CN108590667B

CN108590667B - Tunnel excavation and primary support method based on regional surrounding rock fracture evolution analysis

Info

Publication number: CN108590667B
Application number: CN201810338168.1A
Authority: CN
Inventors: 于远祥; 王赋宇; 王京滨; 柯达
Original assignee: Guangdong Construction Engineering Co Ltd
Current assignee: Guangdong Construction Engineering Co ltd; Shenzhen Mingyu Intellectual Property Operations Co ltd
Priority date: 2018-04-16
Filing date: 2018-04-16
Publication date: 2020-02-07
Anticipated expiration: 2038-04-16
Also published as: CN108590667A

Abstract

The invention discloses a tunnel excavation and preliminary bracing method based on regional rupture evolution analysis of surrounding rocks, which comprises the steps of excavating a constructed tunnel and carrying out preliminary bracing construction on the constructed tunnel by a plurality of sections from back to front along a longitudinal extension direction; when any segment is excavated and initially supported, the method comprises the following steps: firstly, excavating a tunnel; secondly, determining basic mechanical parameters of the surrounding rock; thirdly, carrying out regional fracture evolution analysis on the surrounding rock; fourthly, judging primary support of the tunnel; fifthly, determining a primary tunnel supporting structure; sixthly, performing primary support construction of the tunnel; seventhly, excavating the next section and constructing the surrounding rock support of the roadway; and eighthly, repeating the step seven for multiple times until the whole excavation and primary support construction process of the constructed tunnel is completed. The method has the advantages of simple steps, reasonable design, convenience in implementation and good use effect, purposefully carries out the radial grouting reinforcement and the primary support of the surrounding rock according to the analysis result of the regional fracture evolution of the surrounding rock, and can effectively ensure the stability and the safety of the surrounding rock of the tunnel.

Description

Tunnel excavation and primary support method based on regional surrounding rock fracture evolution analysis

Technical Field

The invention belongs to the technical field of tunnel construction, and particularly relates to a tunnel excavation and primary support method based on surrounding rock partition fracture evolution analysis.

Background

Underground caverns are not only used for transportation, water and electricity, mines and the like, but also widely used for underground city construction, refrigeration, oil storage, water storage, environmental engineering, national defense engineering and the like in modern times, and the caverns can be divided into two categories of water passing (such as water diversion tunnels) and water non-passing (such as traffic tunnels). A deeply buried cavern (also called a deeply buried underground cavern) refers to an underground cavern buried more than 50m deep. Among them, the tunnel is the main deep buried cavern, especially the construction project of tunnel of growing up nowadays is increasing day by day.

In recent years, deep rock mass engineering has been increasing with the rapid increase in demand for underground space and resources. According to incomplete statistics, the foreign mining depth of metal mines exceeding 1000m reaches hundreds of seats; the mining depth of a plurality of mines in China exceeds 1000m, and most of domestic mines enter the mining depth of 1000 m-2000 m within 10 years-20 years in the future. Meanwhile, a large number of deeply buried underground cavern projects, such as mountain traffic tunnels, large hydroelectric engineering diversion tunnels, deep nuclear waste disposal wells, petroleum war-reserve storage projects and the like, are being or planned to be constructed at home and abroad. These deep rock mass projects face complex geological environments of high ground stress, high ground temperature and high pore water pressure, and show significant nonlinear deformation and destruction characteristics different from shallow rock masses, such as zone rupture, severe rock burst, surrounding rock extrusion large deformation and the like. The surrounding rock is broken in a subarea manner, so that the deep-buried cavern faces a plurality of worldwide technical problems to be solved in the excavation and supporting process, and the surrounding rock is one of hot spots and difficulties in the research of the deep rock engineering field.

The zonal fracture is a special geological phenomenon generated by alternation of a fractured zone and a non-fractured zone in the surrounding rock of a deep-buried cavern, the zonal fracture mechanism of the surrounding rock is deeply researched by means of theoretical derivation, experimental analysis, numerical simulation and the like for a long time, and in the early 80 s of the last century, the phenomenon of zonal fracture of the surrounding rock is found in a deep M a як mine by using a resistivity instrument, and is shown in figure 1.

The method includes the steps of analyzing the development and formation of stope roof interval fracture with time and mining activity by field monitoring data, investigating the relationship between mine earthquake and roof zonal fracture, performing experimental study on the influence of discontinuity in the surrounding rock on interval fracture by E.J.Serler and P.Klerck, analyzing the physical basis of zonal fracture by using the unbalanced thermodynamic equation and performing calculation on the zonal fracture by M.B.Kyp. H.H.O.P.H.O.P.laneway я and B.H.O.P.P.H.P.P.P.E.H.P.P.P.E.P.E.H.P.E.P.E.P.P.P.H.O.P.P.P.laneway, simulating the fracture zone radius and thickness calculation formula applicable to a specific mining area, analyzing the physical basis of zonal fracture by using the unbalanced thermodynamic equation and performing calculation on the peripheral fracture zone, and performing calculation on the peripheral fracture zone fracture displacement calculation, and explaining that the peripheral fracture displacement is not changed due to the change of the initial fracture stress generation condition, and the peripheral fracture generation of the peripheral fracture generation is considered to no change of the peripheral fracture zone stress generation of the peripheral rock E.E.P.P.P.P.P.P.P.P.P.P.E.P.P.P.P.P.E.P.P.P.P.P.P.P.P.E.P.P.P.E.P.P.P.P.P.E.P.P.P.P.P.P.E. к у.

In China, the concept of 'partition cracking' is firstly put forward in China by Qian seven tigers, and the generation conditions, the main characteristics and the change rule of partition cracking are analyzed; the RFPA numerical software is applied to the Thangchuan and the like to research a rock mass interval fracture mechanism and an evolution rule; the analytical relation between the partition fracture radius and the roadway excavation radius is provided by performing site monitoring on surrounding rocks of the Huainan Ding ore collection deep-buried roadway on plum operation, a great deal of development and the like; the width and the number of the cracking area and the non-cracking area of the surrounding rock of the deep-buried spherical chamber are studied by the circumference; a kinetic theory solution of a chamber excavation instant surrounding rock radial stress field under the equivalent symmetrical stress field of the construction work indicates that the radii of all fracture areas of the subareas have an equal ratio relation; the method is based on a thick-walled cylinder three-dimensional line elastic analysis model, and discusses the action mechanism of horizontal stress and axial pressure on the zonal fracture of the surrounding rock; the Zuoyun and the like research the mechanical mechanism of the zonal fracture of the surrounding rock of the deep roadway under the dynamic and static combination conditions; the formation mechanism and the anchoring characteristic of the zonal rupture of the surrounding rock under high ground stress are discussed by the Chenxu light; the Wangchi and the like simulate the zonal damage of the surrounding rock of the deep roadway based on loading and unloading models, and the unloading models are considered to be closer to the actual engineering; model test research is carried out on the zonal fracture of the surrounding rock of the deep cavern by Zhang waves and the like after the King of jin.

In conclusion, domestic and foreign experts have obtained a series of research results on the regional fracture of the deep surrounding rock, but due to the high complexity of the environment of the deep rock engineering and the deformation of the deep rock engineering, the research on the regional fracture of the surrounding rock is still in the initial stage at present, and particularly, the research results on determining the thickness and the number of the fractured regions of the surrounding rock are less. Accordingly, the safety risk existing in the excavation construction process of the underground cavern with the deep surrounding rock zone fracture is very large.

Disclosure of Invention

The invention aims to solve the technical problem of providing a tunnel excavation and primary support method based on the regional rupture evolution analysis of the surrounding rock, which has the advantages of simple steps, reasonable design, convenient implementation and good use effect, purposefully carries out the radial grouting reinforcement and the primary support of the surrounding rock according to the regional rupture evolution analysis result of the surrounding rock, and can effectively ensure the stability of the surrounding rock of the tunnel and the safety of the tunnel.

In order to solve the technical problems, the invention adopts the technical scheme that: a tunnel excavation and primary support method based on surrounding rock partition fracture evolution analysis is characterized by comprising the following steps: excavating and primary supporting construction are carried out on the constructed tunnel by dividing the tunnel into a plurality of sections from back to front along the longitudinal extension direction, and the excavating and primary supporting construction methods of the plurality of sections are the same; when any segment is excavated and initially supported, the method comprises the following steps:

step one, tunnel excavation: excavating the current construction segment;

step two, determining basic mechanical parameters of the surrounding rock: testing basic mechanical parameters of surrounding rocks of the currently constructed section excavated in the step one by performing an indoor test on a field-taken rock sample, and synchronously recording a test result;

step three, carrying out zonal rupture evolution analysis on surrounding rocks: according to the basic mechanical parameters of the surrounding rock determined in the second step, carrying out regional surrounding rock fracture evolution analysis on the currently constructed section, and respectively determining the number M of fracture regions and the thickness of each fracture region on the surrounding rock of the currently constructed cavern after excavation is finished according to the analysis result; wherein M is an integer and M is not less than 0; when M is 0, the fact that no cracking zone exists on the surrounding rock of the currently constructed section is indicated; the currently constructed cavern is a tunnel cave of the currently constructed section formed by excavation in the step one;

when carrying out the regional rupture evolution analysis of surrounding rock to the segment of being under construction at present, divide the surrounding rock of cavern of being under construction at present into a plurality of surrounding rock subregion from inside to outside to from inside to outside a plurality of the surrounding rock subregion carries out the rupture analysis respectively, and the process is as follows:

step 301, carrying out zonal fracture analysis on the first surrounding rock: the method for analyzing the fracture of the first surrounding rock subarea outside the currently constructed cavern comprises the following steps:

step 3011, determining the thickness of the first surrounding rock partition: according to the formula

(I) calculating the thickness l of the first surrounding rock subarea₀，l₀The unit of (a) is m; in the formula (I), R₀The unit of the equivalent excavation radius of the currently constructed cavern is m; rho₀The radius of a neutral point of the anchor rod in the first surrounding rock zone is the sum of the radius of the neutral point of the anchor rod in the first surrounding rock zone and the equivalent excavation radius of the currently constructed cavern, and the radius of the neutral point of the anchor rod in the first surrounding rock zone is the distance between the front end of the anchor rod in the first surrounding rock zone and the neutral point;

wherein

U is the cross section perimeter of the anchor rod adopted when the current constructed cavern is supported and the unit is m, A is the cross section area of the anchor rod and the unit is m²，E_bThe unit of the elastic modulus of the anchor rod is Pa, and the unit of the K is the shear stiffness coefficient of the anchor rod body in unit length and is Pa/m;

step 3012, fracture determination: for [ sigma ]_r0-μ(σ_θ0+σ_z0) I and sigma_tAnd | comparing difference values, and judging whether the first surrounding rock subarea is broken or not according to the comparison result of the difference values: when sigma_r0-μ(σ_θ0+σ_z0)|≥|σ_tIf yes, judging that the first surrounding rock partition is broken and the first surrounding rock partition is a broken surrounding rock partition at the moment, and entering step 3013; otherwise, judging that no fracture zone exists on the surrounding rock of the currently constructed cavern and M is 0, and completing the regional fracture evolution analysis process of the surrounding rock of the currently constructed cavern;

the fracture surrounding rock is divided into a fracture area and a non-fracture area located outside the fracture area;

wherein, | σ_tL is σ_tAbsolute value of (a)_tIs the tensile strength of the surrounding rock of the currently constructed cavern and has the unit of Pa,

wherein m is a coefficient related to the rock type and integrity of the surrounding rock of the currently constructed cavern and is 0.001-25, s is a rock integrity coefficient of the surrounding rock of the currently constructed cavern, and sigma is_cThe uniaxial compressive strength of the surrounding rock mass of the currently constructed cavern is Pa;

|σ_r0-μ(σ_θ0+σ_z0) L is σ_r0-μ(σ_θ0+σ_z0) Absolute value of (d);

mu is the Poisson's ratio of the tunnel surrounding rock mass of the currently constructed cavern, and sigma is_r0The radial stress of the rock mass at the elastic-plastic boundary of the first surrounding rock partition under the action of the supporting pressure peak value is Pa;whereinIs the internal friction angle, P, of the surrounding rock mass of the currently constructed cavern₀' is a supporting counter force on the elastic-plastic interface of the first surrounding rock subarea;is the outer diameter of a plastic zone of the surrounding rock in the first surrounding rock zone and

c is cohesive force of the surrounding rock mass of the currently constructed cavern and the unit of the cohesive force is Pa; a. the₀And t are both a coefficient of the sum,

g is the shear modulus of the surrounding rock mass of the currently constructed cavern and the unit of G is Pa; b is a support coefficient, b is a constant and is more than 0 and less than 1;the displacement value of the surrounding rock on the surface of the currently constructed cavern before supporting is the unit of m and r_b0The distance r from the outer end of the anchor rod to the center of the currently constructed cavern in the first surrounding rock subarea_b0＝l₀+R₀；N_max0The maximum axial force is applied to the anchor rod at the neutral point of the anchor rod in the first surrounding rock subarea

