10-lower lock pin anchor pipe;
11-steel arch centering; 11-1-arch wall section steel support; 11-2-inverted arch type steel support;
12-preliminary bracing structure of arch wall; 13-primary support inverted arch; 17-movable inverted arch trestle;
18-short side wall; 19-arch wall concrete spraying layer;
20-an inverted arch concrete spraying layer; 21-wet spraying mechanical arm; 22-grouting small guide pipe;
23-a ditch cable trough; 24-sideform; 25-front template;
26-an isolating layer; 27-inner concrete sprayed layer;
28-radial grouting holes; 29-cement mixing pile; 30-stirring pile reinforcing structure.
Detailed Description
As shown in figure 1, the tunnel portal section pre-reinforcing and excavation construction method based on the partition blasting is characterized in that the cross section of the constructed tunnel portal section is larger than 100m2The tunnel section is positioned in the earth-rock boundary stratum, the rear end of the constructed tunnel portal section is a tunnel portal, and the length of the tunnel portal section is 70-100 m; referring to fig. 7, the soil-rock boundary stratum includes a loess stratum 3 and a rock stratum 4 located below the loess stratum 3, and an interface between the loess stratum 3 and the rock stratum 4 is a soil-rock interface; the tunnel cave 1 of the tunnel cave mouth section under construction is divided into an upper cave body 1-1, a middle cave body 1-2 and a lower cave body 1-3 from top to bottom, wherein the upper cave body 1-1 is a cave body formed by carrying out upper step excavation on the tunnel cave mouth section under construction from back to front, the middle cave body 1-2 is a cave body formed by carrying out middle step excavation on the tunnel cave mouth section under construction from back to front, the lower cave body 1-3 is a cave body formed by carrying out lower step excavation on the tunnel cave mouth section under construction from back to front, the earth-stone interface is positioned in the upper cave body 1-1, and the upper cave body 1-1 and the middle cave body 1-2 form the upper cave body;
a backfill soil layer exists in a construction area where a tunnel portal section to be constructed is located, the backfill soil layer is formed after backfilling cracks or caves existing on the ground surface of a construction area to be treated, and the backfill soil layer is a loess layer; the construction area to be processed is a construction area where a tunnel portal section is located; the tunnel section with the backfill soil layer in the tunnel portal section is a backfill section;
when the pre-reinforcing and excavating construction is carried out on the tunnel portal section, the method comprises the following steps:
firstly, dewatering and pre-reinforcing: constructing two rows of precipitation wells 3-2 in a construction area where the tunnel portal section is located, and synchronously precipitating the construction area where the tunnel portal section is located through the two rows of precipitation wells 3-2 to enable the underground water level of the construction area where the tunnel portal section is located to be reduced to be below an excavation contour line of the tunnel portal section;
as shown in fig. 11, 12 and 13, two rows of dewatering wells 3-2 are respectively arranged at the left side and the right side of the tunnel portal section, each row of dewatering wells 3-2 comprises a plurality of dewatering wells 3-2 arranged from back to front along the longitudinal extension direction of the tunnel, a plurality of dewatering wells 3-2 in each row of dewatering wells 3-2 are uniformly arranged, and the dewatering wells 3-2 in the two rows of dewatering wells 3-2 are arranged in a staggered manner;
step two, pre-reinforcing the earth surface: reinforcing the earth surface of the backfill segment in the tunnel portal section by using a cement soil mixing pile 29 to obtain a mixing pile reinforcing structure 30;
the mixing pile reinforcing structure 30 is arranged along the longitudinal extension direction of the tunnel of the backfill segment, and the longitudinal length of the mixing pile reinforcing structure 30 is the same as that of the backfill segment; the width of the mixing pile reinforcing structure 30 is larger than the excavation width of the backfill segment; the tunnel buried depth of the backfill segment is 12 m-15 m, the mixing pile reinforcing structure 30 is a reinforcing structure formed by reinforcing the loess stratum 3 of the region where the backfill segment is located by adopting a plurality of cement mixing piles 29, the plurality of cement mixing piles 29 are arranged in a quincunx shape, the plurality of cement mixing piles 29 are uniformly arranged and are vertically arranged, and the bottom of each cement mixing pile 29 is supported on the rock stratum 4; the distance L0 between two adjacent cement soil mixing piles 29 is 70-80 cm, and the pile bodies of two adjacent cement soil mixing piles 29 are meshed with each other; many the structure and the size of cement mixing pile 29 are all the same, the height of cement mixing pile 29 is the same as the vertical height of mixing pile reinforced structure 30, cement mixing pile 29 is a cylindrical pile and its pile diameter
Wherein d0 > L0;
step three, tunnel excavation construction: after the ground surface pre-reinforcement is completed in the second step, excavating construction is carried out on the tunnel portal section under construction;
when the excavation construction is carried out on the tunnel portal section, the excavation construction is carried out on the tunnel portal section by a plurality of excavation sections from back to front along the longitudinal extension direction of the tunnel, and the excavation construction methods of all the excavation sections are the same; when any excavation segment of the tunnel portal section under construction is excavated, the process is as follows:
step 301, measurement and paying-off: respectively measuring and paying off the excavation contour lines of the upper cavity body 1-1, the middle cavity body 1-2 and the lower cavity body 1-3 on the current construction excavation surface, and simultaneously respectively measuring and paying off the number of blastholes required to be arranged on the excavation surface of the upper cavity body 1-1, the middle cavity body 1-2 and the lower cavity body 1-3 in the current construction excavation segment and the arrangement positions of the blastholes; the current construction excavation surface is the excavation surface of the current construction excavation segment;
the blasting excavation surface of the upper cave body 1-1 is divided into a left upper blasting area 1-11 and a right upper blasting area 1-12 positioned on the right side of the left upper blasting area 1-11, and the blasting excavation surface of the upper cave body 1-1 is positioned below the earth-rock interface; the blasting excavation surface of the middle hole body 1-2 is divided into a left blasting area 1-21, a middle blasting area 1-22 and a right blasting area 1-23 from left to right, and the left blasting area 1-21 and the right blasting area 1-23 are symmetrically arranged on the left side and the right side of the middle blasting area 1-22;
the medium explosion area 1-22 is a cut area and is provided with four groups of cut holes 1-4, and each group of cut holes 1-4 comprises a plurality of cut holes 1-4 distributed on the same vertical surface from top to bottom; the four groups of the cutting holes 1-4 comprise a left group of inner cutting holes and a right group of outer cutting holes which are symmetrically distributed, and the two groups of the inner cutting holes are positioned between the two groups of the outer cutting holes; the inner side cutting holes and the outer side cutting holes are arranged in a staggered manner;
a plurality of peripheral holes 1-5 are arranged from top to bottom on the left side of the left upper explosion area 1-11, the right side of the right upper explosion area 1-12, the left side of the left explosion area 1-21 and the right side of the right explosion area 1-23;
three rows of auxiliary eyes 1-6 are distributed on the left explosion area 1-21 and the right explosion area 1-23 from left to right, and each row of auxiliary eyes 1-6 on the left explosion area 1-21 and the right explosion area 1-23 comprises a plurality of auxiliary eyes 1-6 distributed on the same vertical plane from top to bottom; an upper row and a lower row of auxiliary eyes 1-6 are uniformly distributed on the left upper explosion area 1-11 and the right upper explosion area 1-12, and each row of auxiliary eyes 1-6 on the left upper explosion area 1-11 and the right upper explosion area 1-12 comprises a plurality of auxiliary eyes 1-6 arranged from left to right;
the blasting excavation surface of the upper hole body is divided into 5 blasting areas, and the 5 blasting areas are respectively a left upper blasting area 1-11, a right upper blasting area 1-12, a left blasting area 1-21, a middle blasting area 1-22 and a right blasting area 1-23; the left explosion area 1-21 and the right explosion area 1-23 in the 5 explosion areas are simultaneously detonated, the left upper explosion area 1-11 and the right upper explosion area 1-12 are simultaneously detonated, and the middle explosion area 1-22, the right upper explosion area 1-23 and the right upper explosion area 1-12 are detonated in sequence from first to last;
the cutting holes 1-4, the peripheral holes 1-5 and the auxiliary holes 1-6 are blast holes;
step 302, drilling and blasting construction: according to the arrangement positions of the blastholes obtained by measuring and setting out in the step 301, drilling all the blastholes on the current construction excavation surface by adopting drilling equipment, respectively charging the blastholes formed by drilling, and detonating for blasting after charging is completed;
step 303, excavating an upper hole body: excavating an upper hole body 1-1 of the currently constructed excavation section from back to front along the longitudinal extension direction of the tunnel;
excavating the loess stratum 3 in the upper cavity 1-1 from back to front when the upper cavity 1-1 of the current construction excavation section is excavated from back to front; in the excavation process of the loess stratum 3 in the upper cave body 1-1 from back to front, a ballast conveying vehicle is adopted to convey the ballast generated after the inner explosion of the upper cave body 1-1 from back to front to the outer side of the tunnel cave mouth section to be constructed, so that the excavation construction process of the upper cave body 1-1 is completed;
step 304, excavating a middle hole body: excavating the middle hole body 1-2 of the currently constructed excavation section from back to front along the longitudinal extension direction of the tunnel;
when the middle tunnel body 1-2 of the current constructed excavation section is excavated from back to front, the slag transport vehicle is adopted to transport the slag generated after the internal explosion of the middle tunnel body 1-2 to the outer side of the tunnel portal section to be constructed from back to front, so as to finish the excavation construction process of the middle tunnel body 1-2;
step 305, excavating a lower cavity: excavating the lower cavity body 1-3 of the currently constructed excavation section from back to front along the longitudinal extension direction of the tunnel, and finishing the excavation construction process of one excavation section;
when the lower tunnel body 1-3 of the current constructed excavation section is excavated from back to front, the slag conveying vehicle is adopted to convey the slag generated after the inner explosion of the lower tunnel body 1-3 to the outer side of the tunnel portal section to be constructed from back to front, so that the excavation construction process of the lower tunnel body 1-3 is completed, and the tunnel portal 1 formed by construction is obtained;
step 306, excavating construction of the next excavation segment: excavating the next excavation section of the tunnel portal section according to the construction process from the step 301 to the step 305;
and 307, repeating the step 306 for multiple times until all excavation construction processes of the tunnel portal section are completed.
In this embodiment, the tunnel portal section is horizontally arranged and is a linear tunnel.
In this embodiment, before the precipitation pre-reinforcement in the first step, the cracks or caves existing on the ground surface of the construction area to be treated are backfilled respectively, and a backfill soil layer is obtained. And when backfilling the backfill soil layer, carrying out layered backfilling from bottom to top by adopting loess and tamping. Since the filling layer is a loess layer, the filling layer is a loess layer 3.
The cave refers to a cave formed by the subsurface water collecting in the joint cracks for corrosion. Cave is a unique erosion phenomenon in the hilly gully region of loess plateau. Because the unevenness of loess accumulation layer texture, surface water infiltrates along the crack or the hole in the loess, produces erosion and erosion to the loess to leaching the soluble salt, cause the lower side to undercut, when the soil body on the upper side loses the top and holds in the palm, arouse the collapse of loess, form and fall cave. The caved loess refers to a caved loess, which is a caved pit exposed on the surface of the loess area.
In this embodiment, the backfill segment is present on the tunnel opening section under construction. And one or more of the backfill layers are present on the backfill segments. In the step one, the two rows of dewatering wells 3-2 are respectively positioned at the left side and the right side of the mixing pile reinforcing structure 30.
In this embodiment, the length of the backfill segment is 10 m-20 m.
During actual construction, the number of the backfill segments and the length of each backfill segment on the tunnel opening section of the constructed tunnel can be adjusted correspondingly according to specific requirements.
The surrounding rock grading is to divide an infinite rock mass sequence into a finite number of categories with different stability degrees according to indexes such as the integrity degree of the rock mass, the strength of the rock mass and the like, namely, to classify some surrounding rocks with similar stability into one category, and to classify all the surrounding rocks into a plurality of categories. In the railway tunnel design specification (TB10003-2005), the grade of the surrounding rock of the tunnel is divided into 6 grades, i, ii, iii, iv, v and vi grades respectively, and the smaller the number, the better the surrounding rock property is. In this embodiment, the surrounding rock level of the tunnel cave 1 is v level or vi level, and specifically, the surrounding rock level of the rock stratum 4 around the tunnel cave 1 is v level or vi level.
The blasting excavation surface of the upper hole body 1-1 is an upper blasting area, the upper blasting area is positioned below the earth-rock interface, and the upper blasting area is the excavation surface of a rock stratum 4 in the upper hole body 1-1; the excavation surface of the middle hole body 1-2 is a middle blasting area, and the excavation surface of the lower hole body 1-3 is a lower blasting area.
During actual construction, the excavation height of the tunnel hole 1 is 11 m-15 m, and the excavation width of the tunnel hole 1 is 10 m-15 m.
In this embodiment, the excavation height of the tunnel cave 1 is 12m, the height of the upper cave body 1-1 (i.e., the height of the upper step) is 4m, the height of the middle cave body 1-2 (i.e., the height of the middle step) is 3.5m, and the excavation height of the lower cave body 1-3 is 2.4m to 2.7 m. In the actual construction process, the excavation height of the tunnel cave 1, the height of the upper cave body 1-1 and the height of the middle cave body 1-2 can be correspondingly adjusted according to specific requirements.
The cutting holes 1-4, the peripheral holes 1-5 and the auxiliary holes 1-6 are all cylindrical drill holes drilled into the rock stratum 4 from back to front. As shown in fig. 10, each of the slitting holes 1 to 4 and each of the auxiliary holes 1 to 6 in the middle blasting zone are gradually inclined inward from rear to front, and each of the peripheral holes 1 to 5 in the upper blasting zone and the middle blasting zone are gradually inclined outward from rear to front.
In this embodiment, in step 301, each group of the inner slitting holes includes two slitting holes 1 to 4, and each group of the outer slitting holes includes three slitting holes 1 to 4. During actual construction, the number of the inner side cutting holes included in each inner side cutting hole and the arrangement positions of the inner side cutting holes can be correspondingly adjusted according to specific requirements, and the number of the outer side cutting holes included in each outer side cutting hole and the arrangement positions of the outer side cutting holes can be correspondingly adjusted according to specific requirements.
Each column of the auxiliary eyes 1-6 on the left burst area 1-21 and the right burst area 1-23 comprises 3 or 4 auxiliary eyes 1-6. In this embodiment, each row of the auxiliary eyes 1 to 6 in the right burst area 1 to 23 includes 4 auxiliary eyes 1 to 6, and the number of the auxiliary eyes 1 to 6 included in the three rows of the auxiliary eyes 1 to 6 in the left burst area 1 to 21 is 4, 3, and 4 respectively from left to right. During actual construction, the number of the auxiliary eyes 1-6 included in each column of the auxiliary eyes 1-6 on the left explosion area 1-21 and the right explosion area 1-23 and the arrangement positions of the auxiliary eyes 1-6 can be adjusted correspondingly according to specific requirements.
Each row of the auxiliary eyes 1-6 on the left upper explosion area 1-11 and the right upper explosion area 1-12 comprises 3 or 4 auxiliary eyes 1-6.
With reference to fig. 7 and 9, in this embodiment, in step 301, the two groups of detonators for inside slotted hole blasting have 1 section, the group of detonators for outside slotted hole blasting close to the right blasting region 1-23 have 3 sections, and the group of detonators for outside slotted hole blasting close to the left blasting region 1-21 have 5 sections;
the three rows of the blasting detonators for the auxiliary eyes 1-6 on the left blasting area 1-21 are respectively 3 sections, 5 sections and 7 sections from right to left, and the three rows of the blasting detonators for the auxiliary eyes 1-6 on the right blasting area 1-23 are respectively 3 sections, 5 sections and 7 sections from left to right;
the section positions of all the blasting detonators for the peripheral holes 1-5 on the left blasting area 1-21 and the right blasting area 1-23 are 9 sections.
In this embodiment, the two rows of the auxiliary holes 1 to 6 in the upper left explosion area 1 to 11 and the upper right explosion area 1 to 12 are respectively an upper row of auxiliary holes and a lower row of auxiliary holes.
The section positions of all the blasting detonators for 1-6 in the lower auxiliary hole row on the left upper blasting area 1-11 are 3 sections, and the section positions of all the blasting detonators for 1-6 in the lower auxiliary hole row on the right upper blasting area 1-12 are 3 sections;
one auxiliary eye 1-6 positioned at the leftmost side in the upper row of auxiliary eyes on the upper left blasting area 1-11 is an upper left auxiliary eye, and the section positions of all auxiliary eyes 1-6 blasting detonators except the upper left auxiliary eye in the upper row of auxiliary eyes on the upper left blasting area 1-11 are 5 sections;
one auxiliary eye 1-6 which is positioned at the rightmost side in the upper row of auxiliary eyes on the right upper explosion area 1-12 is a right upper auxiliary eye, and the section positions of all auxiliary eyes 1-6 blasting detonators except the right upper auxiliary eye in the upper row of auxiliary eyes on the right upper explosion area 1-12 are 5 sections;
the blasting detonators for the auxiliary eye on the left side and the auxiliary eye on the right side are 7 in section.
