CN110863832A - Large-section tunnel stability control construction method for penetrating through earth-rock boundary stratum - Google Patents

Large-section tunnel stability control construction method for penetrating through earth-rock boundary stratum Download PDF

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Publication number
CN110863832A
CN110863832A CN201911118119.8A CN201911118119A CN110863832A CN 110863832 A CN110863832 A CN 110863832A CN 201911118119 A CN201911118119 A CN 201911118119A CN 110863832 A CN110863832 A CN 110863832A
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tunnel
arch
section
excavation
blasting
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CN110863832B (en
Inventor
任少强
谢江胜
刘之涛
马传明
张会安
王森
葛亮亮
曹运祥
王建军
高王峰
申运涛
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China Railway 20th Bureau Group Corp
China Railway Group Ltd CREC
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China Railway Group Ltd CREC
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/003—Linings or provisions thereon, specially adapted for traffic tunnels, e.g. with built-in cleaning devices
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/04—Lining with building materials
    • E21D11/10—Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/14—Lining predominantly with metal
    • E21D11/18—Arch members ; Network made of arch members ; Ring elements; Polygon elements; Polygon elements inside arches
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
    • E21D9/006—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries by making use of blasting methods
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F42—AMMUNITION; BLASTING
    • F42D—BLASTING
    • F42D3/00—Particular applications of blasting techniques
    • F42D3/04—Particular applications of blasting techniques for rock blasting

Abstract

The invention discloses a construction method for controlling the stability of a large-section tunnel penetrating through an earth-rock boundary stratum, wherein an earth-rock interface is positioned in an upper hole body of the constructed tunnel; when the excavation construction is carried out on the constructed tunnel, the method comprises the following steps: firstly, excavating and constructing an upper middle step: carrying out upper-middle step excavation construction on the constructed tunnel by dividing the tunnel into a plurality of excavation sections from back to front; when any excavation segment is subjected to upper and middle step excavation construction, the process is as follows: measuring and setting out, drilling and blasting construction, upper cavity excavation and middle cavity excavation; and secondly, excavating and constructing the lower step. The invention has reasonable design, simple and convenient construction and good use effect, respectively divides the upper blasting area in the upper step and the middle blasting area on the middle step, limits the arrangement position of each blast hole in each blasting area, can effectively prevent the tunnel face collapse or vault collapse caused by large vibration generated by blasting when the once explosive loading of the large section is excessive, ensures the safety and reliability of the tunnel excavation process and can ensure the stable tunnel structure.

Description

Large-section tunnel stability control 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 stability control construction method for a large-section tunnel 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.
A large amount of traffic infrastructure is built in northwest areas of China, so that more and more tunnel projects penetrate through loess strata. 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; third, the expansive soil expands when meeting waterThe expansion causes deformation and cracking of the primary support, and the deformation structure of the primary support arch frame is damaged to lose the supporting 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 technical problem to be solved by the invention is to provide a construction method for controlling the stability of a large-section tunnel penetrating through an earth-rock boundary stratum, which has the advantages of reasonable design, simple and convenient construction and good use effect, wherein an upper blasting area in an upper step and a middle blasting area on a middle step are respectively divided, and the arrangement positions of blastholes in the blasting areas are limited, so that the tunnel face collapse or vault collapse caused by large vibration generated by blasting when the large-section loading is too much at one time can be effectively prevented, the safety and reliability of the tunnel excavation process can be ensured, and the stable structure of the tunnel can be ensured.
In order to solve the technical problems, the invention adopts the technical scheme that: pass through earth and stone boundaryThe stability control construction method of the large-section tunnel of the stratum is characterized by comprising the following steps of: the cross section of the constructed tunnel is more than 100m2The constructed tunnel is positioned in a soil-rock boundary stratum, the soil-rock boundary stratum comprises a loess stratum and a rock stratum positioned 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, the lower hole body is formed after the lower step excavation is carried out on the constructed tunnel from back to front, the earth and stone interface is positioned in the upper hole body, and the upper hole body and the middle hole body form an upper tunnel hole body;
when the construction tunnel is excavated, the method comprises the following steps:
step one, excavating construction on an upper middle step: carrying out upper and middle step excavation construction on the constructed tunnel by dividing the tunnel into a plurality of excavation sections from back to front along the longitudinal extension direction of the tunnel, wherein the upper and middle step excavation construction methods of all the excavation sections are the same;
when any excavation segment of the constructed tunnel is subjected to upper and middle step excavation construction, the process is as follows:
step J1, measuring and setting out: measuring and paying off the excavation contour lines of the upper hole body and the middle hole body in the current constructed excavation section on the excavation surface of the upper hole body of the tunnel, and measuring and paying off the number of the blastholes to be arranged on the excavation surface of the upper hole body and the middle hole body in the current constructed excavation section and the arrangement positions of the blastholes;
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 upper cutting hole, the peripheral hole and the auxiliary hole of the excavation surface of the tunnel upper hole body are blast holes;
step J2, drilling and blasting construction: according to the arrangement positions of the blastholes obtained by measuring and setting out in the step J1, drilling all the blastholes on the excavation face of the tunnel upper hole body in the current construction excavation section by adopting drilling equipment, respectively charging the blastholes formed in the drilling, and detonating to blast after charging is finished;
step J3, 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;
excavating the loess stratum in the upper cavity from back to front when the upper cavity of the currently constructed excavation segment is excavated from back to front; in the process of excavating the loess stratum in the upper cave from back to front, a ballast conveying vehicle is adopted to convey the crushed stones generated after the inner explosion of the upper cave to the outer side of the tunnel portal of the constructed tunnel from back to front so as to finish the excavating construction process of the upper cave;
step J4, 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;
in this step, the excavation surface of the middle hole body is located at the rear side of the excavation surface of the upper hole body in the step J3;
step J5, excavating construction of the next excavation segment: performing excavation construction on the next excavation section according to the method in the steps J1 to J4;
step two, excavating and constructing the lower step: in the first step excavation construction process, excavating a lower hole body from back to front by adopting a drilling and blasting method;
in this step, the excavation surface of the lower cavity is located behind the excavation surface of the middle cavity in step J4.
The construction method for controlling the stability of the large-section tunnel penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: in step J1, each group of the inner slitting holes comprises two slitting holes, and each group of the outer slitting holes comprises three slitting 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 3 or 4 auxiliary eyes.
The construction method for controlling the stability of the large-section tunnel penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: in the step J1, the section positions of the 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 are 3 sections, and the section positions of one group of detonators for the outer undermining eye blasting close to a left blasting area are 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;
and 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 construction method for controlling the stability of the large-section tunnel penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: the two rows of auxiliary holes in the left upper explosion area and the right upper explosion area are respectively an upper row of auxiliary holes and a lower row of auxiliary holes;
the section positions of the blasting detonators for the auxiliary holes in the lower row of the auxiliary holes in the upper left blasting area are all 3 sections, and the section positions of the blasting detonators for the auxiliary holes in the lower row of the auxiliary holes in the upper right blasting area are all 3 sections;
one auxiliary eye positioned at the leftmost side in the upper row of auxiliary eyes on the upper left blasting area is an upper left auxiliary eye, and the section positions of all auxiliary-eye blasting detonators except the upper left auxiliary eye in the upper row of auxiliary eyes on the upper left blasting area are 5 sections;
one auxiliary eye positioned on the rightmost side in the upper row of auxiliary eyes on the right upper explosion area is a right upper auxiliary eye, and the section positions of all auxiliary-eye blasting detonators except the right upper auxiliary eye in the upper row of auxiliary eyes on the right upper explosion area 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.
The construction method for controlling the stability of the large-section tunnel penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: 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 construction method for controlling the stability of the large-section tunnel penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: in the step J3, excavating the loess stratum in the upper cavity from back to front by adopting an 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 internal loess stratum in upper portion hole, will again the scarifier is demolishd and is adopted the excavator excavates the internal loess stratum in upper portion hole.
The construction method for controlling the stability of the large-section tunnel penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: 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;
in the step J3, in the process of excavating the upper cavity of the currently constructed excavation section from back to front, the arch part of the upper cavity formed by excavation is subjected to net spraying support from back to front, and meanwhile, an upper arch frame is installed in the upper cavity formed by excavation from back to front, so that the excavation and primary support construction processes of the upper cavity are completed;
in the step J4, in the process of excavating the middle hole body of the currently constructed excavation section from back to front, the left side and the right side of the excavated and molded middle hole body are respectively supported by net spraying from back to front, and meanwhile, the left side and the right side of the excavated and molded middle hole body are respectively provided with middle side brackets from back to front, and each middle side bracket is fixedly connected with the upper arch frame in the step J3 into a whole, so that the excavation and primary support construction processes of the middle hole body are completed;
the horizontal distance between the excavation surface of the middle hole body in the step J4 and the excavation surface of the upper hole body in the step J3 is 4-6 m;
in the second step, in the process of excavating the lower cavity from back to front, respectively carrying out net spraying support on the left side and the right side of the excavated and molded lower cavity from back to front, and in the process of net spraying support, respectively installing lower side supports on the left side and the right side of the excavated and molded lower cavity from back to front synchronously, and enabling each lower side support to be fixedly connected with the middle side support in the step J4 into a whole; meanwhile, a tunnel inverted arch support is arranged at the bottom of the lower hole body from back to front, and the arranged tunnel inverted arch support is fixedly connected with lower side supports arranged at the left side and the right side of the lower hole body into a whole; in the installation process of the tunnel inverted arch support, synchronously spraying a layer of concrete at the bottom of the tunnel from back to front to form an inverted arch concrete spraying layer, fixing the tunnel inverted arch support in the inverted arch concrete spraying layer, and completing the excavation of a lower part of a tunnel body and the primary support construction process;
in the second step, in the process of excavating the lower hole body from back to front, an excavated tunnel is obtained; respectively carrying out net-spraying support on the left side and the right side of the excavated and molded lower hole body from back to front to obtain the constructed and molded arch wall net-spraying support structure; the arch wall mesh spraying support structure is connected with the inverted arch concrete spraying layer;
and in the second step, the horizontal distance between the excavation surface of the lower cavity and the excavation surface of the middle cavity in the step J4 is 18 m-21 m, and the horizontal distance between the excavation surface of the lower cavity and the excavation surface of the upper cavity in the step J3 is not more than 25 m.
