CN110778318B - Tunnel pre-reinforcing and excavating construction method for penetrating through earth-rock boundary stratum - Google Patents

Tunnel pre-reinforcing and excavating construction method for penetrating through earth-rock boundary stratum Download PDF

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CN110778318B
CN110778318B CN201911138650.1A CN201911138650A CN110778318B CN 110778318 B CN110778318 B CN 110778318B CN 201911138650 A CN201911138650 A CN 201911138650A CN 110778318 B CN110778318 B CN 110778318B
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tunnel
section
excavation
arch
blasting
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CN110778318A (en
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吴小波
刘德兵
李瑛�
常运超
李世军
王存宝
张博
魏军
何精伟
李明辉
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Sixth Engineering Co Ltd of China Railway 20th Bureau Group Co Ltd
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Sixth Engineering Co Ltd of China Railway 20th Bureau Group Co Ltd
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    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D9/00Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
    • E21D9/006Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries by making use of blasting methods
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/04Lining with building materials
    • E21D11/10Lining 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
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/14Lining predominantly with metal
    • E21D11/18Arch members ; Network made of arch members ; Ring elements; Polygon elements; Polygon elements inside arches
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/14Lining predominantly with metal
    • E21D11/28Longitudinal struts, i.e. longitudinal connections between adjoining arches
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D9/00Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
    • E21D9/001Improving soil or rock, e.g. by freezing; Injections
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21FSAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F16/00Drainage
    • E21F16/02Drainage of tunnels
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F42AMMUNITION; BLASTING
    • F42DBLASTING
    • F42D1/00Blasting methods or apparatus, e.g. loading or tamping
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F42AMMUNITION; BLASTING
    • F42DBLASTING
    • F42D3/00Particular applications of blasting techniques
    • F42D3/04Particular applications of blasting techniques for rock blasting

Abstract

The invention discloses a tunnel pre-reinforcing and excavating construction method for penetrating through an earth-rock boundary stratum, which comprises the following steps of: firstly, dewatering and pre-reinforcing; secondly, excavating and constructing a rear side tunnel section; thirdly, excavating and constructing the middle tunnel section; fourthly, excavating and constructing a front side tunnel section; the middle tunnel section and the front side tunnel section are three-step synchronous excavation tunnel sections; and in the excavation process from back to front in the second step, the third step and the fourth step, the tunnel hole formed by excavation is synchronously supported from back to front for the initial stage. The method has the advantages of reasonable design, simple and convenient construction and good use effect, reduces the underground water level through precipitation pre-reinforcement, effectively reinforces the surrounding rock, selects a proper drilling and blasting method according to the position relation between the earth and stone interface and the tunnel hole, adopts a three-step synchronous excavation mode to carry out blasting excavation, can ensure the safe and reliable excavation process of the tunnel passing through the earth and stone boundary stratum, and can ensure the stable tunnel structure.

Description

Tunnel pre-reinforcing and excavating construction method for penetrating through earth-rock boundary stratum
Technical Field
The invention belongs to the technical field of tunnel construction, and particularly relates to a tunnel pre-reinforcing and excavation construction method for penetrating through an earth-rock boundary stratum.
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 an upper step, a middle step or a lower step, the most adverse condition is that the earth-rock interface is positioned on the upper step, and a blasting area is closest to the arch crown and the tunnel face during blasting, so that the collapse of the arch crown and the tunnel face is easily caused.
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.
Disclosure of Invention
The invention aims to solve the technical problems in the prior art and provides a tunnel pre-reinforcement and excavation construction method for traversing an earth-rock boundary stratum, which has the advantages of reasonable design, simple and convenient construction and good use effect.
In order to solve the technical problems, the invention adopts the technical scheme that: a tunnel pre-reinforcement and excavation construction method for penetrating through an earth-rock boundary stratum is characterized by comprising the following steps: the cross section of the constructed tunnel is larger than 100m2The shallow tunnel is positioned in the earth-rock boundary stratum, and the surrounding rock grade of a tunnel hole in the constructed tunnel is IV grade or V grade; 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 hole of the constructed tunnel is divided into an upper hole body, a middle hole body and a lower hole body from top to bottom, the upper hole body is formed after the upper step excavation is carried out on the constructed tunnel from back to front, the middle hole body is formed after the middle step excavation is carried out on the constructed tunnel from back to front, and the lower hole body is formed after the lower step excavation is carried out on the constructed tunnel from back to front; the middle upper hole body and the middle hole body in the tunnel hole form a tunnel upper hole body, and the middle hole body and the lower hole body in the tunnel hole form a tunnel lower hole body;
the constructed tunnel is a linear tunnel and is divided into a rear side tunnel section, a middle tunnel section and a front side tunnel section from back to front, the middle tunnel section is connected between the rear side tunnel section and the front side tunnel section, and the rear side tunnel section, the middle tunnel section and the front side tunnel section are all one tunnel section of the constructed tunnel; the rear side tunnel section and the middle tunnel section are connected to form a rear tunnel section, the length of the rear tunnel section is 70-100 m, the length of the rear side tunnel section is not less than 50m, and the length of the middle tunnel section is not less than 15 m;
the rear side tunnel section is positioned in a rock stratum, a tunnel hole of the rear side tunnel section is positioned below the soil-rock interface, and the vertical distance between the top of an excavation contour line of the tunnel hole in the rear side tunnel section and the soil-rock interface positioned above the top of the excavation contour line is less than 5 m; the earth-rock interface in the middle tunnel section is positioned in the upper cavity, and the earth-rock interface in the front tunnel section is positioned in the middle cavity or the lower cavity;
when the constructed tunnel is constructed, the method comprises the following steps:
firstly, precipitation pre-reinforcement of a rear tunnel section: constructing two rows of precipitation wells in the construction area of the rear tunnel section, and synchronously precipitating the construction area of the rear tunnel section through the two rows of precipitation wells to reduce the underground water level of the construction area of the rear tunnel section to be below the excavation contour line of the tunnel cave;
two rows of the dewatering wells are respectively arranged on the left side and the right side of the rear tunnel section, 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, excavation construction of a rear side tunnel section: excavating the rear side tunnel section from back to front along the longitudinal extension direction of the tunnel, and obtaining an excavated tunnel;
step three, excavating and constructing the middle tunnel section: after the excavation of the rear side tunnel section in the step two is finished, excavating the middle tunnel section from back to front along the longitudinal extension direction of the tunnel, and obtaining an excavated tunnel hole;
fourthly, excavation construction of the front side tunnel section: after the middle tunnel section is excavated in the third step, excavating the front side tunnel section from back to front along the longitudinal extension direction of the tunnel, obtaining an excavated tunnel hole, and finishing the excavation construction process of the constructed tunnel;
the rear side tunnel section, the middle tunnel section and the front side tunnel section are all three-step synchronous excavation tunnel sections; the rear side tunnel section, the middle tunnel section and the front side tunnel section are divided into a plurality of excavation sections from back to front along the longitudinal extension direction of the tunnel for excavation construction, the excavation construction methods of the excavation sections in the rear side tunnel section are the same, and the excavation construction methods of the excavation sections in the front side tunnel section are the same;
in the second step and in the third step, when the excavation construction is performed on any one of the excavation sections in the rear tunnel section, 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 constructed excavation surface is the excavation surface of the current constructed excavation section in the rear tunnel section;
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 tunnel upper hole body is divided into 5 blasting areas, and the 5 blasting areas are respectively an upper left blasting area, an upper right blasting area, a left blasting area, an intermediate blasting area and a right blasting area; 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;
when the upper tunnel body of the current constructed excavation section is excavated from back to front, a slag conveying vehicle is adopted to convey the slag in the upper tunnel body from back to front to the outer side of the tunnel portal of the constructed tunnel, so that the excavation construction process of the upper tunnel body is completed;
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 inner explosion of the middle tunnel body from back to front to the outer side of the tunnel portal of the constructed tunnel, so that 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 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 from back to front to the outer side of the tunnel portal of the constructed tunnel, so that the excavation construction process of the lower tunnel body is completed, and the constructed and formed tunnel portal is obtained;
the rock stratum in the front side tunnel section and positioned in the lower hole body of the tunnel is a rock stratum to be blasted;
in the fourth step, when the excavation construction is performed on any one of the excavation sections in the front side tunnel section, the process is as follows:
step 401, drilling and blasting construction: carrying out drilling and blasting construction on the rock stratum to be blasted of the currently constructed excavation section in the front side tunnel section;
step 402, excavating an upper cavity: excavating the upper cavity of the currently constructed excavation segment from back to front along the longitudinal extension direction of the tunnel;
step 403, 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;
step 404, excavating a lower cavity: and excavating the lower part 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 to obtain a constructed and formed tunnel.