In this embodiment, the width of the left upper explosion area 1-11 is greater than the width of the right upper explosion area 1-12. The lower row of auxiliary eyes on the left upper explosion area 1-11 comprises 4 auxiliary eyes 1-6, the lower row of auxiliary eyes on the right upper explosion area 1-12 comprises 3 auxiliary eyes 1-6, the auxiliary eye 1-6 positioned at the rearmost side in the lower row of auxiliary eyes on the left upper explosion area 1-11 is a left lower auxiliary eye, and the left lower auxiliary eye is positioned on the tunnel centerline of the tunnel hole 1. The left lower auxiliary eyes are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the rest auxiliary eyes 1-6 except the left lower auxiliary eyes in the upper blasting area are gradually inclined inwards from back to front.
In this embodiment, the upper rows of auxiliary eyes on the left upper explosion area 1-11 and the right upper explosion area 1-12 respectively include 4 auxiliary eyes 1-6.
During actual construction, the number of the auxiliary eyes 1-6 in each row of the auxiliary eyes 1-6 on the left upper explosion area 1-11 and the right upper explosion area 1-12 and the arrangement positions of the auxiliary eyes 1-6 can be adjusted correspondingly according to specific requirements.
In this embodiment, the detonators with the upper sections of 5 sections in the middle explosion area 1-22 are connected with the detonators for blast hole blasting in the left explosion area 1-21 through detonating tubes, and the detonators with the upper sections of 3 sections in the middle explosion area 1-22 are connected with the detonators for blast hole blasting in the right explosion area 1-23 through detonating tubes;
the detonators with the 5 sections at the upper sections of the left explosion area 1-21 are connected with the detonators for blast hole blasting on the left explosion area 1-11 through detonating tubes, and the detonators with the 5 sections at the upper sections of the right explosion area 1-23 are connected with the detonators for blast hole blasting on the right explosion area 1-12 through detonating tubes.
In this embodiment, an upper auxiliary eye 1-6 and a lower auxiliary eye 1-6 are arranged between the peripheral eyes 1-5 and the upper auxiliary eye on the left side on the upper left blasting area 1-11, and the section positions of the blasting detonators for the two auxiliary eyes 1-6 are 7 sections; an upper auxiliary eye 1-6 and a lower auxiliary eye 1-6 are arranged between the peripheral eyes 1-5 and the auxiliary eye on the right side on the upper right explosion area 1-12, and the section positions of the blasting detonators for the two auxiliary eyes 1-6 are 7 sections.
When the lower cavity body 1-3 is excavated from back to front, the conventional drilling and blasting method is adopted for construction. Therefore, the arrangement of the blastholes on the lower holes 1-3 has no special requirements.
In this embodiment, as shown in fig. 8, a plurality of the peripheral holes 1 to 5 are distributed from left to right at the bottom of the lower blasting region, 4 of the cutting holes 1 to 4 are arranged in the middle of the lower blasting region, the 4 cutting holes 1 to 4 are distributed in two rows, one row being upper and the other being lower, and each row of the cutting holes 1 to 4 includes two cutting holes 1 to 4 on the left and the right; the area where the 4 cutting holes 1-4 are located is a middle cutting area, two groups of auxiliary holes 1-6 are symmetrically distributed on the left side and the right side of the middle cutting area, each group of auxiliary holes 1-6 comprises a left auxiliary hole 1-6 and a right auxiliary hole 1-6, and each row of auxiliary holes 1-6 comprises an upper auxiliary hole 1-6 and a lower auxiliary hole 1-6.
During actual construction, the number of the cutting holes 1-4 and the auxiliary holes 1-6 and the arrangement positions of the cutting holes 1-4 and the auxiliary holes 1-6 in the lower blasting area can be adjusted correspondingly according to specific requirements.
In this embodiment, the section positions of the plurality of blasting detonators for the peripheral holes 1 to 5 in the lower blasting region are all 11 sections, and the section positions of the 4 blasting detonators for the slotted holes 1 to 4 in the middle slotted zone are all 1 section; the section positions of one row of the auxiliary hole 1-6 blasting detonators close to the middle cut area in each group of the auxiliary holes 1-6 in the lower blasting area are 5 sections, and the section positions of the other row of the auxiliary hole 1-6 blasting detonators in each group of the auxiliary holes 1-6 are 7 sections.
And the detonators with 5 sections at the upper sections of the left upper blasting area 1-11 are connected with the detonators for blasting blastholes on the lower blasting area through detonating tubes.
According to the above, when drilling and blasting construction is carried out on any one excavation section, the left blasting area 1-21 and the right blasting area 1-23 are auxiliary areas, and the left upper blasting area 1-11 and the right upper blasting area 1-12 are pressure blasting areas. And when the lower blasting area is blasted, the upper blasting area and the middle blasting area are both blasting areas.
In this embodiment, the depths of the blast holes in the upper blasting area, the middle blasting area and the lower blasting area, except for the inner side cutting hole, in the longitudinal extension direction of the tunnel are all 1.4 m. During actual construction, the depths of the rest blast holes except the inner side cutting hole in the upper blasting area, the middle blasting area and the lower blasting area along the longitudinal extension direction of the tunnel can be correspondingly adjusted according to specific requirements.
During actual construction, the section position and the delay time of each detonator for blast hole blasting are detailed in table 1:
TABLE 1 statistical table of blasting detonator segment position and delay time
| |
1 | 3 | 5 | 7 | 9 | 11 |
| Delay time (unit: ms) | 0 | 50 | 110 | 200 | 310 | 460 |
In this embodiment, the explosives contained in all the blastholes on the upper blasting area, the middle blasting area and the lower blasting area are emulsion explosives.
The hole depth of the inner cutting holes is 0.92m, the loading amount of each inner cutting hole is 0.43kg, and the delay time of the detonator for blasting the inner cutting holes is 0 ms; the depth of the outer cutting holes is 1.99m, and the loading amount of each outer cutting hole is 0.65 kg; the delay time of a group of detonators for the external slotted hole blasting close to the right blasting area 1-23 is 50ms, and the delay time of a group of detonators for the external slotted hole blasting close to the left blasting area 1-21 is 110 ms;
three rows of auxiliary eyes 1-6 on the right burst area 1-23 are respectively a first auxiliary eye, a second auxiliary eye and a third auxiliary eye from left to right; the hole depth of the first auxiliary hole is 1.72m, the loading capacity in the first auxiliary hole is 0.65kg, and the delay time of the first auxiliary hole blasting detonator is 100ms (namely 50ms +50 ms); the hole depth of the second auxiliary hole is 1.52m, the loading capacity in the second auxiliary hole is 0.65kg, and the delay time of the detonator for blasting the second auxiliary hole is 160ms (namely 50ms +110 ms); the hole depth of the second auxiliary hole is 1.42m, the loading capacity of the third auxiliary hole is 0.54kg, and the delay time of the detonator for blasting the third auxiliary hole is 250ms (namely 50ms +200 ms); the hole depth of each peripheral hole 1-5 on the right explosion area 1-23 is 1.41m, the loading capacity of each peripheral hole 1-5 on the right explosion area 1-23 is 0.22kg, and the delay time of each peripheral hole 1-5 blasting detonator on the right explosion area 1-23 is 360ms (namely 50ms +310 ms);
three rows of auxiliary eyes 1-6 on the left burst area 1-21 are respectively a fourth auxiliary eye, a fifth auxiliary eye and a sixth auxiliary eye from right to left; the hole depth of the fourth auxiliary hole is 1.72m, the loading capacity in the fourth auxiliary hole is 0.65kg, and the delay time of the fourth auxiliary hole blasting detonator is 160ms (namely 110ms +50 ms); the hole depth of the fifth auxiliary hole is 1.52m, the loading capacity in the fifth auxiliary hole is 0.65kg, and the delay time of the detonator for blasting the fifth auxiliary hole is 220ms (namely 110ms +110 ms); the hole depth of the sixth auxiliary hole is 1.44m, the loading capacity in the sixth auxiliary hole is 0.54kg, and the delay time of the detonator for blasting the sixth auxiliary hole is 310ms (namely 110ms +200 ms); the hole depth of each peripheral hole 1-5 on the left blasting area 1-21 is 1.41m, the loading capacity of each left blasting area 1-21 on the left blasting area 1-21 is 0.22kg, and the delay time of each peripheral hole 1-5 blasting detonator on the left blasting area 1-21 is 420ms (namely 110ms +310 ms);
the inner parts of the peripheral holes 1-5 of the right explosion area 1-23 and the left explosion area 1-21 are charged in an air-isolated charging mode;
the hole depth of each peripheral hole 1-5 on the upper blasting area is 1.3m, and the explosive loading of each peripheral hole 1-5 on the upper blasting area is 0.22 kg; the hole depth of each auxiliary hole 1-6 on the upper blasting area is 1.3m, and the explosive loading of each peripheral hole 1-5 on the upper blasting area is 0.44 kg;
the delay time of each peripheral eye 1-5 blasting detonator in the upper right blasting area 1-12 is 470ms (namely 50ms +110ms +310ms), and the delay time of each peripheral eye 1-5 blasting detonator in the upper left blasting area 1-11 is 530ms (namely 110ms +110ms +310 ms);
the delay time of each detonator for blasting of the auxiliary eye 1-6 in the lower row of auxiliary eyes in the upper right blasting area 1-12 is 210ms (namely 50ms +110ms +50ms), and the delay time of each detonator for blasting of the auxiliary eye 1-6 in the lower row of auxiliary eyes in the upper left blasting area 1-11 is 270ms (namely 110ms +110ms +50 ms);
the delay time of the auxiliary eye blasting detonator on the right side is 360ms (namely 50ms +110ms +200ms), and the delay time of the auxiliary eye blasting detonator on the left side is 420ms (namely 110ms +110ms +200 ms); the delay time of each blasting detonator 1-6 for the auxiliary eyes except the auxiliary eye on the right side in the upper row of auxiliary eyes on the upper right blasting areas 1-12 is 270ms (namely 50ms +110ms +110ms), and the delay time of each blasting detonator 1-6 for the auxiliary eyes except the auxiliary eye on the left side in the upper row of auxiliary eyes on the upper left blasting areas 1-11 is 330ms (namely 110ms +110ms +110 ms).
When a traditional mining method is adopted to blast and excavate a tunnel with an excavation width of 12m, explosives are generally divided into 7 to 8 sections for detonation, namely 1 section, 3 sections, 5 sections, 7 sections, 9 sections, 11 sections, 13 sections and 15 sections, the maximum explosive amount is in a slotted hole of 1 section, and the total explosive amount of the slotted hole is 8.7 kg. The upper blasting area and the middle blasting area are divided into 5 blasting areas, and the 5 blasting areas are respectively a left upper blasting area 1-11, a right upper blasting area 1-12, a left blasting area 1-21, a middle blasting area 1-22 and a right blasting area 1-23; and (3) simultaneously detonating a left detonation zone 1-21 and a right detonation zone 1-23 in the 5 detonation zones, simultaneously detonating a left upper detonation zone 1-11 and a right upper detonation zone 1-12, and detonating the middle detonation zone 1-22, the right upper detonation zone 1-23 and the right upper detonation zone 1-12 in a sequence from first to last. Meanwhile, the area needing blasting during traditional middle step blasting excavation is divided into five blasting areas, the traditional 8 holes are changed into 10 holes, and the total explosive amount of the traditional cut holes is divided into 1.72kg (namely the total explosive amount of 4 inner cut holes) and two 1.95kg, wherein 1.95kg is the total explosive amount of a group of outer cut holes.
In this embodiment, the delay time of each detonator for blasting of the slotted holes 1 to 4 in the lower blasting region is 330ms (i.e., 110ms +110ms +110 ms); the delay time of one row of the auxiliary hole 1-6 blasting detonators close to the middle cutting area in each group of the auxiliary holes 1-6 in the lower blasting area is 440ms (namely 110ms +110ms +110ms), and the delay time of the other row of the auxiliary hole 1-6 blasting detonators in each group of the auxiliary holes 1-6 is 530ms (namely 110ms +110ms +110ms +200 ms); the delay time of each detonator for blasting of the peripheral holes 1-5 on the lower blasting area is 790ms (namely 110ms +110ms +110ms +460 ms). Therefore, the blasting process of the lower blasting area is finally carried out, so that overlarge vibration generated during centralized blasting of the tunnel face is avoided, and the upper blasting area and the middle blasting area after blasting can also suppress and restrict the vibration generated in the blasting process of the lower blasting area.
In this embodiment, in the step 303, when the loess stratum 3 in the upper cavity 1-1 is excavated from back to front, an excavator is used for excavation;
before adopting the excavator to excavate, firstly install a scarifier on excavator's grab bucket and pass through the scarifier loosens the soil to the loess stratum 3 in the upper portion hole body 1-1, will again the scarifier demolishs and adopts the excavator excavates the loess stratum 3 in the upper portion hole body 1-1.
When the excavator is adopted to excavate the loess stratum 3 in the upper portion hole body 1-1, a mechanical excavation mode is adopted, the excavation efficiency is higher, and a scarifier is installed on a grab bucket of the excavator, so that the excavator has the characteristics of small disturbance, good visual effect, high disassembly and assembly speed and the like, the over-excavation phenomenon of tunnel excavation can be effectively solved, and the construction efficiency is improved.
According to the content, when the tunnel opening section to be constructed is excavated, only the rock stratum 4 in the tunnel hole 1 needs to be blasted and excavated, and the loess stratum 3 in the tunnel hole 1 is excavated by the excavator. In order to avoid collapse of the soil-rock layer caused by blasting of the soil-rock boundary stratum; and (4) dividing an explosion area for the rock stratum 4 in the tunnel hole 1, and carrying out sectional explosion.
As shown in fig. 2 and 3, the preliminary tunnel supporting structure of the tunnel cave 1 is divided into an arch wall preliminary supporting structure 12 for preliminary supporting the arch wall of the tunnel cave 1 and a preliminary supporting inverted arch 13 for preliminary supporting the bottom of the tunnel cave 1;
the tunnel primary support structure comprises a full-section support structure for performing full-section support on the tunnel hole 1, an arch wall net-jet support structure for performing primary support on an arch wall of the tunnel hole 1 and an inverted arch primary support structure for performing primary support on the bottom of the tunnel hole 1; the full-section supporting structure comprises a plurality of full-section supporting frames which are arranged from back to front along the longitudinal extension direction of the tunnel, the two adjacent full-section supporting frames at the front and the back are fixedly connected into a whole through a plurality of longitudinal connecting reinforcing steel bars, the longitudinal connecting reinforcing steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal connecting reinforcing steel bars are arranged along the contour line of the full-section supporting frames; a plurality of full-section support frames in the full-section support structure are uniformly distributed, the distance between two adjacent full-section support frames in the front and the back is L, and the value range of L is 0.5-0.8 m;
the shape of the full-section support frame is the same as the shape of the cross section of the tunnel hole 1, each full-section support frame is formed by splicing an arch wall support arch frame for supporting an arch wall of the tunnel hole 1 and a tunnel inverted arch support frame 2 for supporting the bottom of the tunnel hole 1, the tunnel inverted arch support frame 2 is positioned right below the arch wall support arch frame, the arch wall support arch frame and the tunnel inverted arch frame are positioned on the same tunnel cross section, and the tunnel inverted arch support frame 2 and the arch wall support arch frame form a closed full-section support; the inverted arch primary support structure is an inverted arch concrete injection layer 20 injected at the bottom of the tunnel hole 1, and the tunnel inverted arch support 2 is fixed in the inverted arch concrete injection layer 20;
the arch wall mesh-spraying supporting structure and all arch wall steel arch frames in the full-section supporting structure form an arch wall primary supporting structure 12, and the inverted arch primary supporting structure and all tunnel inverted arch brackets 2 in the full-section supporting structure form a primary supporting inverted arch 13;
the arch wall supporting arch comprises an upper arch 2-1 positioned in an upper hole body 1-1, two middle side brackets 5 symmetrically arranged below the left side and the right side of the upper arch 2-1 and positioned in a middle hole body 1-2, and two lower side brackets 6 symmetrically arranged below the left side and the right side of the upper arch 2-1 and positioned in a lower hole body 1-3, wherein the tunnel inverted arch bracket 2 is positioned in a lower hole body 1-3; each middle side bracket 5 is connected between the upper end of one lower side bracket 6 and one end of the upper arch 2-1; the left end of the tunnel inverted arch support 2 is fixedly connected with the bottom of one lower side support 6, and the right end of the tunnel inverted arch support 2 is fixedly connected with the bottom of the other lower side support 6.
As the soil layer and the rock stratum in the tunnel 1 in the earth-rock boundary stratum are uneven in hardness, the deformation amount and the speed of the surrounding rock are not uniform, the deformation of the earth stratum is larger than that of the rock stratum, the tunnel excavation construction process encounters mudstone kaolinization expansive soil, the initial deformation structure is damaged in the initial construction stage, and the supporting structure needs to be reinforced. Although various surrounding rocks have certain self-stability after being exposed, the time is not too long, so that the steel arch 11 is installed and the concrete is sprayed and protected immediately in the tunnel excavation process, and the exposure time caused by no support after the surrounding rocks are excavated is shortened.