The construction method for controlling the stability of the large-section tunnel penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: a reinforcing sleeve arch is arranged on the inner side of the primary supporting structure of the tunnel;
the tunnel primary supporting structure and the reinforcing sleeve arch are full-section supporting structures for supporting a tunnel hole in a full-section mode, and the tunnel primary supporting structure and the reinforcing sleeve arch positioned on the inner side of the tunnel primary supporting structure form a reinforced primary supporting structure;
the reinforced arch comprises a plurality of arch units, the arch units are identical in structure and are arranged from back to front along the longitudinal extension direction of the tunnel, an isolation layer is arranged between each arch unit and the primary tunnel supporting structure, the isolation layer is a full-section isolation layer formed by non-woven fabrics paved between the arch units and the primary tunnel supporting structure, and the cross section of the isolation layer is identical to that of the tunnel;
each arch sheathing unit comprises M 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 steel arch frames are uniformly arranged, and the distance between two adjacent steel arch frames in the front and the back is 0.8-1.2M; each structural steel arch is a full-section support for full-section supporting of a tunnel hole, M structural steel arches are fixed in the inner side concrete injection layer, the shape of each structural steel arch is the same as the shape of the cross section of the tunnel hole, wherein M is a positive integer and is more than or equal to 4; m steel arch frames in each arch sheathing unit are fixedly connected into a whole through a plurality of longitudinal steel bars, the longitudinal steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal steel bars are arranged along the contour line of the steel arch frames; each structural steel arch comprises an arch wall structural steel support for supporting an arch wall of a tunnel hole and an inverted arch structural steel support for supporting the bottom of the tunnel hole, the inverted arch structural steel support is positioned under the arch wall structural steel support, the arch wall structural steel support and the inverted arch structural steel support are both arch supports, the left end of the inverted arch structural steel support is fixedly connected with the bottom of the left end of the arch wall structural steel support, and the right end of the inverted arch structural steel support is fixedly connected with the bottom of the right end of the arch wall structural steel support;
in the step J4, in the process of excavating the lower cavity from back to front, the reinforcing sleeve arch is constructed on the inner side of the constructed primary tunnel supporting structure from back to front along the longitudinal extension direction of the tunnel, so as to obtain the constructed and shaped 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 in the step one, 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 construction method for controlling the stability of the large-section tunnel penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: d1, connecting the primary support section to be reinforced by a large deformation section and two deformation transition sections respectively positioned at the front side and the rear side of the large deformation section, wherein the large deformation section is a tunnel section of which the vault sinking value of the tunnel hole exceeds 10mm and/or the horizontal convergence value exceeds 5mm within 24 hours after the construction of the primary tunnel support structure is completed, the vault sinking value of the tunnel hole is the absolute sinking value of the vault inner wall of the primary tunnel support structure, and the horizontal convergence value of the tunnel hole is the horizontal convergence value of the inner wall of the primary tunnel support structure at the maximum excavation position of the tunnel hole; 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.
The construction method for controlling the stability of the large-section tunnel penetrating through the earth-rock boundary stratum is characterized by comprising the following steps of: after the concrete is sprayed in the step D4, radial grouting reinforcement is needed to be performed on the arch wall of the primary support section to be reinforced in the step D1, and a radial grouting reinforcement structure is obtained;
the upper hole body and the middle hole body form an upper tunnel body, and the radial grouting reinforcement structure is positioned on the outer side of the upper tunnel body;
the radial grouting reinforcement structure is formed by grouting and reinforcing soil outside the tunnel upper hole body through a plurality of rows of radial grouting holes, the plurality of rows of radial grouting holes are arranged from back to front along the extending direction of the tunnel, each row of radial grouting holes comprises a plurality of radial grouting holes which are arranged on the section of the same tunnel from left to right along the excavation contour line of the tunnel upper hole body, each radial grouting hole is a drill hole which is drilled into the soil from the inside to the outside of the tunnel upper hole body, a plurality of radial grouting holes in each row of radial grouting holes are uniformly arranged, and the radial grouting holes in the front and back adjacent two rows of radial grouting holes are arranged in a staggered manner; the length of the radial grouting hole is not less than 3 m;
each row of radial grouting holes are located between two front and rear adjacent full-section supporting frames, and each row of radial grouting holes are located between two front and rear adjacent profile steel arches;
and D1, when the arch wall of the primary support section to be reinforced is reinforced by radial grouting, the arch wall is reinforced by grouting from back to front through a plurality of rows of radial grouting holes.
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.
2. The invention adopts a partition blasting mode to respectively divide an upper blasting area in the upper step and a middle blasting area on the middle step into blasting areas and limit the arrangement position of each blast hole in each blasting area, thereby effectively preventing the tunnel face collapse or the vault collapse caused by large vibration generated by blasting when the large-section primary explosive loading is excessive and ensuring the safety and reliability of the tunnel excavation process.
3. The upper and middle bench blasting excavation adopts the partition blasting, the blasting area is divided reasonably, the number and the position of blastholes are designed reasonably, the construction is simple and convenient, the partition delay blasting is realized by limiting the section position and the detonation network of the blasting cap in each blasthole, the upper blasting area positioned in the upper bench is the blasting area of delay detonation after the blastholes in the middle blasting area are detonated, so the upper blasting area in the upper bench is the pressure blasting area, the vibration generated in the blasting process of the middle blasting area is suppressed and restrained, and the damage of the vibration generated in the blasting process to the tunnel face and the vault is further reduced; the middle blasting area is divided into a left blasting area, a middle blasting area and a right blasting area from left to right, the middle blasting area is a cut-out area, the cut-out holes are changed from traditional 8 holes to 10 holes in the middle blasting area, and the total explosive loading of the traditional cut-out holes is further reduced and decomposed, so that the vibration generated in the blasting process can be effectively reduced; meanwhile, the outer slotted holes on the left side and the right side in the middle explosion area are detonated first and then, the left explosion area and the right explosion area are auxiliary areas, and the left explosion area and the right explosion area are detonated first and then, so that the middle explosion area, the left explosion area and the right explosion area adopt an asymmetric detonation mode, and the vibration generated in the blasting process can be further reduced.
4. The lower blasting area is farthest away from the arch crown and the tunnel face of the upper hole body, so that the blasting vibration influence is minimum, and the rock and soil generated in the blasting process of the lower blasting area can be suppressed and restrained by the upper blasting area and the rock and soil generated in the middle blasting, so that the vibration generated in the blasting process can be effectively reduced.
5. The reinforced primary support structure has reasonable design, simple and convenient construction and good use effect, the reinforced sleeve arch is adopted to reinforce the primary support structure of the tunnel and form the reinforced primary support structure, the primary support effect of the tunnel can be effectively realized, and the primary support deformation of the deeply-buried loess tunnel is effectively controlled; meanwhile, an isolation layer is arranged between the reinforcing sleeve arch and the primary supporting structure of the tunnel, so that the deformation of the soil body outside the reinforcing sleeve arch can be further controlled; and the reinforcing sleeve arch adopts a plurality of sleeve arch units to reinforce the tunnel primary support structure in a sectional mode, so that the construction is simple and convenient, the reinforced primary support structure formed by construction has certain self-adaptive capacity, the deformation condition of the soil body on the periphery of the tunnel can be effectively adapted, and the deformation resistance of the reinforced primary support structure is effectively reduced.
6. The full-section support frame can support the tunnel hole in a full-section manner, the support is stable and reliable, the full-section support frame is formed by assembling an arch wall support arch frame and a tunnel inverted arch frame, the arch wall support arch frame is formed by assembling an upper arch frame, two middle side supports and two lower side supports, the assembly can be simply and conveniently carried out when the tunnel is actually excavated, the requirement of supporting the section of the tunnel hole in blocks is met, the primary support of the upper hole body is not influenced by the primary support construction in the middle hole body and the lower hole body, the primary support of the middle hole body is not influenced by the primary support construction in the lower hole body, the primary support of the upper hole body and the primary support of the middle hole body are constructed immediately after the excavation is finished, so that the support is timely and stable, the tunnel hole is not completely excavated at the moment, and the support stability of the primary support structure in the upper hole body and the middle hole body of the tunnel is further ensured, and the preliminary bracing process in tunnel upper portion cavern body and the middle part cavern body is changeed in going on, and it is more powerful to strut simultaneously, more is favorable to tunnel construction safety.
7. And the anchoring system is adopted to fix the surrounding rock of the tunnel in a full section manner, so that the primary support stability is further improved. And moreover, the anchoring system and the full-section support frame are connected into a whole, the overall stability is further improved, and meanwhile, the construction is simple and convenient.
8. The advance support adopts advance little pipe slip casting supporting construction, and the construction is simple and convenient and the efficiency of construction is high, can effectively ensure the advance support intensity and the effect of strutting in big section tunnel, can effectively restrict loess tunnel hunch portion deformation. The adopted advanced small conduit grouting supporting structure is reasonable in design, simple and convenient to construct and good in using effect, effectively reinforces the arch part of the tunnel and forms a stable arch wall bearing ring, can effectively improve the self-stabilizing capacity of rock strata on the periphery of a tunnel body, can effectively save construction cost and save construction period, and meanwhile, construction equipment is simple, and the preliminary bracing construction is timely carried out after the tunnel entering construction, and the working procedures are closely linked. Moreover, the disturbance to the soil layers on the peripheral sides in the supporting process is small, the construction cost is low, the problems that the arch part of the tunnel is easy to deform and settle under the influence of horizontal pressure generated after the tunnel is excavated can be effectively solved, and the arch part of the tunnel can be stably supported.
9. The reinforcing cover arch structure that adopts reasonable in design just strengthens tunnel primary support structure sectional type through a plurality of cover arch units, and not only the construction is simple and convenient to form the full section supporting construction of a transition nature between tunnel primary support structure and tunnel secondary lining structure, can warp tunnel primary support structure and effectively cushion and correct, thereby can tunnel hole overall structure more firm, and tunnel deformation control effect is better.
10. The tunnel 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 adopted radial grouting reinforcement structure has reasonable design, simple and convenient construction and good use effect, and can further supplement the combined supporting effect of the reinforced primary support structure; and when the reinforced primary support structure invades the secondary lining of the tunnel and needs to be arched, the stability of the tunnel hole in the arch changing process can be effectively improved, and safety accidents are avoided.