B is a coefficient related to the deformation of surrounding rock of the currently constructed cavern

E_rIs the comprehensive elastic modulus of the surrounding rock mass of the currently constructed cavern and has the unit of Pa, P₀The method comprises the steps of (1) determining the original rock stress of the surrounding rock mass of a currently constructed cavern before excavation, wherein the unit of the original rock stress is Pa; r_p0The unit of the radius of the plastic zone of the surrounding rock of the currently constructed grotto under the elastic-plastic condition after excavation is m,

σ_θ0for the tangential stress at the elastoplastic boundary of the first wall rock zone and

σ_z0for axial stress at elastoplastic boundary of surrounding rock in first surrounding rock zone and sigma_z0＝(1+2μ)P₀，σ_θ0And σ_z0The unit of (A) is Pa;

step 3013, determining the thickness of the fracture zone in the first surrounding rock zone: according to the formula

(II) thickness d of the fracture zone in the first surrounding rock zone_s0Determining;

wherein the content of the first and second substances,

is the outer diameter of the inner cracking zone of the first surrounding rock zone andinner diameter of fracture zone in first surrounding rock zone

Step 302, next surrounding rock partition fracture analysis: performing fracture analysis on the next surrounding rock subarea outside the currently constructed cavern; in the step, the surrounding rock partition for fracture analysis is the Kth surrounding rock partition outside the currently constructed cavern, wherein K ' is a positive integer and K ' is not less than 2, K ' is K +1, and K is a positive integer and K is not less than 1; in the step, the fracture analysis process is completed on the K surrounding rock subareas positioned on the inner side of the K' th surrounding rock subarea;

when fracture analysis is carried out on the Kth surrounding rock subarea, the method comprises the following steps:

step 3021, determining the thickness of the Kth surrounding rock partition: according to the formula

(III) calculating the thickness l of the Kth surrounding rock subarea_k，l_kThe unit of (a) is m;

in the formula (III), ρ_kThe radius of a neutral point of the anchor rod in the Kth surrounding rock zone is the sum of the radius of the neutral point of the anchor rod in the Kth surrounding rock zone and the equivalent excavation radius of the currently constructed cavern, and the radius of the neutral point of the anchor rod in the Kth surrounding rock zone is the distance between the front end of the anchor rod and the neutral point in the Kth surrounding rock zone;

wherein,. DELTA.l_kzFor K said walls located inside the K' th wall rock zoneThe sum of the zonal thicknesses of the zones of rock and in units of m;

step 3022, fracture determination: for [ sigma ]_rk-μ(σ_θk+σ_zk) I and sigma_tAnd | comparing difference values, and judging whether the Kth surrounding rock subarea is broken or not according to the comparison result of the difference values: when sigma_rk-μ(σ_θk+σ_zk)|≥|σ_tIf yes, judging that the K 'surrounding rock subarea is broken and the K' surrounding rock subarea is a broken surrounding rock subarea at the moment, and entering step 3023; otherwise, judging that no fracture zone exists in the Kth surrounding rock partition and M is equal to K, and completing the surrounding rock partition fracture evolution analysis process of the currently constructed cavern;

wherein, | σ_rk-μ(σ_θk+σ_zk) L is σ_rk-μ(σ_θk+σ_zk) Absolute value of (d);

σ_rkthe radial stress of the rock mass at the elastic-plastic boundary of the Kth surrounding rock partition under the action of the supporting pressure peak value is expressed by Pa;

P_kis the supporting counter force on the elastic-plastic interface in the K' th surrounding rock subarea and has the unit of Pa,

τ_sis the residual shear strength of the surrounding rock of the currently constructed cavern and has the unit of Pa,

the outer diameter of the cracking zone in the kth surrounding rock zone which is positioned at the inner side of the kth surrounding rock zone and is adjacent to the kth surrounding rock zone,

the inner diameter of a fracture zone in the kth surrounding rock zone;

is the outer diameter of a plastic zone of surrounding rock in the K' th surrounding rock subareaA_kIs a coefficient of

Wherein r is_bkThe sum of the thickness of a cracking zone in the Kth surrounding rock partition and the equivalent excavation radius of the currently constructed cavern is r_bk＝l_k+R₀；N_maxkThe maximum axial force is applied to the anchor rod at the neutral point of the anchor rod in the Kth surrounding rock zone

σ_θkFor the tangential stress at the elastoplastic boundary of the surrounding rock in the Kth surrounding rock zoneσ_zkFor the axial stress at the elastoplastic boundary of the surrounding rock in the Kth surrounding rock zone and sigma_zk＝(1+2μ)P₀，σ_θkAnd σ_zkThe unit of (A) is Pa;

step 3023, determining the thickness of the fracture zone in the Kth surrounding rock zone: according to the formula

(IV) thickness d of the fracture zone in the Kth surrounding rock zone_skDetermining;

wherein the content of the first and second substances,is the outer diameter of the cracking zone in the K' th surrounding rock zone andΔR_k＝R₀+Δl_kz(ii) a Inner diameter of fracture zone in Kth' surrounding rock zone

Step 303, repeating step 302 once or for multiple times until the surrounding rock zonal fracture evolution analysis process of the currently constructed cavern is completed;

step four, judging the primary support of the tunnel: and according to the number M of the cracking zones determined in the third step, judging whether the tunnel primary support is needed for the currently constructed cavern: when M is equal to 0, judging that the currently constructed grotto does not need to be subjected to tunnel primary support, and entering a seventh step; otherwise, entering the step five;

step five, determining a tunnel primary support structure: the adopted primary tunnel supporting structure is an anchor net-blasting primary supporting structure for supporting the tunnel arch wall of the currently constructed cavern, and the anchor net-blasting primary supporting structure is a primary supporting structure formed by construction by adopting an anchor net-blasting supporting method; the anchor net-blasting primary support structure comprises a plurality of tunnel anchoring support systems which are arranged in a currently constructed tunnel from back to front along the extending direction of the tunnel, and the structures of the tunnel anchoring support systems are the same;

each tunnel anchoring support system comprises a tunnel arch support system for supporting the arch of the currently constructed cavern and a tunnel side wall support system for supporting the side wall of the currently constructed cavern, and the tunnel arch support system and the tunnel side wall support system are arranged on the same tunnel cross section; the tunnel side wall supporting system comprises a left side wall supporting unit and a right side wall supporting unit which respectively support the left side wall and the right side wall of the currently constructed grotto, the two side wall supporting units are symmetrically arranged, and the two side wall supporting units are arranged on the cross section of the same tunnel;

the tunnel arch supporting system comprises M tunnel arch supporting structures which respectively support the M cracking zones, and the M tunnel arch supporting structures are uniformly distributed on the same tunnel cross section; each tunnel arch supporting structure comprises a plurality of arch anchoring pieces which are arranged on the arch of the currently constructed cavern from left to right, wherein each arch anchoring piece is an anchor rod or an anchor cable;

when the tunnel arch supporting structure for supporting the cracking zone in the first surrounding rock zone is determined, the first surrounding rock zone is determined according to the step 3013Thickness d of inner rupture zone_s0Determining the length of an arch anchoring piece in the tunnel arch supporting structure;

when the tunnel arch supporting structure for supporting the cracking zone in the Kth surrounding rock partition is determined, the supporting structure is determined according to the delta l determined in the step 3021_kzAnd the thickness d of the fracture zone in the Kth' surrounding rock zone determined in step 3023_skDetermining the length of an arch anchoring piece in the tunnel arch supporting structure;

each side wall supporting unit comprises a plurality of side wall anchoring pieces which are arranged on the cross section of the same tunnel from top to bottom, and the side wall anchoring pieces are horizontally arranged and are anchor rods or anchor cables;

when the supporting structure adopted by the side wall supporting unit is determined, the Δ l determined in the step 3021 is used as the basis_kzAnd the thickness d of the fracture zone in the Kth' surrounding rock zone determined in step 3023_skDetermining the length of the side wall anchor;

step six, primary support construction of the tunnel: according to the tunnel primary support structure determined in the fifth step, performing primary support on the currently constructed cavern excavated and formed in the first step from back to front;

seventhly, excavating the next section and constructing surrounding rock support of the roadway: repeating the first step to the sixth step, and performing excavation and primary support construction on the next segment;

and step eight, repeating the step seven for multiple times until the whole excavation and primary support construction process of the constructed tunnel is completed.

The tunnel excavation and primary support method based on the surrounding rock partition fracture evolution analysis is characterized by comprising the following steps: step 3013 is also performed according to formula d_ns0＝l₀-d_s0Calculating the thickness d of the non-cracking zone in the first surrounding rock zone_ns0；

Step 3023 also requires a formula d_nsk＝l_k-d_skAnd calculating the thickness d of the non-cracking zone in the Kth surrounding rock zone_nsk。

The tunnel excavation and primary support method based on the surrounding rock partition fracture evolution analysis is characterized by comprising the following steps: before basic mechanical parameters of the surrounding rock are determined in the second step, a section is selected from a currently constructed grotto and used as a test section to be excavated;

when basic mechanical parameters of the surrounding rock are determined in the second step, taking a rock sample from the test section to perform an indoor test, wherein the obtained test result is the basic mechanical parameters of the surrounding rock of the currently constructed grotto after excavation;

the longitudinal lengths of the segments are all 10-50 m;

and fifthly, the distance between the front and back adjacent two tunnel anchoring and supporting systems is 0.8-1.2 m.

The tunnel excavation and primary support method based on the surrounding rock partition fracture evolution analysis is characterized by comprising the following steps: and fifthly, when the tunnel arch supporting structure for supporting the inner cracking zone of the first surrounding rock zone is determined, all arch anchoring pieces in the tunnel arch supporting structure are the same in length, and the lengths of all arch anchoring pieces in the tunnel arch supporting structure are not less than L₁Wherein L is₁＝l₁'+d_s0+l₂'；l₁' and l₂Are all constants,/₁'＝0.1m～15cm，l₂'＝0.3m～0.4m；

When the tunnel arch supporting structure for supporting the inner cracking zone of the Kth surrounding rock partition is determined, all arch anchoring pieces in the tunnel arch supporting structure are the same in length, and the lengths of all arch anchoring pieces in the tunnel arch supporting structure are not less than L_kWherein L is_k＝l₁'+Δl_kz+d_sk+l₂'；

When the supporting structure adopted by the side wall supporting unit is determined, the lengths of all the side wall anchoring pieces are the same, and the length of each side wall anchoring piece is not less than L₂Wherein L is₂＝l₁'+Δl_(M-1)z+d_s(M-1)+l₂' M is the number of the cracking zones on the surrounding rock of the currently constructed cavern determined in the third step.