In the embodiment, after the excavation of the upper hole body 1-1 of the currently constructed excavation section is finished in the step 303, an upper arch frame 2-1 is installed in the excavated and formed upper hole body 1-1 from back to front; simultaneously entering step 304, excavating the middle hole body 1-2 of the currently constructed excavation section from back to front;
in step 304, after the excavation of the middle hole body 1-2 of the currently constructed excavation section is finished, respectively installing middle side brackets 5 at the left side and the right side of the middle hole body 1-2 which is excavated and formed from back to front, and firmly connecting each middle side bracket 5 with an upper arch frame 2-1 positioned above the middle side bracket into a whole; simultaneously, step 305 is carried out, and the lower hole body 1-3 of the currently constructed excavation segment is excavated from back to front;
step 305, after the excavation of the lower hole body 1-3 of the currently constructed excavation section is finished, respectively installing lower side supports 6 at the left side and the right side of the excavated and formed lower hole body 1-3 from back to front, and fixedly connecting each lower side support 6 with a middle side support 5 positioned above the lower side support into a whole; simultaneously, by back forward at the lower part cave body 1-3 bottom installation tunnel invert support 2 and make the tunnel invert support 2 of installing as an organic whole with the lower part collateral branch frame 6 fastening connection that the 1-3 left and right sides of lower part cave body installed, obtain to erect the completion the full section support frame, and through the multichannel longitudinal connecting reinforcement will be adjacent two around the full section support frame fastening connection is as an organic whole.
In this embodiment, the arch wall mesh-grouting support structure includes an arch wall reinforcing mesh piece hung on the arch wall of the tunnel cave 1 and an arch wall concrete spraying layer 19 sprayed on the arch wall of the tunnel cave 1, the arch wall reinforcing mesh piece is fixed on the arch wall steel arch, and the arch wall reinforcing mesh piece and the arch wall steel arch are both fixed in the arch wall concrete spraying layer 19. The arch wall concrete injection layer 19 and the inverted arch concrete injection layer 20 are both concrete layers formed by injection using a wet-jet robot 21.
During actual construction, after the excavation of the upper hole body 1-1 of the currently constructed excavation section is finished in the step 303, firstly, an arch reinforcing mesh is hung on the arch part of the upper hole body 1-1 from back to front, meanwhile, an upper arch frame 2-1 is installed in the upper hole body 1-1 from back to front, and the hung arch reinforcing mesh is tightly connected with the installed upper arch frame 2-1;
after the excavation of the middle hole body 1-2 of the currently constructed excavation section is finished in step 304, respectively hanging middle reinforcing mesh sheets on the left and right sides of the middle hole body 1-2 from back to front, respectively installing middle side brackets 5 on the left and right sides of the middle hole body 1-2 from back to front, respectively fastening and connecting the hung middle reinforcing mesh sheets with the installed middle side brackets 5, and simultaneously fastening and connecting the hung middle reinforcing mesh sheets with the arch reinforcing mesh sheets positioned above the middle reinforcing mesh sheets;
after the excavation of the lower hole body 1-3 of the currently constructed excavation section is finished in the step 305, respectively hanging lower reinforcing mesh sheets on the left and right sides of the lower hole body 1-3 from back to front, respectively installing lower side brackets 6 on the left and right sides of the lower hole body 1-3 from back to front, respectively, and enabling the hung lower reinforcing mesh sheets to be fixedly connected with the installed lower side brackets 6 and the hung lower reinforcing mesh sheets to be fixedly connected with the middle reinforcing mesh sheets positioned above the hung lower reinforcing mesh sheets;
in the process of respectively installing lower side brackets 6 at the left side and the right side of the lower hole body 1-3 from back to front, installing a tunnel inverted arch bracket 2 at the bottom of the lower hole body 1-3 from back to front, and firmly connecting the installed tunnel inverted arch bracket 2 with the lower side brackets 6 installed at the left side and the right side of the lower hole body 1-3 into a whole to obtain the supported full-section supporting frame;
after all full-section support frames in the current constructed excavation section are erected and two adjacent full-section support frames are connected through a plurality of longitudinal connecting steel bars, respectively performing concrete spraying construction on an upper hole body 1-1, a middle hole body 1-2 and a lower hole body 1-3 of the current constructed excavation section from top to bottom;
when the concrete spraying construction is carried out on the upper hole body 1-1 of the current constructed excavation section, a layer of concrete is sprayed on the inner wall of the upper hole body 1-1 formed by excavation from back to front to form an arch concrete spraying layer, and the hung arch reinforcing mesh and the installed upper arch frame 2-1 are fixed in the arch concrete spraying layer, so that the excavation and primary support construction processes of the upper hole body 1-1 are completed;
when concrete spraying construction is carried out on the middle hole body 1-2 of the current constructed excavation section, a layer of concrete is respectively sprayed on the inner walls of the left side and the right side of the middle hole body 1-2 from back to front to form a middle concrete spraying layer, the middle concrete spraying layer is connected with the arch concrete spraying layer positioned above the middle concrete spraying layer, the hung middle reinforcing mesh and the installed middle side support 5 are fixed in the middle concrete spraying layer, and the excavation and primary support construction process of the middle hole body 1-2 is completed;
when concrete spraying construction is carried out on the lower hole body 1-3 of the currently constructed excavation section, a layer of concrete is respectively sprayed on the inner walls of the left side and the right side of the lower hole body 1-3 from back to front to form a lower concrete spraying layer, the lower concrete spraying layer is connected with the middle concrete spraying layer positioned above the lower concrete spraying layer, the hung lower reinforcing mesh and the installed lower side bracket 6 are fixed in the lower concrete spraying layer, and the arch wall mesh spraying and supporting structure formed by construction is obtained; meanwhile, spraying a layer of concrete at the bottom of the lower hole body 1-3 from back to front to form an inverted arch concrete spraying layer 20, connecting the inverted arch concrete spraying layer 20 with the lower concrete spraying layer positioned above the inverted arch concrete spraying layer, and fixing the tunnel inverted arch bracket 2 in the inverted arch concrete spraying layer 20;
the arch part reinforcing bar net piece the middle part reinforcing bar net piece with the lower part reinforcing bar net piece is connected from top to bottom and is constituteed arch wall reinforcing bar net piece, the arch part concrete sprays the layer the middle part concrete spray the layer with the lower part concrete spray layer is connected from top to bottom and is constituteed arch wall concrete spray layer 19.
In this embodiment, the arch wall supporting arch frame and the tunnel inverted arch support 2 are all grid steel frames.
In this embodiment, each of the excavated segments has a length of 2L.
Because the invention adopts the three-step synchronous excavation method for construction and adopts the partition blasting mode, the excavation footage can be increased to 2L, and the excavation footage is generally only L when the existing V-level surrounding rock tunnel excavation construction is carried out. The invention can effectively accelerate the construction speed and shorten the construction period while ensuring the safe and smooth construction of the tunnel.
In this embodiment, referring to fig. 2, an anchoring system is disposed outside the full-section supporting structure, the anchoring system includes a plurality of anchoring groups disposed from back to front along a longitudinal extension direction of the tunnel, one anchoring group is disposed outside each full-section supporting frame, and each full-section supporting frame and the anchoring group disposed thereon are disposed on a same cross section of the tunnel 1;
each anchoring group comprises a left group of upper foot-locking anchor pipes 8, a right group of middle foot-locking anchor pipes 9 and a left group of lower foot-locking anchor pipes 10, wherein the left group of upper foot-locking anchor pipes 8, the right group of middle foot-locking anchor pipes 9 and the left group of lower foot-locking anchor pipes 10 are symmetrically arranged at the outer sides of the bottoms of the left side and the right side of the upper arch 2-1; the outer side of the bottom of each middle side bracket 5 is provided with a group of middle locking leg anchor pipes 9, and the outer side of the bottom of each lower side bracket 6 is provided with a group of lower locking leg anchor pipes 10; each group of the upper lock leg anchor pipes 8 comprises an upper lock leg anchor pipe 8 and a lower lock leg anchor pipe 8 which are arranged in parallel, each group of the middle lock leg anchor pipes 9 comprises an upper middle lock leg anchor pipe 9 and a lower middle lock leg anchor pipe 9 which are arranged in parallel, and each group of the lower lock leg anchor pipes 10 comprises an upper lower lock leg anchor pipe 10 which are arranged in parallel; the upper foot-locking anchor pipe 8, the middle foot-locking anchor pipe 9 and the lower foot-locking anchor pipe 10 are foot-locking anchor pipes which enter the soil layer on the periphery of the tunnel cave 1 from inside to outside, and the foot-locking anchor pipes gradually incline downwards from inside to outside.
In order to ensure the anchoring effect, in the embodiment, the included angles between the middle and lower lock leg anchor tubes 9 and 10 and the vertical plane are both 45 °.
The upper arch 2-1 is arc-shaped, and the included angle between each upper lockpin anchor pipe 8 and the arch tangent plane of the upper arch 2-1 at the connecting position of the upper lockpin anchor pipe is 45 degrees; the tangent plane of the arch frame is a plane which is vertically arranged with the outer contour line of the upper arch frame 2-1. The tangent plane of the upper arch 2-1 at the position where each upper lock leg anchor pipe 8 is connected is a plane which is vertically arranged with the outer contour line of the upper arch 2-1 at the position where the upper lock leg anchor pipe 8 is connected.
In this embodiment, the upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 are all seamless steel pipes with a wall thickness of 5mm, a length of 4m and a diameter of phi 42mm, and the inner ends of the upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 are all welded and fixed on the full-section support frame through connecting steel bars. The lengths and the driving angles of the upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 are reasonable in design, so that the deformation of surrounding rock is limited, and the bearing capacity of a supporting structure is exerted. In addition, the number of the upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 at each anchoring position is two, so that the anchoring effect can be further improved.
The construction of the anchor pipe (rod) with locking feet is called 'life-saving locking feet', which shows the importance degree. Because the length and the angle of the lock pin anchor pipe are important components for supporting the grid steel frame to stably prevent the grid steel frame from settling, the lock pin anchor pipe also has an effective stabilizing effect on the horizontal pressure generated after tunnel excavation, the length and the angle of the lock pin anchor pipe are ensured to meet the design requirements during construction, the operating angle of the lock pin is ensured to be 45 degrees, the optimal shear-resistant and tensile-resistant stress effect is fully exerted, the number of the lock pin anchor pipes at each node is increased from two originally designed lock pin anchor pipes to 4 lock pin anchor pipes so as to enhance the capability of the steel frame for resisting the extrusion deformation of surrounding rocks, and meanwhile, the lock pin and the grid steel.
The upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 are inclined anchor pipes, when the inclined anchor pipes are installed, drill holes installed in the inclined anchor pipes firstly, and due to the fact that the operation space is limited, in order to practically and effectively guarantee the drilling depth and angle of the lock leg anchor pipes, drilling is conducted by adopting a 'three-time drilling method', drill rods with the lengths of 2m, 3m and 4m are selected in sequence, and the drilling depth is gradually drilled to the designed depth according to the sequence of 1.5m, 2.5m and 4 m. And after the drilling is finished, the inclined anchor pipe is installed, and the inclined anchor pipe is directly driven into the drilled hole by using a pipe receiving and conveying device of a rock drill during installation. In this embodiment, the excavation progress of the lower cavity 1-3 is the same as the construction progress of the primary support inverted arch 13, and when constructing the lower lock anchor pipe 10, a constructor cannot normally perform 45-degree drilling operation, so that a steel bar support is respectively processed on the left side and the right side of the tunnel inverted arch support 2 to perform construction as a lock anchor pipe drilling platform, and the angle and the construction quality of the lock anchor pipe are ensured.
Because the installation of the grid steel frame is finished and before the ring is formed, the arch feet of the grid steel frame must be compactly and firmly supported. If the bottom of the arch foot of the grid steel frame is suspended or not supported, when the locking anchor pipe loses the action, the stress at the bottom of the arch foot is in a freely telescopic shape, the deformation and the deformation speed can be rapidly developed when the arch foot is deformed and extruded by surrounding rocks, particularly expansive soil is expanded and extruded, the initial deformation is very easy to be large, the structure is damaged, and therefore the arch foot support of the grid steel frame needs to be compact.
During actual construction, in the process of installing the upper arch 2-1 in the excavated and formed upper hole body 1-1 from back to front, wood base plates are respectively arranged at the bottoms of the left side and the right side of each installed upper arch 2-1 to control displacement and settlement, and locking anchor pipes 8 are respectively arranged at the left side and the right side of each installed upper arch 2-1; meanwhile, a sand cushion layer is paved at the bottom of the left side and the right side of each installed upper arch 2-1 respectively so as to facilitate the bolt connection of the upper arch 2-1 and the middle side bracket 5. The wood base plate can be a flexible plate, can meet the supporting requirement on the rock stratum 4, and guarantees that the arch foot supporting pad of the grid steel frame is compact.
Correspondingly, in the process of respectively installing the middle side brackets 5 on the left side and the right side of the middle hole body 1-2 which is formed by excavation from back to front, wood base plates are respectively arranged at the bottom of each installed middle side bracket 5 to control displacement and settlement, and middle locking anchor pipes 9 are respectively arranged on the outer sides of each installed middle side bracket 5; meanwhile, a layer of sand cushion is paved at the bottom of each installed middle side bracket 5 respectively so as to facilitate the bolt connection of the middle side bracket 5 and the lower side bracket 6.
And in the process of respectively installing the lower side brackets 6 at the left side and the right side of the lower hole body 1-3 which is excavated and formed from back to front, wood base plates are respectively arranged at the bottom of each installed lower side bracket 6 to control displacement and settlement, and a lower lock pin anchor pipe 10 is respectively arranged at the outer side of each installed lower side bracket 6.
As the tunnel portal section to be constructed is excavated by the step method, in the process of excavating the tunnel portal section to be constructed, the full-section support frame is installed step by step and cannot be temporarily closed to form a ring, so that the primary support is easy to deform greatly. The invention adopts the upper foot-locking anchor pipe 8, the middle foot-locking anchor pipe 9 and the lower foot-locking anchor pipe 10 to respectively restrain the arch feet of the upper arch 2-1, the middle side bracket 5 and the lower side bracket 6, can effectively prevent the arch feet of the upper arch 2-1, the middle side bracket 5 and the lower side bracket 6 from rotating and moving, improves the integral stability of the grid steel frame, and prevents the large deformation of the initial expenditure.
In this embodiment, before the drilling and blasting construction in step 302, advance support needs to be performed on the arch part of the tunnel hole 1, and a tunnel advance support structure is obtained;
as shown in fig. 2 and 3, the tunnel advance support structure comprises a plurality of small advance conduit grouting support structures for advancing the arch part of the tunnel cave 1 from back to front along the longitudinal extension direction of the tunnel; the structures of the advanced small conduit grouting support structures are the same, and the lap joint length between two adjacent advanced small conduit grouting support structures in the front and back is not less than 0.5 m;
each advanced small conduit grouting supporting structure comprises a plurality of small grouting conduits 22 which are drilled into the soil body in front of the tunnel face of the tunnel cave 1 from back to front and a small conduit guide frame for guiding the small grouting conduits 22, wherein the small grouting conduits 22 are distributed on the same tunnel section from left to right along the arch contour line of the upper tunnel body 1-1; all the small grouting pipes 22 in each advanced small pipe grouting support structure are the same in structure and size; the small guide pipe guide frame is the upper arch frame 2-1, a plurality of guide holes for guiding the small grouting guide pipes 22 are formed in the small guide pipe guide frame, and the guide holes are arranged from left to right along the arch contour line of the upper hole body 1-1.
In this embodiment, the tunnel advance support structure includes a plurality of small advance conduit grouting support structures for advance supporting the arch part of the tunnel 1 from back to front along the longitudinal extension direction of the tunnel; the structures of the advanced small conduit grouting support structures are the same, and the lap joint length between two adjacent advanced small conduit grouting support structures in the front and back is not less than 0.5 m;
each advanced small conduit grouting supporting structure comprises a plurality of small grouting conduits 22 which are drilled into the soil body in front of the tunnel face of the tunnel cave 1 from back to front and a small conduit guide frame for guiding the small grouting conduits 22, wherein the small grouting conduits 22 are distributed on the same tunnel section from left to right along the arch contour line of the upper tunnel body 1-1; all the small grouting pipes 22 in each advanced small pipe grouting support structure are the same in structure and size; the small guide pipe guide frame is the upper arch frame 2-1, a plurality of guide holes for guiding the small grouting guide pipes 22 are formed in the small guide pipe guide frame, and the guide holes are arranged from left to right along the arch contour line of the upper hole body 1-1.
In this embodiment, the small grouting pipes 22 are hot-rolled seamless steel pipes with a diameter of phi 42mm and a wall thickness of 3.5mm, the small grouting pipes 22 are 3.5m to 4.0m long, the small grouting pipes 22 are arranged in the range of 120 degrees of the arch part 1 of the tunnel, and the circumferential distance between the small grouting pipes 22 is 40 cm. And in the step 301, before tunnel excavation and primary support are carried out, the advanced small conduit grouting support structure is adopted to advance support the arch part of the tunnel portal section under construction.