The tunnel pre-reinforcing and excavating construction method for penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: 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 pre-reinforcing and excavating construction method for penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: 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 pre-reinforcing and excavating construction method for penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: when drilling and blasting construction is carried out on the rock stratum to be blasted in the step 401, full-face blasting construction is carried out on the rock stratum to be blasted of the currently constructed excavation section by adopting a full-face blasting method.
The tunnel pre-reinforcing and excavating construction method for penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: the primary tunnel supporting structure of the rear side tunnel section, the primary tunnel supporting structure of the middle tunnel section and the primary tunnel supporting structure of the front side tunnel section are identical in structure and are tunnel primary supporting structures of tunnel holes;
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;
the length of each excavation section is 2L;
in the second step, in the process of excavating the rear side tunnel section from back to front, the tunnel hole formed by excavation is synchronously supported from back to front, and a tunnel primary support structure of the rear side tunnel section is obtained;
in the third step, in the process of excavating the middle tunnel section from back to front, the tunnel hole formed by excavation is synchronously supported from back to front, and a tunnel primary support structure of the middle tunnel section is obtained;
and in the fourth step, in the process of excavating the front side tunnel section from back to front, the tunnel hole formed by excavation is synchronously supported from back to front, and the tunnel primary support structure of the front side tunnel section is obtained.
The tunnel pre-reinforcing and excavating construction method for penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: 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 pre-reinforcing and excavating construction method for penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: after the excavation of the upper cavity of the currently constructed excavation section is finished in the step 402, installing an upper arch frame in the excavated and formed upper cavity from back to front; simultaneously, in step 403, excavating the middle cavity of the currently constructed excavation segment from back to front;
in step 403, 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 entering step 404, excavating the lower cavity of the currently constructed excavation section from back to front;
after the excavation of the lower cavity of the currently constructed excavation section is finished in the step 404, 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 pre-reinforcing and excavating construction method for penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: the front side tunnel section comprises a front end tunnel section and a rear end tunnel section positioned at the rear side of the front end tunnel section, and the rear end tunnel section is connected between the front end tunnel section and the middle tunnel section; the earth-rock interface in the front end tunnel section is positioned in the lower cavity, and the earth-rock interface in the rear end tunnel section is positioned in the middle cavity;
when the front side tunnel section is excavated from back to front in the fourth step, the rear end tunnel section is excavated from back to front, and then the front end tunnel section is excavated from back to front;
reinforcing sleeve arches are uniformly distributed on the inner sides of the tunnel primary supporting structures of the rear tunnel section and the rear end tunnel section;
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;
constructing the reinforcing 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 in the excavation process of the lower hole body from back to front in the step 304 and the excavation process of the lower hole body of the rear-end tunnel section from back to front in the step 403, and obtaining the construction-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 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, 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 pre-reinforcing and excavating construction method for penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: radial grouting reinforcement structures are arranged on the outer sides of the primary support sections to be reinforced in the rear tunnel section and the rear end tunnel section, and are positioned on the outer sides of the tunnel upper hole bodies of the rear tunnel section and the rear end tunnel section;
in the excavation construction process of the rear side tunnel section, in the excavation construction process of the middle tunnel section in the step three and in the excavation construction process of the rear end tunnel section in the step four, after concrete spraying is carried out in the step D4, radial grouting reinforcement is further carried out on the arch wall of the primary support section to be reinforced in the step D1, and the radial grouting reinforcement structure is obtained;
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 in the excavation construction process of the rear side tunnel section, the excavation construction process of the middle tunnel section in the step three and the excavation construction process of the rear end tunnel section in the step four, when the arch wall of the primary support section to be reinforced in the step D1 is subjected to radial grouting reinforcement, grouting reinforcement is respectively carried out through a plurality of rows of radial grouting holes from back to front.
The tunnel pre-reinforcing and excavating construction method for penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: in the excavation construction process of the rear side tunnel section, in the excavation construction process of the middle tunnel section in the step three and in the excavation construction process of the rear end tunnel section in the step four, 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 also needed to be carried out on the arch-needing changing section of the rear tunnel section and the rear end tunnel section; the rear tunnel section and the rear end tunnel section are both tunnel sections needing arch change;
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 tunnel section needing arch replacement, and the two extension sections are tunnel sections which are adjacent to and communicated with the limit invasion section in the tunnel section needing arch replacement; 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, in the tunnel section needing to be changed 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.
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, and effectively reinforces the surrounding rock while reducing the underground water level of the earth-rock boundary stratum through precipitation pre-reinforcement before tunnel excavation, thereby avoiding the problems of water burst, collapse and the like on the tunnel face in the tunnel excavation process.
2. The invention adopts a partition blasting mode to respectively divide the upper blasting area in the upper step and the middle blasting area on the middle step, and limits 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 one-time explosive loading of the large section is too much, and ensuring the safety and reliability of the tunnel excavation process.
3. Selecting a reasonable tunnel excavation mode according to the surrounding rock conditions of the tunnel hole, wherein tunnel sections (including a middle tunnel section and a rear tunnel section) with poor surrounding rock conditions are excavated by blasting in an upper-middle step, the blasting areas are divided reasonably, the number and the positions of blastholes are designed reasonably, the construction is simple and convenient, the sectional delay blasting is realized by limiting the section positions of detonators for blasting in each blasthole and a blasting network, and the upper blasting area positioned in the upper step is a blasting area which is detonated in a delayed manner after the blastholes in the middle blasting area are detonated, so that the upper blasting area in the upper step is a pressure blasting area, and 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 a tunnel face and a 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. 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.
4. For the front side tunnel section with good surrounding rock conditions, the conventional drilling and blasting method is adopted for rapid construction, so that the construction period can be effectively ensured, and the tunnel construction progress is accelerated. And in order to reduce the damage to the loess stratum on the tunnel face in the blasting excavation process, the three-step synchronous excavation method is adopted for excavation construction.
5. The adopted reinforced primary support structure has reasonable design, simple and convenient construction and good use effect, and the reinforced primary support structure of the front side tunnel section and the middle tunnel section is reinforced by the reinforcing sleeve arch to form the reinforced primary support structure, so that the primary support effect of the tunnel can be effectively realized, and the primary support deformation of the 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.