The tunnel excavation and primary support method based on the surrounding rock partition fracture evolution analysis is characterized by comprising the following steps: in the third step, the surrounding rock partition is positioned outside the currently constructed cavern, and the cross sections of the surrounding rock partition, the fractured zone and the non-fractured zone are the same as the cross section of the currently constructed cavern;

in step 3012, m is 0.01, s is 0 to 1, and b is 0.8.

The tunnel excavation and primary support method based on the surrounding rock partition fracture evolution analysis is characterized by comprising the following steps: fifthly, each tunnel anchoring support system also comprises a tunnel bottom support system for supporting the bottom of the currently constructed cavern, and the tunnel bottom support system, the tunnel arch support system and the tunnel side wall support system are arranged on the same tunnel cross section;

the tunnel bottom supporting system comprises a plurality of bottom anchoring pieces which are arranged at the bottom of the currently constructed grotto from left to right, and the bottom anchoring pieces are uniformly distributed on the cross section of the same tunnel; the bottom anchoring piece is an anchor rod or an anchor cable;

when the supporting structure adopted by the tunnel bottom supporting system is determined, the determined delta l in the step 3021 is used as the basis_kzAnd the thickness d of the fracture zone in the Kth' surrounding rock zone determined in step 3023_skThe length of the bottom anchor is determined.

The tunnel excavation and primary support method based on the surrounding rock partition fracture evolution analysis is characterized by comprising the following steps: before the tunnel primary support construction in the sixth step, whether the currently constructed grotto needs surrounding rock radial grouting reinforcement or not is judged according to the number M of the cracking zones determined in the third step: when M is equal to 0, judging that the currently constructed grotto does not need to be subjected to surrounding rock radial grouting reinforcement; otherwise, judging that the currently constructed cavern needs to be reinforced by surrounding rock radial grouting, and before the tunnel primary support construction in the sixth step, carrying out surrounding rock radial grouting reinforcement on the currently constructed cavern for multiple times from back to front along the longitudinal extension direction;

the method for reinforcing the surrounding rock by multiple times of radial grouting is the same; when the radial grouting reinforcement of the surrounding rock is carried out each time, the process is as follows:

step C1, determining the position of the cracking zone: respectively determining the positions of the M breaking zones outside the currently constructed cavern according to the thicknesses of the K surrounding rock zones outside the currently constructed cavern and the thicknesses of the M breaking zones determined in the third step;

step C2, grouting and reinforcing the cracking zone: according to the positions of the M cracking zones determined in the step C1, grouting and reinforcing the M cracking zones by grouting pipes respectively;

when grouting reinforcement is carried out on any one of the fracture areas, grouting reinforcement is carried out by adopting a grouting pipe inserted into the fracture area from inside to outside from the currently constructed cavern; the grouting pipe is a hollow steel pipe which is inserted into the cracking zone from inside to outside and the front end of the grouting pipe is provided with a grouting hole, the front end of the grouting pipe is positioned in the cracking zone, and the rear end of the grouting pipe is connected with grouting equipment through a grouting pipeline;

c2, when grouting reinforcement is carried out on the fractured zone, all grouting pipes are positioned on the same cross section of the currently constructed cavern; the cross section of the currently constructed cavern where the grouting pipe is located is a grouting reinforcement position;

and the distance between grouting reinforcement positions during two adjacent times of surrounding rock radial grouting reinforcement is 3-8 m.

The tunnel excavation and primary support method based on the surrounding rock partition fracture evolution analysis is characterized by comprising the following steps: c2, the grouting pipe is a hollow drill rod drilled from the inside to the outside from the currently constructed chamber;

the distance between the grouting reinforcement position on the last side in the currently constructed cavern and the rear end face of the currently constructed cavern is 3-8 m, and the distance between the grouting reinforcement position on the foremost side in the currently constructed cavern and the front end face of the currently constructed cavern is 3-8 m;

c2, when grouting reinforcement is carried out on any one of the fracture areas, two groups of symmetrically arranged grouting pipes are adopted for grouting reinforcement; the two groups of grouting pipes are respectively arranged above the left side and the right side of the currently constructed cavern, and each group of grouting pipes comprises one grouting pipe or a plurality of grouting pipes arranged from left to right along the excavation contour line of the currently constructed cavern; and the two groups of grouting pipes are positioned on the same cross section of the currently constructed cavern.

The tunnel excavation and primary support method based on the surrounding rock partition fracture evolution analysis is characterized by comprising the following steps: when grouting reinforcement is respectively carried out on the M cracking zones in the step C2, grouting reinforcement is respectively carried out on the M cracking zones from outside to inside or from inside to outside by adopting the same grouting pipe group;

when the same grouting pipe group is adopted to respectively perform grouting reinforcement on the M fracture zones from outside to inside, the process is as follows:

step A1, grouting and reinforcing a fractured zone of the Mth surrounding rock zone: grouting reinforcement is carried out on the fracture area of the Mth surrounding rock partition by adopting the grouting pipe group;

the grouting pipe group comprises two groups of symmetrically arranged grouting pipes, the two groups of grouting pipes are respectively arranged above the left side and the right side of the currently constructed cavern, and each group of grouting pipes comprises one grouting pipe or a plurality of grouting pipes arranged from left to right along the excavation contour line of the currently constructed cavern; the two groups of grouting pipes are positioned on the same cross section of the currently constructed cavern;

in the step, the front end of each grouting pipe in the two groups of grouting pipes is inserted into a fracture zone of the Mth surrounding rock zone;

step A2, grouting reinforcement ending judgment: judging whether the grouting reinforcement processes of the M fracture zones are all completed or not: after the grouting reinforcement processes of the M cracking areas are all completed, the excavation construction process of the currently constructed grotto is completed; otherwise, go to step A3;

step A3, grouting and reinforcing a fractured zone of the next surrounding rock zone: moving each grouting pipe in the grouting pipe group backwards to the position, at the front end, of the grouting pipe group in the fracture area of the next surrounding rock partition, and grouting and reinforcing the fracture area of the next surrounding rock partition by adopting the grouting pipe group; thereafter, return to step a 2;

when the same grouting pipe group is adopted to carry out grouting reinforcement on the M fracturing zones from inside to outside, the process is as follows:

step B1, grouting and reinforcing the fractured zone of the 1 st surrounding rock zone: grouting and reinforcing the fracture area of the 1 st surrounding rock partition by adopting the grouting pipe group;

in the step, the front end of each grouting pipe in the two groups of grouting pipes is inserted into a cracking zone of the 1 st surrounding rock partition;

step B2, grouting reinforcement ending judgment: judging whether grouting reinforcement of a fractured zone of the Mth surrounding rock zone is completed: after the grouting reinforcement process of the fractured zone of the Mth surrounding rock zone is completed, the excavation construction process of the currently constructed grotto is completed; otherwise, go to step B3;

step B3, grouting and reinforcing a fractured zone of the next surrounding rock zone: each grouting pipe (2) in the grouting pipe group is moved forwards until the front end of each grouting pipe is positioned in the fracture area of the next surrounding rock partition, and then the grouting pipe group is adopted to perform grouting reinforcement on the fracture area of the next surrounding rock partition; thereafter, the process returns to step B2.

The tunnel excavation and primary support method based on the surrounding rock partition fracture evolution analysis is characterized by comprising the following steps: in step C1, according to the thicknesses of the M surrounding rock sub-areas and the thicknesses of the M cracking areas outside the currently constructed cavern determined in step three, when the positions of the M cracking areas outside the currently constructed cavern are determined, the positions of the M cracking areas are determined from inside to outside, respectively, and the method includes the following steps:

step C11, determining the position of a cracking zone in the first surrounding rock zone: determining the position of the cracking area of the first surrounding rock partition according to the arch excavation contour line of the currently constructed cavern and the thickness of the cracking area in the first surrounding rock partition determined in the step three;

the cracking zone of the first surrounding rock zone is positioned outside the excavation contour line of the currently constructed grotto and has the width d_s0The area of (a);

step C12, determining and ending the position of the rupture zone: judging whether the positions of the M cracking zones are determined: when the positions of the M cracking zones are determined, the position determination process of the M cracking zones is completed; otherwise, go to step C13;

step C13, determining the position of the cracking zone in the next surrounding rock zone: determining the position of the cracking zone in the next surrounding rock partition according to the total thickness of all the surrounding rock partitions positioned on the inner sides of the surrounding rock partitions and the thickness of the cracking zone in the surrounding rock partition determined in the step three;

in this step, the next surrounding rock partition is a Kth surrounding rock partition, and the fracture area of the Kth surrounding rock partition is located outside the outer contour line of the Kth surrounding rock partition and has a width of d_skThe area of (a); the shape of the outer contour line of the kth surrounding rock partition is the same as that of the excavation contour line of the currently constructed cavern, and the distance between the outer contour line and the excavation contour line is delta l_kz。

Compared with the prior art, the invention has the following advantages:

1. the method has simple steps, convenient realization and low investment cost.

2. The tunnel excavation method is reasonable in design and convenient to achieve, in order to ensure the excavation effect, the tunnel is excavated by a plurality of sections from back to front along the longitudinal extension direction of the tunnel, the construction is simple and convenient, the construction process is easy to control, and the operability is high.

3. The method for analyzing the zonal rupture evolution of the surrounding rock has the advantages of simple steps, convenient implementation and low investment cost, and can complete the analysis process within minutes, even tens of seconds by adopting data processing equipment.

4. After the excavation is finished, basic mechanical parameters of the surrounding rock are determined, and then the surrounding rock zonal rupture evolution analysis is carried out on the currently constructed cavern according to the determined basic mechanical parameters of the surrounding rock, so that the analysis result of the surrounding rock zonal rupture evolution analysis is accurate and reliable, and the operability is high.

5. The analysis design of the regional fracture evolution of the surrounding rock is reasonable, aiming at the characteristic that the deformation of the surrounding rock tends to be stable after a period of excavation and support of a deep-buried grotto, an analysis model is established by starting from the stress analysis of a full-length anchoring anchor rod adopted in the construction of the initial excavation support, the fracture analysis is respectively carried out on the surrounding rock regions by determining the radius of a neutral point of the anchor rod and the maximum axial force of the anchor rod, and the fracture analysis result is very close to the actual engineering. Because the stress of the surrounding rock is redistributed after the cavern is excavated, when the tensile stress generated by the rock on the elastic-plastic interface under the maximum tangential supporting pressure exceeds the ultimate tensile strength, the rock is radially fractured and a plurality of fractured regions and non-fractured regions are alternately distributed; the difference of the rock mass displacement rate in the fractured zone and the non-fractured zone can cause a plurality of neutral points of the anchor rod along the length direction; and the thickness of the wall rock cracking area is approximately in a gradually decreasing trend until the wall rock cracking stops. According to the stress deformation characteristic of anchor rod tension-pressure stress alternative distribution under the condition of surrounding rock zone rupture, a novel method for carrying out inversion analysis on surrounding rock zone rupture through the anchor rod stress law is provided. Based on the coordinated deformation principle of the rod body and the surrounding rock, a mechanical model of interaction of the full-length anchoring bolt and the surrounding rock is established, and the thicknesses of a cracking area and a non-cracking area of the surrounding rock in each surrounding rock partition are obtained through corresponding analysis. Based on the Griffis strength theory, a mechanical criterion (namely a fracture judgment basis) for tensile fracture of the elastoplastic interface rock body after the stress redistribution of the surrounding rock is provided, and the total quantity (namely M) of fracture areas of the surrounding rock is further determined.

6. The method for analyzing the regional rupture evolution of the surrounding rock has a good using effect, analyzes the basic evolution law of the regional rupture of the surrounding rock based on the coordinated deformation principle of the anchor rod and the surrounding rock, and reasonably determines the thickness and the number of the ruptured regions of the surrounding rock of the deeply buried cavern to provide important theoretical basis for cavern excavation and supporting. The analysis shows that: the thickness of each surrounding rock partition and the thickness of each cracking area are approximately in a gradually decreasing trend from the tunnel wall to the depth of the surrounding rock, the total number of the cracking areas obtained through analysis and the thickness and the position of each cracking area can effectively and reasonably determine the excavation scheme of the deeply buried tunnel and the surrounding rock supporting parameters of the deeply buried tunnel, and a new thought is provided for the research of the deep rock mass engineering surrounding rock partition cracking.