The small grouting guide pipe 22 is drilled according to the design requirement, and then the small grouting guide pipe 22 penetrates through the small grouting guide pipe guide frame and is jacked by a hammering or drilling machine, the jacking length is not less than 90% of the total length of the small grouting guide pipe 22, the exposed length is favorable for the access of a grouting pipeline, and sand in a steel pipe is blown out by high-pressure air. And, when adopting the slip casting ductule 22 slip casting, the slip casting liquid is cement mortar to strengthen the intensity of the slip casting ductule 22.
In the actual construction process, the post reinforcement is a reinforcement and reinforcement remedial measure under the condition that primary support deformation and damage occur due to inaccurate judgment of surrounding rock levels and non-blocking of steel frame selection on site. And when the primary supporting structure of the tunnel is closed into a ring, the primary supporting structure is deformed and damaged, and temporary reinforcement measures are immediately carried out to ensure the safety of constructors and construction in the tunnel.
In the embodiment, in order to further ensure the stability of the tunnel, a reinforcing sleeve arch is adopted as a temporary reinforcing measure, and the reinforcing sleeve arch is distributed on the inner side of the primary tunnel supporting structure;
the tunnel primary supporting structure and the reinforcing sleeve arch are full-section supporting structures for supporting a full section of the tunnel hole 1, and the tunnel primary supporting structure and the reinforcing sleeve arch positioned on the inner side of the tunnel primary supporting structure form a reinforced primary supporting structure;
with reference to fig. 2, the reinforced arch comprises a plurality of arch units, the arch units have the same structure and are arranged from back to front along the longitudinal extension direction of the tunnel, an isolation layer 26 is arranged between each arch unit and the primary tunnel supporting structure, the isolation layer 26 is a full-section isolation layer formed by non-woven fabrics paved between the arch units and the primary tunnel supporting structure, and the cross section of the isolation layer 26 has the same shape as that of the cross section of the tunnel 1;
each arch sheathing unit comprises M steel arches 11 arranged from back to front along the longitudinal extension direction of the tunnel and an inner concrete spraying layer 27 formed by concrete sprayed on the isolation layer 26, the thickness of the inner concrete spraying layer 27 is not less than 25cm, the M steel arches 11 are uniformly arranged, and the distance between two adjacent steel arches 11 is 0.8-1.2M; each structural steel arch 11 is a full-section support for performing full-section supporting on the tunnel cave 1, M structural steel arches 11 are fixed in the inner side concrete spraying layer 27, the shape of each structural steel arch 11 is the same as the shape of the cross section of the tunnel cave 1, wherein M is a positive integer and is more than or equal to 4; m steel arch frames 11 in each arch sheathing unit are fixedly connected into a whole through a plurality of longitudinal steel bars, the longitudinal steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal steel bars are arranged along the contour line of the steel arch frames 11; each steel arch 11 comprises an arch wall steel support 11-1 for supporting an arch wall of a tunnel 1 and an inverted arch steel support 11-2 for supporting the bottom of the tunnel 1, the inverted arch steel support 11-2 is located right below the arch wall steel support 11-1 and is an arch support, the left end of the inverted arch steel support 11-2 is fixedly connected with the bottom of the left end of the arch wall steel support 11-1, and the right end of the inverted arch steel support 11-2 is fixedly connected with the bottom of the right end of the arch wall steel support 11-1;
in the step 304, in the process of excavating the lower cavity 1-3 from back to front, constructing the reinforced sleeve arch on the inner side of the constructed primary tunnel supporting structure from back to front along the longitudinal extension direction of the tunnel to obtain a constructed and molded reinforced primary support structure;
when the reinforcing sleeve arch is constructed from back to front, a plurality of sleeve arch units in the reinforcing sleeve arch are constructed from back to front respectively, and the construction methods of the plurality of sleeve arch units are the same; the tunnel primary supporting structure section with the arch sheathing units distributed on the inner side in the tunnel primary supporting structure is a primary supporting section to be reinforced;
when any one of the set arch units in the reinforced set arch is constructed, the process is as follows:
d1, paving an isolation layer: paving a layer of isolation layer 26 on the inner wall of the primary support section to be enhanced outside the currently constructed arch sheathing unit from back to front;
step D2, installing the profile steel arch frame: in the process of laying the isolation layer 26 from back to front in the step D1, respectively installing M steel arches 11 of the currently constructed arch sheathing unit from back to front in the primary support section to be reinforced in the step 301, enabling each steel arch 11 to be supported at the inner side of the isolation layer 26 in the step D1, and simultaneously enabling the isolation layer 26 in the step D1 to be padded between the installed M steel arches 11 and the inner wall of the primary support section to be reinforced;
step D3, longitudinal steel bar installation: d2, after M steel arches 11 are installed, firmly connecting M steel arches 11 into a whole through a plurality of longitudinal steel bars;
step D4, concrete spraying: spraying concrete on the isolating layer 26 from back to front in the step D1 to form an inner concrete spraying layer 27, fixing M steel arches 11 in the step D2 and a plurality of longitudinal steel bars in the step D3 in the inner concrete spraying layer 27, and padding the isolating layer 26 between the primary support section to be reinforced and the inner concrete spraying layer 27 in the step D1.
The distance between two front and rear adjacent section steel arches 11 in each arch sheathing unit is larger than the distance between two front and rear adjacent full-section support frames, and each section steel arch 11 is positioned between two front and rear adjacent full-section support frames. Therefore, the supporting effects of the profile steel arch 11 and the full-section supporting frame can be mutually supplemented and the stress can be mutually shared, and the situation of serious deformation on the same supporting section can not occur; and after the primary support invasion limit occurs, the arch sheathing unit is dismantled, so that the support effect of the full-section support frame is not greatly influenced, and the construction safety in the arch changing process is ensured.
In this embodiment, L is 0.6M, and the distance between two adjacent front and rear steel arches 11 among M steel arches 11 is 1M.
During actual construction, the value of L and the distance between two adjacent front and rear steel arches 11 in the M steel arches 11 can be adjusted accordingly according to specific needs.
In this embodiment, in step D1, the primary support section to be reinforced is formed by connecting a large deformation section and two deformation transition sections located on the front and rear sides of the large deformation section, where the large deformation section is a tunnel section where the vault crown subsidence value of the tunnel cave 1 exceeds 10mm and/or the horizontal convergence value exceeds 5mm within 24 hours after the construction of the primary support structure of the tunnel is completed, the vault crown subsidence value of the tunnel cave 1 is an absolute subsidence value of the vault inner wall of the primary support structure of the tunnel, and the horizontal convergence value of the tunnel cave 1 is a horizontal convergence value of the inner wall of the primary support structure of the tunnel at the maximum excavation position of the tunnel cave 1; and the two deformation transition sections are the tunnel sections which are adjacent to the large deformation section and are communicated with each other in the tunnel opening section under construction, and the length of the two deformation transition sections is not less than 3L. Therefore, the primary tunnel supporting structure can be effectively reinforced in the early deformation stage, the deformation of the primary tunnel supporting structure is effectively controlled, the primary tunnel supporting effect is ensured, and the construction safety is ensured.
After the reinforcing sleeve arch is adopted to reinforce the primary tunnel supporting structure, the primary tunnel supporting deformation is effectively controlled, and the construction safety in the tunnel can be ensured. In this embodiment, in order to permanently solve the problem of the ability of the primary support to resist the deformation of the surrounding rock, after the concrete is sprayed in step D4, the arch wall of the primary support section to be reinforced in step D1 needs to be reinforced by radial grouting, and a radial grouting reinforced structure is obtained, so that the radial grouting reinforced structure and the inner concrete spraying layer 27 in the primary support section to be reinforced are fastened and connected into a whole, the soil body outside the reinforced primary support structure is reinforced, and the deformation of the reinforced primary support structure is further controlled from the source. And radial grouting is adopted to perform grouting reinforcement and reinforcement on surrounding rocks outside the primary support structure, so that the stability and the bearing capacity of the rock stratum after primary support and back support are improved, and the purpose of preventing the surrounding rocks from continuing to deform is achieved.
The upper tunnel body 1-1 and the middle tunnel body 1-2 form an upper tunnel body of the tunnel, and the radial grouting reinforcement structure is positioned on the outer side of the upper tunnel body of the tunnel;
with reference to fig. 5 and 6, the radial grouting reinforcement structure is a reinforcement structure formed by grouting into a soil body outside the tunnel upper cavity through multiple rows of radial grouting holes 28, the multiple rows of radial grouting holes 28 are arranged from back to front along the extending direction of the tunnel, each row of radial grouting holes 28 includes multiple radial grouting holes 28 arranged on the same tunnel section from left to right along the excavation contour line of the tunnel upper cavity, each radial grouting hole 28 is a drill hole drilled into the soil body from inside to outside from the inside of the tunnel upper cavity, multiple radial grouting holes 28 in each row of radial grouting holes 28 are uniformly arranged, and the radial grouting holes 28 in two adjacent rows of the radial grouting holes 28 are arranged in a staggered manner; the length of the radial grouting holes 28 is not less than 3 m;
each row of the radial grouting holes 28 are positioned between two front and rear adjacent full-section supporting frames, and each row of the radial grouting holes 28 is positioned between two front and rear adjacent profile steel arches 11;
and D1, when the arch wall of the primary support section to be reinforced is reinforced by radial grouting, the arch wall is reinforced by grouting from back to front through a plurality of rows of radial grouting holes 28.
In this embodiment, the circumferential distance between the inner ends of two adjacent radial grouting holes 28 in each row of the radial grouting holes 28 is 1.2m to 1.8m, the distance between two adjacent front and rear rows of the radial grouting holes 28 is 1.8m to 2.2m, and the length of each radial grouting hole 28 is 3 m.
During actual construction, the circumferential distance between the inner ends of two adjacent radial grouting holes 28 in each row of the radial grouting holes 28, the distance between two adjacent rows of the radial grouting holes 28 in the front and back direction, and the length of the radial grouting holes 28 can be respectively and correspondingly adjusted according to specific requirements.
In this step, when the radial grouting holes 28 are arranged in multiple rows for grouting reinforcement, the grouting liquid is a shrinkage-free cement-based grouting material, and the radial grouting reinforcement effect can be effectively enhanced.
During actual construction, the grouting liquid can also be common pure cement paste with the water-cement ratio of 0.5: 1-1: 1.
When the radial grouting reinforcement is actually carried out, the grouting pressure is 1.5 MPa-2.0 MPa, the grouting sequence is carried out from bottom to top according to two-sequence holes, namely, the holes are jumped first, the rows of the single-sequence holes are jumped, and then the rest two-sequence holes are grouted. And the grouting ending standard is that the grouting pressure is increased to 1.0MPa and the grouting is continued for more than 10min, and the grouting is ended at 1/4 the grouting amount of which is less than the initial grouting amount.
In this embodiment, in the radial grouting reinforcement process of the arch wall of the primary support section to be reinforced in step D1, an arch change of an arch section to be changed, which is to be subjected to arch change in the tunnel portal section to be constructed, is also performed;
the arch section to be changed is formed by connecting an intrusion limit section and two extension sections which are respectively positioned at the front side and the rear side of the intrusion limit section, and the primary supporting structure of the arch section to be changed is the reinforced primary supporting structure; the limit invasion section is a tunnel section of the reinforced primary support structure in the constructed tunnel portal section, and the two extension sections are adjacent to and communicated with the limit invasion section in the constructed tunnel portal section; the length of each of the two extension sections is not less than 3L;
and when the arch of the section needing to be changed, which needs to be changed, of the tunnel portal section to be constructed is changed, the reinforced primary support structure in the section needing to be changed is dismantled, and primary support construction is synchronously carried out on the section needing to be changed in the dismantling process, so that the primary support structure of the tunnel after being changed is obtained.
All arch wall supporting frames in the arch section needing to be replaced are supporting frames needing to be replaced, and all arch wall section steel brackets 11-1 in the arch section needing to be replaced are section steel brackets needing to be replaced.
In this embodiment, the arch-changing section to be changed is divided into a plurality of arch-changing sections from back to front along the longitudinal extension direction of the tunnel, each arch-changing section is provided with one arch-covering unit, and each arch-covering unit is located in one arch-changing section;
when the arch-changing construction is carried out on the arch-changing sections, the arch-changing construction is respectively carried out on the plurality of arch-changing sections from back to front along the longitudinal extension direction of the tunnel; the arch-changing construction methods of the plurality of arch-changing sections are the same;
when the arch replacing construction is carried out on any one of the arch replacing sections, the method comprises the following steps:
step E1, removing the reinforcing sleeve arch: dismantling the set of arch units in the currently constructed arch-changing segment;
step E2, replacing the primary supporting structure of the tunnel: after the set of arch units in the currently constructed arch-changing section are dismantled, dismantling the primary tunnel supporting structure in the currently constructed arch-changing section; and in the tunnel primary supporting structure dismantling process, primary supporting construction is synchronously carried out on the currently constructed arch-replacing segment.
In this embodiment, when the arch sheathing unit in the currently constructed arch replacing segment is removed, the inner concrete spraying layer 27 located inside the isolation layer 26 is chiseled from back to front along the longitudinal extension direction of the tunnel; in the process of chiseling the inner concrete spray layer 27, the exposed arch wall type steel brackets 11-1 after chiseling the inner concrete spray layer 27 are removed one by one from back to front.
In this embodiment, the replaced tunnel primary support structure is a steel arch and mesh-shotcrete combined support structure which is constructed and formed by a steel arch and mesh-shotcrete combined support method, and the structure and the size of the steel arch are the same as those of the support frame to be replaced;
the steel arch and net spraying combined supporting structure comprises a plurality of steel arches, a steel bar net piece and an arch wall concrete spraying layer, wherein the steel arches are arranged from back to front along the longitudinal extension direction of a tunnel, the steel bar net piece is hung on the plurality of steel arches, the arch wall concrete spraying layer is sprayed on the inner wall of an arch wall of a tunnel hole 1, the steel bar net piece and the plurality of steel arches are fixed in the arch wall concrete spraying layer, and the steel arches are positioned on the inner sides of the steel bar net piece; a plurality of steel arch frames in the replaced tunnel primary supporting structure are fixedly connected into a whole through a plurality of longitudinal horizontal steel bars, and the plurality of longitudinal horizontal steel bars are horizontally arranged and arranged along the contour line of the steel arch frames;
when the tunnel primary supporting structure is dismantled in the step E2, the arch wall supporting frames in the currently constructed arch-replacing section are replaced one by one from the front end to the rear end towards the middle;
when any one of the arch wall support frames in the currently constructed arch replacing section is replaced, the concrete spraying layer on the peripheral side of the arch wall support frame is chiseled, the exposed arch wall support frame after the concrete spraying layer is chiseled is replaced, and the replaced arch wall support frame and the tunnel inverted arch support frame 2 positioned below the replaced arch wall support frame are fixedly connected into a whole. In addition, in the process of dismantling the tunnel primary support structure in the step E2, the concrete is sprayed on the inner wall of the arch-replacing section to be replaced of the arch wall support frame from back to front along the longitudinal extension direction of the tunnel, so as to obtain the replaced tunnel primary support structure, and the construction is very simple and convenient.
With reference to fig. 4, a tunnel bottom backfill soil layer 7 is arranged behind the excavation surface of the lower cavity 1-3, and the tunnel bottom backfill soil layer 7 is located in the lower cavity 1-3; and the tunnel bottom backfill soil layer 7 is a temporary platform for the wet spraying manipulator 21 to move back and forth. Meanwhile, the structural stability of the bottom of the tunnel 1 can be further improved through the backfill soil layer 7 at the bottom of the tunnel.
In this embodiment, the upper arch 2-1 and the middle side bracket 5, the middle side bracket 5 and the lower side bracket 6, and the lower side bracket 6 and the tunnel inverted arch bracket 2 are fixedly connected by connecting bolts. And connecting steel plates for mounting the connecting bolts are arranged at the two ends of the upper arch frame 2-1, the two ends of the middle side support 5, the two ends of the lower side support 6 and the two ends of the tunnel inverted arch support 2.
In order to ensure the processing quality and improve the on-site construction efficiency, the full-section support frame adopts factory centralized processing and distribution and meets the requirement of in-place distribution in half an hour on all working faces.
In the step 305, in the process of excavating the lower hole body 1-3, carrying out primary support on the lower hole body 1-3 formed by excavation in time, and obtaining a primary support inverted arch 13; and after the primary support of the lower hole bodies 1-3 is finished, backfilling the tunnel bottom backfill soil layer 7 on the primary support inverted arch 13 in time. When the tunnel bottom backfill soil layer 7 is backfilled, the tunnel bottom backfill soil layer 7 is backfilled by using hole slag (namely, muck) in the lower hole bodies 1-3.
During the excavation process of the upper cavity 1-1, the middle cavity 1-2 and the lower cavity 1-3, the excavation slag formed by excavation is loaded to a dump truck by adopting an excavator and is transported out by the dump truck. When the excavated hole slag is transported outwards, the hole slag used for backfilling the tunnel bottom backfill soil layer 7 needs to be reserved, and the reserved hole slag (namely, muck and ballast) is placed on one side of the inner side of the lower hole body 1-3 so as to be convenient for backfilling the tunnel bottom backfill soil layer 7 in time.