12. The construction is simple and convenient, the use effect is good, and the stability of the excavated molded tunnel is ensured by adopting a three-step excavation mode and carrying out partition blasting; reinforcing the primary tunnel supporting structure by adopting a reinforcing sleeve arch and forming a reinforced primary support structure, so that the primary tunnel supporting effect can be effectively achieved, and the primary supporting deformation of the earth-rock boundary tunnel can be effectively controlled; meanwhile, an isolation layer is arranged between the reinforcing sleeve arch and the primary supporting structure of the tunnel, so that the deformation of the soil body outside the reinforcing sleeve arch can be further controlled; and the reinforcing sleeve arch adopts a plurality of sleeve arch units to reinforce the tunnel primary support structure in a sectional mode, so that the construction is simple and convenient, the reinforced primary support structure formed by construction has certain self-adaptive capacity, the deformation condition of the soil body on the periphery of the tunnel can be effectively adapted, and the deformation resistance of the reinforced primary support structure is effectively reduced. In addition, the full-section support frame structure tunnel is adopted for layered supporting, and an anchoring system is adopted for integrally reinforcing the outer side of the tunnel, so that the structural stability of the large-section tunnel is ensured, and the construction safety is ensured; simultaneously, the excavation in-process carries out the purpose that the concrete sprays through wet blasting manipulator, can effectively accelerate the construction progress to enable the preliminary bracing to seal the cyclization fast, further ensure the tunnel structure steadiness, the construction is simple, and construction speed is fast, and the work progress is safe, reliable. According to the above contents, the adopted supporting method has the characteristics of safety, reliability, high degree of mechanization, high construction speed, low labor intensity, advanced construction period, cost saving and the like through a three-step construction method, and the lower step and the primary support of the inverted arch are constructed simultaneously according to the geological characteristics of soil and stones in the loess stratum, so that the short time of sealing and looping can be ensured, the overlarge deformation of surrounding rocks can be prevented, and the construction safety can be ensured; in addition, the construction method is simplified, the interference among all the procedures is prevented, the mechanized construction can be met to the maximum extent, the labor intensity is reduced, the space full-section flow construction is adopted, the construction efficiency can be improved, and the engineering cost is reduced. In addition, the temporary inverted arch is cancelled, so that the engineering cost is reduced, and the safety risk in the process of dismantling the temporary inverted arch is avoided.
13. The tunnel excavation construction speed is high, the construction period can be effectively ensured, and the excavation process of the IV-level surrounding rock large-section tunnel can be effectively accelerated because the excavation process of the upper middle step and the excavation process of the lower step are not interfered with each other.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a block diagram of the process flow of the present invention.
Fig. 2 is a schematic cross-sectional structure diagram of the primary tunnel supporting structure and the cover arch according to the present invention.
Fig. 3 is a schematic longitudinal section structure view of the preliminary tunnel supporting structure of the present invention.
FIG. 4 is a schematic view of the construction state of the wet-spraying manipulator of the present invention.
Fig. 5 is a schematic cross-sectional structure diagram of the radial grouting reinforcement structure of the invention.
Fig. 6 is a schematic longitudinal section structure diagram of the radial grouting reinforcement structure of the invention.
Fig. 7 is a schematic diagram of the arrangement positions of blastholes on the upper blasting area and the middle blasting area.
Fig. 8 is a schematic diagram of the arrangement position of blastholes on the lower blasting area.
Figure 9 is a schematic diagram of the initiation network of the upper and middle blast zones of the present invention.
Fig. 10 is a schematic plan view showing the arrangement positions of the slitting holes, the peripheral holes and the auxiliary holes in the blasting region according to the present invention.
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;
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; 23-a ditch cable trough;
24-sideform; 25-front template; 26-an isolating layer;
27-inner concrete sprayed layer; 28-radial grouting holes.
Detailed Description
As shown in figure 1, the construction method for controlling the stability of the large-section tunnel penetrating through the earth-rock boundary stratum has the cross section of more than 100m2Referring to fig. 7, the constructed tunnel is located in a soil-rock boundary stratum, the soil-rock boundary stratum comprises 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, 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, the lower hole body 1-3 is formed by performing lower step excavation on the constructed tunnel from back to front, an earth and stone interface is positioned in the upper hole body 1-1, and the upper hole body 1-1 and the middle hole body 1-2 form an upper tunnel hole body;
when the construction tunnel is excavated, the method comprises the following steps:
step one, excavating construction on an upper middle step: carrying out upper and middle step excavation construction on the constructed tunnel by dividing the tunnel into a plurality of excavation sections from back to front along the longitudinal extension direction of the tunnel, wherein the upper and middle step excavation construction methods of all the excavation sections are the same;
when any excavation segment of the constructed tunnel is subjected to upper and middle step excavation construction, the process is as follows:
step J1, measuring and setting out: respectively measuring and paying off the excavation contour lines of the upper hole body 1-1 and the middle hole body 1-2 in the current constructed excavation section on the excavation surface of the tunnel upper hole body, and simultaneously respectively measuring and paying off the number of blastholes to be arranged on the excavation surface of the upper hole body 1-1 and the middle hole body 1-2 in the current constructed excavation section and the arrangement positions of the blastholes;
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 upper cutting holes 1-4, the peripheral holes 1-5 and the auxiliary holes 1-6 of the excavation surface of the tunnel upper hole body are blast holes;
step J2, drilling and blasting construction: according to the arrangement positions of the blastholes obtained by measuring and setting out in the step J1, drilling all the blastholes on the excavation face of the tunnel upper hole body in the current construction excavation section by adopting drilling equipment, respectively charging the blastholes formed in the drilling, and detonating to blast after charging is finished;
step J3, 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;
excavating the loess stratum 3 in the upper cavity 1-1 from back to front when the upper cavity 1-1 of the current construction excavation section is excavated from back to front; in the process of excavating the loess stratum 3 in the upper cave body 1-1 from back to front, a ballast conveying vehicle is adopted to convey the ballast generated after the inner explosion of the upper cave body 1-1 from back to front to the outer side of the tunnel portal of the constructed tunnel, so that the excavation construction process of the upper cave body 1-1 is completed;
step J4, 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;
in the step, the excavation surface of the middle hole body 1-2 is positioned at the rear side of the excavation surface of the upper hole body 1-1 in the step J3;
step J5, excavating construction of the next excavation segment: performing excavation construction on the next excavation section according to the method in the steps J1 to J4;
step two, excavating and constructing the lower step: in the step one, in the process of excavating the upper and middle steps, excavating the lower cavity body 1-3 from back to front by adopting a drilling and blasting method;
in this step, the excavation surface of the lower cavity 1-3 is located behind the excavation surface of the middle cavity 1-2 in step J4.
The blasting excavation surface of the upper hole body 1-1 is an upper blasting area, the upper blasting area is positioned below the earth-rock interface, and the upper blasting area is the excavation surface of a rock stratum 4 in the upper hole body 1-1; the excavation surface of the middle hole body 1-2 is a middle blasting area, and the excavation surface of the lower hole body 1-3 is a lower blasting area.
During actual construction, the excavation height of the tunnel hole 1 is 11 m-15 m, and the excavation width of the tunnel hole 1 is 10 m-15 m.
In this embodiment, the excavation height of the tunnel cave 1 is 12m, the height of the upper cave body 1-1 (i.e., the height of the upper step) is 4m, the height of the middle cave body 1-2 (i.e., the height of the middle step) is 3.5m, and the excavation height of the lower cave body 1-3 is 2.4m to 2.7 m. In the actual construction process, the excavation height of the tunnel cave 1, the height of the upper cave body 1-1 and the height of the middle cave body 1-2 can be correspondingly adjusted according to specific requirements.
The cutting holes 1-4, the peripheral holes 1-5 and the auxiliary holes 1-6 are all cylindrical drill holes drilled into the rock stratum 4 from back to front. As shown in fig. 10, each of the slitting holes 1 to 4 and each of the auxiliary holes 1 to 6 in the middle blasting zone are gradually inclined inward from rear to front, and each of the peripheral holes 1 to 5 in the upper blasting zone and the middle blasting zone are gradually inclined outward from rear to front.
In this embodiment, in step J1, each group of the inner slitting holes includes two slitting holes 1 to 4, and each group of the outer slitting holes includes three slitting holes 1 to 4. During actual construction, the number of the inner side cutting holes included in each inner side cutting hole and the arrangement positions of the inner side cutting holes can be correspondingly adjusted according to specific requirements, and the number of the outer side cutting holes included in each outer side cutting hole and the arrangement positions of the outer side cutting holes can be correspondingly adjusted according to specific requirements.
Each column of the auxiliary eyes 1-6 on the left burst area 1-21 and the right burst area 1-23 comprises 3 or 4 auxiliary eyes 1-6. In this embodiment, each row of the auxiliary eyes 1 to 6 in the right burst area 1 to 23 includes 4 auxiliary eyes 1 to 6, and the number of the auxiliary eyes 1 to 6 included in the three rows of the auxiliary eyes 1 to 6 in the left burst area 1 to 21 is 4, 3, and 4 respectively from left to right. During actual construction, the number of the auxiliary eyes 1-6 included in each column of the auxiliary eyes 1-6 on the left explosion area 1-21 and the right explosion area 1-23 and the arrangement positions of the auxiliary eyes 1-6 can be adjusted correspondingly according to specific requirements.
Each row of the auxiliary eyes 1-6 on the left upper explosion area 1-11 and the right upper explosion area 1-12 comprises 3 or 4 auxiliary eyes 1-6.
With reference to fig. 7 and 9, in this embodiment, in step J1, the positions of the two groups of blasting detonators for inside slotted hole blasting are both 1, the positions of the group of blasting detonators for outside slotted hole blasting close to the right blasting area 1-23 are both 3, and the positions of the group of blasting detonators for outside slotted hole blasting close to the left blasting area 1-21 are both 5;
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.
And in the second step, when the drilling and blasting method is adopted to excavate the lower hole body 1-3 from back to front, the conventional drilling and blasting method is adopted to carry out construction.
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.
As can be seen from the above, the left explosion area 1-21 and the right explosion area 1-23 are auxiliary areas, and the left upper explosion area 1-11 and the right upper explosion area 1-12 are pressure explosion 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
Segment position 1 3 5 7 9 11
Delay time (unit: ms) 0 50 110 200 310 460
In this embodiment, the explosives contained in all the blastholes on the upper blasting area, the middle blasting area and the lower blasting area are emulsion explosives.