7. The method for reinforcing the surrounding rock by radial grouting is simple, reasonable in design, simple and convenient to construct and good in reinforcing effect, the targeted grouting reinforcement is carried out on the basis of accurately judging the fracture position and thickness, the stability and the safety of the surrounding rock of the currently constructed cavern can be effectively guaranteed, the grouting reinforcement effect is very good, and the construction process is simple.

8. The tunnel preliminary bracing structural design who adopts is reasonable and strut effectually, including a plurality ofly by laying forward after and carry out the anchor net that full section was strutted to the cavern and spout preliminary bracing structure, can be simple and convenient, carry out preliminary bracing to excavation fashioned cavern fast. All set up anchor assembly on the arch portion of cavern, bottom and left and right sides limit wall to the length and the interval of anchor assembly reasonable in design can further improve the preliminary bracing effect in tunnel.

9. The method for determining the tunnel primary support structure is simple, reasonable in design, convenient to implement, good in using effect, capable of simply, conveniently and quickly determining the effective length of the adopted anchoring piece and correspondingly determining the length of the adopted anchoring piece, reasonable in length design of the anchoring piece, capable of effectively reinforcing all the fracture areas of tunnel surrounding rock integrally, labor-saving, material-saving and time-saving.

10. The method has good use effect, adopts the modes of sectional excavation and sectional support, carries out radial grouting reinforcement and primary support on the surrounding rock according to the regional fracture evolution analysis result of the surrounding rock, can effectively reinforce and support the tunnel, can effectively ensure the primary support effect of the long-distance tunnel, and has lower construction cost.

In conclusion, the method has the advantages of simple steps, reasonable design, convenience in implementation and good use effect, the number of the cracking zones outside the currently constructed cavern and the thickness and the position of each cracking zone can be obtained through the surrounding rock partition cracking evolution analysis, the surrounding rock radial grouting reinforcement and the primary support are purposefully carried out according to the surrounding rock partition cracking evolution analysis result, and the stability of the surrounding rock of the cavern and the safety of cavern excavation construction can be effectively ensured. In the tunnel excavation work progress, carry out the radial slip casting of surrounding rock to the fashioned cavern of excavation in step and consolidate to according to the tunnel primary support structure confirmed, carry out the preliminary bracing by the back forward to the cavern after the radial slip casting of surrounding rock is consolidated, construction period is short and the work progress is safe, reliable, can effectively guarantee tunnel surrounding rock steadiness and tunnel security.

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 diagram showing the distribution state of a fracture zone formed by the zone fracture of surrounding rock of the arch part of the deep-buried cavern.

Fig. 3 is a schematic diagram of the arrangement position of a grouting pipe used for grouting reinforcement of a cracking zone in the 1 st surrounding rock partition.

Fig. 4 is a schematic diagram of the arrangement position of a grouting pipe used for grouting reinforcement of a fracture zone in the 2 nd surrounding rock zone.

Fig. 5 is a schematic diagram of the arrangement position of a grouting pipe used for grouting reinforcement of a fractured zone in the 3 rd surrounding rock zone.

Fig. 6 is a schematic diagram of the arrangement position of a grouting pipe used for grouting reinforcement of a fractured zone in the 4 th surrounding rock zone.

Fig. 7 is a structural schematic view of the tunnel arch support system of the invention.

Description of reference numerals:

1, constructing a tunnel; 1-a surrounding rock partition cracking zone;

1-2-surrounding rock partition non-cracking zone; 2-grouting pipe; 3-arch anchoring;

4-side wall anchoring member; 5-bottom anchor.

Detailed Description

As shown in fig. 1, in the tunnel excavation and preliminary bracing method based on the regional cracking evolution analysis of the surrounding rock, excavation and preliminary bracing construction are performed on a constructed tunnel 1 by dividing the tunnel into a plurality of sections from back to front along a longitudinal extension direction, and the excavation and preliminary bracing construction methods of the plurality of sections are the same; when any segment is excavated and initially supported, the method comprises the following steps:

step one, tunnel excavation: excavating the current construction segment;

step 3011, determining the thickness of the first surrounding rock partition: according to the formula(I) calculating the thickness l of the first surrounding rock subarea₀，l₀The unit of (a) is m; in the formula (I), R₀The unit of the equivalent excavation radius of the currently constructed cavern is m; rho₀The radius of a neutral point of the anchor rod in the first surrounding rock zone is the sum of the radius of the neutral point of the anchor rod in the first surrounding rock zone and the equivalent excavation radius of the currently constructed cavern, and the radius of the neutral point of the anchor rod in the first surrounding rock zone is the distance between the front end of the anchor rod in the first surrounding rock zone and the neutral point;

wherein

|σ_r0-μ(σ_θ0+σ_z0) L is σ_r0-μ(σ_θ0+σ_z0) Absolute value of (d);

mu is the Poisson's ratio of the tunnel surrounding rock mass of the currently constructed cavern, and sigma is_r0The radial stress of the rock mass at the elastic-plastic boundary of the first surrounding rock partition under the action of the supporting pressure peak value is Pa;

wherein

Is the internal friction angle, P, of the surrounding rock mass of the currently constructed cavern₀' is the first elastic-plastic interface of surrounding rock partitionUpper supporting counter force;

is the outer diameter of a plastic zone of the surrounding rock in the first surrounding rock zone andc is cohesive force of the surrounding rock mass of the currently constructed cavern and the unit of the cohesive force is Pa; a. the₀And t are both a coefficient of the sum,

wherein the content of the first and second substances,

is the outer diameter of the inner cracking zone of the first surrounding rock zone and

inner diameter of fracture zone in first surrounding rock zone

(Ⅲ)，Calculating to obtain the K' th surrounding rock partition thickness l_k，l_kThe unit of (a) is m;

wherein,. DELTA.l_kzThe sum of the sectional thicknesses of K surrounding rock sections positioned at the inner side of the K' th surrounding rock section is m;

σ_rkthe radial stress of the rock mass at the elastic-plastic boundary of the Kth surrounding rock partition under the action of the supporting pressure peak value is expressed by Pa;P_kis the supporting counter force on the elastic-plastic interface in the K' th surrounding rock subarea and has the unit of Pa,

the inner diameter of a fracture zone in the kth surrounding rock zone;

is the outer diameter of a plastic zone of surrounding rock in the K' th surrounding rock subarea

A_kIs a coefficient of

σ_θkFor the tangential stress at the elastoplastic boundary of the surrounding rock in the Kth surrounding rock zone

σ_zkFor the axial stress at the elastoplastic boundary of the surrounding rock in the Kth surrounding rock zone and sigma_zk＝(1+2μ)P₀，σ_θkAnd σ_zkThe unit of (A) is Pa;

step 3023, determining the thickness of the fracture zone in the Kth surrounding rock zone: according to the formula(IV) thickness d of the fracture zone in the Kth surrounding rock zone_skDetermining;

wherein the content of the first and second substances,

is the outer diameter of the cracking zone in the K' th surrounding rock zone and

ΔR_k＝R₀+Δl_kz(ii) a Inner diameter of fracture zone in Kth' surrounding rock zone

as shown in fig. 7, each of the tunnel anchoring support systems includes a tunnel arch support system for supporting an arch of a currently constructed cavern and a tunnel side wall support system for supporting a side wall of the currently constructed cavern, and the tunnel arch support system and the tunnel side wall support system are arranged on a cross section of a same tunnel; the tunnel side wall supporting system comprises a left side wall supporting unit and a right side wall supporting unit which respectively support the left side wall and the right side wall of the currently constructed grotto, the two side wall supporting units are symmetrically arranged, and the two side wall supporting units are arranged on the cross section of the same tunnel;

the tunnel arch supporting system comprises M tunnel arch supporting structures which respectively support the M cracking zones, and the M tunnel arch supporting structures are uniformly distributed on the same tunnel cross section; each tunnel arch supporting structure comprises a plurality of arch anchoring pieces 3 arranged on the arch of the currently constructed cavern from left to right, and each arch anchoring piece 3 is an anchor rod or an anchor cable;

when the tunnel arch supporting structure for supporting the cracking zone in the first surrounding rock zone is determined, the thickness d of the cracking zone in the first surrounding rock zone determined in the step 3013 is determined_s0Determining the length of an arch anchoring part 3 in the tunnel arch supporting structure;

when the tunnel arch supporting structure for supporting the cracking zone in the Kth surrounding rock partition is determined, the supporting structure is determined according to the delta l determined in the step 3021_kzAnd the thickness d of the fracture zone in the Kth' surrounding rock zone determined in step 3023_skDetermining the length of an arch anchoring part 3 in the tunnel arch supporting structure;

each side wall supporting unit comprises a plurality of side wall anchoring pieces 4 which are arranged on the cross section of the same tunnel from top to bottom, and the side wall anchoring pieces 4 are horizontally arranged and are anchor rods or anchor cables;

when the supporting structure adopted by the side wall supporting unit is determined, the Δ l determined in the step 3021 is used as the basis_kzAnd the thickness d of the fracture zone in the Kth' surrounding rock zone determined in step 3023_skDetermining the length of the side wall anchor 4;

and step eight, repeating the step seven for multiple times until the whole excavation and primary support construction process of the constructed tunnel 1 is completed.

In the embodiment, the longitudinal lengths of the segments are all 10-50 m.

During actual construction, the longitudinal lengths of the segments can be adjusted correspondingly according to specific requirements.

In this embodiment, before determining the basic mechanical parameters of the surrounding rock in the second step, a section is selected from the currently constructed cavern as a test section to be excavated;

and step two, when basic mechanical parameters of the surrounding rock are determined, taking a rock sample from the test section to perform an indoor test, wherein the obtained test result is the basic mechanical parameters of the surrounding rock of the currently constructed grotto after excavation.

In this embodiment, the test section is located at the rear end of the currently constructed section and has a length of 1 m.

In this embodiment, the currently constructed cavern is a deep-buried cavern with a buried depth greater than 50 m. Thus, the constructed tunnel 1 is a deep buried tunnel.

The burial depth of the currently constructed cavern refers to the vertical distance from the top of the excavated section of the cavern to the natural ground.

As shown in fig. 7, in the fifth embodiment, each tunnel anchoring and supporting system in the step five further includes a tunnel bottom supporting system for supporting the bottom of the currently constructed cavern, and the tunnel bottom supporting system, the tunnel arch supporting system, and the tunnel side wall supporting system are arranged on the same tunnel cross section;

the tunnel bottom supporting system comprises a plurality of bottom anchoring pieces 5 which are arranged at the bottom of the currently constructed grotto from left to right, and the bottom anchoring pieces 5 are uniformly distributed on the cross section of the same tunnel; the bottom anchoring piece 5 is an anchor rod or an anchor cable;

when the supporting structure adopted by the tunnel bottom supporting system is determined, the determined delta l in the step 3021 is used as the basis_kzAnd the thickness d of the fracture zone in the Kth' surrounding rock zone determined in step 3023_skDetermining the length of the bottom anchor 5;

the arch anchoring piece 3, the side wall anchoring piece 4 and the bottom anchoring piece 5 are all anchoring pieces for tunnel supporting. During actual construction, determining the type of the anchoring piece for tunnel support according to the length of the anchoring piece for tunnel support, wherein when the length of the anchoring piece for tunnel support is less than 5m, the type of the anchoring piece for tunnel support is an anchor rod, and the anchor rod is a grouting anchor rod; when the length of the anchoring piece for tunnel support is more than or equal to 5m, the type of the anchoring piece for tunnel support is an anchor rope.