As shown in fig. 3, in this embodiment, when tunnel excavation construction is performed on a tunnel entrance section to be constructed, the wet blasting manipulator 21 moves forward through the tunnel bottom backfill layer 7 for multiple times along the longitudinal extension direction of the tunnel, and the forward movement distance of each time is the same as the length of one excavated segment.
After the wet spraying manipulator 21 moves forwards to the right position each time, the length of the excavated molded tunnel 1 in front of the tunnel bottom backfill layer 7 is the same as that of one excavated segment, and at the moment, the excavated molded tunnel 1 in front of the tunnel bottom backfill layer 7 is the current excavated segment; and after the wet spraying mechanical arm 21 moves forwards to the right place each time, concrete spraying is carried out on the current excavated segment from top to bottom, and the excavation and primary support construction process of the current excavated segment is completed. After the excavation and primary support construction process of the current excavated segment is completed, a tunnel bottom backfill soil layer 7 is constructed on the primary support inverted arch 13 which is constructed and formed in the current excavated segment, and the constructed tunnel bottom backfill soil layer 7 is a moving platform for the wet spraying manipulator 21 to move forwards next time.
In this embodiment, in order to avoid damage to the wet blasting manipulator 21 during the blasting process and enable concrete spraying to be immediately performed after the tunnel cave 1 is excavated and formed to ensure that primary support is rapidly performed, the wet blasting manipulator 21 is moved forward to a proper position after the drilling and blasting construction process of the front side excavated segment is completed and before the excavation of the lower cave body 1-3 of the front side excavated segment is completed, so that the wet blasting manipulator 21 is used to perform concrete spraying in time. The front side excavation section is one excavation section which is located in front of the current excavation section and adjacent to the current excavation section.
According to the above content, the tunnel excavation process of one excavation section and the construction process of the primary tunnel supporting structure in the excavation section are synchronously carried out, so that the primary support can be ensured to be sealed and looped in time, the primary support can be ensured to be sealed and looped in the shortest time, the excessive deformation of surrounding rocks is prevented, and the construction safety is ensured. And after the primary support is sealed into a ring, convenience is improved for the large-scale machinery to move in the hole, so that the requirement of large-scale mechanized construction can be met to the maximum extent, the labor intensity is reduced, synchronous operation of an upper step, a middle step and a lower step is realized, full-section flow line construction is realized, the construction efficiency can be effectively improved, the engineering cost is reduced, and the purposes of safe, economic and efficient construction are achieved.
The lower blasting area is farthest away from the arch crown and the tunnel face of the upper hole body, so that the influence of blasting vibration is minimum, and the rock and soil generated in the blasting process of the lower blasting area can be suppressed and restrained by the upper blasting area and the rock and soil generated in the middle blasting, so that the vibration generated in the blasting process can be effectively reduced.
In this embodiment, the thickness of each of the arch wall concrete spray layer 19 and the inverted arch concrete spray layer 20 is 30cm, and C25 concrete is used.
The wet spraying manipulator 21 is a mobile concrete spraying manipulator. In this embodiment, the wet spraying manipulator 21 is an HPS301 3016S type wet spraying manipulator (also called HPS3016 tire type concrete spraying trolley) produced by the china iron re-engineering group ltd or a TKJ-20 type wet spraying manipulator (also called TKJ-20 type concrete spraying manipulator) produced by the china iron and rock frontier science and technology ltd.
When the arch wall concrete spraying layer 19 and the inverted arch concrete spraying layer 20 are sprayed, the primary spraying is firstly carried out, and then the secondary spraying is carried out. When the initial spraying is actually carried out, the spraying is started from one side arch springing along the tunnel excavation section, and the spraying is finished from the arch part to the other side arch springing; the spraying thickness should be controlled at 10-15 cm of side wall and 5-10 cm of arch part when spraying for the first time.
After the initial setting of the initial sprayed concrete, the secondary spraying is carried out according to the sequence from bottom to top. When the inverted arch is sprayed, the middle part of the inverted arch is firstly sprayed and then the two sides of the inverted arch are sprayed, and the thickness of the middle spraying is larger than that of the two sides of the inverted arch.
And when the side wall is re-sprayed, directly spraying to the designed thickness on the basis of primary spraying for the first time. The thickness of each spraying of the arch part is controlled to be 4-5 cm, and the interval of each spraying is 5-10 min, so that the rebound quantity can be greatly reduced. In the spraying process, the distance between the nozzle and the sprayed surface is preferably 1.0 cm-1.5 m, and the nozzle moves continuously and slowly in the transverse direction or the annular direction in the spraying process. If the sprayed surface is shielded by the steel frame and the reinforcing mesh, the spraying angle of the nozzle and the distance between the nozzle and the sprayed surface are changed according to specific conditions, and the steel frame and the reinforcing mesh are densely sprayed and filled behind the steel frame and the reinforcing mesh. When the crack water leakage occurs on the sprayed surface in the spraying process, the water-free part is firstly sprayed and gradually covered to the water seepage part, the dosage of the accelerating agent can be increased by 0.5-2.0 percent based on the standard dosage when the water seepage part is sprayed, and the total dosage cannot exceed 6.0 percent of the dosage of the cement.
After the concrete is sprayed, moist curing is carried out immediately, and curing is generally carried out for not less than 14 days. The environment temperature of the sprayed concrete operation is not lower than 5 ℃.
For further improving the stability of the tunnel entrance to a cave section bottom of being under construction, two adjacent pin around in the tunnel primary bracing structure all carry out the fastening connection through the longitudinal tie piece that multichannel from left to right laid between the tunnel invert support 2, multichannel the longitudinal tie piece all is the level and lays and its edge the outline line of tunnel invert support is laid.
In this embodiment, the longitudinal connector is a channel steel.
During actual construction, other types of section steel can be adopted as the longitudinal connecting piece.
Because the rock stratum 4 in the earth-rock boundary stratum is a strongly weathered sandstone stratum and/or a mudstone layer, the rock stratum is of a horizontal structure, the rock stratum is thin, the rock mass is broken and is of a block-fragment-shaped embedded structure, the cracks of the underground rock stratum are developed by water, loess pores are saturated by water, and underground water at the position of the earth-rock interface is rich, before the excavation of the tunnel portal section under construction, precipitation pre-reinforcement is required according to the method in the step one.
As shown in fig. 11, 12 and 13, all the dewatering wells 3-2 in two rows of dewatering wells 3-2 have the same structure and size, and each dewatering well 3-2 is vertically arranged; the distance between two adjacent dewatering wells 3-2 in the two rows of dewatering wells 3-2 is 2d, wherein the value range of d is 12-16 m; each dewatering well 3-2 in the two rows of dewatering wells 3-2 is positioned on one tunnel cross section of the constructed tunnel portal section, the tunnel cross section where each dewatering well 3-2 is positioned is a tunnel dewatering surface, and the distance between the front and back adjacent tunnel dewatering surfaces on the constructed tunnel portal section is d; the distance between the two rows of precipitation wells 3-2 and the tunnel center line of the tunnel portal section to be constructed is the same, and the distance between the two rows of precipitation wells 3-2 is 9-11 m larger than the excavation width of the tunnel portal section to be constructed;
the tunnel portal section is a tunnel which penetrates through a soil-rock boundary stratum and is buried deeper than 30m, the soil-rock boundary stratum comprises a loess stratum 3 located in a valley and a rock stratum 4 located below the loess stratum 3, the loess stratum 3 and the rock stratum 4 are both horizontally arranged, and an interface between the loess stratum 3 and the rock stratum 4 is a soil-rock interface; the soil-stone interface is positioned above the tunnel portal section under construction, and the vertical distance between the soil-stone interface and the top of the excavation contour line of the tunnel portal section under construction is more than 15 m;
the well bores 3-5 of the dewatering wells 3-2 are vertically arranged, the hole bottoms of the well bores are positioned below the tunnel portal section under construction, the vertical distance between the hole bottoms of the well bores 3-5 and the bottom of the excavation contour line of the tunnel portal section under construction is H1, the value range of H1 is 3.5 m-4.5 m, and the hole diameters of the well bores 3-5 are
The bottom of the excavation contour line of the constructed tunnel entrance section refers to the bottom of the tunnel excavation section of the constructed tunnel entrance section, and the top of the excavation contour line of the constructed tunnel entrance section refers to the vault of the excavation contour line of the constructed tunnel entrance section (namely the top of the tunnel excavation section of the constructed tunnel). The buried depth of the tunnel portal section to be constructed refers to the vertical distance from the top of the tunnel excavation section to the natural ground (i.e., the earth surface).
The height of the sedimentation pipes 3-6 is 1 m-2 m.
In this embodiment, the excavation width of the tunnel portal section to be constructed is denoted as D1, where D1 is 12 m. The excavation height of the tunnel portal section is marked as H2, wherein H2 is 12 m. The buried depth of the tunnel opening section is marked as H4, and H4 is 22 m. The vertical spacing between the earth-rock interface and the earth's surface is designated as H5, and H5 is 23 m.
The vertical distance between the earth and stone interface and the ground surface refers to the vertical distance between the earth and stone interface and the ground surface in the middle of the upper cave body 1-1.
In the embodiment, the distance between the two rows of dewatering wells 3-2 is 10m larger than the excavation width of the tunnel portal section under construction. The distance between two rows of the dewatering wells 3-2 is marked as D2, and D2 is D1+10m is 22 m.
In this embodiment, d is 15m, and H1 is 4 m. The height of the precipitation tubes 3-6 is designated as H3, H3 ═ 2 m.
During actual construction, the values of D2, D, H1 and H3 can be adjusted correspondingly according to specific requirements. The depth H0 of the dewatering well 3-2 is H4+ H2+ H1 is 22+12+4 is 38 m. The depth H0 of the dewatering well 3-2 is the depth of the well hole 3-5.
As shown in fig. 14, each dewatering well 3-2 comprises a settling pipe 3-6 which is lowered into the well bore 3-5 from top to bottom and a strainer 3-7 which is arranged right above the settling pipe 3-6, and the settling pipe 3-6 and the strainer 3-7 are coaxially arranged with the well bore 3-5; the sedimentation pipes 3-6 and the water filter pipes 3-7 are connected into a whole and are both cement gravel pipes or concrete pipes, the outer diameters of the sedimentation pipes 3-6 and the water filter pipes 3-7 are the same, and the outer diameters of the sedimentation pipes 3-6 and the water filter pipes 3-7 are both the same
The wall thicknesses of the sedimentation pipe 3-6 and the water filter pipe 3-7 are the same and are both 4 cm-6 cm.
In the embodiment, the bottom ends of the settling pipes 3-6 are level with the bottoms of the wells 3-5, filter material filling layers 3-8 are respectively arranged between the settling pipe 2 and the wells 3-5 and between the middle lower part of the water filter pipes 3-7 and the wells 3-5, clay blocking layers 3-9 are arranged between the upper parts of the water filter pipes 3-7 and the wells 3-5, the thickness of the clay blocking layers 3-9 is 1.8-2.5 m and are positioned above the filter material filling layers 3-8, and the upper surfaces of the clay blocking layers 3-9 are level with the ground; the height of the top ends of the water filter pipes 3 to 7 extending out of the ground is 0.5m to 1 m; the water filtering pipes 3-7 are divided into an upper pipe section and a lower water filtering section connected to the position right below the upper pipe section, a plurality of water filtering holes are formed in the pipe wall of the lower water filtering section, a layer of filter screen 3-10 is wrapped on the outer side of the lower water filtering section, and the lower water filtering section is located below the earth-rock interface. In practical use, the lower water filtering section is a water permeable pipe section, and the upper pipe section and the settling pipe 3-6 are both non-porous pipe sections, so that the pipe walls of the upper pipe section and the settling pipe 3-6 are both closed pipe walls without water filtering holes, and the settling pipe 3-6 has the function of gathering fine sand grains and rock debris flowing into the lower water filtering section through the filter screen 3-10 and preventing the lower water filtering section from being blocked by sediment.
The height of the lower water filtering section is 2 m-5 m, and the bottom end of the lower water filtering section is flush with the bottom ends of the water filtering pipes 3-7. In this embodiment, the height of the lower water filtering section is 2.2m, and the height of the clay plugging layer 3-9 is 2 m. During actual construction, the height of the lower water filtering section and the height of the clay plugging layers 3-9 can be adjusted correspondingly according to specific requirements.
As shown in fig. 14, the bottom of the well 3-5 is provided with a hemispherical hole, a bottom filter material filling layer 3-1 is arranged in the hemispherical hole, and the settling pipe 3-6 is supported on the bottom filter material filling layer 3-1. Wherein the bottom of the well 3-5 refers to the upper surface of the hemispherical hole. In this embodiment, the bottom filter material filling layer 3-1 is a gravel filling layer.
In this embodiment, the filter material filling layers 3 to 8 are gravel filling layers.
And the gravel packing layer is formed by the diameter of
The gravel is filled.
In this embodiment, the filter screens 3 to 10 are double-layer permeable geotextiles.
In order to ensure the precipitation effect, the tunnel precipitation surface positioned at the last side of the constructed tunnel portal section is a rear end precipitation surface, the tunnel precipitation surface positioned at the foremost side of the constructed tunnel portal section is a front end precipitation surface, and the distance between the rear end precipitation surface and the rear end of the constructed tunnel portal section and the distance between the front end precipitation surface and the rear end of the constructed tunnel portal section are both smaller than d.
In this embodiment, the tunnel opening section is located in the gully and has a length of 80 m.
In this embodiment, the apertures of the wells 3-5 are
The outer diameters of the sedimentation pipes 3-6 and the water filter pipes 3-7 are both
And the wall thickness of both is 4 cm. Wherein the inner diameters of the settling tube 3-6 and the water filter tube 3-7 are both marked as D, and
in the embodiment, the soil-rock boundary stratum is a stratum with underground water, one row of dewatering wells 3-2 is an upstream dewatering well positioned at the upstream of the underground water, and the other row of dewatering wells 3-2 is a downstream dewatering well positioned at the upstream of the underground water; the number of the upstream dewatering wells is even, the number of the downstream dewatering wells is odd, the number of the downstream dewatering wells is one more than that of the upstream dewatering wells, and each downstream dewatering well is positioned between two adjacent upstream dewatering wells in front and at the back. Therefore, the total number of the dewatering wells 3-2 in the two rows of the dewatering wells 3-2 is odd, the total number of the dewatering wells 3-2 in the two rows of the dewatering wells 3-2 is marked as n, wherein n is a positive integer and is more than or equal to 3.
Before the dewatering wells 3-2 are actually constructed, the total number n of the dewatering wells 3-2 in the two rows of the dewatering wells 3-2 is determined.
When the total number n of the dewatering wells 3-2 in the two rows of dewatering wells 3-2 is determined, the tunnel water inflow Q of the tunnel portal section under construction and the single well water outflow Q of the dewatering well 3-2 are determined, and the process is as follows:
step H1, calculating the minimum precipitation well quantity: n1 according to the formula
Calculating to obtain the minimum precipitation well number n1 of the tunnel portal section under construction; in the formula
Represents rounding up;
step H2, determining the number of precipitation wells: judging whether n1 is an odd number in the step H1, and when n1 is an odd number and n1 is not less than 3, n is n 1; when n1 is an even number, n is n1+ 1.
Wherein, the water inflow of the tunnel
Unit of Q is m3D; k is the permeability coefficient of the earth-rock boundary stratum where the tunnel portal section is constructed; h is the thickness of a water-bearing stratum of an earth-rock boundary stratum where the tunnel portal section is constructed, S is the precipitation depth of the tunnel portal section, S is H, and the units of H and S are m; b is the width of a dewatering area of an earth-rock boundary stratum where the tunnel portal section is located, and b is D2, wherein the unit of b is m; r is0The equivalent precipitation quotation radius of the cross section of the tunnel cave 1 of the constructed tunnel cave mouth section is m,
a is the length of the precipitation area of the earth-rock boundary stratum where the tunnel portal section is located and a is the same as the longitudinal length of the tunnel portal section,η is a correction coefficient, and η is 0.13.
Single well water yield of dewatering well 3-2
The unit of K is m3D; l is the height of the lower water filtering section and the unit of l is m; gamma is the radius of the lower filter segment and gamma is D/2.
In the embodiment, K is 0.19 m/d;
s is the vertical distance between the earth-rock interface and the bottom end of the lower water filtering section, and S is H0-H3-H5, and S is H0-H3-H5-38-2-23 is 13 m; h13 m, b 22m, a 80m, l 2.2m, γ 0.2/2 0.1m,
water inflow in tunnel
Single well water yield of dewatering well 3-2
When the minimum precipitation well number calculation is performed in step H1,
when the number of dewatering wells is determined in step H2, n is n1+1 is 7. Thus, the total number n of dewatering wells 3-2 in the two rows of dewatering wells 3-2 is 7.
In this embodiment, each dewatering well 3-2 further comprises a water pumping pipe 3-4 inserted into the bottom end of the lower water filtering section from top to bottom and a water pumping device 3-3 connected with the upper end of the water pumping pipe 3-4. The upper ends of the water pumping pipes 3-4 extend out of the outer side of the upper pipe section, and the water pumping equipment 3-3 is a water pumping pump.