The hole depth of the inner cutting holes is 0.92m, the loading amount of each inner cutting hole is 0.43kg, and the delay time of the detonator for blasting the inner cutting holes is 0 ms; the depth of the outer cutting holes is 1.99m, and the loading amount of each outer cutting hole is 0.65 kg; the delay time of a group of detonators for the external slotted hole blasting close to the right blasting area 1-23 is 50ms, and the delay time of a group of detonators for the external slotted hole blasting close to the left blasting area 1-21 is 110 ms;
three rows of auxiliary eyes 1-6 on the right burst area 1-23 are respectively a first auxiliary eye, a second auxiliary eye and a third auxiliary eye from left to right; the hole depth of the first auxiliary hole is 1.72m, the loading capacity in the first auxiliary hole is 0.65kg, and the delay time of the detonator for blasting the first auxiliary hole 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, in the step J3, when the loess stratum 3 in the upper cavity 1-1 is excavated from back to front, an excavator is used for excavation;
before adopting the excavator to excavate, firstly install a scarifier on excavator's grab bucket and pass through the scarifier loosens the soil to the loess stratum 3 in the upper portion hole body 1-1, will again the scarifier demolishs and adopts the excavator excavates the loess stratum 3 in the upper portion hole body 1-1.
When the excavator is adopted to excavate the loess stratum 3 in the upper portion hole body 1-1, a mechanical excavation mode is adopted, the excavation efficiency is higher, and a scarifier is installed on a grab bucket of the excavator, so that the excavator has the characteristics of small disturbance, good visual effect, high disassembly and assembly speed and the like, the over-excavation phenomenon of tunnel excavation can be effectively solved, and the construction efficiency is improved.
According to the above, when the constructed tunnel 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 the excavator. In order to avoid collapse of the soil-rock layer caused by blasting of the soil-rock boundary stratum; and (4) dividing an explosion area for the rock stratum 4 in the tunnel hole 1, and carrying out sectional explosion.
As shown in fig. 2 and 3, the preliminary tunnel supporting structure of the tunnel cave 1 is divided into an arch wall preliminary supporting structure 12 for preliminary supporting the arch wall of the tunnel cave 1 and a preliminary supporting inverted arch 13 for preliminary supporting the bottom of the tunnel cave 1;
the tunnel primary support structure comprises a full-section support structure for performing full-section support on the tunnel hole 1, an arch wall net-jet support structure for performing primary support on an arch wall of the tunnel hole 1 and an inverted arch primary support structure for performing primary support on the bottom of the tunnel hole 1; the full-section supporting structure comprises a plurality of full-section supporting frames which are arranged from back to front along the longitudinal extension direction of the tunnel, the two adjacent full-section supporting frames at the front and the back are fixedly connected into a whole through a plurality of longitudinal connecting reinforcing steel bars, the longitudinal connecting reinforcing steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal connecting reinforcing steel bars are arranged along the contour line of the full-section supporting frames; a plurality of full-section support frames in the full-section support structure are uniformly distributed, the distance between two adjacent full-section support frames in the front and the back is L, and the value range of L is 0.5-0.8 m;
the shape of the full-section support frame is the same as the shape of the cross section of the tunnel hole 1, each full-section support frame is formed by splicing an arch wall support arch frame for supporting an arch wall of the tunnel hole 1 and a tunnel inverted arch support frame 2 for supporting the bottom of the tunnel hole 1, the tunnel inverted arch support frame 2 is positioned right below the arch wall support arch frame, the arch wall support arch frame and the tunnel inverted arch frame are positioned on the same tunnel cross section, and the tunnel inverted arch support frame 2 and the arch wall support arch frame form a closed full-section support; the inverted arch primary support structure is an inverted arch concrete injection layer 20 injected at the bottom of the tunnel hole 1, and the tunnel inverted arch support 2 is fixed in the inverted arch concrete injection layer 20;
the arch wall mesh-spraying supporting structure and all arch wall steel arch frames in the full-section supporting structure form an arch wall primary supporting structure 12, and the inverted arch primary supporting structure and all tunnel inverted arch brackets 2 in the full-section supporting structure form a primary supporting inverted arch 13;
the arch wall supporting arch comprises an upper arch 3 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 3 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 3 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 3; the left end of the tunnel inverted arch support 2 is fixedly connected with the bottom of one lower side support 6, and the right end of the tunnel inverted arch support 2 is fixedly connected with the bottom of the other lower side support 6.
As the soil layer and the rock stratum in the tunnel 1 in the earth-rock boundary stratum are uneven in hardness, the deformation amount and the speed of the surrounding rock are not uniform, the deformation of the earth stratum is larger than that of the rock stratum, the tunnel excavation construction process encounters mudstone kaolinization expansive soil, the initial deformation structure is damaged in the initial construction stage, and the supporting structure needs to be reinforced. Although various surrounding rocks have certain self-stability after being exposed, the time is not too long, so that the steel arch 11 is installed and the concrete is sprayed and protected immediately in the tunnel excavation process, and the exposure time caused by no support after the surrounding rocks are excavated is shortened.
The arch wall mesh-shotcrete supporting structure comprises an arch wall reinforcing mesh piece hung on an arch wall of a tunnel hole 1 and an arch wall concrete spraying layer 19 sprayed on the arch wall of the tunnel hole 1, the arch wall reinforcing mesh piece is fixed on an arch wall steel arch frame, and the arch wall reinforcing mesh piece and the arch wall steel arch frame are fixed in the arch wall concrete spraying layer 19. In this embodiment, the arch wall concrete spraying layer 19 and the inverted arch concrete spraying layer 20 are both concrete layers formed by spraying with a wet spraying manipulator 21.
In the embodiment, in the step J3, in the excavation process of the upper hole body 1-1 of the currently constructed excavation section from back to front, the arch part of the upper hole body 1-1 formed by excavation is subjected to net-spraying support from back to front, and meanwhile, the upper arch frame 2-1 is installed in the upper hole body 1-1 formed by excavation from back to front, so that the excavation and initial support construction processes of the upper hole body 1-1 are completed;
in the step J4, in the process of excavating the middle hole body 1-2 of the currently constructed excavation section from back to front, respectively carrying out net-spraying support on the left side and the right side of the middle hole body 1-2 formed by excavation from back to front, and simultaneously respectively installing middle side brackets 5 on 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 the upper arch frame 2-1 in the step J3 into a whole, so that the excavation and primary support construction processes of the middle hole body 1-2 are completed;
the horizontal distance between the excavation surface of the middle hole body 1-2 in the step J4 and the excavation surface of the upper hole body 1-1 in the step J3 is 4 m-6 m;
in the second step, in the process of excavating the lower hole body 1-3 from back to front, the left side and the right side of the excavated and molded lower hole body 1-3 are respectively supported by net spraying from back to front, in the process of net spraying and supporting, the left side and the right side of the excavated and molded lower hole body 1-3 are respectively provided with a lower side support 6 from back to front synchronously, and each lower side support 6 is fixedly connected with the middle side support 5 in the step J4 into a whole; meanwhile, a tunnel inverted arch support 2 is arranged at the bottom of the lower hole body 1-3 from back to front, and the arranged tunnel inverted arch support 2 is fixedly connected with lower side supports 6 arranged at the left side and the right side of the lower hole body 1-3 into a whole; in the installation process of the tunnel inverted arch support 2, synchronously spraying a layer of concrete at the bottom of the tunnel hole 1 from back to front to form an inverted arch concrete spraying layer 20, and fixing the tunnel inverted arch support 2 in the inverted arch concrete spraying layer 20 to finish the excavation and primary support construction process of the lower hole body 1-3;
in the second step, the tunnel 1 formed by excavation is obtained in the process of excavating the lower hole body 1-3 from back to front; respectively carrying out net-spraying support on the left side and the right side of the lower hole body 1-3 which is formed by excavation from back to front to obtain the constructed and formed arch wall net-spraying support structure; the arch wall mesh spraying support structure is connected with an inverted arch concrete spraying layer 20;
and in the second step, the horizontal distance between the excavation surface of the lower hole body 1-3 and the excavation surface of the middle hole body 1-2 in the step J4 is 18 m-21 m, and the horizontal distance between the excavation surface of the lower hole body 1-3 in the second step and the excavation surface of the upper hole body 1-1 in the step J3 is not more than 25 m.
In the second step, the excavation surface of the lower cavity 1-3 is located at the rear side of the excavation surface of the middle cavity 1-2 in the step J4, and the horizontal distance between the excavation surface of the lower cavity 1-3 and the excavation surface of the middle cavity 1-2 is 18 m-21 m. Therefore, after the upper and middle steps of the constructed tunnel are excavated to 18-21 m, the lower step excavation is started. In this embodiment, a horizontal distance between the excavation surface of the lower cavity 1-3 and the excavation surface of the middle cavity 1-2 is denoted as L0, and L0 is 20 m. During actual construction, the value of L0 can be adjusted accordingly according to specific needs.
The surrounding rock grading is to divide an infinite rock mass sequence into a finite number of categories with different stability degrees according to indexes such as the integrity degree of the rock mass, the strength of the rock mass and the like, namely, to classify some surrounding rocks with similar stability into one category, and to classify all the surrounding rocks into a plurality of categories. In the railway tunnel design specification (TB10003-2005), the grade of the surrounding rock of the tunnel is divided into 6 grades, i, ii, iii, iv, v and vi grades respectively, and the smaller the number, the better the surrounding rock property is. In this embodiment, the surrounding rock level of the tunnel cave 1 is an iv level, and specifically, the surrounding rock level of the rock stratum 4 around the tunnel cave 1 is an iv level.
In this embodiment, the arch wall supporting arch frame and the tunnel inverted arch support 2 are all grid steel frames.