The anchor net spraying primary support structure further comprises a reinforcing mesh layer paved on the wall of the currently constructed chamber and a concrete layer sprayed on the wall of the currently constructed chamber, and the inner end of each anchoring piece for tunnel support in the tunnel anchoring support system and the reinforcing mesh layer are fixed in the concrete layer. In this embodiment, the concrete layer is a steel fiber concrete layer, and the thickness of the layer is 20cm to 30 cm.

And sixthly, when the preliminary tunnel supporting construction is carried out, carrying out preliminary supporting by adopting an anchor net spraying supporting method to obtain the preliminary tunnel supporting structure formed by construction. The adopted anchor net spraying support method is a conventional tunnel anchor net spraying support method.

In this embodiment, in the fifth step, all the anchoring parts for tunnel support in each tunnel anchoring support system are uniformly distributed on the same tunnel cross section.

In the fifth step, the distance between the front and rear adjacent two tunnel anchoring and supporting systems is 0.8-1.2 m.

During actual construction, the distance between the front and rear adjacent two tunnel anchoring and supporting systems can be correspondingly adjusted according to specific requirements.

In this embodiment, when the tunnel arch supporting structure for supporting the cracking zone in the first surrounding rock partition is determined in the step five, the lengths of all the arch anchoring pieces 3 in the tunnel arch supporting structure are the same, and the lengths of all the arch anchoring pieces 3 in the tunnel arch supporting structure are not less than L₁Wherein L is₁＝l₁'+d_s0+l₂'；l₁' and l₂Are all constants,/₁'＝0.1m～15cm，l₂'＝0.3m～0.4m；

When the tunnel arch supporting structure for supporting the inner cracking zone of the Kth surrounding rock partition is determined, all the arch anchoring pieces 3 in the tunnel arch supporting structure are the same in length, and the lengths of all the arch anchoring pieces 3 in the tunnel arch supporting structure are not less than L_kWherein L is_k＝l₁'+Δl_kz+d_sk+l₂'；

When the supporting structure adopted by the side wall supporting unit is determined, the lengths of all the side wall anchoring pieces 4 are the same, and the length of each side wall anchoring piece 4 is not less than L₂Wherein L is₂＝l₁'+Δl_(M-1)z+d_s(M-1)+l₂' M is the number of the cracking zones on the surrounding rock of the currently constructed cavern determined in the third step.

Wherein, the delta l_(M-1)zThe sum of the subarea thicknesses of M-1 surrounding rock subareas positioned at the inner side of the Mth surrounding rock subarea is M, d_s(M-1)Is the thickness of the fracture zone in the mth surrounding rock zone.

When the supporting structure adopted by the tunnel bottom supporting system is determined, all the bottom anchoring pieces 5 are the same in length, and the length of each bottom anchoring piece 5 is not less than L₂。

In the embodiment, the length of the arch anchoring piece 3 for supporting the cracking zone in the first surrounding rock zone is less than l₀Length < (Δ l) of arch anchor 3 supporting fractured zone in K' th surrounding rock zone_kz+l_k) The length of the side wall anchor 4 is less than (delta l_(M-1)z+l_(M-1)) The length of the bottom anchor 5 < (Δ l)_(M-1)z+l_(M-1)). Wherein l_(M-1)Is the thickness of the Mth surrounding rock subarea.

In this embodiment, the arch anchoring members 3 for supporting the fractured zone in any one surrounding rock zone are divided into two left and right groups, and the two groups of arch anchoring members 3 are respectively arranged above the left and right sides of the currently constructed cavern.

Each group of arch anchoring parts 3 comprises one arch anchoring part 3 or a plurality of arch anchoring parts 3 which are arranged from left to right along the excavation contour line of the currently constructed grotto; and the two groups of arch anchoring parts 3 are positioned on the same cross section of the currently constructed cavern.

In this embodiment, each set of the arch anchors 3 includes two arch anchors 3.

During actual construction, the number of the arch anchoring elements 3 included in each set of the arch anchoring elements 3 and the arrangement position of each arch anchoring element 3 can be adjusted correspondingly according to specific needs.

In this embodiment, the number of the side wall anchoring members 4 included in the side wall supporting unit is three, and the three side wall anchoring members 4 are uniformly distributed.

During actual construction, the number of the side wall anchoring members 4 included in the side wall supporting unit and the arrangement positions of the side wall anchoring members 4 can be adjusted correspondingly according to specific requirements.

In this embodiment, the bottom anchoring members 5 in the tunnel bottom supporting system are divided into two groups, i.e., a left group and a right group, and the two groups of bottom anchoring members 5 are respectively arranged below the left side and the right side of the currently constructed cavern.

Each group of bottom anchoring parts 5 comprises one bottom anchoring part 5 or a plurality of bottom anchoring parts 5 which are arranged from left to right along the excavation contour line of the currently constructed grotto; the two groups of bottom anchoring parts 5 are positioned on the same cross section of the currently constructed cavern.

In this embodiment, each set of bottom anchors 5 comprises one bottom anchor 5.

During actual construction, the number of the bottom anchors 5 included in each group of bottom anchors 5 and the arrangement position of each bottom anchor 5 can be adjusted accordingly according to specific needs.

In this embodiment, before the preliminary tunnel support construction in step six, it is further determined whether the currently constructed cavern needs to be reinforced by surrounding rock radial grouting according to the number M of fractured zones determined in step three: when M is equal to 0, judging that the currently constructed grotto does not need to be subjected to surrounding rock radial grouting reinforcement; otherwise, judging that the currently constructed cavern needs to be reinforced by surrounding rock radial grouting, and before the tunnel primary support construction in the sixth step, carrying out surrounding rock radial grouting reinforcement on the currently constructed cavern for multiple times from back to front along the longitudinal extension direction;

with reference to fig. 3, 4, 5 and 6, the multiple times of the surrounding rock radial grouting reinforcement method are the same; when the radial grouting reinforcement of the surrounding rock is carried out each time, the process is as follows:

step C2, grouting and reinforcing the cracking zone: according to the positions of the M cracking zones determined in the step C1, grouting and reinforcing the M cracking zones by using grouting pipes 2 respectively;

when grouting reinforcement is carried out on any one of the fracture areas, grouting reinforcement is carried out by adopting a grouting pipe 2 inserted into the fracture area from inside to outside from the currently constructed cavern; the grouting pipe 2 is a hollow steel pipe which is inserted into the cracking zone from inside to outside and the front end of which is provided with a grouting hole, the front end of the grouting pipe 2 is positioned in the cracking zone, and the rear end of the grouting pipe is connected with grouting equipment through a grouting pipeline;

when grouting reinforcement is carried out on the fractured zone in the step C2, all adopted grouting pipes 2 are positioned on the same cross section of the currently constructed cavern; the cross section of the currently constructed cavern where the grouting pipe 2 is located is a grouting reinforcement position;

The grouting pipe 2 is a straight steel pipe with a sealed pipe body, namely the grouting pipe 2 is a seamless steel pipe, and the pipe wall of the grouting pipe 2 is not provided with grouting holes.

The distance between the grouting reinforcement positions of the two adjacent surrounding rock radial grouting reinforcements refers to the distance between the grouting reinforcement positions of the two adjacent surrounding rock radial grouting reinforcements along the longitudinal extension direction of the currently constructed cavern.

In this embodiment, when grouting reinforcement is performed on the fractured zone in step C2, a conventional grouting reinforcement method for a tunnel (also referred to as a grouting method for a tunnel) is used for reinforcement.

When actually carrying out the district slip casting that breaks and consolidate, will consolidate through slip casting pipe 2 and pour into with the thick liquid it solidifies to break in the district, increases the compressive strength and the adhesion of the internal country rock mass of district that breaks, realizes consolidating the purpose, ensures the security in the district's reinforced country rock stability and tunnel that breaks. The adopted slurry for reinforcement is slurry adopted by the conventional tunnel grouting reinforcement method, such as cement slurry and the like.

In this example, the reinforcing slurry used was cement slurry.

According to the common knowledge in the field, curtain grouting is to inject slurry into cracks, gaps and water seepage places of a broken rock stratum (namely a broken zone) and a soft sand layer by utilizing the principle of pressure, so that the slurry forms a firm whole after solidification, and the phenomenon of water seepage is relieved.

In this embodiment, for convenience of construction, when grouting reinforcement is performed on any one of the cracking zones in step C2, grouting reinforcement is performed on the cracking zone according to a conventional tunnel curtain grouting method (specifically, a tunnel full-section curtain grouting method).

Therefore, the actual construction is very simple and convenient, the full-section curtain grouting method for the tunnel is adopted to perform grouting on the fractured zone, so that the fractured zone forms a reinforced wall body similar to a curtain, and the stability of surrounding rocks and the safety of the tunnel can be effectively ensured. The shape of the reinforced wall body is the same as the shape of the cross section of the currently constructed cavern.

In this embodiment, the grouting pipe 2 in step C2 is a hollow drill rod that drills from inside to outside from the currently constructed cavity.

In order to ensure the surrounding rock grouting reinforcement effect, the distance between the grouting reinforcement position on the rearmost side in the currently constructed cavern and the rear end face of the currently constructed cavern is 3 m-8 m, and the distance between the grouting reinforcement position on the foremost side in the currently constructed cavern and the front end face of the currently constructed cavern is 3 m-8 m.

In this embodiment, when grouting reinforcement is performed on any one of the fracture regions in step C2, two groups of symmetrically arranged grouting pipes 2 are used for grouting reinforcement. The two groups of grouting pipes 2 are respectively arranged above the left side and the right side of the currently constructed cavern, and each group of grouting pipes 2 comprises one grouting pipe 2 or a plurality of grouting pipes 2 arranged from left to right along the excavation contour line of the currently constructed cavern; and the two groups of grouting pipes 2 are positioned on the same cross section of the currently constructed cavern.

In actual construction, when grouting is performed on any one of the fracture regions in step C2, the number of grouting pipes 2 and the arrangement positions of the grouting pipes 2 may be determined according to a full-face curtain grouting method for a tunnel.

In this embodiment, each group of grouting pipes 2 includes one grouting pipe 2, and the grouting pipes 2 are located in the arch of the currently constructed cavern. Therefore, when grouting reinforcement is performed on any one of the fracture regions in the step C2, two grouting pipes 2 symmetrically arranged from left to right are used for grouting reinforcement.

To accelerate the grouting reinforcement time, the number of the grouting pipes 2 may be increased.

During actual construction, when grouting reinforcement is respectively performed on the M cracking zones in the step C2, grouting reinforcement is respectively performed on the M cracking zones from outside to inside or from inside to outside by using the same grouting pipe group;

the grouting pipe group comprises two groups of symmetrically arranged grouting pipes 2, the two groups of grouting pipes 2 are respectively arranged above the left side and the right side of the currently constructed cavern, and each group of grouting pipes 2 comprises one grouting pipe 2 or a plurality of grouting pipes 2 arranged from left to right along the excavation contour line of the currently constructed cavern; the two groups of grouting pipes 2 are positioned on the same cross section of the currently constructed cavern; in the step, the front end of each grouting pipe 2 in the two groups of grouting pipes 2 is inserted into a fracture zone of the Mth surrounding rock zone;

step A2, grouting reinforcement ending judgment: judging whether the grouting reinforcement processes of the M fractured zones are all completed (namely judging whether the grouting reinforcement process of the fractured zone of the 1 st surrounding rock zone is completed): after the grouting reinforcement processes of the M cracking areas are all completed, the excavation construction process of the currently constructed grotto is completed; otherwise, go to step A3;

step A3, grouting and reinforcing a fractured zone of the next surrounding rock zone: moving each grouting pipe 2 in the grouting pipe group backwards to the position, at the front end, of the grouting pipe group in the fracture area of the next surrounding rock partition, and grouting and reinforcing the fracture area of the next surrounding rock partition by adopting the grouting pipe group; thereafter, return to step a 2;

in the step, the front end of each grouting pipe 2 in the two groups of grouting pipes 2 is inserted into a cracking zone of the 1 st surrounding rock zone;

step B3, grouting and reinforcing a fractured zone of the next surrounding rock zone: moving each grouting pipe 2 in the grouting pipe group forwards until the front end of each grouting pipe is positioned in the fracture area of the next surrounding rock partition, and grouting and reinforcing the fracture area of the next surrounding rock partition by adopting the grouting pipe group; thereafter, the process returns to step B2.