And when the ground surface is pre-reinforced in the second step, the values of L0 and d0 can be correspondingly adjusted according to specific requirements. In this embodiment, when the ground surface is pre-reinforced in the second step, a plurality of soil cement mixing piles 29 are used to reinforce the ground surface of the backfill segment from back to front along the tunnel extension direction, and a mixing pile reinforcing structure 30 is formed. The cement-soil mixing pile 29 is a cement-soil mixing pile known to those skilled in the art, and the construction method thereof is a conventional construction method known to those skilled in the art, the construction is simple and convenient, and the construction quality is easy to control. The cement-soil mixing pile 29 uses cement as a curing agent, forcibly mixes the soft soil and the curing agent in the deep part of the foundation by a special mixing machine, and hardens the soft soil into a cement-soil pile with integrity and water stability by a series of physical and chemical reactions between the curing agent and the soft soil.
In this embodiment, the permeability coefficient of the construction area to be treated is not greater than 10-7cm/s, the cement mixing amount in the cement slurry adopted during construction of the cement-soil mixing pile 29 is not less than 17%, the water-cement ratio is 0.7-1, and the unconfined compressive strength of the mixing pile reinforcing structure 30 after construction for 28d is not less than 1.0 MPa.
The mixing pile reinforcing structure 30 is located right above the tunnel portal section to be constructed, the width of the mixing pile reinforcing structure 30 is marked as D0, wherein D0 is 5 m-8 m larger than the excavation width of the tunnel portal section to be constructed. In this embodiment, D0 is 6m larger than the excavation width of the tunnel portal section being constructed. During actual construction, the value of D0 can be adjusted accordingly according to specific needs.
The tunnel primary support structure is characterized in that a tunnel secondary lining is arranged on the inner side of the tunnel primary support structure, the tunnel primary support structure and the tunnel secondary lining are full-section support structures for supporting a full section of the tunnel cave 1, and the tunnel secondary lining is a reinforced concrete lining.
In this embodiment, as shown in fig. 2 and 3, the tunnel secondary lining is divided into an arch wall secondary lining 14 for supporting an arch wall of the tunnel cave 1 and an inverted arch secondary lining 15 for supporting the bottom of the tunnel cave 1; the inverted arch secondary lining 15 is positioned above a primary supporting inverted arch 13, an inverted arch backfill layer 16 is arranged on the inverted arch secondary lining 15, the upper surface of the inverted arch secondary lining 15 is a horizontal plane, the bottoms of the left side and the right side of the arch wall secondary lining 14 are horizontal planes, the arch wall secondary lining 14 is supported on the inverted arch secondary lining 15 and poured into a whole, and the inverted arch backfill layer 16 is a concrete filling layer;
in the third step, in the process of excavating the tunnel portal section to be constructed, constructing the secondary lining of the tunnel from back to front on the inner side of the primary tunnel supporting structure which is constructed and formed;
when the tunnel secondary lining is constructed from back to front, the inverted arch secondary lining 15 is constructed on the constructed primary support inverted arch 13 from back to front, and the inverted arch secondary lining 15 formed by construction is obtained; in the process of constructing the inverted arch secondary lining 15 from back to front, constructing the arch wall secondary lining 14 on the constructed inverted arch secondary lining 15 from back to front, and connecting the constructed arch wall secondary lining 14 and the inverted arch secondary lining 15 positioned below the constructed arch wall secondary lining into a whole to obtain the tunnel secondary lining formed by construction;
in the third step, in the process of constructing the inverted arch secondary lining 15 from back to front, the inverted arch backfill layer 16 is constructed on the constructed inverted arch secondary lining 15 from back to front along the longitudinal extension direction of the tunnel.
In this embodiment, when the secondary lining 14 of the arch wall is constructed, the secondary lining 14 of the arch wall is constructed by using a two-lining trolley from back to front along the longitudinal extension direction of the tunnel. Therefore, the actual construction is simple and convenient, the construction efficiency is high, and the construction quality is easy to ensure.
The left and right short side walls 18 of the tunnel secondary lining are lining sections at the bottoms of the left and right sides of the arch wall secondary lining 14.
When the secondary lining 14 of the arch wall is constructed, the construction process of the two short side walls 18 is synchronously completed, and the left and right short side walls 18 are also constructed by adopting a two-lining trolley. The two-lining trolley is a conventional lining trolley, and the forming template of the lining trolley is processed according to the cross section shape of the arch wall secondary lining 14. Therefore, the forming template arranged on the two-lining trolley is the forming template of the arch wall secondary lining 14, in particular to an arc-shaped template for forming the inner wall of the arch wall secondary lining 14, and the two-lining trolley has a simple structure and is simple and convenient to construct. In addition, because the upper surface of the inverted arch secondary lining 15 is a horizontal plane, the forming template can be stably supported on the inverted arch secondary lining 15, the support is stable and reliable, and the construction quality of the constructed and formed tunnel secondary lining can be effectively ensured.
Actually right when the tunnel secondary lining is under construction, the construction progress of invert secondary lining 15 is faster than the construction progress of arch wall secondary lining 14 to can further ensure the steadiness of the tunnel portal section bottom of being under construction, and can effectively accelerate the seal looping time of tunnel secondary lining.
According to the common knowledge in the field, the secondary lining (called secondary lining or secondary lining for short) of the tunnel is a molded concrete or reinforced concrete lining which is applied on the inner side of a primary supporting structure (called primary support or primary support for short) of the tunnel in the tunnel engineering construction, and the molded concrete or reinforced concrete lining and the primary supporting structure of the tunnel form a composite lining together. The tunnel secondary lining comprises a left short side wall 18 and a right short side wall 18, the two short side walls 18 are symmetrically arranged above the left side and the right side of the two-lining inverted arch, and the short side walls 18 are a term in the secondary lining of the railway tunnel and are also called as small side walls. Tunnel secondary lining is by lining cutting at the bottom of the tunnel and laying two lining arch wall lining cutting directly over the tunnel invert are connected and are formed, lining cutting at the bottom of the tunnel is by two lining arches and two short side wall 18 connects and constitutes, lining cutting also is called the tunnel invert at the bottom of the tunnel, therefore two short side wall 18 does a part of tunnel invert, the tunnel invert sets up the reverse arch structure in the tunnel bottom for improving upper portion supporting structure atress condition, is one of tunnel structure's main component part. The two short side walls 18 are symmetrically arranged above the left side and the right side of the two lining arch arches, the bottoms of the left side and the right side of the lining of the two lining arch walls are connected with the two lining arch arches through the short side walls 18, the lining of the tunnel bottom and the lining of the two lining arch walls are both reinforced concrete lining, and the cross sections of the two lining arch walls are both arched.
At present, when the composite lining of the tunnel is constructed, a method of constructing an initial support and the two lining inverted arches together is generally adopted, short side walls 18 with a certain height are constructed on the two lining inverted arches, and then inverted arch filling is carried out, so that the problems of multiple construction procedures, low efficiency and the like exist. Meanwhile, since the inverted arch filling should be poured after the concrete of the two-lined inverted arch is finally set, and the arc shape of the two-lined inverted arch must be ensured, this requires that the construction of the two-lined inverted arch and the short-side wall 18 must be formed by means of a formwork, otherwise the inverted arch construction will have the following problems: first, it is not well formed; secondly, the vibration is difficult to carry out, because the concrete slides down towards the bottom once vibrated. In addition, at present, few tunnel construction adopt the inverted arch template, often only install short side wall side form at the inverted arch top surface position of filling, inverted arch fill with two lining inverted arches pour simultaneously. After the inverted arch is filled in place, workers shovel the concrete into the short side wall formwork and do little inserting and tamping and dare not to vibrate. As a result, the quality of the short side wall 18 is greatly compromised, and the concrete filled in the two inverted arches and the inverted arch are different in grade, and the concrete filled in the two inverted arches is poured into the tunnel bottom first and then poured into the inverted arch, and the two concrete are mixed together. Since the short side wall 18 is originally an inverted arch of the tunnel, but filled with concrete, and not vibrated, the strength of the short side wall 18 is substantially low. Moreover, as can be seen from the removal of the mold, the surface of the honeycomb is serious, the appearance quality is barely seen, and the honeycomb is only covered by applying prepared cement paste; the problems of repeated utilization of the templates, unevenness, no finishing, no coating of a release agent and the like exist, and the step line type of the constructed and formed low-side wall 18 is extremely poor, so that the templates of the two-lining trolley are not tightly contacted with the template, and the slab staggering and the slurry leakage are serious. Therefore, the secondary lining structure is properly optimized, and the construction efficiency can be effectively improved on the premise of ensuring the safety of the tunnel structure, so that the project is more economic and reasonable.
In this embodiment, two of the short side walls 18 are lining segments at the bottom of the left and right sides of the arch wall secondary lining 14, and thus two of the short side walls 18 are a part of the arch wall secondary lining 7.
In order to ensure the construction quality of the inverted arch secondary lining 15 and the short side wall 18 and effectively improve the construction efficiency, the interface of the inverted arch secondary lining 15 and the inverted arch filling layer 16 is adjusted to be a plane, and the inverted arch filling layer 16 and the inverted arch secondary lining 15 can be poured simultaneously, so that the construction process of the inverted arch secondary lining 15 and the inverted arch filling layer 16 can be greatly simplified, the concrete of the inverted arch secondary lining 15 and the inverted arch filling layer 16 cannot be mixed into a whole, the construction quality of the inverted arch secondary lining 15 and the inverted arch filling layer 16 can be effectively ensured, and the problems that the construction quality of the inverted arch secondary lining 15 and the inverted arch filling layer 16 cannot be ensured and the like due to different concrete grades are solved. Meanwhile, the upper surface of the inverted arch secondary lining 15 is a horizontal plane, the arc shape of the inverted arch secondary lining 15 does not need to be guaranteed in the concrete pouring process, an arc-shaped template does not need to be adopted, pouring is convenient and simple to achieve by a large margin, pouring is simple and convenient, and the construction quality of the inverted arch secondary lining 15 is easy to guarantee.
Ditch cable grooves 23 are symmetrically formed in the left side and the right side of the tunnel secondary lining, and the ditch cable grooves 23 are pre-designed grooves used for drainage and cabling in the tunnel entrance section 1 under construction. In this embodiment, the inverted arch filler 16 is disposed between the two ditch cable grooves 23. Two ditch cable duct 23 symmetry supports in the left and right sides top of invert secondary lining 15, two ditch cable duct 23 symmetry lays in the left and right sides of invert filling layer 16.
When the upper surface of the inverted arch secondary lining 15 is cast into a plane and the height of the upper surface of the inverted arch secondary lining 15 is determined, the intersection point between the inner contour of the tunnel inverted arch (i.e., the designed inner contour of the tunnel inverted arch, which is an arc-shaped contour) designed in advance and the bottom of the trench cable groove 23 designed in advance is determined, and the intersection points between the upper surface of the inverted arch secondary lining 15 and the designed inner contour of the tunnel inverted arch and the bottom of the trench cable groove 23 designed in advance are arranged on the same horizontal plane. In this embodiment, the inverted arch secondary lining 15 is formed by once casting concrete of the same reference number as that of the inverted arch of the tunnel designed in advance, and the inverted arch filling layer 16 is formed by once casting concrete of the same reference number as that of the inverted arch designed in advance. In this embodiment, the inverted arch filler 16 is cast using C20 concrete. The inverted arch secondary lining 15 is cast separately from the inverted arch filler layer 16. And strictly vibrating the inverted arch secondary lining 15 and the inverted arch filling layer 16 in a layering manner according to large-volume concrete in the concrete pouring process.
In this embodiment, when the inverted arch secondary lining 15 is poured, the movable inverted arch trestle 17 is adopted to perform the whole pouring, and the middle arc-shaped part inside the inverted arch secondary lining 15 is optimized to be a horizontal plane, which is shown in detail in fig. 3.
The invert secondary lining 15 after optimizing makes the whole promotion by a wide margin of the rigidity of tunnel invert structure to need not to install the arc template in the construction, concrete vibrates portably and the quality of vibrating is easily controlled, and the external dimension and the construction quality of invert secondary lining 15 change in the control, and can improve the efficiency of construction of tunnel invert by a wide margin, tunnel secondary lining's seal time shortens greatly to do not have the interference of arc template to make the invert concrete easily vibrate, the concrete quality promotes greatly. In this embodiment, since the upper surface of the inverted arch secondary lining 15 is a horizontal plane, when the concrete is poured into the inverted arch secondary lining 15, it is only necessary to monitor the height of the upper surface of the poured concrete without using a forming template, and when the height of the upper surface of the poured concrete is the same as the height of the upper surface of the inverted arch secondary lining 15, the concrete pouring construction process of the inverted arch secondary lining 15 is completed, so that the construction process of the inverted arch secondary lining 15 can be greatly simplified.
In addition, it should be noted that: according to the invention, the concrete of the inverted arch secondary lining 15 is not only poured into a plane, but the upper surface of the inverted arch reinforcement cage in the inverted arch secondary lining 15 is also set to be a horizontal plane, so that the reinforcement cage is arranged in the whole transverse section of the inverted arch secondary lining 15, and the upper surface of the inverted arch reinforcement cage is a horizontal plane, so that the binding process of the inverted arch reinforcement cage can be effectively simplified.
In this embodiment, the existing two-lined arch wall lining and two short side walls 18 are connected to form the arch wall secondary lining 14, so that the existing two-lined arch wall lining and two short side walls 18 are constructed as an integral lining, and the arch wall secondary lining 14 is constructed by using a two-lined trolley. Therefore, the existing two-lining arch wall lining and the two short side walls 18 are formed by one-step construction by adopting a two-lining trolley, the construction efficiency of the tunnel secondary lining can be further improved, the closing time of the tunnel secondary lining is shortened, the ring sealing time of the tunnel secondary lining is shortened, and the structural stability of the tunnel opening section under construction is further improved.
In addition, the existing two-lining arch wall lining and the two short side walls 18 are poured into a whole, so that construction joints in the tunnel secondary lining can be effectively reduced, the integrity of the tunnel secondary lining is stronger, and the integral stress effect is better. Meanwhile, the following problems existing in the prior tunnel secondary lining construction method that the inverted arch is constructed in advance and then the combined steel template is used for constructing the short side wall can be effectively solved: firstly, the damage to the constructed double-lined inverted arch possibly caused by the construction process of the short side wall 18 when the short side wall 18 is constructed by utilizing the combined steel template after the inverted arch is constructed in advance is avoided; secondly, in order to prevent the short side wall 18 from damaging the constructed secondary substrate inverted arch 8 in the construction process, the short side wall 18 must be constructed after the secondary substrate inverted arch is finally set, so that the construction efficiency is greatly improved, and the construction period is effectively shortened; and the construction quality and the connection strength of the joint of the third and the short side walls 18 and the second lining inverted arch can be ensured, the construction cost can be effectively saved, the construction efficiency can be further improved, and the later reinforcing measure construction cost and the construction period can be reduced.
The primary pouring length of the inverted arch secondary lining 15 is determined according to the length of a two-lining trolley for constructing the arch wall secondary lining 14, and the primary pouring length of the inverted arch secondary lining 15 is 2 times or 3 times of the length of the two-lining trolley (namely the longitudinal length of the one-ring arch wall secondary lining 14), so that the construction efficiency of the tunnel inverted arch can be greatly improved, and the stability of the tunnel opening section 1 to be constructed is further ensured. In this embodiment, the primary casting length of the inverted arch secondary lining 15 is 2 times of the length of a secondary lining trolley (i.e., the longitudinal length of the secondary lining 14 of the one-ring arch wall), the length of the secondary lining trolley is 12m, and the primary maximum casting length of the inverted arch secondary lining 15 is 24 m.
In the process of excavating the tunnel portal section to be constructed, when the inverted arch secondary lining 15 is poured, the inverted arch secondary lining is excavated once, the bottom is cleaned once and pouring is performed in multiple times, so that the construction interference among the working procedures is reduced, the construction joints are reduced, and the construction quality is ensured. And, when carrying out the construction to inverted arch secondary lining 15, clear the end first, then carry out reinforcement, concrete pouring at last.