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 advance support structure for advance support of the tunnel arch of the constructed tunnel and the reinforced primary support structure for full-section support of the tunnel effectively control the deformation of the large-section tunnel, and can effectively improve the stability of the earth-rock boundary tunnel.
11. The radial grouting reinforcement structures adopted in the rear tunnel section and the rear end tunnel section are reasonable in design, simple and convenient to construct and good in using 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, the rear tunnel section and the middle tunnel section adopt a three-step synchronous excavation mode and are subjected to partition blasting, and the stability of the excavated molded tunnel is ensured; 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. And the front side tunnel section adopts a conventional three-step synchronous excavation method to carry out excavation construction, so that the construction is simple, convenient and quick, and the construction process is safe and reliable.
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 the IV or V-level surrounding rock large-section tunnel can be effectively accelerated, and the safety and the reliability of the construction process can be ensured.
14. 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 constructed tunnel in a staggered mode, the underground water level of the soil-stone boundary stratum where the tunnel is located is reduced to the bottom 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.
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 structural view of a tunnel preliminary bracing structure and a mantle arch in the rear tunnel section and the rear-end tunnel section of the present invention.
Fig. 3 is a schematic longitudinal sectional view of the tunnel supporting structure of the present invention.
FIG. 4 is a schematic view showing the construction state of the wet-jet manipulator in preliminary bracing construction according to the present invention.
Fig. 5 is a cross-sectional structural view of the radial grouting reinforcement structure in the rear tunnel segment and the rear end tunnel segment according to the present invention.
Fig. 6 is a schematic longitudinal section structure view of the rear tunnel section and the radial grouting reinforcement structure in the rear tunnel section according to the present invention.
Fig. 7 is a schematic diagram of the arrangement positions of blastholes on the upper blasting area and the middle blasting area of the middle tunnel segment in the invention.
Fig. 8 is a schematic diagram showing the arrangement positions of blastholes on the lower blasting regions of the middle tunnel section and the rear tunnel section in the present invention.
Fig. 9 is a schematic diagram of the initiation network of the upper and middle blast zones of the middle tunnel segment of the present invention.
Fig. 10 is a schematic plan layout position view of the slitting holes, the peripheral holes and the auxiliary holes in the middle blasting region of the middle tunnel section and the rear side tunnel section in 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 diagram of the arrangement position of an earth-rock interface in the rear end tunnel segment according to the invention.
FIG. 16 is a schematic diagram of the arrangement position of an earth-rock interface in the front-end tunnel segment.
Fig. 17 is a schematic cross-sectional structural view of a preliminary tunnel supporting structure in a front-end tunnel segment according to the present invention.
Fig. 18 is a schematic diagram showing the arrangement positions of blastholes in the upper blasting area and the middle blasting area of the rear tunnel segment according to the 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;
19-arch wall concrete spraying layer; 20-an inverted arch concrete spraying layer;
21-wet spraying mechanical arm; 22-grouting small guide pipe; 26-an isolating layer;
27-inner concrete sprayed layer; 28-radial grouting holes.
Detailed Description
As shown in figure 1, the construction method for pre-reinforcing and excavating the tunnel penetrating through the earth-rock boundary stratum is characterized in that the cross section of the constructed tunnel is more than 100m2The shallow tunnel is positioned in the earth-rock boundary stratum, and the surrounding rock grade of a tunnel hole 1 in the constructed tunnel is IV grade or V grade; 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 hole 1 of the constructed tunnel is divided into an upper hole body 1-1, a middle hole body 1-2 and a lower hole body 1-3 from top to bottom, wherein the upper hole body 1-1 is formed by performing upper step excavation on the constructed tunnel from back to front, the middle hole body 1-2 is formed by performing middle step excavation on the constructed tunnel from back to front, and the lower hole body 1-3 is formed by performing lower step excavation on the constructed tunnel from back to front; an upper tunnel body 1-1 and a middle tunnel body 1-2 in the tunnel hole 1 form an upper tunnel body, and a lower tunnel body 1-2 and a lower tunnel body 1-3 in the tunnel hole 1 form a lower tunnel body;
the constructed tunnel is a linear tunnel and is divided into a rear side tunnel section, a middle tunnel section and a front side tunnel section from back to front, the middle tunnel section is connected between the rear side tunnel section and the front side tunnel section, and the rear side tunnel section, the middle tunnel section and the front side tunnel section are all one tunnel section of the constructed tunnel; the rear side tunnel section and the middle tunnel section are connected to form a rear tunnel section, the length of the rear tunnel section is 70-100 m, the length of the rear side tunnel section is not less than 50m, and the length of the middle tunnel section is not less than 15 m;
the rear side tunnel section is positioned in the rock stratum 4, the tunnel hole 1 of the rear side tunnel section is positioned below the earth-rock interface, and the vertical distance between the top of the excavation contour line of the tunnel hole 1 in the rear side tunnel section and the earth-rock interface positioned above the excavation contour line is less than 5 m; the earth-rock interface in the middle tunnel section is positioned in the upper tunnel body 1-1, and the earth-rock interface in the front tunnel section is positioned in the middle tunnel body 1-2 or the lower tunnel body 1-3;
when the constructed tunnel is constructed, the method comprises the following steps:
firstly, precipitation pre-reinforcement of a rear tunnel section: constructing two rows of precipitation wells 3-2 in the construction area of the rear tunnel section, and synchronously precipitating the construction area of the rear tunnel section through the two rows of precipitation wells 3-2 so as to reduce the underground water level of the construction area of the rear tunnel section to be below the excavation contour line of the tunnel cave 1;
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 rear tunnel 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, excavation construction of a rear side tunnel section: excavating the rear side tunnel section from back to front along the longitudinal extension direction of the tunnel, and obtaining an excavated tunnel hole 1;
step three, excavating and constructing the middle tunnel section: after the excavation of the rear side tunnel section in the step two is finished, excavating the middle tunnel section from back to front along the longitudinal extension direction of the tunnel, and obtaining an excavated tunnel hole 1;
fourthly, excavation construction of the front side tunnel section: after the middle tunnel section is excavated in the third step, excavating the front side tunnel section from back to front along the longitudinal extension direction of the tunnel, obtaining an excavated tunnel hole 1, and finishing the excavation construction process of the constructed tunnel;
in the second step, in the process of excavating the rear side tunnel section from back to front, the tunnel hole 1 formed by excavation is synchronously supported from back to front, and a tunnel primary support structure of the rear side tunnel section is obtained;
in the third step, in the process of excavating the middle tunnel section from back to front, the tunnel hole 1 formed by excavation is synchronously supported from back to front, and a tunnel primary support structure of the middle tunnel section is obtained;
in the fourth step, in the process of excavating the front side tunnel section from back to front, the tunnel hole 1 formed by excavation is synchronously supported from back to front, and a tunnel primary support structure of the front side tunnel section is obtained;
the rear side tunnel section, the middle tunnel section and the front side tunnel section are all three-step synchronous excavation tunnel sections; the rear side tunnel section, the middle tunnel section and the front side tunnel section are divided into a plurality of excavation sections from back to front along the longitudinal extension direction of the tunnel for excavation construction, the excavation construction methods of the excavation sections in the rear side tunnel section are the same, and the excavation construction methods of the excavation sections in the front side tunnel section are the same;
in the second step and in the third step, when the excavation construction is performed on any one of the excavation sections in the rear tunnel section, 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 constructed excavation surface is the excavation surface of the current constructed excavation section in the rear tunnel section;
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 tunnel upper cavern 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;
when the upper tunnel body 1-1 of the current constructed excavation section is excavated from back to front, a slag conveying vehicle is adopted to convey the slag in the upper tunnel body 1-1 from back to front to the outer side of the tunnel portal of the constructed tunnel, so that the excavation construction process of the upper tunnel 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 inner explosion of the middle tunnel body 1-2 to the outer side of the tunnel portal of the constructed tunnel from back to front, and the excavation construction process of the middle tunnel body 1-2 is completed;
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 of the constructed tunnel from back to front, so as to complete the excavation construction process of the lower tunnel body 1-3 and obtain the tunnel portal 1 formed by construction;
the rock stratum 4 in the front side tunnel section and positioned in the lower hole body of the tunnel is a rock stratum to be blasted;
in the fourth step, when the excavation construction is performed on any one of the excavation sections in the front side tunnel section, the process is as follows:
step 401, drilling and blasting construction: carrying out drilling and blasting construction on the rock stratum to be blasted of the currently constructed excavation section in the front side tunnel section;
step 402, excavating an upper cavity: 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;
step 403, 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;
step 404, excavating a lower cavity: and excavating the lower hole body 1-3 of the currently constructed excavation section from back to front along the longitudinal extension direction of the tunnel, finishing the excavation construction process of the excavation section and obtaining the tunnel hole 1 formed by construction.