In this embodiment, referring to fig. 2, an anchoring system is disposed outside the full-section supporting structure, the anchoring system includes a plurality of anchoring groups disposed from back to front along a longitudinal extension direction of the tunnel, one anchoring group is disposed outside each full-section supporting frame, and each full-section supporting frame and the anchoring group disposed thereon are disposed on a same cross section of the tunnel 1;
each anchoring group comprises a left group of upper locking leg anchor pipes 8, a right group of middle locking leg anchor pipes 9 and a left group of lower locking leg anchor pipes 10, wherein the left group of upper locking leg anchor pipes 8, the right group of middle locking leg anchor pipes 9 and the left group of lower locking leg 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 centering 3; the outer side of the bottom of each middle side bracket 5 is provided with a group of middle locking leg anchor pipes 9, and the outer side of the bottom of each lower side bracket 6 is provided with a group of lower locking leg anchor pipes 10; each group of the upper lock leg anchor pipes 8 comprises an upper lock leg anchor pipe 8 and a lower lock leg anchor pipe 8 which are arranged in parallel, each group of the middle lock leg anchor pipes 9 comprises an upper middle lock leg anchor pipe 9 and a lower middle lock leg anchor pipe 9 which are arranged in parallel, and each group of the lower lock leg anchor pipes 10 comprises an upper lower lock leg anchor pipe 10 which are arranged in parallel; the upper foot-locking anchor pipe 8, the middle foot-locking anchor pipe 9 and the lower foot-locking anchor pipe 10 are foot-locking anchor pipes which enter the soil layer on the periphery of the tunnel cave 1 from inside to outside, and the foot-locking anchor pipes gradually incline downwards from inside to outside.
In order to ensure the anchoring effect, in the embodiment, the included angles between the middle and lower lock leg anchor tubes 9 and 10 and the vertical plane are both 45 °.
The upper arch 2-1 is arc-shaped, and the included angle between each upper lockpin anchor pipe 8 and the arch tangent plane of the upper arch 2-1 at the connecting position of the upper lockpin anchor pipe is 45 degrees; the tangent plane of the arch frame is a plane which is vertically arranged with the outer contour line of the upper arch frame 2-1. The tangent plane of the upper arch 2-1 at the position where each upper lock leg anchor pipe 8 is connected is a plane which is vertically arranged with the outer contour line of the upper arch 2-1 at the position where the upper lock leg anchor pipe 8 is connected.
In this embodiment, the upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 are all seamless steel pipes with a wall thickness of 5mm, a length of 4m and a diameter of phi 42mm, and the inner ends of the upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 are all welded and fixed on the full-section support frame through connecting steel bars. The lengths and the driving angles of the upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 are reasonable in design, so that the deformation of surrounding rock is limited, and the bearing capacity of a supporting structure is exerted. In addition, the number of the upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 at each anchoring position is two, so that the anchoring effect can be further improved.
The construction of the anchor pipe (rod) with locking feet is called 'life-saving locking feet', which shows the importance degree. Because the length and the angle of the lock pin anchor pipe are important components for supporting the grid steel frame to stably prevent the grid steel frame from settling, the lock pin anchor pipe also has an effective stabilizing effect on the horizontal pressure generated after tunnel excavation, the length and the angle of the lock pin anchor pipe are ensured to meet the design requirements during construction, the operating angle of the lock pin is ensured to be 45 degrees, the optimal shear-resistant and tensile-resistant stress effect is fully exerted, the number of the lock pin anchor pipes at each node is increased from two originally designed lock pin anchor pipes to 4 lock pin anchor pipes so as to enhance the capability of the steel frame for resisting the extrusion deformation of surrounding rocks, and meanwhile, the lock pin and the grid steel.
The upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 are inclined anchor pipes, when the inclined anchor pipes are installed, drill holes installed in the inclined anchor pipes firstly, and due to the fact that the operation space is limited, in order to practically and effectively guarantee the drilling depth and angle of the lock leg anchor pipes, drilling is conducted by adopting a 'three-time drilling method', drill rods with the lengths of 2m, 3m and 4m are selected in sequence, and the drilling depth is gradually drilled to the designed depth according to the sequence of 1.5m, 2.5m and 4 m. And after the drilling is finished, the inclined anchor pipe is installed, and the inclined anchor pipe is directly driven into the drilled hole by using a pipe receiving and conveying device of a rock drill during installation. In this embodiment, the excavation progress of the lower cavity 1-3 is the same as the construction progress of the primary support inverted arch 13, and when constructing the lower lock anchor pipe 10, a constructor cannot normally perform 45-degree drilling operation, so that a steel bar support is respectively processed on the left side and the right side of the tunnel inverted arch support 2 to perform construction as a lock anchor pipe drilling platform, and the angle and the construction quality of the lock anchor pipe are ensured.
Because the installation of the grid steel frame is finished and before the ring is formed, the arch feet of the grid steel frame must be compactly and firmly supported. If the bottom of the arch foot of the grid steel frame is suspended or not supported, when the locking anchor pipe loses the action, the stress at the bottom of the arch foot is in a freely telescopic shape, the deformation and the deformation speed can be rapidly developed when the arch foot is deformed and extruded by surrounding rocks, particularly expansive soil is expanded and extruded, the initial deformation is very easy to be large, the structure is damaged, and therefore the arch foot support of the grid steel frame needs to be compact.
During actual construction, in the process of installing the upper arch 2-1 in the excavated and formed upper hole body 1-1 from back to front, wood base plates are respectively arranged at the bottoms of the left side and the right side of each installed upper arch 2-1 to control displacement and settlement, and locking anchor pipes 8 are respectively arranged at the left side and the right side of each installed upper arch 2-1; meanwhile, a sand cushion layer is paved at the bottom of the left side and the right side of each installed upper arch 2-1 respectively so as to facilitate the bolt connection of the upper arch 2-1 and the middle side bracket 5. The wood base plate can be a flexible plate, can meet the supporting requirement on the rock stratum 4, and guarantees that the arch foot supporting pad of the grid steel frame is compact.
Correspondingly, in the process of respectively installing the middle side brackets 5 on the left side and the right side of the middle hole body 1-2 which is formed by excavation from back to front, wood base plates are respectively arranged at the bottom of each installed middle side bracket 5 to control displacement and settlement, and middle locking anchor pipes 9 are respectively arranged on the outer sides of each installed middle side bracket 5; meanwhile, a layer of sand cushion is paved at the bottom of each installed middle side bracket 5 respectively so as to facilitate the bolt connection of the middle side bracket 5 and the lower side bracket 6.
And in the process of respectively installing the lower side brackets 6 at the left side and the right side of the lower hole body 1-3 which is excavated and formed from back to front, wood base plates are respectively arranged at the bottom of each installed lower side bracket 6 to control displacement and settlement, and a lower lock pin anchor pipe 10 is respectively arranged at the outer side of each installed lower side bracket 6.
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 the embodiment, before the excavation construction of the upper and middle steps in the first step, advance support needs to be carried out on the arch part of the tunnel 1, and a tunnel advance support structure is obtained;
as shown in fig. 2 and 3, the tunnel advance support structure comprises a plurality of small advance conduit grouting support structures for advancing the arch part of the tunnel cave 1 from back to front along the longitudinal extension direction of the tunnel; the structures of the advanced small conduit grouting support structures are the same, and the lap joint length between two adjacent advanced small conduit grouting support structures in the front and back is not less than 0.5 m;
each advanced small conduit grouting supporting structure comprises a plurality of small grouting conduits 22 which are drilled into the soil body in front of the tunnel face of the tunnel hole 1 from back to front and a small conduit guide frame for guiding the plurality of small grouting conduits 22, wherein the plurality of small grouting conduits 22 are distributed on the same tunnel section from left to right along the arch contour line of the upper hole 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 3, a plurality of guide holes for guiding the small grouting guide pipes 22 are formed in the small guide pipe guide frame, and the plurality of guide holes are arranged from left to right along the arch contour line of the upper hole body 1-1.
In this embodiment, the tunnel advance support structure includes a plurality of small advance conduit grouting support structures for advance supporting the arch part of the tunnel 1 from back to front along the longitudinal extension direction of the tunnel; the structures of the advanced small conduit grouting support structures are the same, and the lap joint length between two adjacent advanced small conduit grouting support structures in the front and back is not less than 0.5 m;
each advanced small conduit grouting supporting structure comprises a plurality of small grouting conduits 22 which are drilled into the soil body in front of the tunnel face of the tunnel hole 1 from back to front and a small conduit guide frame for guiding the plurality of small grouting conduits 22, wherein the plurality of small grouting conduits 22 are distributed on the same tunnel section from left to right along the arch contour line of the upper hole 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 first step, before tunnel excavation and primary support, 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 the embodiment, in order to further ensure the stability of the tunnel, a reinforcing sleeve arch is adopted as a temporary reinforcing measure, and the reinforcing sleeve arch is distributed on the inner side of the primary tunnel supporting structure;
the tunnel primary supporting structure and the reinforcing sleeve arch are full-section supporting structures for supporting a full section of the tunnel hole 1, and the tunnel primary supporting structure and the reinforcing sleeve arch positioned on the inner side of the tunnel primary supporting structure form a reinforced primary supporting structure;
with reference to fig. 2, the reinforced arch comprises a plurality of arch units, the arch units have the same structure and are arranged from back to front along the longitudinal extension direction of the tunnel, an isolation layer 26 is arranged between each arch unit and the primary tunnel supporting structure, the isolation layer 26 is a full-section isolation layer formed by non-woven fabrics paved between the arch units and the primary tunnel supporting structure, and the cross section of the isolation layer 26 has the same shape as that of the cross section of the tunnel 1;
each arch sheathing unit comprises M steel arch frames 11 which are 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 arch frames 11 are uniformly arranged, and the distance between two adjacent steel arch frames 11 is 0.8-1.2M; each structural steel arch 11 is a full-section support for performing full-section supporting on the tunnel cave 1, M structural steel arches 11 are fixed in the inner side concrete spraying layer 27, the shape of each structural steel arch 11 is the same as the shape of the cross section of the tunnel cave 1, wherein M is a positive integer and is more than or equal to 4; m steel arch frames 11 in each arch sheathing unit are fixedly connected into a whole through a plurality of longitudinal steel bars, the longitudinal steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal steel bars are arranged along the contour line of the steel arch frames 11; each steel arch 11 comprises an arch wall steel support 11-1 for supporting an arch wall of a tunnel 1 and an inverted arch steel support 11-2 for supporting the bottom of the tunnel 1, the inverted arch steel support 11-2 is located right below the arch wall steel support 11-1 and is an arch support, the left end of the inverted arch steel support 11-2 is fixedly connected with the bottom of the left end of the arch wall steel support 11-1, and the right end of the inverted arch steel support 11-2 is fixedly connected with the bottom of the right end of the arch wall steel support 11-1;
in the step J4, in the process of excavating the lower cavity 1-3 from back to front, the reinforcing sleeve arch is constructed on the inner side of the constructed primary tunnel supporting structure from back to front along the longitudinal extension direction of the tunnel, so that the reinforced primary support structure formed by construction is obtained;
when the reinforcing sleeve arch is constructed from back to front, a plurality of sleeve arch units in the reinforcing sleeve arch are constructed from back to front respectively, and the construction methods of the plurality of sleeve arch units are the same; the tunnel primary supporting structure section with the arch sheathing units distributed on the inner side in the tunnel primary supporting structure is a primary supporting section to be reinforced;
when any one of the set arch units in the reinforced set arch is constructed, the process is as follows:
d1, paving an isolation layer: paving a layer of isolation layer 26 on the inner wall of the primary support section to be enhanced outside the currently constructed arch sheathing unit from back to front;
step D2, installing the profile steel arch frame: in the process of laying the isolation layer 26 from back to front in the step D1, respectively installing M steel arches 11 of the currently constructed arch sheathing unit from back to front in the primary support section to be reinforced in the step one, 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 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 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 steel arch 11 is located 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 the M steel arches 11 is 1M.