In the embodiment, the inverted arch secondary lining 15 and the arch wall secondary lining 14 are both reinforced concrete linings;
when the inverted arch secondary lining 15 is constructed from back to front, binding a reinforcement cage in the inverted arch secondary lining 15 on the constructed primary support inverted arch 13 from back to front, wherein the bound reinforcement cage is an inverted arch reinforcement cage; in the process of binding the inverted arch reinforcement cage from back to front, performing concrete pouring on the inverted arch secondary lining 15 from back to front, pouring the bound inverted arch reinforcement cage in the inverted arch secondary lining 15, and simultaneously, tightly connecting the constructed inverted arch secondary lining 15 and a primary support inverted arch 13 positioned below the inverted arch secondary lining 15 into a whole;
when the secondary lining 14 of the arch wall is constructed from back to front, binding a reinforcement cage in the secondary lining 14 of the arch wall on the constructed inverted arch secondary lining 15 from back to front, and tightly connecting the bound reinforcement cage with the inverted arch reinforcement cage positioned right below the reinforcement cage, wherein the bound reinforcement cage is the reinforcement cage of the arch wall; in the process of binding the arch wall reinforcement cage from back to front, performing concrete casting on an arch wall secondary lining 14 from back to front, so that the bound arch wall reinforcement cage is cast in the arch wall secondary lining 14, the constructed arch wall secondary lining 14 is tightly connected with a primary support inverted arch 13 positioned below the constructed arch wall secondary lining 14 into a whole, and the constructed arch wall secondary lining 14 is tightly connected with an arch wall primary support structure 12 positioned outside the constructed arch wall secondary lining 14 into a whole;
the binding progress of the inverted arch reinforcement cage is faster than that of the arch wall reinforcement cage, and the concrete pouring progress of the inverted arch secondary lining 15 is faster than that of the arch wall secondary lining 14. In this embodiment, the upper surface of the inverted arch reinforcement cage is a horizontal plane.
As shown in fig. 3, in this embodiment, when the tunnel secondary lining is constructed, the construction progress of the inverted arch backfill layer 16 is the same as the construction progress of the inverted arch secondary lining 15, which can effectively accelerate the tunnel construction progress, and the concrete pouring of the inverted arch backfill layer 16 and the inverted arch secondary lining 15 is not affected by each other because the interface between the inverted arch backfill layer 16 and the inverted arch secondary lining 15 is a horizontal plane, so that the problem that the construction quality of the inverted arch backfill layer 16 and the inverted arch secondary lining 15 is affected by the concrete mixing of the inverted arch backfill layer 16 and the inverted arch secondary lining 15 does not occur.
During actual construction, the inverted arch backfill layer 16 and the inverted arch secondary lining 15 form a tunnel inverted arch and backfill structure, the construction progress of the inverted arch backfill layer 16 and the inverted arch secondary lining 15 is the same, when the tunnel inverted arch and backfill structure are constructed, the adopted forming templates are formed by splicing a left side template 24 and a right side template 24 which are symmetrically arranged and a front template 25 which is used for forming the front side wall of the tunnel inverted arch and backfill structure, a template is not required to be adopted on the upper surface of the inverted arch secondary lining 15, the forming templates are simple in structure, the side templates 24 are rectangular templates and vertical templates which are used for forming the left side wall or the right side wall of the inverted arch backfill layer 16, the two side templates 24 are arranged along the longitudinal extension direction of the tunnel, and the clear distance between the two side templates 24 is the same as the transverse width of the inverted arch backfill layer 16; the heights of the two side templates 24 are not less than the thickness of the inverted arch backfill layer 16, the bottom surfaces of the two side templates 24 are arranged on the same horizontal plane, and the bottom surfaces of the two side templates are flush with the height of the upper surface of the inverted arch secondary lining 15; the front template 25 and the side templates 24 are vertically arranged, and the front template 25 is a vertical template for molding the front side wall of the inverted arch backfill layer 16 and the front side wall of the inverted arch secondary lining 15; with reference to fig. 17, the front template 25 is composed of an upper template and a lower template located right below the upper template, the lower template is a template for molding the front side wall of the inverted arch secondary lining 15, the shape and size of the lower template are the same as the cross-sectional shape and size of the inverted arch secondary lining 15, and the bottom of the lower template is supported on the primary supporting inverted arch 13; the upper template is a template for molding the front side wall of the inverted arch backfill layer 16, the upper template is a rectangular template, the height of the upper template is not less than the thickness of the inverted arch backfill layer 16, and the bottom surface of the upper template is flush with the upper surface of the inverted arch secondary lining 15. In this embodiment, the upper mold plate and the lower mold plate are processed and manufactured as a whole.
In this embodiment, portable invert trestle 17 includes the trestle body and installs trestle body bottom the shaping template.
In the embodiment, the constructed tunnel portal section is divided into a plurality of tunnel sections from back to front along the longitudinal extension direction of the tunnel;
the inverted arch backfill layer 16 and the inverted arch secondary lining 15 form an inverted arch and backfill structure of the tunnel, and when the second lining construction is carried out in the second step, a movable inverted arch trestle 17 is adopted to carry out construction on the inverted arch and the backfill structure of the tunnel from back to front;
when the movable inverted arch trestle 17 is adopted to construct the tunnel inverted arch and the backfill structure from back to front, the tunnel inverted arch and the backfill construction are respectively carried out on a plurality of tunnel sections of the tunnel opening section to be constructed from back to front, and the length of each tunnel section is not greater than the working length of the movable inverted arch trestle 17; the construction methods of the inverted arches and the backfilling of the tunnel sections are the same;
when tunnel inverted arch and backfill construction are carried out on any one of the tunnel sections of the constructed tunnel portal section, the process is as follows:
step A1: horizontally moving the trestle forwards: horizontally moving the movable inverted arch trestle 17 forwards to the construction position of the section of the tunnel portal section constructed currently along the longitudinal extension direction of the tunnel;
step A2, pouring an inverted arch secondary lining: concrete pouring is carried out on the inverted arch secondary lining 15 of the tunnel portal section currently constructed from bottom to top by adopting the movable inverted arch trestle 17 moved in place in the step A1;
step A3, inverted arch backfilling: after the inverted arch secondary lining is poured in the step A2, concrete is poured on the inverted arch backfill layer 16 of the tunnel portal section currently constructed from bottom to top by adopting the movable inverted arch trestle 17 which is moved in place in the step A1;
finishing tunnel inverted arch and backfill construction processes of the tunnel portal section currently constructed after the concretes poured in the step A2 and the step A3 are finally set;
and step A4, returning to the step A1, and performing tunnel inverted arch and backfill construction on one tunnel section.
The movable inverted arch trestle 17 is an inverted arch construction trestle, and because the upper surface of the tunnel bottom backfill layer 7 is flush with the upper surface of the inverted arch backfill layer 16, the tunnel bottom backfill layer 7 and the inverted arch backfill layer 16 form a horizontal moving platform for the movable inverted arch trestle 17 to move. As shown in fig. 7, the movable inverted arch trestle 17 is supported on the tunnel bottom backfill layer 7 at the front side thereof, and supported on the inverted arch backfill layer 16 which is formed by construction at the rear side thereof, so that the actual construction is very simple.
In this embodiment, before any one of the tunnel sections of the tunnel portal section under construction is subjected to tunnel inverted arch and backfill construction, the tunnel bottom backfill soil layer 7 in the tunnel portal section under construction is firstly cleaned from back to front along the longitudinal extension direction of the tunnel.
In the embodiment, the bottom of the inverted arch reinforcement cage comprises a plurality of arched reinforcements arranged from back to front, each arched reinforcement is positioned on the cross section of one tunnel of the tunnel cave 1, the plurality of arched reinforcements are arranged in parallel, and the shapes of the arched reinforcements are the same as those of the inverted arch secondary lining 15; the left end and the right end of each arch-shaped reinforcing steel bar extend to the positions above the inverted arch secondary lining 15, and the sections, extending from the two ends of each arch-shaped reinforcing steel bar to the positions above the inverted arch secondary lining 15, are reinforcing steel bar exposed sections used for connecting the arch wall reinforcing steel bar cage;
and in the process of binding the arch wall reinforcement cage from back to front, the bound arch wall reinforcement cage is fixedly connected with the reinforcement exposed section below the arch wall reinforcement cage.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.
Claims (10)
1. A tunnel portal section pre-reinforcing and excavating construction method based on partition blasting is characterized by comprising the following steps: the section of the tunnel portal is a cross section of more than 100m2The tunnel section is positioned in the earth-rock boundary stratum, the rear end of the constructed tunnel portal section is a tunnel portal, and the length of the tunnel portal section is 70-100 m; the soil-stone boundary stratum comprises a loess stratum (3) and a rock stratum (4) positioned below the loess stratum (3), and an interface between the loess stratum (3) and the rock stratum (4) is a soil-stone interface; the tunnel cave (1) of the tunnel cave mouth section is divided into an upper cave body (1-1), a middle cave body (1-2) and a lower cave body (1-3) from top to bottom, the upper cave body (1-1) is a cave body formed by performing upper step excavation on the tunnel cave mouth section to be constructed from back to front, the middle cave body (1-2) is a cave body formed by performing middle step excavation on the tunnel cave mouth section to be constructed from back to front, the lower cave body (1-3) is a cave body formed by performing lower step excavation on the tunnel cave mouth section to be constructed from back to front, an earth-rock interface is positioned in the upper cave body (1-1), and the upper cave body (1-1) and the middle cave body (1-2) form the upper cave body;
a backfill soil layer exists in a construction area where a tunnel portal section to be constructed is located, the backfill soil layer is formed after backfilling cracks or caves existing on the ground surface of a construction area to be treated, and the backfill soil layer is a loess layer; the construction area to be processed is a construction area where a tunnel portal section is located; the tunnel section with the backfill soil layer in the tunnel portal section is a backfill section;
when the pre-reinforcing and excavating construction is carried out on the tunnel portal section, the method comprises the following steps:
firstly, dewatering and pre-reinforcing: two rows of precipitation wells (3-2) are constructed in the construction area where the tunnel portal section is located, and precipitation is synchronously performed on the construction area where the tunnel portal section is located through the two rows of precipitation wells (3-2), so that the underground water level of the construction area where the tunnel portal section is located is reduced to be below the excavation contour line of the tunnel portal section;
two rows of the dewatering wells (3-2) are respectively arranged at the left side and the right side of the tunnel portal section under construction, each row of the dewatering wells (3-2) comprises a plurality of dewatering wells (3-2) arranged from back to front along the longitudinal extension direction of the tunnel, a plurality of the dewatering wells (3-2) in each row of the dewatering wells (3-2) are uniformly arranged, and the dewatering wells (3-2) in the two rows of the dewatering wells (3-2) are arranged in a staggered manner;
step two, pre-reinforcing the earth surface: reinforcing the earth surface of the backfill segment in the tunnel portal section by adopting a cement soil mixing pile (29), and obtaining a mixing pile reinforcing structure (30);
the mixing pile reinforcement structure (30) is arranged along the longitudinal extension direction of the tunnel of the backfill segment, and the longitudinal length of the mixing pile reinforcement structure (30) is the same as that of the backfill segment; the width of the mixing pile reinforcing structure (30) is larger than the excavation width of the backfill section; the tunnel buried depth of the backfill segment is 12 m-15 m, the stirring pile reinforcing structure (30) is formed by reinforcing a loess stratum (3) of the region where the backfill segment is located by adopting a plurality of cement soil stirring piles (29), the plurality of cement soil stirring piles (29) are arranged in a quincunx shape, the plurality of cement soil stirring piles (29) are uniformly arranged and are vertically arranged, and the bottom of each cement soil stirring pile (29) is supported on a rock stratum (4); the distance L0 between two adjacent cement soil mixing piles (29) is 70-80 cm, and the pile bodies of the two adjacent cement soil mixing piles (29) are meshed with each other; many the structure and the size of cement mixing pile (29) are all the same, the height of cement mixing pile (29) is the same with the vertical height of mixing pile reinforced structure (30), cement mixing pile (29) is the cylinder pile and its stake footpath
Wherein d0 > L0;
step three, tunnel excavation construction: after the ground surface pre-reinforcement is completed in the second step, excavating construction is carried out on the tunnel portal section under construction;
when the excavation construction is carried out on the tunnel portal section, the excavation construction is carried out on the tunnel portal section by a plurality of excavation sections from back to front along the longitudinal extension direction of the tunnel, and the excavation construction methods of all the excavation sections are the same; when any excavation segment of the tunnel portal section under construction is excavated, the process is as follows:
step 301, measurement and paying-off: respectively measuring and paying off the excavation contour lines of the upper hole body (1-1), the middle hole body (1-2) and the lower hole body (1-3) on the current construction excavation surface, and simultaneously respectively measuring and paying off the number of blastholes to be arranged and the arrangement positions of the blastholes on the excavation surface of the upper hole body (1-1), the middle hole body (1-2) and the lower hole body (1-3) of the current construction excavation segment; the current construction excavation surface is the excavation surface of the current construction excavation segment;
the blasting excavation surface of the upper cave body (1-1) is divided into a left upper blasting area (1-11) and a right upper blasting area (1-12) positioned on the right side of the left upper blasting area (1-11), and the blasting excavation surface of the upper cave body (1-1) is positioned below the earth-rock interface; the blasting excavation surface of the middle hole body (1-2) is divided into a left blasting area (1-21), a middle blasting area (1-22) and a right blasting area (1-23) from left to right, and the left blasting area (1-21) and the right blasting area (1-23) are symmetrically arranged on the left side and the right side of the middle blasting area (1-22);
the medium explosion area (1-22) is a cut area and is provided with four groups of cut holes (1-4), and each group of cut holes (1-4) comprises a plurality of cut holes (1-4) distributed on the same vertical surface from top to bottom; the four groups of the cutting holes (1-4) comprise a left group of inner cutting holes and a right group of outer cutting holes which are symmetrically distributed, and the two groups of the inner cutting holes are positioned between the two groups of the outer cutting holes; the inner side cutting holes and the outer side cutting holes are arranged in a staggered manner;
a plurality of peripheral eyes (1-5) are arranged on the left side of the left upper explosion area (1-11), the right side of the right upper explosion area (1-12), the left side of the left explosion area (1-21) and the right side of the right explosion area (1-23) from top to bottom;
three rows of auxiliary eyes (1-6) are distributed on the left explosion area (1-21) and the right explosion area (1-23) from left to right, and each row of auxiliary eyes (1-6) on the left explosion area (1-21) and the right explosion area (1-23) comprises a plurality of auxiliary eyes (1-6) distributed on the same vertical plane from top to bottom; an upper row and a lower row of auxiliary eyes (1-6) are uniformly distributed on the left upper explosion area (1-11) and the right upper explosion area (1-12), and each row of auxiliary eyes (1-6) on the left upper explosion area (1-11) and the right upper explosion area (1-12) comprises a plurality of auxiliary eyes (1-6) distributed from left to right;
the blasting excavation surface of the upper hole body is divided into 5 blasting areas, and the 5 blasting areas are respectively a left upper blasting area (1-11), a right upper blasting area (1-12), a left blasting area (1-21), a middle blasting area (1-22) and a right blasting area (1-23); the left explosion area (1-21) and the right explosion area (1-23) in the 5 explosion areas are simultaneously detonated, the left upper explosion area (1-11) and the right upper explosion area (1-12) are simultaneously detonated, and the middle explosion area (1-22), the right explosion area (1-23) and the right upper explosion area (1-12) are detonated from first to last;
the cutting holes (1-4), the peripheral holes (1-5) and the auxiliary holes (1-6) are blast holes;
step 302, drilling and blasting construction: according to the arrangement positions of the blastholes obtained by measuring and setting out in the step 301, drilling all the blastholes on the current construction excavation surface by adopting drilling equipment, respectively charging the blastholes formed by drilling, and detonating for blasting after charging is completed;
step 303, excavating an upper hole body: excavating an upper hole body (1-1) of the currently constructed excavation section from back to front along the longitudinal extension direction of the tunnel;
when the upper cavity body (1-1) of the current construction excavation section is excavated from back to front, the loess stratum (3) in the upper cavity body (1-1) is excavated from back to front; in the process of excavating the loess stratum (3) in the upper cave body (1-1) from back to front, a ballast conveying vehicle is adopted to convey the ballast generated after the inner explosion of the upper cave body (1-1) from back to front to the outer side of the tunnel portal section to be constructed, and the excavation construction process of the upper cave body (1-1) is completed;
step 304, excavating a middle hole body: excavating a middle hole body (1-2) of the currently constructed excavation section from back to front along the longitudinal extension direction of the tunnel;
when the middle tunnel body (1-2) of the current constructed excavation section is excavated from back to front, the slag conveying vehicle is adopted to convey the slag generated after the inner explosion of the middle tunnel body (1-2) to the outer side of the tunnel portal section to be constructed from back to front, so that the excavation construction process of the middle tunnel body (1-2) is completed;
step 305, excavating a lower cavity: excavating a lower cavity body (1-3) of the currently constructed excavation section from back to front along the longitudinal extension direction of the tunnel to finish the excavation construction process of one excavation section;
when the lower tunnel body (1-3) of the current constructed excavation section is excavated from back to front, the slag conveying vehicle is adopted to convey slag stones generated after the inner explosion of the lower tunnel body (1-3) to the outer side of the tunnel portal section to be constructed from back to front, so that the excavation construction process of the lower tunnel body (1-3) is completed, and the tunnel portal (1) formed by construction is obtained;
step 306, excavating construction of the next excavation segment: excavating the next excavation section of the tunnel portal section according to the construction process from the step 301 to the step 305;
and 307, repeating the step 306 for multiple times until all excavation construction processes of the tunnel portal section are completed.
2. The method for pre-reinforcing and excavating construction of the tunnel portal section based on the zone blasting according to claim 1, which is characterized in that: in step 301, each group of the inner undercutting holes comprises two undercutting holes (1-4), and each group of the outer undercutting holes comprises three undercutting holes (1-4);
the left explosion area (1-21) and the right explosion area (1-23) comprise 3 or 4 auxiliary eyes (1-6) in each column of the auxiliary eyes (1-6);
each row of the auxiliary eyes (1-6) on the left upper explosion area (1-11) and the right upper explosion area (1-12) comprises 4 auxiliary eyes (1-6).