In the front side tunnel section, the distance between the earth and rock interface and the vault of the tunnel hole 1 and the excavation surface of the upper hole body 1-1 are shorter, so that the blasting excavation process of the rock layer to be blasted has less influence on the vault and the tunnel face of the tunnel, and in order to accelerate the tunnel construction efficiency, in the embodiment, when the drilling and blasting construction is performed on the rock layer to be blasted in the step 401, a full-section blasting method is adopted to perform full-section drilling and blasting construction on the rock layer to be blasted of the currently constructed excavation section. Therefore, when the drilling and blasting construction is performed on the rock stratum to be blasted in step 401, the construction may be performed according to a conventional drilling and blasting method, specifically, a plurality of blast holes are drilled in the rock stratum to be blasted by using drilling equipment, and the plurality of blasts are blasted synchronously. During actual construction, in order to ensure construction safety, the rock stratum to be blasted can also adopt a zone blasting mode.
In this embodiment, the front tunnel segment includes a front tunnel segment and a rear tunnel segment located at the rear side of the front tunnel segment, and the rear tunnel segment is connected between the front tunnel segment and the middle tunnel segment; the earth-rock interface in the front end tunnel section is positioned in the lower cavity 1-3, and the earth-rock interface in the rear end tunnel section is positioned in the middle cavity 1-2.
And in the fourth step, when the front side tunnel section is excavated from back to front, the rear end tunnel section is excavated from back to front, and then the front end tunnel section is excavated from back to front. When the rear end tunnel segment and the front end tunnel segment are actually excavated, the excavation sections of any one of the rear end tunnel segment and the front end tunnel segment are respectively constructed according to the methods in the steps 401 to 403.
In this embodiment, in step 303, when the upper cavern body 1-1 of the currently constructed excavation section in the rear tunnel section is excavated from back to front, the cavern slag is ballast stone generated after the inner explosion of the upper cavern body 1-1;
in the step 303, when the upper cave body 1-1 of the currently constructed excavation section in the middle tunnel section is excavated from back to front, the cave residues comprise the slag generated after the inner explosion of the upper cave body 1-1 and the loess and soil residues formed after the inner excavation of the upper cave body 1-1;
in the step 303, when the upper hole body 1-1 of the currently constructed excavation section in the middle tunnel section is excavated from back to front, the loess stratum 3 in the upper hole body 1-1 is excavated from back to front; and in the process of excavating the loess stratum 3 in the upper cave body 1-1 from back to front, a slag conveying vehicle is adopted to convey the cave slag in the upper cave body 1-1 from back to front to the outer side of the tunnel opening of the constructed tunnel, so that the excavation construction process of the upper cave body 1-1 is completed.
In this embodiment, in step 303, when the upper cavity 1-1 of the currently constructed excavation section in the middle tunnel segment is excavated from back to front, the loess stratum 3 in the upper cavity 1-1 is excavated from back to front by using the excavator.
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 above, when the front side tunnel section is excavated, only the rock stratum 4 in the tunnel cave 1 needs to be blasted and excavated, and the loess stratum 3 in the tunnel cave 1 is excavated by adopting 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.
The top of the excavation contour line of the tunnel cave 1 refers to the vault of the excavation contour line of the tunnel cave 1 (namely the top of the tunnel excavation section of the constructed tunnel), and correspondingly, the bottom of the excavation contour line of the tunnel cave 1 refers to the bottom of the excavation contour line of the constructed tunnel. In this embodiment, the shallow tunnel refers to a tunnel buried depth of less than 50m, and the tunnel buried depth refers to a vertical distance from the top of an excavation section of the tunnel to a natural ground (i.e., a ground surface). Wherein the tunnel burial depth of the constructed tunnel is less than 50 m. Thus, the tunnel burial depths of the rear side tunnel segment, the middle tunnel segment and the front side tunnel segment are all less than 50 m.
In this embodiment, when the upper cavity 1-1 of the currently constructed excavation section in the front side tunnel segment is excavated from back to front in step 402, the loess stratum 3 in the upper cavity 1-1 is excavated from back to front by using the excavator, and the ballast (specifically, loess and soil slag) in the upper cavity 1-1 is transported to the outer side of the tunnel opening of the constructed tunnel by using the ballast transporting vehicle, so as to complete the excavation construction process of the upper cavity 1-1.
In the step 403, when the middle hole body 1-2 of the currently constructed excavation section in the rear end tunnel section is excavated from back to front, the loess stratum 3 in the middle hole body 1-2 is excavated from back to front; in the process of excavating the loess stratum 3 in the middle tunnel body 1-2 from back to front by adopting the excavator, the dregs (including loess dregs and broken stones generated after blasting) in the middle tunnel body 1-2 are conveyed to the outer side of the tunnel opening of the constructed tunnel from back to front by adopting a dregs conveying vehicle, and the excavation construction process of the middle tunnel body 1-2 is completed.
In step 403, when the middle tunnel body 1-2 of the currently constructed excavation section in the front end tunnel segment is excavated from back to front, the loess stratum 3 in the middle tunnel body 1-2 is excavated from back to front by using an excavator, and the ballast (specifically, loess and soil slag) in the middle tunnel body 1-2 is transported to the outer side of the tunnel opening of the constructed tunnel by using a ballast transporting vehicle, so that the excavation construction process of the middle tunnel body 1-2 is completed.
In step 404, when the lower tunnel body 1-3 of the currently constructed excavation section in the rear-end tunnel section is excavated from back to front, the slag transport vehicle is used to transport the slag (specifically, the slag stone generated after blasting) in the lower tunnel body 1-3 from back to front to the outer side of the tunnel portal of the constructed tunnel, so as to complete the excavation construction process of the lower tunnel body 1-3.
In the step 404, when the lower hole body 1-3 of the currently constructed excavation section in the front end tunnel section is excavated from back to front, the loess stratum 3 in the lower hole body 1-3 is excavated from back to front by adopting an excavator; in the process of excavating the loess stratum 3 in the lower cave body 1-3 from back to front by adopting an excavator, the cave residues (comprising the loess soil residues and the slag stones generated after the blasting) in the lower cave body 1-3 are conveyed to the outer side of the tunnel opening of the constructed tunnel from back to front by adopting a slag conveying vehicle, and the excavation construction process of the lower cave body 1-3 is completed.