During actual construction, the value of L and the distance between two adjacent front and rear steel arches 11 in the M steel arches 11 can be adjusted accordingly according to specific needs.
In this embodiment, in step D1, the primary support section to be reinforced is formed by connecting a large deformation section and two deformation transition sections located on the front and rear sides of the large deformation section, where the large deformation section is a tunnel section where the vault crown subsidence value of the tunnel cave 1 exceeds 10mm and/or the horizontal convergence value exceeds 5mm within 24 hours after the construction of the primary support structure of the tunnel is completed, the vault crown subsidence value of the tunnel cave 1 is an absolute subsidence value of the vault inner wall of the primary support structure of the tunnel, and the horizontal convergence value of the tunnel cave 1 is a horizontal convergence value of the inner wall of the primary support structure of the tunnel at the maximum excavation position of the tunnel cave 1; and the two deformation transition sections are 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 primary tunnel supporting structure, the primary tunnel supporting deformation is effectively controlled, and the construction safety in the tunnel can be ensured. In this embodiment, in order to permanently solve the problem of the ability of the primary support to resist the deformation of the surrounding rock, after the concrete is sprayed in step D4, the arch wall of the primary support section to be reinforced in step D1 needs to be radially grouted and reinforced, and a radially grouted and reinforced structure is obtained, so that the radially grouted and reinforced structure and the inner concrete sprayed layer 27 in the primary support section to be reinforced are fastened and connected into a whole, the soil body outside the reinforced primary support structure is reinforced, and the deformation of the reinforced primary support structure is further controlled from the source. And radial grouting is adopted to perform grouting reinforcement and reinforcement on surrounding rocks outside the primary support structure, so that the stability and the bearing capacity of the rock stratum after primary support and back support are improved, and the purpose of preventing the surrounding rocks from continuing to deform is achieved.
The upper tunnel body 1-1 and the middle tunnel body 1-2 form an upper tunnel body of the tunnel, and the radial grouting reinforcement structure is positioned on the outer side of the upper tunnel body of the tunnel;
with reference to fig. 5 and 6, the radial grouting reinforcement structure is a reinforcement structure formed by grouting into a soil body outside the tunnel upper cavity through multiple rows of radial grouting holes 28, the multiple rows of radial grouting holes 28 are arranged from back to front along the extending direction of the tunnel, each row of radial grouting holes 28 includes multiple radial grouting holes 28 arranged on the same tunnel section from left to right along the excavation contour line of the tunnel upper cavity, each radial grouting hole 28 is a drill hole drilled into the soil body from inside to outside from the inside of the tunnel upper cavity, multiple radial grouting holes 28 in each row of radial grouting holes 28 are uniformly arranged, and the radial grouting holes 28 in two adjacent rows of the radial grouting holes 28 are arranged in a staggered manner; the length of the radial grouting holes 28 is not less than 3 m;
each row of the radial grouting holes 28 are positioned between two front and rear adjacent full-section supporting frames, and each row of the radial grouting holes 28 is positioned between two front and rear adjacent profile steel arches 11;
and D1, when the arch wall of the primary support section to be reinforced is reinforced by radial grouting, the arch wall is reinforced by grouting from back to front through a plurality of rows of radial grouting holes 28.
In this embodiment, the circumferential distance between the inner ends of two adjacent radial grouting holes 28 in each row of the radial grouting holes 28 is 1.2m to 1.8m, the distance between two adjacent front and rear rows of the radial grouting holes 28 is 1.8m to 2.2m, and the length of each radial grouting hole 28 is 3 m.
During actual construction, the circumferential distance between the inner ends of two adjacent radial grouting holes 28 in each row of the radial grouting holes 28, the distance between two adjacent rows of the radial grouting holes 28 in the front and back direction, and the length of the radial grouting holes 28 can be respectively and correspondingly adjusted according to specific requirements.
In this step, when the radial grouting holes 28 are arranged in multiple rows for grouting reinforcement, the grouting liquid is a shrinkage-free cement-based grouting material, and the radial grouting reinforcement effect can be effectively enhanced.
During actual construction, the grouting liquid can also be common pure cement paste with the water-cement ratio of 0.5: 1-1: 1.
When the radial grouting reinforcement is actually carried out, the grouting pressure is 1.5 MPa-2.0 MPa, the grouting sequence is carried out from bottom to top according to two-sequence holes, namely, the holes are jumped first, the rows of the single-sequence holes are jumped, and then the rest two-sequence holes are grouted. And the grouting ending standard is that the grouting pressure is increased to 1.0MPa and the grouting is continued for more than 10min, and the grouting is ended at 1/4 the grouting amount of which is less than the initial grouting amount.
With reference to fig. 4, a tunnel bottom backfill soil layer 7 is arranged behind the excavation surface of the lower cavity 1-3, and the tunnel bottom backfill soil layer 7 is located in the lower cavity 1-3; and the tunnel bottom backfill soil layer 7 is a temporary platform for the construction equipment to move back and forth. Meanwhile, the structural stability of the bottom of the tunnel 1 can be further improved through the backfill soil layer 7 at the bottom of the tunnel.
In this embodiment, the upper surface of the lower step is horizontally arranged, and the upper surface of the lower step is a temporary moving platform for the wet spraying manipulator 21 to move back and forth. The upper surface of the lower step is the bottom surface of the middle hole body 1-2 which is formed by excavating and forming the lower hole body 1-3 before excavating. Meanwhile, the tunnel bottom backfill soil layer 7 is also a temporary moving platform for the wet spraying manipulator 21 to move back and forth.
The number of the wet spraying mechanical arms 21 is two, one wet spraying mechanical arm 21 is a front side mechanical arm for spraying concrete to the upper hole body 1-1 and the middle hole body 1-2, and the front side mechanical arm moves back and forth on the upper surface of the lower step; and the other wet spraying manipulator 21 is a rear manipulator for constructing the inverted arch concrete spraying layer 20, the rear manipulator is positioned at the rear side of the front manipulator, and the rear manipulator moves back and forth on the backfill layer 7 at the bottom of the tunnel.
In this embodiment, the upper arch 2-1 and the middle side bracket 5, the middle side bracket 5 and the lower side bracket 6, and the lower side bracket 6 and the tunnel inverted arch bracket 2 are fixedly connected by connecting bolts. And connecting steel plates for mounting the connecting bolts are arranged at the two ends of the upper arch frame 2-1, the two ends of the middle side support 5, the two ends of the lower side support 6 and the two ends of the tunnel inverted arch support 2.
In order to ensure the processing quality and improve the on-site construction efficiency, the full-section support frame adopts factory centralized processing and distribution and meets the requirement of in-place distribution in half an hour on all working faces.
In the second step, in the process of excavating the lower hole body 1-3, carrying out primary support on the lower hole body 1-3 formed by excavation in time, and obtaining a primary support inverted arch 13; and after the primary support of the lower hole bodies 1-3 is finished, backfilling the tunnel bottom backfill soil layer 7 on the primary support inverted arch 13 in time. When the tunnel bottom backfill soil layer 7 is backfilled, the tunnel bottom backfill soil layer 7 is backfilled by using hole slag (namely, muck) in the lower hole bodies 1-3.
During the excavation process of the upper cavity 1-1, the middle cavity 1-2 and the lower cavity 1-3, the excavation slag formed by excavation is loaded to a dump truck by adopting an excavator and is transported out by the dump truck. When the excavated hole slag is transported outwards, the hole slag used for backfilling the tunnel bottom backfill soil layer 7 needs to be reserved, and the reserved hole slag (namely, muck and ballast) is placed on one side of the inner side of the lower hole body 1-3 so as to be convenient for backfilling the tunnel bottom backfill soil layer 7 in time.
In order to ensure construction safety and structural stability of the tunnel cave 1, the excavation footage of the upper cave body 1-1 and the middle cave body 1-2 is 2L-3L. In this embodiment, the excavation footage of the upper cavity 1-1 and the middle cavity 1-2 is 2L.
When the arch part of the upper hole body 1-1 is subjected to net-jet support from back to front, firstly, an arch part reinforcing steel net piece 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 part reinforcing steel net piece is tightly connected with the installed upper arch frame 2-1; spraying a layer of concrete 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 fixing the hung arch reinforcing mesh and the installed upper arch frame 2-1 in the arch concrete spraying layer to finish the excavation and primary support construction process of the upper hole body 1-1;
when the left side and the right side of the middle hole body 1-2 are respectively supported by the net spraying from back to front, the middle reinforcing mesh sheets are respectively hung on the left side and the right side of the middle hole body 1-2 from back to front, meanwhile, the middle side brackets 5 are respectively installed on the left side and the right side of the middle hole body 1-2 from back to front, the hung middle reinforcing mesh sheets are fixedly connected with the installed middle side brackets 5, and meanwhile, the hung middle reinforcing mesh sheets are fixedly connected with the arch reinforcing mesh sheets positioned above the middle reinforcing mesh sheets; respectively spraying a layer of concrete 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, connecting the middle concrete spraying layer with the arch concrete spraying layer, fixing the hung middle reinforcing mesh and the installed middle side support 5 in the middle concrete spraying layer, and completing the excavation and initial support construction process of the middle hole body 1-2;
when the left and right sides of the lower hole bodies 1-3 are respectively supported by net spraying from back to front, lower reinforcing mesh sheets are respectively hung on the left and right sides of the lower hole bodies 1-3 from back to front, meanwhile, lower side brackets 6 are respectively installed on the left and right sides of the lower hole bodies 1-3 from back to front, the hung lower reinforcing mesh sheets are fixedly connected with the installed lower side brackets 6, and meanwhile, the hung lower reinforcing mesh sheets are fixedly connected with the middle reinforcing mesh sheets positioned above the hung lower reinforcing mesh sheets; respectively spraying a layer of concrete 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, connecting the lower concrete spraying layer with the middle concrete spraying layer, fixing the hung lower reinforcing mesh and the installed lower side bracket 6 in the lower concrete spraying layer, completing the mesh spraying support process of the left side and the right side of the lower hole body 1-3, and obtaining the constructed and formed arch wall mesh spraying support structure;
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.