In this embodiment, since the grouting pipes 2 are hollow drill pipes, when the front end of each grouting pipe 2 in the two groups of grouting pipes 2 is inserted into the fractured zone of the mth surrounding rock zone in step a1, the front end of each grouting pipe 2 is drilled into the fractured zone of the mth surrounding rock zone by a drilling machine; and step A3, moving each grouting pipe 2 of the grouting pipe group backwards to the position where the front end of each grouting pipe 2 is located in the fracture zone of the next surrounding rock zone, and moving each grouting pipe 2 backwards to the position along the central axis of each grouting pipe 2. Correspondingly, when the front end of each grouting pipe 2 in the two groups of grouting pipes 2 is inserted into the cracking zone of the 1 st surrounding rock partition in the step B1, drilling the front end of each grouting pipe 2 into the cracking zone of the 1 st surrounding rock partition by a drilling machine; and B3, when the front end of each grouting pipe 2 in the grouting pipe group is moved forwards to be located in the fracture zone of the next surrounding rock zone, respectively continuing to drill each grouting pipe 2 forwards to a position along the central axis of each grouting pipe 2 by using a drilling machine.

C2, when grouting reinforcement is carried out on any one of the cracking zones, whether the grouting pipe 2 is inserted in place is judged according to the insertion depth of the grouting pipe 2 into the surrounding rock;

when the same grouting pipe group is adopted to perform grouting reinforcement on the M cracking zones from inside to outside, the M cracking zones are sequentially subjected to grouting reinforcement from inside to outside according to the arrangement positions of the M cracking zones, namely, the cracking zone positioned at the innermost side (namely, the cracking zone of the first surrounding rock partition) is firstly subjected to grouting reinforcement, and the cracking zone positioned at the outermost side (namely, the cracking zone of the Mth surrounding rock partition) is finally subjected to grouting reinforcement. Correspondingly, when the same grouting pipe group is adopted to perform grouting reinforcement on the M cracking zones from outside to inside, the M cracking zones are sequentially subjected to grouting reinforcement from outside to inside according to the arrangement positions of the M cracking zones, namely the cracking zone positioned on the outermost side is firstly subjected to grouting reinforcement, and the cracking zone positioned on the innermost side is finally subjected to grouting reinforcement.

In this embodiment, according to the inside-out subregion analysis result that breaks after the excavation of surrounding rock, M the fracture district is located the most inboard fracture district and forms at first, for further increasing construction safety nature and surrounding rock steadiness, adopts same slip casting nest of tubes from inside to outside to M the fracture district is carried out slip casting respectively and is consolidated.

As shown in fig. 3, the cracking zone of the 1 st surrounding rock zone is groutedThe depth of insertion of each grouting pipe 2 during the reinforcement is designated d1, where 0 < d1 < d_s0；

As shown in FIGS. 4, 5 and 6, when the fractured zone of the Kth' surrounding rock zone is grouted and reinforced, the insertion depth of each grouting pipe 2 is denoted as d_kWherein Δ l_kz＜d_k＜(Δl_kz+d_sk)。

In this embodiment, in step C1, when the positions of the M outer fracture zones of the currently constructed cavern are determined according to the thicknesses of the M surrounding rock partitions and the thicknesses of the M fracture zones determined in step three, the positions of the M fracture zones are determined from inside to outside, respectively, and the method includes the following steps:

in this step, the next surrounding rock partition is a Kth surrounding rock partition, and the fracture area of the Kth surrounding rock partition is located outside the outer contour line of the Kth surrounding rock partition and has a width of d_skThe area of (a). The shape of the outer contour line of the kth surrounding rock partition is the same as that of the excavation contour line of the currently constructed cavern, and the distance between the outer contour line and the excavation contour line is delta l_kz. SaidΔl_kzIs the sum of the thicknesses of all the surrounding rock subareas positioned at the K' th surrounding rock subarea.

As shown in fig. 2, in step three, the surrounding rock partition is located outside the currently constructed cavern, and the cross-sectional shapes of the surrounding rock partition, the fractured zone and the non-fractured zone are all the same as the cross-sectional shape of the currently constructed cavern.

That is, when the surrounding rock has zonal fracture, the surrounding rock around the currently constructed cavern has zonal fracture.

As shown in fig. 2, each of the fractured wall rock sections is composed of one fractured zone and one non-fractured zone located outside the fractured zone. The cracking zone is a surrounding rock partition cracking zone 1-1, and the non-cracking zone is a surrounding rock partition non-cracking zone 1-2.

In step 3012, s is 0 to 1.

In this embodiment, m is 0.01, s is 1, and b is 0.8 in step 3012. During actual construction, the values of m, s and b can be adjusted correspondingly according to specific requirements.

P as described in step 3012₀The supporting counter force of the surrounding rock on the wall of the currently constructed cavern is the same as that of the surrounding rock on the wall of the currently constructed cavern when the anchor rod is adopted to support the currently constructed cavern. In this embodiment, for simple calculation, the anchor is used as a non-prestressed anchor, and the P is₀' -0 Pa. In order to ensure accurate data, a test method can be adopted to test the supporting counter force borne by the surrounding rock on the wall of the currently constructed grotto during supporting the currently constructed grotto, and the P is measured according to the supporting counter force obtained by the test₀' make the determination.

The radius of the neutral point of the anchor rod in the first surrounding rock subarea is

The radius of a neutral point of the anchor rod in the Kth surrounding rock zone is

Δ R as described in step 3023_kIs the k-thAnd the distance from the outer edge of the surrounding rock partition to the center of the cavern.

The rock mass in the crust which is not affected by human engineering activities (such as digging tunnels, coal mine underground roadways and the like) is called as the original rock mass, and is called as the original rock mass for short. The virgin rock stress described in step 2012 refers to the natural stress present in the formation without engineering disturbance, also referred to as the initial stress, the absolute stress, or the ground stress of the rock mass.

At the initial stage of excavation of the cavern, the stress of the surrounding rock is secondarily distributed, the tangential compressive stress applied to the surrounding rock of the cavern wall is sharply increased, and the cavern wall is in an elastic or elastic-plastic state. Because the wall of the hole is a free surface, the surrounding rock can only generate transverse tensile expansion into the hole under the tangential pressure. When the tensile deformation of the surrounding rock under tangential pressure reaches its ultimate strain, the hole wall exhibits a first fracture zone, the "false face". For shallow rock masses, it is not possible to create a second fracture zone after stress relief due to the lower ground stress level; for deep rock mass under high ground stress conditions, the outer boundary of the first fractured zone generated after stress release is equivalent to a new excavation boundary, so that the stress is redistributed again. When the redistributed stress field meets the rock mass failure condition, the stress is released again to form a second fracture area. By analogy, the phenomenon continues until the maximum radial tensile strain of the surrounding rock generated by the axial supporting pressure is smaller than the limit tensile strain of the rock body, and finally, the zonal fracture phenomenon is formed in the surrounding rock, and finally, the zonal fracture phenomenon of the deep surrounding rock is formed.

For a long time, full-length anchor bolts have been widely used in cavity surrounding rock supports (particularly in cavity primary supports, such as cavity primary supports). And (3) setting surrounding rocks in an elastic-plastic state at the initial stage of excavation of the cavern, and forming a cracking area after the surface surrounding rocks continuously deform into the cavern space under the action of vertical pressure. For ease of discussion, assume: firstly, the cross section of the cavern is equivalent to a circle, the longitudinal length of the cavern is far greater than the transverse width of the cavern, and the cavern belongs to the problem of plane strain; secondly, simplifying the rock mass around the anchor rod into a homogeneous, continuous and isotropic elastoplastic body; thirdly, no relative sliding is generated between any point on the surface of the anchor rod and the rock mass around the anchor rod; fourthly, the tensile strength of the anchor rod is far greater than that of the surrounding rock mass, and the length of the anchor rod is from the surface of the surrounding rock to the outer boundary of the elastic zone. According to the invention, the cavern surrounding rock is simplified into an ideal elastoplastic medium, and the full-length anchoring bolts are arranged in the cavern surrounding rock.

After the soft rock cavern is excavated, a surrounding rock crushing area, a plastic area and an elastic area are sequentially arranged along the length direction of the arch wall supporting anchor rod 2 from inside to outside, and as rock masses in all areas have different radial deformation, the closer to the surface of the cavern, the greater the radial displacement rate of the surrounding rock is. A section of rod body close to the surface of the cavern has the tendency of preventing the rock mass in the crushing area from deforming into the cavern, and the surface of the rod body generates positive frictional resistance pointing to the cavern; because the displacement rate of the elastoplastic region rock mass is smaller than that of the crushing region, the other section of the rod body generates negative frictional resistance pointing to the deep surrounding rock under the drawing action of the rod body close to the surface of the cavern. The interface of the positive and negative frictional resistance of the rod body is the neutral point of the anchor rod, the relative displacement and the surface frictional resistance of the rod body and the surrounding rock mass are zero, but the axial tension thereof reaches the maximum value. Thus, there is a demarcation point on the arch wall support bolt 2 where the surface frictional resistance points oppositely, the demarcation point is a neutral point where the relative displacement of the arch wall support bolt 2 and the surrounding rock mass is zero, and the point frictional resistance is zero. However, at the dividing point, the axial tension of the anchor rod 2 reaches the maximum, and the axial tension gradually decreases from the dividing point to the two ends of the arch wall supporting anchor rod 2 and tends to zero.

Thus, the invention is based on the coordinated deformation principle of the anchor rod and the surrounding rock, analyzes the distribution rule of the surface friction resistance and the axial force of the anchor rod by establishing a mechanical model of the interaction between the anchor rod body and the surrounding rock for supporting the arch wall (namely the arch part and the side wall) of the excavated chamber, and deduces the neutral point position and the maximum axial tension value of the relative displacement between the anchor rod body and the rock mass to be zero according to the static balance condition of the rod body.

Because each subarea rock mass has different radial deformation, the closer to the tunnel wall, the greater the radial displacement rate of the surrounding rock mass. A section of the rod body close to the tunnel wall has the tendency of preventing the rock mass in the crushing area from deforming into the tunnel, and the surface of the rod body generates negative frictional resistance pointing to the interior of the tunnel; the displacement rate of the elastic plastic zone rock mass is smaller than that of the crushing zone, the other sections of the rod bodies generate positive frictional resistance pointing to the deep surrounding rock under the drawing action of the rod bodies close to the wall of the hole, the interface of the positive frictional resistance and the negative frictional resistance of the rod bodies is an anchor rod neutral point, the relative displacement between the rod bodies and the surrounding rock mass at the point and the surface frictional resistance of the rod bodies are zero, but the axial tension of the rod bodies reaches the maximum value.

The stress of the surrounding rock of the cavern is continuously transmitted to the deep part of the surrounding rock through repeated redistribution. In the process of zonal fracture of the surrounding rock, new neutral points continuously appear on the anchor rod along the length direction of the rod body, a crushing area with a larger deformation rate is arranged inside each neutral point, and the negative frictional resistance acting on the rod body points into the hole; the outer side is a non-cracking area with a smaller deformation rate, and the positive frictional resistance of the non-cracking area acting on the rod body points to the deep surrounding rock. As the radial displacement and the radial strain of the surrounding rock fluctuate at wave crests and wave troughs, the full-length anchoring bolts in the surrounding rock are alternately distributed by tension-compression stress. These phenomena are well documented: and a zone fracture phenomenon that fractured zones and non-fractured zones alternate exists in the surrounding rock of the deep-buried cavern.