In this embodiment, after the measurement and setting out are performed in step 301, detailed layout positions of blastholes formed on the excavation surfaces of the upper hole body 1-1 and the middle hole body 1-2 in the middle tunnel section are shown in fig. 7; in addition, after the measurement and setting-out are performed in step 301, the arrangement positions of the blastholes arranged on the excavation surfaces of the upper hole body 1-1 and the middle hole body 1-2 in the rear side tunnel section are shown in detail in fig. 18.
As shown in fig. 7, blastholes formed in the upper cavern 1-1 in the middle tunnel section are all located below the earth-rock interface. As shown in fig. 18, the number of blastholes opened on the excavation surface of the middle hole body 1-2 in the rear tunnel section and the arrangement positions of the blastholes are the same as the number of blastholes opened on the excavation surface of the middle hole body 1-2 in the middle tunnel section and the arrangement positions of the blastholes. Compared with the blastholes arranged in the upper hole body 1-1 in the middle tunnel section, the blastholes arranged in the upper hole body 1-1 in the middle tunnel section are different only in that: because the earth-rock interface in the rear side tunnel section is positioned above the tunnel cave 1, a plurality of peripheral eyes 1-5 are arranged on the arch part of the upper cave body 1-1 in the rear side tunnel section, and the number of the peripheral eyes 1-5 in the upper cave body 1-1 in the rear side tunnel section is larger.
In this embodiment, the constructed tunnels are horizontally arranged.
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 means that the surrounding rock level of the rock stratum 4 on the peripheral side of the tunnel cave 1 is an iv level or a v level.
The underground water at the earth-rock interface in the construction area of the constructed tunnel is rich, the constructed tunnel is positioned below the loess valley, the earth surface has water all the year round, the underground water level is higher according to the field exploration hole, and the underground water level is usually 2.0m below the earth surface; the rock mass of the rock stratum 4 at the earth-rock interface is more broken and has a block-shaped mosaic structure, the fracture water of the underground rock stratum develops, and the loess pore water is saturated. Although the region of the rear side tunnel section is located below the earth-rock interface, the region of the rear side tunnel section is close to the earth-rock interface, and the surrounding rock condition of the rear side tunnel section is poor; and the earth-rock interface in the middle tunnel section is positioned in the upper tunnel body 1-1, so that the surrounding rock condition of the front side tunnel section is worse. The earth-rock interface in the front side tunnel section is positioned in the middle tunnel body 1-2 or the lower tunnel body 1-3, so that the surrounding rock condition of the front side tunnel section is poor, but the excavation difficulty is relatively low because the earth-rock interface in the front side tunnel section is far away from the tunnel vault and the excavation surface of the upper tunnel body 1-1; particularly, the earth-rock interface in the front end tunnel section is positioned in the lower cavity body 1-3, so that the influence of the blasting excavation process on the stability of the tunnel structure is very small.
In actual construction, the excavation height of the tunnel hole 1 is 11m to 15m, and the excavation width D1 of the tunnel hole 1 is 10m to 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.
With reference to fig. 7 and 17, the blasting excavation surface of the upper cavern 1-1 in the rear tunnel segment is an upper blasting area, the upper blasting area is located below the earth-rock interface, and the upper blasting area is an excavation surface of the rock stratum 4 in the upper cavern 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.
The cut holes 1-4, the peripheral holes 1-5 and the auxiliary holes 1-6 in the rear tunnel section are all cylindrical drill holes drilled into the rock layer 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, 9, and 18, in this embodiment, in step 301, the two groups of blasting detonators for inner slotted hole blasting have 1 section, the group of blasting detonators for outer slotted hole blasting close to the right blasting area 1-23 have 3 sections, and the group of blasting detonators for outer slotted hole blasting close to the left blasting area 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.
From the above, when drilling and blasting construction is performed on any one of the excavation sections in the rear tunnel section, the left blasting area 1-21 and the right blasting area 1-23 are both auxiliary areas, and the left upper blasting area 1-11 and the right upper blasting area 1-12 are both 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
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 the embodiment, because the rear side tunnel section is close to the earth-rock interface, the surrounding rock condition of the rear side tunnel section is poor, and collapse of the arch part and the tunnel face of the tunnel hole 1 is easy to occur in the tunnel excavation construction process; the earth-rock interface in the middle tunnel section is positioned in the upper tunnel body 1-1, and the surrounding rock condition of the front side tunnel section is worse, so that the middle tunnel section and the rear side tunnel section are excavated by adopting a three-step synchronous excavation method, and the section position and the initiation network of the blasting cap for blasting in each blast hole are limited to realize subarea time-delay blasting, so that the upper blasting area in the upper step is a blasting area of time-delay initiation after blast hole initiation in the middle 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 a tunnel face and an arch crown is further reduced; the middle blasting area 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, the middle blasting area 1-22 is a slotted area, slotted holes are changed from traditional 8 holes to 10 holes in the middle blasting area 1-22, and the total explosive loading of the traditional slotted 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 1-22 are detonated first and then, the left explosion area 1-21 and the right explosion area 1-23 are auxiliary areas, and the two areas are detonated first and then, so that the vibration generated in the blasting process can be further reduced by adopting an asymmetric detonating mode in the middle explosion area 1-22, the left explosion area 1-21 and the right explosion area 1-23.
In this embodiment, the primary tunnel supporting structure of the rear tunnel section, the primary tunnel supporting structure of the middle tunnel section, and the primary tunnel supporting structure of the front tunnel section have the same structure, and all of the structures are the primary tunnel supporting structures of the tunnel cave 1;
as shown in fig. 2, 3 and 17, 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.
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, 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 by a wet injection robot 21, as shown in detail in fig. 4.
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 step 402, after the excavation of the upper hole body 1-1 of the currently constructed excavation section is finished, an upper arch frame 2-1 is installed in the excavated and formed upper hole body 1-1 from back to front; simultaneously, in step 403, excavating the middle hole body 1-2 of the currently constructed excavation segment from back to front;
in the step 403, 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 entering step 404, excavating the lower cavity 1-3 of the currently constructed excavation section from back to front;
after the excavation of the lower hole 1-3 of the currently constructed excavation section is finished in the step 404, respectively installing lower side brackets 6 on the left side and the right side of the excavated and formed lower hole 1-3 from back to front, and fixedly connecting each lower side bracket 6 with a middle side bracket 5 positioned above the lower side bracket 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.
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 and the step 402, 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 in the step 304 and the step 403 is finished, 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, and fixedly connecting the hung middle reinforcing mesh sheets with the installed middle side brackets 5, and simultaneously fixedly 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 completed in the step 305 and the step 404, 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 fixedly connecting the hung lower reinforcing mesh sheets with the installed lower side brackets 6, and simultaneously fixedly connecting the hung lower reinforcing mesh sheets 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.
With reference to fig. 2 and 17, in this embodiment, 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 frame are well welded firmly.
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.
Because the constructed tunnel is excavated by a step method, in the process of excavating the constructed tunnel, 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 and before the drilling and blasting construction in step 401, 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, 3 and 17, the tunnel advance support structure comprises a plurality of small forepoling 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 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 constructed tunnel.