As shown in fig. 3, in this embodiment, the excavation footage of the upper cavity 1-1, the excavation footage of the middle cavity 1-2 and the excavation footage of the lower cavity 1-3 are the same;
when the tunnel excavation and primary support are carried out on the constructed tunnel, the two wet-spraying mechanical arms 21 move forwards for multiple times along the longitudinal extension direction of the tunnel through the tunnel bottom backfill soil layer 7, and the distance of forward movement of each time is the same as the excavation footage of the lower hole bodies 1-3.
After the rear manipulator moves forwards to the right position each time, the length of the excavated and molded lower hole body 1-3 positioned in front of the tunnel bottom backfill soil layer 7 is the same as the excavation footage of the lower hole body 1-3, and the excavated and molded lower hole body 1-3 positioned in front of the tunnel bottom backfill soil layer 7 is the currently excavated lower hole body; after the rear manipulator moves forwards in place each time, the rear manipulator is firstly adopted to synchronously spray the lower concrete spraying layer and the inverted arch concrete spraying layer 20 in the currently excavated lower hole body from back to front, and the excavation and primary support construction process of the currently excavated lower hole body is completed at the same time. After the excavation and primary support construction process of the currently excavated lower hole body 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 currently excavated lower hole body, and the constructed tunnel bottom backfill soil layer 7 is a moving platform for the rear manipulator to move forwards next time.
After the front side manipulator moves forwards in place each time, the front side manipulator is adopted to respectively spray concrete to the upper hole body 1-1 and the middle hole body 1-2 which are positioned at the time of excavation molding from back to front, and the excavation and primary support construction processes of the upper hole body 1-1 and the middle hole body 1-2 are completed simultaneously. After the concrete injection in the upper cavity 1-1 and the middle cavity 1-2 which are formed by excavation is finished at the moment, the front manipulator moves forwards next time so that the front manipulator is adopted to perform the concrete injection in time after the upper cavity 1-1 and the middle cavity 1-2 finish the next excavation process of excavation footage.
From the above, the construction process of the primary support inverted arch 13 and the excavation process of the lower hole body 1-3 are carried out synchronously, so that the excavation of the lower hole body 1-3 and the construction of the primary support inverted arch 13 are carried out synchronously, 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, the convenience is improved for the large-scale machinery to move in the hole, thereby meeting the requirement of large-scale mechanized construction to the maximum extent, reducing the labor intensity, realizing the synchronous operation of an upper step, a middle step and a lower step, realizing the full-section flow construction, effectively improving the construction efficiency, reducing the engineering cost, achieving the purposes of safe, economic and efficient construction, and during the actual construction, the horizontal distance between the excavation surface of the lower cavity body 1-3 and the excavation surface of the middle cavity body 1-2 in the step J4 is 18 m-21 m, the distance is large, the damage to the tunnel face (particularly the tunnel face of the upper cavity body in the tunnel) and the arch part 1 in the tunnel caused by the blasting excavation process of the lower cavity body 1-3 can be effectively reduced or even avoided, the safety, the reliability and the smoothness of the tunnel excavation process can be ensured, and the stability of a large-section tunnel can be ensured. And the distance between the excavation surface of the lower hole body 1-3 and the excavation surface of the tunnel upper hole body is larger, so that the blasting excavation process of the lower hole body 1-3 and the blasting excavation process of the tunnel upper hole body are not influenced mutually, and the vibration generated in the blasting excavation process can be effectively weakened.
The horizontal distance between the front manipulator and the excavation surface of the upper cavity 1-1 is 8-12 m. Therefore, the working length of the wet spraying mechanical arm 21 can be ensured to meet the construction requirement, and the two wet spraying mechanical arms 21 can be ensured to spray the concrete to the upper hole body 1-1, the middle hole body 1-2 and the lower hole body 1-3.
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.
In this embodiment, the excavation heights of the upper cavity 1-1, the middle cavity 1-2 and the lower cavity 1-3 can all meet the operation space of the wet spraying manipulator 21.
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.
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 stability control construction method for a large-section tunnel penetrating through an earth-rock boundary stratum is characterized by comprising the following steps of: the cross section of the constructed tunnel is more than 100m2The constructed tunnel is located in a soil-rock boundary stratum, the soil-rock boundary stratum comprises 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, the upper hole body (1-1) is a hole body formed after upper step excavation is carried out on the constructed tunnel from back to front, the middle hole body (1-2) is a hole body formed after middle step excavation is carried out on the constructed tunnel from back to front, the lower hole body (1-3) is a hole body formed after lower step excavation is carried out on the constructed tunnel from back to front, an earth-stone interface is located in the upper hole body (1-1), and the upper hole body (1-1) and the middle hole body (1-2) form an upper hole body of the tunnel;
when the construction tunnel is excavated, the method comprises the following steps:
step one, excavating construction on an upper middle step: carrying out upper and middle step excavation construction on the constructed tunnel by dividing the tunnel into a plurality of excavation sections from back to front along the longitudinal extension direction of the tunnel, wherein the upper and middle step excavation construction methods of all the excavation sections are the same;
when any excavation segment of the constructed tunnel is subjected to upper and middle step excavation construction, the process is as follows:
step J1, measuring and setting out: respectively measuring and paying off the excavation contour lines of the upper cavity (1-1) and the middle cavity (1-2) of the currently constructed excavation section on the excavation surface of the upper cavity of the tunnel, and simultaneously respectively measuring and paying off the number of blastholes to be arranged on the excavation surface of the upper cavity (1-1) and the middle cavity (1-2) of the currently constructed excavation section and the arrangement positions of the blastholes;
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 upper cutting holes (1-4), the peripheral holes (1-5) and the auxiliary holes (1-6) of the excavation surface of the tunnel upper hole body are blast holes;
step J2, drilling and blasting construction: according to the arrangement positions of the blastholes obtained by measuring and setting out in the step J1, drilling all the blastholes on the excavation face of the tunnel upper hole body in the current construction excavation section by adopting drilling equipment, respectively charging the blastholes formed in the drilling, and detonating to blast after charging is finished;
step J3, 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;
when the upper cavity body (1-1) of the current construction excavation section is excavated from back to front, the loess stratum (3) in the upper cavity body (1-1) is excavated from back to front; in the process of excavating the loess stratum (3) in the upper tunnel body (1-1) from back to front, a ballast conveying vehicle is adopted to convey the ballast stones generated after the inner explosion of 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 excavating construction process of the upper tunnel body (1-1) is completed;
step J4, 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;
in the step, the excavation surface of the middle hole body (1-2) is positioned at the rear side of the excavation surface of the upper hole body (1-1) in the step J3;
step J5, excavating construction of the next excavation segment: performing excavation construction on the next excavation section according to the method in the steps J1 to J4;
step two, excavating and constructing the lower step: in the process of carrying out upper and middle step excavation construction in the first step, excavating the lower hole body (1-3) from back to front by adopting a drilling and blasting method;
in the step, the excavation surface of the lower cavity (1-3) is located at the rear side of the excavation surface of the middle cavity (1-2) in the step J4.
2. The construction method for controlling the stability of the large-section tunnel penetrating through the earth-rock boundary stratum according to claim 1, wherein the construction method comprises the following steps: in step J1, each group of the inner slitting holes comprises two slitting holes (1-4), and each group of the outer slitting holes comprises three slitting 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 3 or 4 auxiliary eyes (1-6).
3. The stability control construction method of the large-section tunnel penetrating through the earth-rock boundary stratum according to claim 1 or 2, characterized by comprising the following steps: in the step J1, the section positions of the two groups of detonators for the inner slotted hole blasting are 1 section, the section positions of one group of detonators for the outer slotted hole blasting close to a right blasting area (1-23) are 3 sections, and the section positions of one group of detonators for the outer slotted hole 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 the blasting detonators of the peripheral holes (1-5) on the left blasting area (1-21) and the right blasting area (1-23) are 9 sections.
4. The construction method for controlling the stability of the large-section tunnel penetrating through the earth-rock boundary stratum according to claim 3, wherein the construction method comprises the following steps: the two rows of auxiliary holes (1-6) on the left upper explosion area (1-11) and the right upper explosion area (1-12) are respectively an upper row of auxiliary holes and a lower row of auxiliary holes;
the blasting detonators for each auxiliary hole (1-6) in the lower row of auxiliary holes in the left upper blasting area (1-11) are all 3 sections, and the blasting detonators for each auxiliary hole (1-6) in the lower row of auxiliary holes in the right upper blasting area (1-12) are all 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 blasting detonators of the auxiliary eyes (1-6) 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) positioned at the rightmost side in the upper row of auxiliary eyes on the right upper explosion area (1-12) is an upper right auxiliary eye, and the blasting detonators of all the auxiliary eyes (1-6) except the upper right 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.
5. The method for controlling and constructing the stability of the large-section tunnel penetrating through the earth-rock boundary stratum according to claim 4, wherein the method comprises the following steps: 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.
6. The stability control construction method of the large-section tunnel penetrating through the earth-rock boundary stratum according to claim 1 or 2, characterized by comprising the following steps: in the step J3, when the loess stratum (3) in the upper cavity (1-1) is excavated from back to front, an excavator is adopted for excavation;
before adopting the excavator to excavate, firstly install a scarifier on excavator's grab bucket and pass through the scarifier loosens the soil to loess stratum (3) in the upper portion hole body (1-1), will again the scarifier is demolishd and is adopted the excavator excavates loess stratum (3) in to the upper portion hole body (1-1).