The analysis shows that: the anchor rod stress in the deep-buried cavern 1 surrounding rock has a plurality of neutral points (also called anchor rod neutral points), and the deep-buried cavern 1 surrounding rock has a plurality of fracture areas and a plurality of non-fracture areas which are distributed at intervals, namely a zone fracture phenomenon. A plurality of the neutral points are respectively M from inside to outside₁、M₂、M₃…. And the distance between each neutral point and the center of the cavern is

Wherein, O₀Is the center of the cavern, M_iIs the ith neutral point in the surrounding rock of the deep-buried cavern 1, i is a positive integer and i is 1, 2, 3 or …; o is₀M_iIs the distance between the ith neutral point and the center of the cavern. And each surrounding rock subarea is provided with one neutral point, when the surrounding rock is broken, the axial force borne by the head end and the tail end of the anchor rod body in each surrounding rock subarea along the length direction of the anchor rod is zero, and the stress and the deformation of the anchor rod body in the adjacent two surrounding rock subareas are not influenced by each other.

The center of the cavern is the geometric center of the cavern excavation section, and the center of the cavern is the circle center of the circular equivalent excavation section of the cavern excavation section.

In this embodiment, step 3013 needs to be according to formula d_ns0＝l₀-d_s0Calculating the thickness d of the non-cracking zone in the first surrounding rock zone_ns0；

In this embodiment, after the excavation of the cavern is completed in the step one, a section is selected from the excavated cavern as the test section.

And step two, when basic mechanical parameters of the surrounding rock are determined, taking a rock sample from the test section to perform an indoor test, wherein the obtained test result is the basic mechanical parameters of the surrounding rock of the test section after excavation. Therefore, the determined mechanical parameters need to be determined on the basis of tests, so that the accuracy and reliability of data can be effectively ensured, and the calculation error is reduced.

In this embodiment, the currently constructed cavern is a tunnel, and when the cavern is excavated in the first step, the full-section excavation method or the step method is adopted for excavation.

Moreover, the adopted full-section excavation method or the step method are both conventional tunnel excavation methods.

In this embodiment, when the basic mechanical parameters of the surrounding rock are determined in the second step, the determined basic mechanical parameters of the surrounding rock at least include the original rock stress P of the surrounding rock mass of the currently constructed cavern before excavation₀Internal friction angle of surrounding rock mass of currently constructed cavern

Poisson ratio mu of surrounding rock mass of currently constructed cavern and supporting counterforce P on elastic-plastic interface of first surrounding rock partition₀', cohesive force c of surrounding rock mass of currently constructed cavern, shear modulus G of surrounding rock mass of currently constructed cavern, and before supportDisplacement value of surrounding rock on surface of currently constructed cavern

Comprehensive elastic modulus E of surrounding rock mass of currently constructed cavern_rResidual shear strength tau of surrounding rock of currently constructed cavern_sAnd uniaxial compressive strength sigma of surrounding rock mass of currently constructed cavern_c。

In addition, the equivalent excavation radius R of the currently constructed cavity is required₀The cross section perimeter U of the anchor rod adopted when the current constructed cavern is supported, the cross section area A of the anchor rod and the elastic modulus E of the anchor rod_bAnd a shear stiffness coefficient K of the anchor rod body per unit length. The shear stiffness coefficient refers to a ratio of corresponding shear stress to shear displacement of the rock test piece under the action of certain normal stress and shear stress.

In this embodiment, the surrounding rock of the currently constructed cavern in the second step is the surrounding rock at the position of the arch part or the side walls on the left and right sides of the currently constructed cavern.

Step 3013 inner diameter of fracture zone in said first wall rock zoneThe distance between the inner boundary line of the inner cracking zone of the first surrounding rock partition and the center of the currently constructed cavern is the outer diameter of the inner cracking zone of the first surrounding rock partition

The distance from the outer boundary line of the inner cracking area of the first surrounding rock partition to the center of the currently constructed cavern is set;

the inner diameter of a fracture zone in the Kth surrounding rock zone in step 3023

The distance between the inner boundary line of the inner cracking zone of the Kth surrounding rock partition and the center of the currently constructed cavern and the outer diameter of the inner cracking zone of the Kth surrounding rock partition

The distance between the outer boundary line of the cracking zone in the Kth surrounding rock partition and the center of the currently constructed cavern is shown.

τ in step 3022_s＝τ_p-c，τ_pThe peak shear strength (also called peak strength) of the surrounding rock of the currently constructed cavern.

In this embodiment, a plurality of the surrounding rock subareas are arranged along the radial direction of the cavern from inside to outside, and the plurality of the surrounding rock subareas are all located on the same cross section of the currently constructed cavern.

In this embodiment, the currently constructed cavern is a straight-wall vault type cavern with equivalent excavation radius R₀2.0m, Poisson's ratio μ 0.25, uniaxial compressive strength σ_c37.7MPa, original rock stress P₀22.8MPa, 12MPa, internal friction angle

Comprehensive modulus of elasticity E of rock mass_r4.2GPa, shear modulus G1.68 GPa, peak shear strength tau_p48 MPa. After a cavern is excavated, a full-length anchoring non-prestressed anchor rod with the diameter of phi 25mm is arranged in surrounding rock, the length of the anchor rod body meets the calculation requirement, the perimeter U of the cross section is 0.08m, and the area A of the cross section is 4.91 multiplied by 10^-4m²Elastic modulus E of the anchor rod_bThe displacement value of the surrounding rock on the surface of the currently constructed cavern before supporting is 40GPa

The shear stiffness coefficient K is 360 MPa/m.

In the present embodiment, the first and second electrodes are,

according to the formula

(I) thickness l of first surrounding rock partition₀When performing the calculation, according to

To give l₀＝3.07m。

τ_s＝τ_p-c＝48×10⁶-12×10⁶＝36MPa；

σ_z0＝(1+2μ)P₀＝＝(1+2×0.25)×22.8×10⁶＝34.2MPa；

σ_r0-μ(σ_θ0+σ_z0)＝(-31.24×10⁶)-0.25×(92.04×10⁶+34.2×10⁶)＝-62.80MPa；

The comparison results in: i sigma_r0-μ(σ_θ0+σ_z0)|＞|σ_tAnd II, so that the first surrounding rock partition is broken and is a broken surrounding rock partition, the rock mass of the tunnel wall in the first surrounding rock partition enters a brittle fracture state from a plastic state, and the first broken region of the surrounding rock is formed after the tunnel wall is unstable.

At the initial stage of excavation of the cavern, the stress of the surrounding rock is secondarily distributed, and the surrounding rock is elastically distributed. According to the theory of elastic mechanics, when the concentrated stress on the surrounding rock at the tunnel wall exceeds the ultimate strength, the surrounding rock at the tunnel wall firstly enters a plastic tensile fracture state.

When the surrounding rock of the tunnel wall enters a fracture state from a plastic state, the stress of the surrounding rock is distributed for three times;

is calculated to obtain

Shear modulus

Correspondingly, calculating the plastic zone outer diameter in a first surrounding rock zone range formed after the stress is distributed for three times after the surrounding rock of the tunnel wall is unstable:

the corresponding calculation results in: thickness d of cracking zone in 1 st zone of surrounding rock_s0Thickness d of non-cracking zone in 1 st section of surrounding rock_ns0＝3.07-0.49＝2.58m；

Similarly, according to the method described in steps 3021 to 3023, the thicknesses of the fractured zone and the non-fractured zone in the kth wall rock zone can be obtained, and the positions of the fractured zone and the non-fractured zone in each wall rock zone are determined according to the determined thicknesses of the fractured zone and the non-fractured zone in each wall rock zone.

In this embodiment, the thicknesses of the fractured zone and the non-fractured zone in the 2 nd, 3 rd and 4 th surrounding rock zones can be determined according to the methods described in steps 3021 to 3023.

Wherein, the 2 nd surrounding rock subarea thickness l₁Thickness d of cracking zone in 2 nd surrounding rock zone as 1.84m_s1Thickness d of non-fractured zone in 2 nd surrounding rock zone of 0.34m_ns1＝1.50m；

Thickness l of 3 rd surrounding rock partition₂Thickness d of cracking zone in 3 rd surrounding rock zone as 3.83m_s2Thickness d of non-fractured zone in 3 rd section of surrounding rock, 0.57m_ns2＝3.26m；

Thickness l of 4 th surrounding rock partition₃Thickness d of cracking zone in 4 th zone of surrounding rock_s3Thickness d of non-fractured zone in 4 th surrounding rock zone of 0.19m_ns3＝0.50m。

Similarly, when fracture analysis is performed on the 5 th surrounding rock zone, Δ l_4z＝l₀+l₁+l₂+l₃＝3.07+1.84+3.83+0.69＝9.43m。

According to

Calculate to obtain l₄＝5.77m；

Correspond toAnd after the instability of the surrounding rock of the tunnel wall, the external diameter of the plastic zone in the 5 th surrounding rock zone formed by five times of distribution of stress is as follows:

support counter force on elastic-plastic interface in 5 th surrounding rock partition

σ_z4＝(1+2×0.25)×22.8×10⁶＝34.2MPa；

σ_r4-μ(σ_θ4+σ_z4)＝-7.78×10⁶-0.25×(68.58×10⁶+34.2×10⁶)＝-33.47MPa；

The comparison shows that: i sigma_r4-μ(σ_θ4+σ_z4)|＜|σ_tAnd if the fracture zone does not exist in the 5 th (namely K) surrounding rock partition and M is 4 (namely K), completing the surrounding rock partition fracture evolution analysis process of the currently constructed cavern. At this point, the currently constructed cavern comprises a total of 4 rupture zones, see fig. 2 for details.

From the above, the result of the zonal rupture calculation of the surrounding rock of the cavern is detailed in table 1:

TABLE 1

In conclusion, according to the regional fracture evolution analysis of the surrounding rock, the thickness and the position of all fracture areas outside the currently constructed cavern are obtained, so that the radial grouting reinforcement scheme and the surrounding rock supporting scheme of the surrounding rock after excavation is completed can be determined, an accurate and reliable basis is provided, and the practical value is very high.

In this embodiment, as shown in fig. 3, fig. 4, fig. 5, and fig. 6, 4 the cracking zones are respectively grouted and reinforced, so that the stability and the safety of the surrounding rock of the currently constructed cavern can be effectively ensured, the grouting reinforcement effect is very good, the targeted grouting reinforcement is performed on the basis of accurately judging the cracking position and the thickness, the reinforcement effect can be effectively ensured, and the construction process is simple.

In the tunnel excavation construction process, surrounding rock radial grouting reinforcement is synchronously performed on the excavated cavity, and according to the tunnel primary support structure determined in the fifth step, primary support is performed on the cavity reinforced by the surrounding rock radial grouting from back to front.