3. The method for pre-reinforcing and excavating construction of the tunnel portal section based on the zone blasting according to claim 1 or 2, characterized by comprising the following steps: in step 301, the section positions of two groups of detonators for the inner undermining eye blasting are 1 section, the section positions of one group of detonators for the outer undermining eye blasting close to a right blasting area (1-23) are 3 sections, and the section positions of one group of detonators for the outer undermining eye blasting close to a left blasting area (1-21) are 5 sections;
the three rows of blasting detonators for the auxiliary eyes (1-6) on the left blasting area (1-21) are respectively 3 sections, 5 sections and 7 sections from right to left, and the three rows of blasting detonators for the auxiliary eyes (1-6) on the right blasting area (1-23) are respectively 3 sections, 5 sections and 7 sections from left to right;
the section positions of all detonators for blasting of all peripheral holes (1-5) on the left blasting area (1-21) and the right blasting area (1-23) are 9 sections;
the detonators with the upper sections of 5 sections in the middle explosion area (1-22) are connected with the detonators for blast hole blasting in the left explosion area (1-21) through detonating tubes, and the detonators with the upper sections of 3 sections in the middle explosion area (1-22) are connected with the detonators for blast hole blasting in the right explosion area (1-23) through detonating tubes;
the detonators with the upper section positions of 5 sections in the left blasting area (1-21) are connected with the detonators for blasting blastholes in the left blasting area (1-11) through detonating tubes, and the detonators with the upper section positions of 5 sections in the right blasting area (1-23) are connected with the detonators for blasting holes in the right blasting area (1-12) through detonating tubes.
4. The method for pre-reinforcing and excavating construction of the tunnel portal section based on the zone blasting according to claim 1 or 2, characterized by comprising the following steps: in the step 303, when the loess stratum (3) in the upper cavity (1-1) is excavated from back to front, an excavator is adopted for excavation;
before adopting the excavator to excavate, firstly install a scarifier on excavator's grab bucket and pass through the scarifier loosens the soil to loess stratum (3) in the upper portion hole body (1-1), will again the scarifier is demolishd and is adopted the excavator excavates loess stratum (3) in to the upper portion hole body (1-1).
5. The method for pre-reinforcing and excavating construction of the tunnel portal section based on the zone blasting according to claim 1 or 2, characterized by comprising the following steps: the tunnel primary supporting structure of the tunnel hole (1) is divided into an arch wall primary supporting structure (12) for carrying out primary supporting on an arch wall of the tunnel hole (1) and a primary supporting inverted arch (13) for carrying out primary supporting on the bottom of the tunnel hole (1);
the tunnel primary support structure comprises a full-section support structure for performing full-section support on the tunnel hole (1), an arch wall net-jet support structure for performing primary support on an arch wall of the tunnel hole (1) and an inverted arch primary support structure for performing primary support on the bottom of the tunnel hole (1); the full-section supporting structure comprises a plurality of full-section supporting frames which are arranged from back to front along the longitudinal extension direction of the tunnel, the two adjacent full-section supporting frames at the front and the back are fixedly connected into a whole through a plurality of longitudinal connecting reinforcing steel bars, the longitudinal connecting reinforcing steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal connecting reinforcing steel bars are arranged along the contour line of the full-section supporting frames; a plurality of full-section support frames in the full-section support structure are uniformly distributed, the distance between two adjacent full-section support frames in the front and the back is L, and the value range of L is 0.5-0.8 m;
the shape of the full-section support frame is the same as the shape of the cross section of the tunnel hole (1), each full-section support frame is formed by splicing an arch wall support arch frame for supporting an arch wall of the tunnel hole (1) and a tunnel inverted arch support frame (2) for supporting the bottom of the tunnel hole (1), the tunnel inverted arch support frame (2) is positioned under the arch wall support arch frame and positioned on the same tunnel cross section, and the tunnel inverted arch support frame (2) and the arch wall support arch frame form a closed full-section support; the inverted arch primary support structure is an inverted arch concrete injection layer (20) injected at the bottom of a tunnel hole (1), and the tunnel inverted arch support (2) is fixed in the inverted arch concrete injection layer (20);
the arch wall mesh-spraying supporting structure and all arch wall steel arches in the full-section supporting structure form an arch wall primary supporting structure (12), and the inverted arch primary supporting structure and all tunnel inverted arch brackets (2) in the full-section supporting structure form a primary supporting inverted arch (13);
the arch wall supporting arch center comprises an upper arch center (2-1) positioned in an upper hole body (1-1), two middle side brackets (5) symmetrically arranged below the left side and the right side of the upper arch center (2-1) and positioned in a middle hole body (1-2), and two lower side brackets (6) symmetrically arranged below the left side and the right side of the upper arch center (2-1) and positioned in a lower hole body (1-3), wherein the tunnel inverted arch bracket (2) is positioned in the lower hole body (1-3); each middle side bracket (5) is connected between the upper end of one lower side bracket (6) and one end of the upper arch (2-1); the left end of the tunnel inverted arch support (2) is fixedly connected with the bottom of one lower side support (6), and the right end of the tunnel inverted arch support (2) is fixedly connected with the bottom of the other lower side support (6);
after the excavation of the upper hole body (1-1) of the currently constructed excavation section is finished in the step 303, installing an upper arch frame (2-1) in the excavated and formed upper hole body (1-1) from back to front; simultaneously entering step 304, and excavating the middle hole body (1-2) of the currently constructed excavation section from back to front;
in the step 304, after the excavation of the middle hole body (1-2) of the currently constructed excavation section is finished, respectively installing middle side brackets (5) at the left side and the right side of the middle hole body (1-2) formed by excavation from back to front, and enabling each middle side bracket (5) to be fixedly connected with an upper arch frame (2-1) positioned above the middle side bracket into a whole; simultaneously, step 305 is carried out, and the lower cavity body (1-3) of the currently constructed excavation segment is excavated from back to front;
after the excavation of the lower hole body (1-3) of the currently constructed excavation section is finished in the step 305, respectively installing lower side supports (6) on the left side and the right side of the excavated and formed lower hole body (1-3) from back to front, and enabling each lower side support (6) to be fixedly connected with a middle side support (5) positioned above the lower side support into a whole; simultaneously, by back forward at lower part cave body (1-3) bottom installation tunnel invert support (2) and make the tunnel invert support (2) of installing and lower part collateral branch frame (6) the fastening connection that the lower part cave body (1-3) left and right sides was installed as an organic whole, obtain and erect the completion the full section support frame, and through the multichannel longitudinal joint reinforcing bar will be adjacent two around the full section support frame fastening connection is as an organic whole.
6. The method for pre-reinforcing and excavating construction of the tunnel portal section based on the zone blasting according to claim 5, characterized in that: a tunnel secondary lining is arranged on the inner side of the tunnel primary supporting structure, the tunnel primary supporting structure and the tunnel secondary lining are full-section supporting structures for supporting a tunnel hole (1) in a full-section mode, and the tunnel secondary lining is a reinforced concrete lining;
the tunnel secondary lining is divided into an arch wall secondary lining (14) for supporting an arch wall of the tunnel hole (1) and an inverted arch secondary lining (15) for supporting the bottom of the tunnel hole (1); the inverted arch secondary lining (15) is positioned above a primary supporting inverted arch (13), an inverted arch backfill layer (16) is arranged on the inverted arch secondary lining (15), the upper surface of the inverted arch secondary lining (15) is a horizontal plane, the bottoms of the left side and the right side of the arch wall secondary lining (14) are horizontal planes, the arch wall secondary lining (14) is supported on the inverted arch secondary lining (15) and poured into a whole, and the inverted arch backfill layer (16) is a concrete filling layer;
in the third step, in the process of excavating the tunnel portal section to be constructed, constructing the secondary lining of the tunnel from back to front on the inner side of the primary tunnel supporting structure which is constructed and formed;
when the tunnel secondary lining is constructed from back to front, the inverted arch secondary lining (15) is constructed on the constructed primary support inverted arch (13) from back to front, and a constructed inverted arch secondary lining (15) is obtained; in the process of constructing the inverted arch secondary lining (15) from back to front, constructing the arch wall secondary lining (14) on the constructed inverted arch secondary lining (15) from back to front, and connecting the constructed arch wall secondary lining (14) and the inverted arch secondary lining (15) positioned below the constructed arch wall secondary lining into a whole to obtain the constructed tunnel secondary lining;
and in the third step, in the construction process of the inverted arch secondary lining (15) from back to front, the inverted arch backfill layer (16) is constructed on the constructed inverted arch secondary lining (15) from back to front along the longitudinal extension direction of the tunnel.
7. The method for pre-reinforcing and excavating construction of the tunnel portal section based on the zone blasting according to claim 5, characterized in that: a reinforcing sleeve arch is arranged on the inner side of the primary supporting structure of the tunnel;
the tunnel primary supporting structure and the reinforcing sleeve arch are full-section supporting structures for supporting a tunnel hole (1) in a full-section mode, and the tunnel primary supporting structure and the reinforcing sleeve arch positioned on the inner side of the tunnel primary supporting structure form a reinforced primary supporting structure;
the reinforced arch comprises a plurality of arch units, the arch units are identical in structure and are arranged from back to front along the longitudinal extension direction of the tunnel, an isolation layer (26) is arranged between each arch unit and the primary tunnel supporting structure, the isolation layer (26) is a full-section isolation layer formed by non-woven fabrics paved between the arch units and the primary tunnel supporting structure, and the cross section of the isolation layer (26) is identical to that of the tunnel hole (1);
each arch sheathing unit comprises M profiled bar arches (11) which are arranged from back to front along the longitudinal extension direction of the tunnel and an inner side concrete spraying layer (27) formed by concrete sprayed on the isolation layer (26), the thickness of the inner side concrete spraying layer (27) is not less than 25cm, the M profiled bar arches (11) are uniformly arranged, and the distance between two adjacent profiled bar arches (11) is 0.8-1.2M; each steel arch (11) is a full-section support for performing full-section supporting on a tunnel hole (1), M steel arches (11) are fixed in the inner side concrete spraying layer (27), the shape of each steel arch (11) is the same as the shape of the cross section of the tunnel hole (1), wherein M is a positive integer and is more than or equal to 4; m steel arch frames (11) in each arch sheathing unit are fixedly connected into a whole through a plurality of longitudinal steel bars, the longitudinal steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal steel bars are arranged along the contour line of the steel arch frames (11); each profile steel arch (11) comprises an arch wall profile steel support (11-1) for supporting an arch wall of a tunnel hole (1) and an inverted arch profile steel support (11-2) for supporting the bottom of the tunnel hole (1), the inverted arch profile steel support (11-2) is located under the arch wall profile steel support (11-1) and is an arch support, the left end of the inverted arch profile steel support (11-2) is fixedly connected with the bottom of the left end of the arch wall profile steel support (11-1), and the right end of the inverted arch profile steel support (11-2) is fixedly connected with the bottom of the right end of the arch wall profile steel support (11-1);
in the step 304, in the process of excavating the lower hole body (1-3) from back to front, the reinforcing sleeve arch is constructed on the inner side of the constructed primary tunnel supporting structure from back to front along the longitudinal extension direction of the tunnel, so that the reinforced primary support structure formed by construction is obtained;
when the reinforcing sleeve arch is constructed from back to front, a plurality of sleeve arch units in the reinforcing sleeve arch are constructed from back to front respectively, and the construction methods of the plurality of sleeve arch units are the same; the tunnel primary supporting structure section with the arch sheathing units distributed on the inner side in the tunnel primary supporting structure is a primary supporting section to be reinforced;
when any one of the set arch units in the reinforced set arch is constructed, the process is as follows:
d1, paving an isolation layer: paving a layer of isolation layer (26) on the inner wall of the primary support section to be enhanced outside the currently constructed arch sheathing unit from back to front;
step D2, installing the profile steel arch frame: in the process of laying an isolation layer (26) from back to front in the step D1, respectively installing M steel arches (11) of the currently constructed arch sheathing unit in the primary support section to be reinforced from back to front in the step 301, enabling each steel arch (11) to be erected on the inner side of the isolation layer (26) in the step D1, and simultaneously enabling the isolation layer (26) in the step D1 to be padded between the M installed steel arches (11) and the inner wall of the primary support section to be reinforced;
step D3, longitudinal steel bar installation: d2, after M structural steel arches (11) are installed, firmly connecting the M structural steel arches (11) into a whole through a plurality of longitudinal steel bars;
step D4, concrete spraying: and D1, spraying concrete on the isolating layer (26) from back to front to form an inner concrete spraying layer (27), fixing M steel arches (11) in the step D2 and a plurality of longitudinal steel bars in the step D3 in the inner concrete spraying layer (27), and padding the isolating layer (26) between the primary support section to be reinforced and the inner concrete spraying layer (27) in the step D1.
8. The method for pre-reinforcing and excavating construction of the tunnel portal section based on the zone blasting according to claim 7, characterized in that: after the concrete is sprayed in the step D4, radial grouting reinforcement is needed to be carried out on the arch wall of the primary support section to be reinforced in the step D1, and a radial grouting reinforcement structure is obtained;
the upper tunnel body (1-1) and the middle tunnel body (1-2) form an upper tunnel body of the tunnel, and the radial grouting reinforcement structure is positioned on the outer side of the upper tunnel body of the tunnel;
the radial grouting reinforcement structure is formed by grouting and reinforcing soil outside the tunnel upper hole body through a plurality of rows of radial grouting holes (28), the radial grouting holes (28) are arranged from back to front along the extending direction of the tunnel, each row of radial grouting holes (28) comprises a plurality of radial grouting holes (28) arranged on the section of the same tunnel from left to right along the excavation contour line of the tunnel upper hole body, each radial grouting hole (28) is a drill hole drilled into the soil from the inside to the outside of the tunnel upper hole body, the radial grouting holes (28) in each row of radial grouting holes (28) are uniformly arranged, and the radial grouting holes (28) in the front and back adjacent rows of radial grouting holes (28) are arranged in a staggered manner; the length of the radial grouting holes (28) is not less than 3 m;
each row of radial grouting holes (28) are positioned between two front and rear adjacent full-section supporting frames, and each row of radial grouting holes (28) are positioned between two front and rear adjacent profile steel arches (11);
and D1, when the arch wall of the primary support section to be reinforced is reinforced by radial grouting, the arch wall is reinforced by grouting from back to front through a plurality of rows of radial grouting holes (28).
9. The method for pre-reinforcing and excavating construction of the tunnel portal section based on the zoning blasting as claimed in claim 8, wherein: in the radial grouting reinforcement process of the arch wall of the primary support section to be reinforced in the step D1, arch changing is carried out on an arch section needing to be subjected to arch changing in the tunnel portal section to be constructed;
the arch section to be changed is formed by connecting an intrusion limit section and two extension sections which are respectively positioned at the front side and the rear side of the intrusion limit section, and the primary supporting structure of the arch section to be changed is the reinforced primary supporting structure; the limit invasion section is a tunnel section of the reinforced primary support structure in the constructed tunnel portal section, and the two extension sections are adjacent to and communicated with the limit invasion section in the constructed tunnel portal section; the length of each of the two extension sections is not less than 3L;
and when the arch of the section needing to be changed, which needs to be changed, of the tunnel portal section to be constructed is changed, the reinforced primary support structure in the section needing to be changed is dismantled, and primary support construction is synchronously carried out on the section needing to be changed in the dismantling process, so that the primary support structure of the tunnel after being changed is obtained.
10. The method for pre-reinforcing and excavating construction of the tunnel portal section based on the zone blasting according to claim 5, characterized in that: the surrounding rock level of the tunnel cave (1) is V level or VI level, and the length of each excavation section is 2L.
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| CN114547721B (en) * | 2021-12-21 | 2022-10-25 | 沈阳工业大学 | Blasting control method for differential directional fracture of local area of deep-buried tunnel |
| CN114622918B (en) * | 2022-03-17 | 2023-05-30 | 中铁三局集团广东建设工程有限公司 | Method for controlling stability of two-layer primary supporting arch springing of large-span structure by weak stratum arch capping method |
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| JP2002188397A (en) * | 2000-12-20 | 2002-07-05 | Maruwa Giken:Kk | Method for repairing outbreak part, and fixing metal fitting used therein |
| CN102997763A (en) * | 2012-11-29 | 2013-03-27 | 青海山金矿业有限公司 | Method for blasting inclined thin ore body by dividing ores and rocks in area in drift driving |
| JP6130706B2 (en) * | 2013-04-09 | 2017-05-17 | 鹿島建設株式会社 | Mobile formwork apparatus and lining concrete construction method |
| CN105606000B (en) * | 2016-01-11 | 2017-04-12 | 德阳坚兵工程技术有限公司 | Partition control blasting method for tunnel rock drilling project |
| CN108871119B (en) * | 2018-07-23 | 2020-05-05 | 中铁十九局集团第六工程有限公司 | Tunnel hole distribution blasting method |
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