7. The stability control construction method of the large-section tunnel penetrating through the earth-rock boundary stratum according to claim 1 or 2, characterized by comprising the following steps: the tunnel primary supporting structure of the tunnel hole (1) is divided into an arch wall primary supporting structure (12) for carrying out primary supporting on an arch wall of the tunnel hole (1) and a primary supporting inverted arch (13) for carrying out primary supporting on the bottom of the tunnel hole (1);
the tunnel primary support structure comprises a full-section support structure for performing full-section support on the tunnel hole (1), an arch wall net-jet support structure for performing primary support on an arch wall of the tunnel hole (1) and an inverted arch primary support structure for performing primary support on the bottom of the tunnel hole (1); the full-section supporting structure comprises a plurality of full-section supporting frames which are arranged from back to front along the longitudinal extension direction of the tunnel, the two adjacent full-section supporting frames at the front and the back are fixedly connected into a whole through a plurality of longitudinal connecting reinforcing steel bars, the longitudinal connecting reinforcing steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal connecting reinforcing steel bars are arranged along the contour line of the full-section supporting frames; a plurality of full-section support frames in the full-section support structure are uniformly distributed, the distance between two adjacent full-section support frames in the front and the back is L, and the value range of L is 0.5-0.8 m;
the shape of the full-section support frame is the same as the shape of the cross section of the tunnel hole (1), each full-section support frame is formed by splicing an arch wall support arch frame for supporting an arch wall of the tunnel hole (1) and a tunnel inverted arch support frame (2) for supporting the bottom of the tunnel hole (1), the tunnel inverted arch support frame (2) is positioned under the arch wall support arch frame and positioned on the same tunnel cross section, and the tunnel inverted arch support frame (2) and the arch wall support arch frame form a closed full-section support; the inverted arch primary support structure is an inverted arch concrete injection layer (20) injected at the bottom of a tunnel hole (1), and the tunnel inverted arch support (2) is fixed in the inverted arch concrete injection layer (20);
the arch wall mesh-spraying supporting structure and all arch wall steel arches in the full-section supporting structure form an arch wall primary supporting structure (12), and the inverted arch primary supporting structure and all tunnel inverted arch brackets (2) in the full-section supporting structure form a primary supporting inverted arch (13);
the arch wall supporting arch center comprises an upper arch center (3) 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 (3) 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 (3) 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 (3); 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 the step J3, in the excavation process of the upper hole body (1-1) of the currently constructed excavation section from back to front, the arch part of the upper hole body (1-1) formed by excavation is supported by net spraying from back to front, and meanwhile, an upper arch frame (2-1) is installed in the upper hole body (1-1) formed by excavation from back to front, so that the excavation and primary support construction processes of the upper hole body (1-1) are completed;
in the step J4, in the process of excavating the middle hole body (1-2) of the currently constructed excavation section from back to front, net-spraying supports are respectively carried out on the left side and the right side of the middle hole body (1-2) formed by excavation from back to front, meanwhile, middle side supports (5) are respectively arranged on the left side and the right side of the middle hole body (1-2) formed by excavation from back to front, each middle side support (5) is fixedly connected with the upper arch frame (2-1) in the step J3 into a whole, and the excavation and primary support construction processes of the middle hole body (1-2) are completed;
the horizontal distance between the excavation surface of the middle hole body (1-2) in the step J4 and the excavation surface of the upper hole body (1-1) in the step J3 is 4-6 m;
in the second step, in the process of excavating the lower hole body (1-3) from back to front, the left side and the right side of the excavated and molded lower hole body (1-3) are respectively supported by net spraying from back to front, in the process of net spraying and supporting, the left side and the right side of the excavated and molded lower hole body (1-3) are synchronously and respectively provided with lower side brackets (6) from back to front, and each lower side bracket (6) is fixedly connected with the middle side bracket (5) in the step J4 into a whole; meanwhile, a tunnel inverted arch support (2) is arranged at the bottom of the lower hole body (1-3) from back to front, and the arranged tunnel inverted arch support (2) is fixedly connected with lower side supports (6) arranged at the left side and the right side of the lower hole body (1-3) into a whole; in the installation process of the tunnel inverted arch support (2), synchronously spraying a layer of concrete from back to front at the bottom of the tunnel hole (1) to form an inverted arch concrete spraying layer (20), and fixing the tunnel inverted arch support (2) in the inverted arch concrete spraying layer (20) to finish the excavation and primary support construction process of the lower hole body (1-3);
in the second step, the lower hole body (1-3) is excavated from back to front to obtain an excavated tunnel (1); respectively carrying out net-spray supporting on the left side and the right side of the lower hole body (1-3) which is formed by excavation from back to front to obtain the constructed and formed arch wall net-spray supporting structure; the arch wall mesh spraying support structure is connected with an inverted arch concrete spraying layer (20);
and in the second step, the horizontal distance between the excavation surface of the lower hole body (1-3) and the excavation surface of the middle hole body (1-2) in the step J4 is 18 m-21 m, and the horizontal distance between the excavation surface of the lower hole body (1-3) and the excavation surface of the upper hole body (1-1) in the step J3 is not more than 25 m.
8. The method for controlling and constructing the stability of the large-section tunnel penetrating through the earth-rock boundary stratum according to claim 7, wherein the method comprises the following steps: a reinforcing sleeve arch is arranged on the inner side of the primary supporting structure of the tunnel;
the tunnel primary supporting structure and the reinforcing sleeve arch are full-section supporting structures for supporting a tunnel hole (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 steel arch frames (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 steel arch frames (11) are uniformly arranged, and the distance between two adjacent steel arch frames (11) is 0.8-1.2M; each steel arch (11) is a full-section support for performing full-section supporting on a tunnel hole (1), M steel arches (11) are fixed in the inner side concrete spraying layer (27), the shape of each steel arch (11) is the same as the shape of the cross section of the tunnel hole (1), wherein M is a positive integer and is more than or equal to 4; m steel arch frames (11) in each arch sheathing unit are fixedly connected into a whole through a plurality of longitudinal steel bars, the longitudinal steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal steel bars are arranged along the contour line of the steel arch frames (11); each profile steel arch (11) comprises an arch wall profile steel support (11-1) for supporting an arch wall of a tunnel hole (1) and an inverted arch profile steel support (11-2) for supporting the bottom of the tunnel hole (1), the inverted arch profile steel support (11-2) is located under the arch wall profile steel support (11-1) and is an arch support, the left end of the inverted arch profile steel support (11-2) is fixedly connected with the bottom of the left end of the arch wall profile steel support (11-1), and the right end of the inverted arch profile steel support (11-2) is fixedly connected with the bottom of the right end of the arch wall profile steel support (11-1);
in the step J4, in the process of excavating the lower cavity body (1-3) from back to front, the reinforcing sleeve arch is constructed on the inner side of the constructed primary tunnel supporting structure from back to front along the longitudinal extension direction of the tunnel, so that the reinforced primary support structure formed by construction is obtained;
when the reinforcing sleeve arch is constructed from back to front, a plurality of sleeve arch units in the reinforcing sleeve arch are constructed from back to front respectively, and the construction methods of the plurality of sleeve arch units are the same; the tunnel primary supporting structure section with the arch sheathing units distributed on the inner side in the tunnel primary supporting structure is a primary supporting section to be reinforced;
when any one of the set arch units in the reinforced set arch is constructed, the process is as follows:
d1, paving an isolation layer: paving a layer of isolation layer (26) on the inner wall of the primary support section to be enhanced outside the currently constructed arch sheathing unit from back to front;
step D2, installing the profile steel arch frame: in the process of laying an isolation layer (26) from back to front in the step D1, respectively installing M steel arches (11) of the currently constructed arch sheathing unit in the primary support section to be reinforced from back to front in the step I, enabling each steel arch (11) to be erected 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 M installed steel arches (11) and the inner wall of the primary support section to be reinforced;
step D3, longitudinal steel bar installation: d2, after M structural steel arches (11) are installed, firmly connecting the M structural steel arches (11) into a whole through a plurality of longitudinal steel bars;
step D4, concrete spraying: and D1, spraying concrete on the isolating layer (26) from back to front to form an inner concrete spraying layer (27), fixing M steel arches (11) in the step D2 and a plurality of longitudinal steel bars in the step D3 in the inner concrete spraying layer (27), and padding the isolating layer (26) between the primary support section to be reinforced and the inner concrete spraying layer (27) in the step D1.
9. The method for controlling and constructing the stability of the large-section tunnel penetrating through the earth-rock boundary stratum according to claim 8, wherein the method comprises the following steps: d1, connecting the primary support section to be reinforced by a large deformation section and two deformation transition sections respectively positioned at the front side and the rear side of the large deformation section, wherein the large deformation section is a tunnel section of which the vault sinking value of the tunnel hole (1) exceeds 10mm and/or the horizontal convergence value exceeds 5mm within 24 hours after the construction of the primary tunnel support structure is completed, the vault sinking value of the tunnel hole (1) is the absolute sinking value of the vault inner wall of the primary tunnel support structure, and the horizontal convergence value of the tunnel hole (1) is the horizontal convergence value of the inner wall of the primary tunnel support structure at the maximum excavation position of the tunnel hole (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.
10. The method for controlling and constructing the stability of the large-section tunnel penetrating through the earth-rock boundary stratum according to claim 8, wherein the method comprises the following steps: after the concrete is sprayed in the step D4, radial grouting reinforcement is needed to be performed on the arch wall of the primary support section to be reinforced in the step D1, and a radial grouting reinforcement structure is obtained;
the upper tunnel body (1-1) and the middle tunnel body (1-2) form an upper tunnel body of the tunnel, and the radial grouting reinforcement structure is positioned on the outer side of the upper tunnel body of the tunnel;
the radial grouting reinforcement structure is formed by grouting and reinforcing soil outside the tunnel upper hole body through a plurality of rows of radial grouting holes (28), the radial grouting holes (28) are arranged from back to front along the extending direction of the tunnel, each row of radial grouting holes (28) comprises a plurality of radial grouting holes (28) arranged on the section of the same tunnel from left to right along the excavation contour line of the tunnel upper hole body, each radial grouting hole (28) is a drill hole drilled into the soil from the inside to the outside of the tunnel upper hole body, the radial grouting holes (28) in each row of radial grouting holes (28) are uniformly arranged, and the radial grouting holes (28) in the front and back adjacent rows of radial grouting holes (28) are arranged in a staggered manner; the length of the radial grouting holes (28) is not less than 3 m;
each row of radial grouting holes (28) are positioned between two front and rear adjacent full-section supporting frames, and each row of radial grouting holes (28) are positioned between two front and rear adjacent profile steel arches (11);
and D1, when the arch wall of the primary support section to be reinforced is reinforced by radial grouting, the arch wall is reinforced by grouting from back to front through a plurality of rows of radial grouting holes (28).
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