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 this embodiment, in order to further ensure tunnel stability, adopt reinforcing cover to encircle as temporary reinforcement measure, because rear portion tunnel section with the country rock situation of rear end tunnel section is relatively poor and the construction degree of difficulty is great, rear portion tunnel section with rear end tunnel section the inboard equipartition of tunnel primary support structure is equipped with reinforcing cover and encircles.
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; every shaped steel bow member 11 all includes one and carries out the arch wall shaped steel support 11-1 that struts to the arch wall of tunnel cave 1 and one and carries out the inverted arch shaped steel support 11-2 that supports to tunnel cave 1 bottom, inverted arch shaped steel support 11-2 is located arch wall shaped steel support 11-1 under and both are the arch support, the left end of inverted arch shaped steel support 11-2 and the left end bottom of arch wall shaped steel support 11-1 are fastened and connected, the right-hand member of inverted arch shaped steel support 11-2 and the right-hand member bottom fastened and connected of arch wall shaped steel support 11-1.
Constructing the reinforcing 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 in the excavation process of the lower hole body 1-3 from back to front in the step 304 and the excavation process of the lower hole body 1-3 of the rear-end tunnel section from back to front in the step 403, and obtaining the construction-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 pieces of the steel arches 11 of the currently constructed arch sheathing unit in the primary support section to be reinforced from back to front, enabling each piece of the steel arch 11 to be supported at the inner side of the isolation layer 26 in the step D1, and enabling the isolation layer 26 in the step D1 to be padded between the installed M pieces of the 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. In this way, the supporting effects of the 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 of the M steel arches 11 can be adjusted 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 tunnel sections which are adjacent to the large deformation section and are communicated with each other in the constructed tunnel, 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 tunnel primary support structure in the rear tunnel section and the rear end tunnel section, the deformation of the tunnel primary support is effectively controlled, and the safety of construction in the tunnel can be ensured. However, because the surrounding rock of the rear tunnel section and the rear end tunnel section is poor, the problem of the ability of primary support in the rear tunnel section and the rear end tunnel section to resist the deformation of the surrounding rock is permanently solved, radial grouting reinforcement structures are arranged on the outer sides of the primary support sections to be reinforced in the rear tunnel section and the rear end tunnel section, and the radial grouting reinforcement structures are located on the outer sides of the tunnel upper hole bodies of the rear tunnel section and the rear end tunnel section.
And in the front-end tunnel section, because the earth-rock interface is positioned in the lower hole body 1-1, the deformation, horizontal convergence, vault settlement and the like of the tunnel are not greatly influenced, so that radial grouting reinforcement construction is not needed, a reinforcing sleeve arch is not needed, labor and time are saved, and the construction cost is saved.
In this embodiment, in the excavation construction process of the rear tunnel section in the second step, the excavation construction process of the middle tunnel section in the third step, and the excavation construction process of the rear tunnel section in the fourth step, after concrete spraying is performed in step D4, radial grouting reinforcement is further performed on the arch wall of the primary support section to be reinforced in step D1, and the radial grouting reinforcement structure is obtained, so that the radial grouting reinforcement structures in the rear tunnel section and the rear tunnel section are all fastened and connected with the inner concrete spraying layer 27 in the primary support section to be reinforced into a whole, the outer soil body of the reinforced primary support structure is reinforced, and deformation of the reinforced primary support structure in the rear tunnel section and the rear tunnel section is further controlled from the source. And adopting radial grouting to carry out grouting reinforcement and reinforcement on surrounding rocks outside the primary support structure in the rear tunnel section and the rear end tunnel section, so that the stability and the bearing capacity of the primary support back rock stratum are improved, and the purpose of preventing the surrounding rocks from continuously deforming is achieved.
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 in the excavation construction process of the rear side tunnel section, the excavation construction process of the middle tunnel section in the third step and the excavation construction process of the rear end tunnel section in the fourth step, when the arch wall of the primary support section to be reinforced in the step D1 is subjected to radial grouting reinforcement, grouting reinforcement is respectively carried out through a plurality of rows of radial grouting holes 28 from back to front.
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.
Correspondingly, in the excavation construction process of the rear side tunnel section in the step two, in the excavation construction process of the middle tunnel section in the step three and in the excavation construction process of the rear end tunnel section in the step four, in the radial grouting reinforcement process of the arch wall of the primary support section to be reinforced in the step D1, arch changing needs to be carried out on the arch-needing section needing arch changing in the rear tunnel section and the rear end tunnel section; the rear tunnel section and the rear end tunnel section are both tunnel sections needing arch change;
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 tunnel section needing arch replacement, and the two extension sections are tunnel sections which are adjacent to and communicated with the limit invasion section in the tunnel section needing arch replacement; 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, in the tunnel section needing to be changed 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.
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.
When the rear side tunnel section, the middle tunnel section or the front side tunnel section is excavated, specifically, during the excavation of the lower hole body 1-3, the excavated and formed lower hole body 1-3 is subjected to primary support in time, and a primary support inverted arch 13 is obtained; 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 backfill soil layer 7 at the bottom of the tunnel is backfilled, the backfill soil layer 7 at the bottom of the tunnel is backfilled by using hole slag (namely, slag stone) 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.
In this embodiment, as shown in fig. 4, tunnel bottom backfill layers 7 are disposed behind the excavation surfaces of the lower caverns 1-3, and the tunnel bottom backfill layers 7 are located in the lower caverns 1-3; 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 the present embodiment, as shown in fig. 3 and 4, the wet-spraying robot 21 moves forward through the tunnel bottom backfill layer 7 in multiple times along the longitudinal extension direction of the tunnel, and each forward movement distance 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 order to avoid damage to the wet spraying manipulator 21 in the blasting process and immediately spray concrete after the tunnel 1 is excavated and formed so as to ensure that primary support is quickly carried out, the wet spraying 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 hole body 1-3 of the front side excavated segment is completed, so that the wet spraying manipulator 21 is adopted to timely spray concrete. 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.
Because the lower blasting area is farthest away from the tunnel face of the vault and the upper hole body, the influence of blasting vibration is minimum, and 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 area, 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 bottom of the constructed tunnel, the tunnel primary supporting structure comprises two adjacent front and back trusses, the tunnel inverted arch supports 2 are fastened and connected through a plurality of longitudinal connecting pieces arranged from left to right, and the longitudinal connecting pieces are horizontally arranged and arranged along the contour lines of the tunnel inverted arch supports.
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 soil and stone 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 fracture water of the underground rock stratum develops, the loess pores are saturated with water, and the underground water at the position of the soil and stone interface is rich. The region of the rear tunnel section is close to the earth-rock interface, and the earth-rock interface in the middle tunnel section is positioned in the upper tunnel body 1-1, so that the ground water level in the rear tunnel section is higher.
When the rear tunnel section is actually excavated, the vault collapse occurs during tunnel excavation because underground water softens rock and soil and underground water is stored in horizontal rock stratum cracks and soil-stone interfaces, and the construction progress is seriously restricted. Therefore, how to solve the problem of underground water stored in the diversion and dumping rock interface and the horizontal rock stratum joint crack, eliminating the 'suspension' rock-soil effect of the underground water and achieving the purpose of consolidating the rock-soil and increasing the self stability of the rock-soil is the key point for preventing the collapse of tunnel excavation or controlling the deformation in the construction process of the rear tunnel section. Therefore, in this embodiment, before the excavation of the constructed tunnel, precipitation pre-reinforcement is performed on the construction area where the rear tunnel section is located according to the method described 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 the cross section of one tunnel of the constructed tunnel, the cross section of the tunnel where each dewatering well 3-2 is positioned is a tunnel dewatering surface, and the distance between the front and the back adjacent tunnel dewatering surfaces on the constructed tunnel is d; the distance between the two rows of precipitation wells 3-2 and the middle line of the constructed tunnel 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 constructed tunnel;
the well bores 3-5 of the dewatering wells 3-2 are vertically arranged, the hole bottoms of the dewatering wells are positioned below the constructed tunnel, the vertical distance between the hole bottoms of the well bores 3-5 and the bottom of the excavation contour line of the constructed tunnel 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 phi 500 mm-phi 600 mm.
The bottom of the excavation contour line of the constructed tunnel refers to the bottom of the excavation section of the constructed tunnel, and the top of the excavation contour line of the constructed tunnel refers to the vault of the excavation contour line of the constructed tunnel (namely the top of the excavation section of the constructed tunnel). The buried depth of the constructed tunnel refers to a vertical distance from the top of an excavated section of the tunnel to a natural ground (i.e., the earth's surface).
The height of the sedimentation pipes 3-6 is 1 m-2 m.
In this embodiment, the excavation width of the constructed tunnel is denoted as D1, where D1 is 12 m. The excavation height of the constructed tunnel is marked as H2, wherein H2 is 12 m. The buried depth of the constructed tunnel is marked as H4, and H4 is 22 m. The vertical distance between the highest groundwater level in the loess formation 3 in the rear side tunnel section and the earth's surface is denoted as H5, and H5 is 15 m. Wherein, the highest ground water level in the loess strata 3 in the rear side tunnel section refers to the ground water level at the highest position of the ground water level in the loess strata 3 above the rear side tunnel section.
In the embodiment, the distance between the two rows of dewatering wells 3-2 is 10m larger than the excavation width of the constructed tunnel. 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 pipe 3-6 and the water filter pipe 3-7 are connected into a whole and are both cement gravel pipes or concrete pipes, the outer diameters of the sedimentation pipe 3-6 and the water filter pipe 3-7 are the same and are both phi 300 mm-phi 400mm, 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 8 m-10 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 8m, 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 packing gravel with the diameter of 5 mm-10 mm.
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 is a rear end precipitation surface, the tunnel precipitation surface positioned at the foremost side of the constructed tunnel is a front end precipitation surface, and the distance between the rear end precipitation surface and the rear end of the constructed tunnel and the distance between the front end precipitation surface and the rear end of the constructed tunnel are both smaller than d.
In this embodiment, the tunnel to be constructed is located in the gully and has a length of 80 m.
In this embodiment, the bore diameter of the well 3-5 is 700mm, the outside diameters of the settling pipe 3-6 and the strainer pipe 3-7 are 400mm, and the wall thicknesses of the settling pipe 3-6 and the strainer pipe are 5 cm. Wherein the inner diameters of the settling tube 3-6 and the strainer 3-7 are both denoted as D, and D is 300mm and 0.3 m.
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 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 formulaCalculating to obtain the minimum number n1 of precipitation wells of the constructed tunnel; in the formulaRepresents 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 tunnelUnit of Q is m3D; k is the permeability coefficient of the soil-rock boundary stratum where the constructed tunnel is located; h is the thickness of a water-bearing stratum of an earth-rock boundary stratum where the constructed tunnel is located, S is the precipitation depth of the constructed tunnel, 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 constructed tunnel is located, and b is D2, wherein the unit of b is m; r is0The equivalent precipitation quoted radius of the cross section of the tunnel cave 1 of the constructed tunnel is m,a is the length of the precipitation area of the earth-rock boundary stratum where the constructed tunnel is located, a is the same as the longitudinal length of the constructed tunnel, eta is a correction coefficient, and eta is 0.13.
Single well water yield of dewatering well 3-2The 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 groundwater level in the loess formation 3 and the bottom end of the lower water filtering section, and S is H0-H3-H5, then S is H0-H3-H5 is 38-2-15 is 21 m; 21m, 22m, 80m, 3.8m, 0.3/2, 0.15m, D/2,wherein the ground water level in the loess formation 3 means the ground water level above the rear side tunnel section.
Water inflow in tunnel
The single well water yield of the dewatering well 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.
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 pre-reinforcement and excavation construction method for penetrating through an earth-rock boundary stratum is characterized by comprising the following steps: the cross section of the constructed tunnel is larger than 100m2The shallow tunnel is positioned in the earth-rock boundary stratum, and the surrounding rock grade of a tunnel hole (1) in the constructed tunnel is IV grade or V grade; 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 hole (1) of the constructed tunnel is divided into an upper hole body (1-1), a middle hole body (1-2) and a lower hole body (1-3) from top to bottom, and the upper hole body (1-1) is used for carrying out upper step opening on the constructed tunnel from back to frontThe middle hole body (1-2) is formed after middle step excavation is carried out on the constructed tunnel from back to front, and the lower hole body (1-3) is formed after lower step excavation is carried out on the constructed tunnel from back to front; the tunnel hole (1) comprises an upper tunnel body (1-1) and a middle tunnel body (1-2) which form an upper tunnel body, and the middle tunnel body (1-2) and the lower tunnel body (1-3) form a lower tunnel body;
the constructed tunnel is a linear tunnel and is divided into a rear side tunnel section, a middle tunnel section and a front side tunnel section from back to front, the middle tunnel section is connected between the rear side tunnel section and the front side tunnel section, and the rear side tunnel section, the middle tunnel section and the front side tunnel section are all one tunnel section of the constructed tunnel; the rear side tunnel section and the middle tunnel section are connected to form a rear tunnel section, the length of the rear tunnel section is 70-100 m, the length of the rear side tunnel section is not less than 50m, and the length of the middle tunnel section is not less than 15 m;
the rear side tunnel section is positioned in the rock stratum (4), the tunnel hole (1) of the rear side tunnel section is positioned below the earth-rock interface, and the vertical distance between the top of the excavation contour line of the tunnel hole (1) in the rear side tunnel section and the earth-rock interface positioned above the excavation contour line is less than 5 m; the earth-rock interface in the middle tunnel section is positioned in the upper tunnel body (1-1), and the earth-rock interface in the front tunnel section is positioned in the middle tunnel body (1-2) or the lower tunnel body (1-3);
when the constructed tunnel is constructed, the method comprises the following steps:
firstly, precipitation pre-reinforcement of a rear tunnel section: two rows of precipitation wells (3-2) are constructed in the construction area of the rear tunnel section, and precipitation is synchronously performed on the construction area of the rear tunnel section through the two rows of precipitation wells (3-2), so that the underground water level of the construction area of the rear tunnel section is reduced to be below the excavation contour line of the tunnel cave (1);
two rows of the dewatering wells (3-2) are respectively arranged at the left side and the right side of the rear tunnel section, each row of the dewatering wells (3-2) comprises a plurality of dewatering wells (3-2) 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 (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, excavation construction of a rear side tunnel section: excavating the rear side tunnel section from back to front along the longitudinal extension direction of the tunnel, and obtaining an excavated tunnel hole (1);
step three, excavating and constructing the middle tunnel section: after the excavation of the rear side tunnel section in the step two is finished, excavating the middle tunnel section from back to front along the longitudinal extension direction of the tunnel, and obtaining an excavated tunnel hole (1);
fourthly, excavation construction of the front side tunnel section: after the middle tunnel section is excavated in the third step, excavating the front side tunnel section from back to front along the longitudinal extension direction of the tunnel, obtaining an excavated tunnel hole (1), and finishing the excavation construction process of the constructed tunnel;
the rear side tunnel section, the middle tunnel section and the front side tunnel section are all three-step synchronous excavation tunnel sections; the rear side tunnel section, the middle tunnel section and the front side tunnel section are divided into a plurality of excavation sections from back to front along the longitudinal extension direction of the tunnel for excavation construction, the excavation construction methods of the excavation sections in the rear side tunnel section are the same, and the excavation construction methods of the excavation sections in the front side tunnel section are the same;
in the second step and in the third step, when the excavation construction is performed on any one of the excavation sections in the rear tunnel section, 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 constructed excavation surface is the excavation surface of the current constructed excavation section in the rear tunnel section;
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 tunnel upper cavern 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 tunnel body (1-1) of the current constructed excavation section is excavated from back to front, a slag conveying vehicle is adopted to convey the slag in the upper tunnel body (1-1) from back to front to the outer side of the tunnel portal of the constructed tunnel, so that the excavation construction process of the upper tunnel 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 slag stones generated after the middle tunnel body (1-2) is implosively broken to the outer side of the tunnel portal of the constructed tunnel from back to front, and 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 of the constructed tunnel from back to front, so that the excavation construction process of the lower tunnel body (1-3) is completed, and the constructed and formed tunnel portal (1) is obtained;
a rock stratum (4) in the front side tunnel section and positioned in the lower hole body of the tunnel is a rock stratum to be blasted;
in the fourth step, when the excavation construction is performed on any one of the excavation sections in the front side tunnel section, the process is as follows:
step 401, drilling and blasting construction: carrying out drilling and blasting construction on the rock stratum to be blasted of the currently constructed excavation section in the front side tunnel section;
step 402, excavating an upper cavity: 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;
step 403, 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;
step 404, excavating a lower cavity: and excavating the lower part cavity body (1-3) of the currently constructed excavation section from back to front along the longitudinal extension direction of the tunnel, finishing the excavation construction process of the excavation section and obtaining the tunnel cavity (1) formed by construction.
2. The tunnel pre-reinforcing and excavation construction method for penetrating through the earth-rock boundary stratum according to claim 1, 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 tunnel pre-reinforcing and excavation construction method for penetrating through the earth-rock boundary stratum 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 tunnel pre-reinforcing and excavation construction method for penetrating through the earth-rock boundary stratum according to claim 1 or 2, characterized by comprising the following steps: when drilling and blasting construction is carried out on the rock stratum to be blasted in the step 401, full-face blasting construction is carried out on the rock stratum to be blasted of the currently constructed excavation section by adopting a full-face blasting method.
5. The tunnel pre-reinforcing and excavation construction method for penetrating through the earth-rock boundary stratum according to claim 1 or 2, characterized by comprising the following steps: the primary tunnel supporting structure of the rear side tunnel section, the primary tunnel supporting structure of the middle tunnel section and the primary tunnel supporting structure of the front side tunnel section are identical in structure and are the primary tunnel supporting structures of tunnel holes (1);
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);
the length of each excavation section is 2L;
in the second step, in the process of excavating the rear side tunnel section from back to front, the initial support is synchronously carried out on the tunnel hole (1) formed by excavation from back to front, and the initial tunnel support structure of the rear side tunnel section is obtained;
in the third step, in the process of excavating the middle tunnel section from back to front, the initial support is synchronously carried out on the tunnel hole (1) formed by excavation from back to front, and the initial tunnel support structure of the middle tunnel section is obtained;
and in the fourth step, in the process of excavating the front side tunnel section from back to front, the initial support is synchronously carried out on the tunnel hole (1) formed by excavation from back to front, and the initial tunnel support structure of the front side tunnel section is obtained.
6. The tunnel pre-reinforcing and excavation construction method for penetrating through the earth-rock boundary stratum according to claim 5, characterized in that: 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.
7. The tunnel pre-reinforcing and excavation construction method for penetrating through the earth-rock boundary stratum according to claim 5, characterized in that: after the excavation of the upper hole body (1-1) of the currently constructed excavation section is finished in the step 402, installing an upper arch frame (2-1) in the excavated and formed upper hole body (1-1) from back to front; simultaneously, in step 403, excavating the middle hole body (1-2) of the currently constructed excavation segment from back to front;
in the step 403, 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 entering step 404, excavating the lower cavity body (1-3) of the currently constructed excavation section 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 404, 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.
8. The tunnel pre-reinforcing and excavation construction method for penetrating through the earth-rock boundary stratum according to claim 5, characterized in that: the front side tunnel section comprises a front end tunnel section and a rear end tunnel section positioned at the rear side of the front end tunnel section, and the rear end tunnel section is connected between the front end tunnel section and the middle tunnel section; the earth-rock interface in the front end tunnel section is positioned in the lower cavity body (1-3), and the earth-rock interface in the rear end tunnel section is positioned in the middle cavity body (1-2);
when the front side tunnel section is excavated from back to front in the fourth step, the rear end tunnel section is excavated from back to front, and then the front end tunnel section is excavated from back to front;
reinforcing sleeve arches are uniformly distributed on the inner sides of the tunnel primary supporting structures of the rear tunnel section and the rear end tunnel section;
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);
constructing the reinforcing 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 in the excavation process of the lower hole body (1-3) from back to front in step 304 and the excavation process of the lower hole body (1-3) of the rear-end tunnel section from back to front in step 403, and obtaining the 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 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, enabling each steel arch (11) to be supported on the inner side of the isolation layer (26) in the step D1, and 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 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.
9. The method for pre-reinforcing and excavating a tunnel penetrating through an earth-rock boundary stratum according to claim 8, which is characterized in that: radial grouting reinforcement structures are arranged on the outer sides of the primary support sections to be reinforced in the rear tunnel section and the rear end tunnel section, and are positioned on the outer sides of the tunnel upper hole bodies of the rear tunnel section and the rear end tunnel section;
in the excavation construction process of the rear side tunnel section, in the excavation construction process of the middle tunnel section in the step three and in the excavation construction process of the rear end tunnel section in the step four, after concrete spraying is carried out in the step D4, radial grouting reinforcement is further carried out on the arch wall of the primary support section to be reinforced in the step D1, and the radial grouting reinforcement structure is obtained;
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 in the excavation construction process of the rear side tunnel section, the excavation construction process of the middle tunnel section in the step three and the excavation construction process of the rear end tunnel section in the step four, when the arch wall of the primary support section to be reinforced in the step D1 is reinforced by radial grouting, the arch wall is reinforced by grouting backwards and forwards through a plurality of rows of radial grouting holes (28).
10. The method for pre-reinforcing and excavating a tunnel penetrating through an earth-rock boundary stratum according to claim 9, which is characterized in that: in the excavation construction process of the rear side tunnel section, in the excavation construction process of the middle tunnel section in the step three and in the excavation construction process of the rear end tunnel section in the step four, 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 also needed to be carried out on the arch-needing changing section of the rear tunnel section and the rear end tunnel section; the rear tunnel section and the rear end tunnel section are both tunnel sections needing arch change;
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 tunnel section needing arch replacement, and the two extension sections are tunnel sections which are adjacent to and communicated with the limit invasion section in the tunnel section needing arch replacement; 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, in the tunnel section needing to be changed 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.
CN201911138650.1A 2019-11-20 2019-11-20 Tunnel pre-reinforcing and excavating construction method for penetrating through earth-rock boundary stratum Active CN110778318B (en)

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