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

1. A tunnel excavation and primary support method based on surrounding rock partition fracture evolution analysis is characterized by comprising the following steps: excavating and primary supporting construction are carried out on the constructed tunnel (1) by a plurality of sections from back to front along the longitudinal extension direction, and the excavating and primary supporting construction methods of the sections are the same; when any segment is excavated and initially supported, the method comprises the following steps:

step one, tunnel excavation: excavating the current construction segment;

Calculating to obtain the first surrounding rock partition thickness l₀，l₀The unit of (a) is m; in the formula (I), R₀The unit of the equivalent excavation radius of the currently constructed cavern is m; rho₀The radius of a neutral point of an anchor rod in a first surrounding rock zone is the sum of the radius of the neutral point of the anchor rod in the first surrounding rock zone and the equivalent excavation radius of a currently constructed cavern, and the radius of the neutral point of the anchor rod in the first surrounding rock zone is the distance between the front end of the anchor rod in the first surrounding rock zone and the neutral point;

wherein

wherein, | σ_tL is σ_tAbsolute value of (a)_tIs the tensile strength of the surrounding rock of the currently constructed cavern and has the unit of Pa,wherein m is a coefficient related to the rock type and integrity of the surrounding rock of the currently constructed cavern and is 0.001-25, s is a rock integrity coefficient of the surrounding rock of the currently constructed cavern, and sigma is_cThe uniaxial compressive strength of the surrounding rock mass of the currently constructed cavern is Pa;

|σ_r0-μ(σ_θ0+σ_z0) L is σ_r0-μ(σ_θ0+σ_z0) Absolute value of (d);

mu is the Poisson's ratio of the tunnel surrounding rock mass of the currently constructed cavern, and sigma is_r0The radial stress of the rock mass at the elastic-plastic boundary of the first surrounding rock partition under the action of the supporting pressure peak value is Pa;wherein

Is the internal friction angle, P, of the surrounding rock mass of the currently constructed cavern₀' is a supporting counter force on the elastic-plastic interface of the first surrounding rock subarea;

is the outer diameter of a plastic zone of the surrounding rock in the first surrounding rock zone and

g is the shear modulus of the surrounding rock mass of the currently constructed cavern and the unit of G is Pa; b is a support coefficient, b is a constant and is more than 0 and less than 1;

the displacement value of the surrounding rock on the surface of the currently constructed cavern before supporting is the unit of m and r_b0The distance r from the outer end of the anchor rod to the center of the currently constructed cavern in the first surrounding rock subarea_b0＝l₀+R₀；N_max0The maximum axial force is applied to the anchor rod at the neutral point of the anchor rod in the first surrounding rock subarea

Er is the comprehensive elastic modulus of the surrounding rock mass of the currently constructed cavern and has the unit of Pa, P₀The method comprises the steps of (1) determining the original rock stress of the surrounding rock mass of a currently constructed cavern before excavation, wherein the unit of the original rock stress is Pa; r_p0The unit of the radius of the plastic zone of the surrounding rock of the currently constructed grotto under the elastic-plastic condition after excavation is m,

Thickness d of cracking zone in first surrounding rock zone_s0Determining;

wherein the content of the first and second substances,

inner diameter of fracture zone in first surrounding rock zone

Calculating to obtain the K' th surrounding rock partition thickness l_k，l_kThe unit of (a) is m;

τ_sis the residual shear strength of the surrounding rock of the currently constructed cavern and has the unit of Pa,the outer diameter of the cracking zone in the kth surrounding rock zone which is positioned at the inner side of the kth surrounding rock zone and is adjacent to the kth surrounding rock zone,

the inner diameter of a fracture zone in the kth surrounding rock zone;

A_kIs a coefficient of

σ_θkIs the K' th enclosureTangential stress at the elastoplastic boundary of the surrounding rock in the lithozone and

Thickness d of cracking zone in K' th surrounding rock zone_skDetermining;

wherein the content of the first and second substances,

the tunnel arch supporting system comprises M tunnel arch supporting structures which respectively support the M cracking zones, and the M tunnel arch supporting structures are uniformly distributed on the same tunnel cross section; each tunnel arch supporting structure comprises a plurality of arch anchoring pieces (3) which are arranged on the arch of the currently constructed cavern from left to right, wherein each arch anchoring piece (3) is an anchor rod or an anchor cable;

when the tunnel arch supporting structure for supporting the cracking zone in the first surrounding rock zone is determined, the thickness d of the cracking zone in the first surrounding rock zone determined in the step 3013 is determined_s0Determining the length of an arch anchoring piece (3) in the tunnel arch supporting structure;

when the tunnel arch supporting structure for supporting the cracking zone in the Kth surrounding rock partition is determined, the supporting structure is determined according to the delta l determined in the step 3021_kzAnd the thickness d of the fracture zone in the Kth' surrounding rock zone determined in step 3023_skDetermining the length of an arch anchoring piece (3) in the tunnel arch supporting structure;

each side wall supporting unit comprises a plurality of side wall anchoring pieces (4) which are arranged on the cross section of the same tunnel from top to bottom, and the side wall anchoring pieces (4) are horizontally arranged and are anchor rods or anchor cables;

when the supporting structure adopted by the side wall supporting unit is determined, the Δ l determined in the step 3021 is used as the basis_kzAnd the thickness d of the fracture zone in the Kth' surrounding rock zone determined in step 3023_skDetermining the length of the side wall anchor (4);

and step eight, repeating the step seven for multiple times until the whole excavation and primary support construction process of the constructed tunnel (1) is completed.

2. The method for excavating and initially supporting the tunnel based on the regional surrounding rock fracture evolution analysis according to claim 1, which is characterized in that: step 3013 is also performed according to formula d_ns0＝l₀-d_s0Calculating the thickness d of the non-cracking zone in the first surrounding rock zone_ns0；

3. The method for excavating and initially supporting the tunnel based on the regional surrounding rock fracture evolution analysis according to claim 1 or 2, which is characterized in that: before basic mechanical parameters of the surrounding rock are determined in the second step, a section is selected from a currently constructed grotto and used as a test section to be excavated;

the longitudinal lengths of the segments are all 10-50 m;

4. The method for excavating and initially supporting the tunnel based on the regional surrounding rock fracture evolution analysis according to claim 1 or 2, which is characterized in that: and fifthly, when the tunnel arch supporting structure for supporting the cracking zone in the first surrounding rock zone is determined, all the arch anchoring pieces (3) in the tunnel arch supporting structure are the same in length, and the lengths of all the arch anchoring pieces (3) in the tunnel arch supporting structure are not less than L₁Wherein L is₁＝l₁'+d_s0+l₂'；l₁' and l₂Are all constants,/₁'＝0.1m～15cm，l₂'＝0.3m～0.4m；

When the tunnel arch supporting structure for supporting the cracking zone in the Kth surrounding rock partition is determined, all arch anchoring pieces (3) in the tunnel arch supporting structure have the same length, and the lengths of all arch anchoring pieces (3) in the tunnel arch supporting structure are not less than L_kWherein L is_k＝l₁'+Δl_kz+d_sk+l₂'；

When the supporting structure adopted by the side wall supporting unit is determined, the lengths of all the side wall anchoring pieces (4) are the same, and the length of each side wall anchoring piece (4) is not less than L₂Wherein L is₂＝l₁'+Δl_(M-1)z+d_s(M-1)+l₂' M is the number of the cracking zones on the surrounding rock of the currently constructed cavern determined in the third step.

5. The method for excavating and initially supporting the tunnel based on the regional surrounding rock fracture evolution analysis according to claim 1 or 2, which is characterized in that: in the third step, the surrounding rock partition is positioned outside the currently constructed cavern, and the cross sections of the surrounding rock partition, the fractured zone and the non-fractured zone are the same as the cross section of the currently constructed cavern;

in step 3012, m is 0.01, s is 0 to 1, and b is 0.8.

6. The method for excavating and initially supporting the tunnel based on the regional surrounding rock fracture evolution analysis according to claim 1 or 2, which is characterized in that: fifthly, each tunnel anchoring support system also comprises a tunnel bottom support system for supporting the bottom of the currently constructed cavern, and the tunnel bottom support system, the tunnel arch support system and the tunnel side wall support system are arranged on the same tunnel cross section;

the tunnel bottom supporting system comprises a plurality of bottom anchoring pieces (5) which are arranged at the bottom of the currently constructed grotto from left to right, and the bottom anchoring pieces (5) are uniformly distributed on the cross section of the same tunnel; the bottom anchoring piece (5) is an anchor rod or an anchor cable;

when the supporting structure adopted by the tunnel bottom supporting system is determined, the determined delta l in the step 3021 is used as the basis_kzAnd the thickness d of the fracture zone in the Kth' surrounding rock zone determined in step 3023_skThe length of the bottom anchor (5) is determined.

7. The method for excavating and initially supporting the tunnel based on the regional surrounding rock fracture evolution analysis according to claim 1 or 2, which is characterized in that: before the tunnel primary support construction in the sixth step, whether the currently constructed grotto needs surrounding rock radial grouting reinforcement or not is judged according to the number M of the cracking zones determined in the third step: when M is equal to 0, judging that the currently constructed grotto does not need to be subjected to surrounding rock radial grouting reinforcement; otherwise, judging that the currently constructed cavern needs to be reinforced by surrounding rock radial grouting, and before the tunnel primary support construction in the sixth step, carrying out surrounding rock radial grouting reinforcement on the currently constructed cavern for multiple times from back to front along the longitudinal extension direction;

step C2, grouting and reinforcing the cracking zone: according to the positions of the M cracking zones determined in the step C1, grouting and reinforcing the M cracking zones by using grouting pipes (2);

when grouting reinforcement is carried out on any one of the fracture areas, grouting reinforcement is carried out by adopting a grouting pipe (2) inserted into the fracture area from inside to outside from the currently constructed cavern; the grouting pipe (2) is a hollow steel pipe which is inserted into the cracking zone from inside to outside and the front end of which is provided with a grouting hole, the front end of the grouting pipe (2) is positioned in the cracking zone, and the rear end of the grouting pipe is connected with grouting equipment through a grouting pipeline;

c2, when grouting reinforcement is carried out on the fractured zone, all adopted grouting pipes (2) are positioned on the same cross section of the currently constructed cavern; the cross section of the currently constructed cavern where the grouting pipe (2) is located is a grouting reinforcement position;

8. The method for tunneling and preliminary bracing based on the zonal rupture evolution analysis of the surrounding rock as claimed in claim 7, wherein: c2, the grouting pipe (2) is a hollow drill rod drilled from inside to outside from the currently constructed cavern;

c2, when grouting reinforcement is carried out on any one of the fracture areas, two groups of symmetrically arranged grouting pipes (2) are adopted for grouting reinforcement; the two groups of grouting pipes (2) are respectively arranged above the left side and the right side of the currently constructed cavern, and each group of grouting pipes (2) comprises one grouting pipe (2) or a plurality of grouting pipes (2) arranged from left to right along the excavation contour line of the currently constructed cavern; and the two groups of grouting pipes (2) are positioned on the same cross section of the currently constructed cavern.

9. The method for tunneling and preliminary bracing based on the zonal rupture evolution analysis of the surrounding rock as claimed in claim 7, wherein: when grouting reinforcement is respectively carried out on the M cracking zones in the step C2, grouting reinforcement is respectively carried out on the M cracking zones from outside to inside or from inside to outside by adopting the same grouting pipe group;

the grouting pipe group comprises two groups of grouting pipes (2) which are symmetrically arranged, the two groups of grouting pipes (2) are respectively arranged above the left side and the right side of the currently constructed cavern, and each group of grouting pipes (2) comprises one grouting pipe (2) or a plurality of grouting pipes (2) which are arranged from left to right along the excavation contour line of the currently constructed cavern; the two groups of grouting pipes (2) are positioned on the same cross section of the currently constructed cavern;

in the step, the front end of each grouting pipe (2) in the two groups of grouting pipes (2) is inserted into a cracking zone of the Mth surrounding rock partition;

step A3, grouting and reinforcing a fractured zone of the next surrounding rock zone: moving each grouting pipe (2) in the grouting pipe group backwards to the position, at the front end, of the grouting pipe group in the fracture area of the next surrounding rock partition, and grouting and reinforcing the fracture area of the next surrounding rock partition by adopting the grouting pipe group; thereafter, return to step a 2;

in the step, the front end of each grouting pipe (2) in the two groups of grouting pipes (2) is inserted into a cracking zone of the 1 st surrounding rock partition;

10. The method for tunneling and preliminary bracing based on the zonal rupture evolution analysis of the surrounding rock as claimed in claim 7, wherein: in step C1, according to the thicknesses of the M surrounding rock sub-areas and the thicknesses of the M cracking areas outside the currently constructed cavern determined in step three, when the positions of the M cracking areas outside the currently constructed cavern are determined, the positions of the M cracking areas are determined from inside to outside, respectively, and the method includes the following steps: