CN108760487A - Deep cavern country rock subregion failure evolvement analysis method based on rockbolt stress analysis - Google Patents

Abstract

The invention discloses a kind of deep cavern country rock subregion failure evolvement analysis methods based on rockbolt stress analysis, including step：Step 1: cavern excavation：Current constructed cavern is excavated；Step 2: country rock basic mechanical parameter determines：The country rock basic mechanical parameter of current constructed cavern is tested；Step 3: country rock subregion failure evolvement is analyzed：According to identified country rock basic mechanical parameter in step 2, the analysis of country rock subregion failure evolvement is carried out to current constructed cavern, and according to analysis result to the quantity M of existing rupture zone and the thickness of each rupture zone are determined respectively on current constructed surrounding rock of chamber after the completion of excavating.Step of the present invention is simple, reasonable design and realization are convenient, using effect is good, the rupture zone quantity on the outside of current constructed cavern and thickness and the position of each rupture zone can be obtained by the analysis of country rock subregion failure evolvement, and reliable basis is provided for follow-up cavern excavation and surrounding rock supporting.

Description

Fracture evolution analysis method of surrounding rock in deep-buried caverns based on force analysis of bolts

technical field

The invention belongs to the technical field of underground cavern construction, and in particular relates to a method for analyzing the regional fracture evolution of the surrounding rock of a deeply buried cavern based on the stress analysis of bolts.

Background technique

Underground caverns are not only used for transportation, hydropower, mines, etc., but also have been widely used in modern underground city construction, refrigeration, oil storage, water storage, environmental engineering and national defense projects. The caverns can be divided into water-passing (such as water diversion) Tunnels) and non-water (such as traffic tunnels) two categories. Deep buried caverns (also known as deeply buried underground caverns) refer to underground caverns buried greater than 50m.

In recent years, with the sharp increase in people's demand for underground space and resources, deep rock mass engineering has continued to increase. According to incomplete statistics, there are hundreds of metal mines with a mining depth of more than 1000m in foreign countries; the mining depth of many mines in my country has exceeded 1000m, and in the next 10 to 20 years, most domestic mines will enter the mining depth of 1000m to 2000m. At the same time, a large number of deep underground cavern projects are being or planned to be built at home and abroad, such as mountain traffic tunnels, water diversion tunnels for large hydropower projects, deep disposal wells for nuclear waste, and oil storage projects for combat readiness. These deep rock mass projects are all faced with complex geological environments of high ground stress, high ground temperature, and high pore water pressure, showing significant nonlinear deformation and failure characteristics different from shallow rock mass, such as zonal rupture, violent rockburst, and surrounding rock squeeze. Compression deformation, etc. Among them, the zonal rupture of the surrounding rock makes the deep buried caverns face many worldwide technical problems that need to be solved urgently in the process of excavation and support, and thus becomes one of the hot spots and difficulties in the field of deep rock mass engineering research.

Zonal rupture is a special geological phenomenon that occurs alternately between ruptured and non-ruptured areas in the surrounding rock of deeply buried caverns. For a long time, people have carried out in-depth research on the partition rupture mechanism through theoretical derivation, experimental analysis and numerical simulation. As early as the 1980s, E.I. Shemyakin discovered the phenomenon of "ring-like fracture" of the surrounding rock in the deep Маяк mine by using a resistivity instrument, as shown in Figure 1.

G.D.Adams and A.J.Jager conducted a drilling survey on the interval rupture phenomenon of the stope roof at a depth of 2000m to 3000m in the Witwatersrand gold mine in South Africa; D.F.Malan and S.M.Spottiswoode used field monitoring data to analyze the interval rupture of the stope roof over time and mining activities. Development and formation, explored the relationship between mine earthquakes and roof partition damage; E.J.Sellers and P.Klerck conducted experimental research on the impact of discontinuities in surrounding rocks on spaced ruptures; M.B.Kypленя and B.H.Oпapин gave the applicable The formula for calculating the radius and thickness of the surrounding rock rupture area in the mining area; I.S.Metlov et al. analyzed the physical basis of the partition rupture by using the non-equilibrium thermodynamic equation, and carried out computer simulation; G.R.Adams and A.J.Jager pointed out that as long as the conditions are met, the roadway surrounding rock Partition fractures will occur, but the reason for the formation of cracks has not yet been theoretically explained; E.И.Шемякин believes that the partition rupture of the surrounding rock is not caused by the disturbance of drilling and blasting construction, but is due to the change of the stress field around the roadway; Based on the time effect, it is proposed that the initial stress value has an important influence on the displacement velocity around the roadway, which is the displacement velocity caused by the unloading of the surrounding rock.

In China, Qian Qihu put forward the concept of "regional rupture" for the first time in China, and analyzed the conditions, main characteristics and changing laws of regional rupture; Tang Chun'an and others used RFPA numerical software to study the mechanism and evolution law of rock mass interval rupture; Li Shucai, Xu Hongfa and others put forward the analytical relationship between the zonal rupture radius and the excavation radius of the roadway through on-site monitoring of the surrounding rock of the deep-buried roadway in Dingji Mine in Huainan; The width and quantity of the width and quantity; Chen Jiangong’s dynamic theoretical solution of the radial stress field of the surrounding rock at the moment of chamber excavation under the equiaxially symmetrical stress field, pointed out that there is an equiproportional relationship between the radii of each rupture zone in the partition; Lu Jianrong based on the three-dimensional linear elasticity of thick-walled cylinder Analytical model, discussing the mechanism of horizontal stress and axial pressure on the regional fracture of surrounding rock; Zuo Yujun et al. studied the mechanical mechanism of regional fracture of surrounding rock in deep roadway under the combination of dynamic and static conditions; Chen Xuguang discussed the surrounding rock under high ground stress. The formation mechanism and anchorage characteristics of rock partition fracture; Wang Xuebin et al. simulated the partition failure of deep roadway surrounding rock based on the loading and unloading model, and believed that the unloading model is closer to the actual engineering; Gu Jincai, Zhang Xutao et al. A model test study was carried out.

To sum up, experts at home and abroad have achieved a series of research results on the zonal rupture of deep surrounding rocks. It is still in its infancy, especially in determining the thickness and quantity of the surrounding rock fracture area.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for analyzing the fracture evolution of the surrounding rock in deep caverns based on the stress analysis of bolts in view of the deficiencies in the above-mentioned prior art. The effect is good. Through the analysis of the fracture evolution of surrounding rock partitions, the number of fractured areas outside the currently constructed cavern as well as the thickness and location of each fractured area can be obtained, which provides a reliable basis for subsequent cavern excavation and surrounding rock support.

In order to solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for analyzing the fracture evolution of the surrounding rock of a deep-buried cavern based on the force analysis of the bolt, which is characterized in that the method includes the following steps:

Step 1, cavern excavation: excavate the cavern currently under construction;

Step 2. Determination of the basic mechanical parameters of the surrounding rock: the basic mechanical parameters of the surrounding rock of the currently constructed cavern are tested through indoor tests on the rock samples taken from the site, and the test results are recorded synchronously;

Step 3. Fracture evolution analysis of surrounding rock partitions: According to the basic mechanical parameters of the surrounding rock determined in step 2, analyze the fracture evolution of the surrounding rock partitions for the currently constructed cavern, and analyze the current construction tunnel after the excavation is completed according to the analysis results. The number M of rupture zones existing on the surrounding rock of the chamber and the thickness of each rupture zone are determined respectively; where M is an integer and M≥0; when M=0, it means that there is no rupture zone on the surrounding rock of the currently constructed cavern ;

When analyzing the fracture evolution of surrounding rock partitions for the currently constructed caverns, the surrounding rocks of the currently constructed caverns are divided into multiple surrounding rock partitions from the inside to the outside, and the multiple surrounding rock partitions are analyzed from the inside to the outside. Fracture analysis, the process is as follows:

Step 301. Fracture analysis of the first surrounding rock partition: performing a fracture analysis on the first surrounding rock partition outside the currently constructed cavern, including the following steps:

Step 3011, determining the thickness of the first surrounding rock partition: according to the formula The thickness of the first surrounding rock partition is calculated l ₀ , and the unit of _{l 0} is m _; The sum of the neutral point radius of the bolt in a surrounding rock partition and the equivalent excavation radius of the currently constructed cavern, the neutral point radius of the bolt in the first surrounding rock partition is the first The distance between the front end of the bolt and the neutral point in the surrounding rock partition; in U is the perimeter of the cross-section of the anchor used to support the cavern currently under construction, and its unit is m, A is the cross-sectional area of the anchor, and its unit is m ² , E _b is the anchor The modulus of elasticity and its unit is Pa, K is the shear stiffness coefficient on the unit length of the anchor rod body and its unit is Pa/m;

Step 3012, determination of fracture: compare the difference between |σ _{r0 -μ} (σ _θ0 +σ _z0 )| When |σ _r0 -μ(σ _θ0 +σ _z0 )|≥|σ _t |, it is judged that there is a fracture in the first surrounding rock partition and at this time the first surrounding rock partition is a fractured surrounding rock partition, and go to step 3013; otherwise , it is judged that there is no fracture zone on the surrounding rock of the currently constructed cavern and M=0, and the analysis process of the regional fracture evolution of the surrounding rock of the currently constructed cavern is completed;

The cracked surrounding rock partition is divided into a cracked zone and a non-cracked zone located outside the cracked zone;

Among them, |σ _t | is the absolute value of σ _t , and σ _t is the tensile strength of the surrounding rock of the currently constructed cavern, and its unit is Pa, Among them, m is the coefficient related to the rock type and integrity of the surrounding rock of the currently constructed cavern and m=0.001~25, s is the rock mass integrity coefficient of the surrounding rock of the currently constructed cavern, and σ _c is the current construction cavern The uniaxial compressive strength of the rock mass surrounding the chamber and its unit is Pa;

|σ _r0 -μ(σ _θ0 +σ _z0 )| is the absolute value of σ _r0 -μ(σ _θ0 +σ _z0 );

Among them, μ is the Poisson’s ratio of the surrounding rock mass of the cavern currently under construction, σ _r0 is the radial stress of the rock mass at the elastic-plastic boundary of the first surrounding rock partition under the peak support pressure, and its unit is Pa;

in is the internal friction angle of the surrounding rock mass in the currently constructed cavern, and P ₀ ' is the supporting reaction force on the elastic-plastic interface of the first surrounding rock partition; is the outer diameter of the plastic zone of the surrounding rock in the first surrounding rock division and c is the cohesion of the surrounding rock mass of the cavern currently under construction, and its unit is Pa; A ₀ and t are coefficients, Among them, G is the shear modulus of the surrounding rock mass of the cavern currently under construction and its unit is Pa; b is the support coefficient, b is a constant and 0<b<1; is the displacement value of the surrounding rock on the surface of the currently constructed cavern before support and its unit is m, r _b0 is the distance from the outer end of the bolt in the first surrounding rock partition to the center of the currently constructed cavern and r _b0 = l ₀ +R ₀ ; N _max0 is the maximum axial force on the bolt at the neutral point of the bolt in the first surrounding rock partition and B is the coefficient related to the deformation of the surrounding rock of the currently constructed cavern and E _r is the comprehensive elastic modulus of the surrounding rock mass of the currently constructed cavern, and its unit is Pa; P ₀ is the original rock stress of the surrounding rock mass of the currently constructed cavern before excavation, and its unit is Pa; R _p0 is the plastic zone radius of the currently constructed cavern surrounding rock under elastic-plastic conditions after excavation, and its unit is m,

σ _θ0 is the tangential stress at the elastic-plastic boundary of the surrounding rock in the first surrounding rock partition and σ _z0 is the axial stress at the elastic-plastic boundary of the surrounding rock in the first surrounding rock partition and σ _z0 = (1+2μ)P ₀ , the units of σ _θ0 and σ _z0 are both Pa;

Step 3013, determine the thickness of the rupture zone in the first surrounding rock partition: according to the formula Determine the thickness d _s0 of the rupture zone in the first surrounding rock subregion;

in, is the outer diameter of the fracture zone in the first surrounding rock partition and Inner diameter of the rupture zone in the first wall rock subdivision

Step 302, Fracture Analysis of the Next Surrounding Rock Partition: Perform a crack analysis on the next surrounding rock partition outside the currently constructed cavern; in this step, the surrounding rock partition for crack analysis is the Kth outside the currently constructed cavern Surrounding rock partition, wherein K is a positive integer and K≥2, K=k+1, k is a positive integer and k≥1; in this step, the k surrounding rock partitions located inside the Kth surrounding rock partition are all The fracture analysis process has been completed;

When performing fracture analysis on the Kth surrounding rock partition, the following steps are included:

Step 3021, determining the thickness of the Kth surrounding rock partition: according to the formula Calculate the thickness l _k of the Kth surrounding rock partition, and the unit of l _k is m;

In formula (Ⅲ), ρ _k is the sum of the neutral point radius of the bolt in the Kth surrounding rock partition and the equivalent excavation radius of the cavern currently under construction, and the anchor in the Kth surrounding rock partition The neutral point radius of the rod is the distance between the front end of the anchor rod and the neutral point in the Kth surrounding rock partition; Wherein, Δl _kz is the sum of the partition thicknesses of the k surrounding rock partitions located inside the K-th surrounding rock partition and its unit is m;

Step 3022, determination of fracture: compare the difference between |σ _{rk -μ} (σ _θk +σ _zk )| When |σ _rk -μ(σ _θk +σ _zk )|≥|σ _t |, it is judged that there is a crack in the Kth surrounding rock partition and at this time the Kth surrounding rock partition is a fractured surrounding rock partition, and then go to step 3023; otherwise , it is judged that there is no fracture zone on the Kth surrounding rock partition and M=k, and the analysis process of the fracture evolution of the surrounding rock partition of the currently constructed cavern is completed;

Among them, |σ _rk -μ(σ _θk +σ _zk )| is the absolute value of σ _rk -μ(σ _θk +σ _zk );

σ _rk is the radial stress of the rock mass at the elastic-plastic boundary of the Kth surrounding rock partition under the action of the peak support pressure, and its unit is Pa; P _k is the supporting reaction force on the elastic-plastic interface in the Kth surrounding rock partition and its unit is Pa, τ _s is the residual shear strength of the surrounding rock of the currently constructed cavern and its unit is Pa, is the outer diameter of the rupture zone in the k-th surrounding rock zone located inside and adjacent to the K-th surrounding rock zone, is the inner diameter of the rupture zone in the kth surrounding rock partition; is the outer diameter of the plastic zone of the surrounding rock in the Kth surrounding rock partition and A _k is the coefficient and Where r _bk is the sum of the thickness of the rupture zone in the Kth surrounding rock subregion and the equivalent excavation radius of the currently constructed cavern and r _bk = l _k + R ₀ ; N _maxk is the sum of the Kth surrounding rock subregion The maximum axial force on the anchor rod at the neutral point of the anchor rod and

σ _θk is the tangential stress at the elastic-plastic boundary of the surrounding rock in the Kth surrounding rock partition and σ _zk is the axial stress at the elastic-plastic boundary of the surrounding rock in the Kth surrounding rock partition and σ _zk =(1+2μ)P ₀ , the unit of σ _θk and σ _zk is Pa;

Step 3023, determine the thickness of the rupture zone in the Kth surrounding rock partition: according to the formula Determining the thickness d _sk of the rupture zone in the Kth surrounding rock partition;

in, is the outer diameter of the fracture zone in the Kth surrounding rock partition and ΔR _k ＝R ₀ +Δl _kz ; the inner diameter of the rupture zone in the Kth surrounding rock partition

Step 303, repeating step 302 one or more times until the process of analyzing the fracture evolution of the surrounding rock partitions of the currently constructed cavern is completed.

The above-mentioned method for analyzing the fracture evolution of the surrounding rock in deep-buried caverns based on the stress analysis of bolts is characterized in that: when excavating the cavern currently under construction in step 1, the excavation of the currently constructed cavern is carried out from the back to the front along the longitudinal extension direction. The cavern shall be excavated and the excavation length shall not exceed 50m.

The above-mentioned cracking evolution analysis method for surrounding rock in deep caverns based on force analysis of bolts is characterized in that: in step 3, the surrounding rock division is located outside the currently constructed cavern, and the surrounding rock division, the rupture area The cross-sectional shape of the non-ruptured zone is the same as the cross-sectional shape of the currently constructed cavern.

The feature of the method for analyzing the fracture evolution of the surrounding rock in deep caverns based on the stress analysis of bolts is that in step 3013, it is also necessary to calculate the first surrounding rock in the subregion according to the formula d _ns0 = l ₀ -d _s0 . The thickness d _ns0 of the non-ruptured zone;

In step 3023, the thickness d _nsk of the non-ruptured zone in the K th surrounding rock partition needs to be calculated according to the formula d _nsk =l _k −d _sk .

The above method for analysis of fracture evolution of surrounding rock in deeply buried caverns based on force analysis of bolts is characterized in that: m=0.01, s=0-1, b=0.8 mentioned in step 3012.

The above-mentioned method for analyzing the fracture evolution of the surrounding rock in deep-buried caverns based on the force analysis of bolts is characterized in that: after the excavation of the cavern is completed in step 1, a section is selected from the excavated cavern as the test section ; When determining the basic mechanical parameters of the surrounding rock in step 2, take rock samples from the test section for indoor testing, and the obtained test results are the basic mechanical parameters of the surrounding rock in the test section after excavation.

The above-mentioned analysis method for regional fracture evolution of surrounding rock in deep-buried caverns based on force analysis of bolts is characterized in that: in step 1, the cavern currently being constructed is a deep-buried tunnel or a coal mine underground roadway.

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

1. The analysis method has simple steps, convenient implementation and low investment cost. The analysis process can be completed within a few minutes or even tens of seconds by using data processing equipment.

2. After the excavation is completed, firstly determine the basic mechanical parameters of the surrounding rock, and then analyze the zonal fracture evolution of the surrounding rock in the currently constructed cavern according to the determined basic mechanical parameters of the surrounding rock. Therefore, the results of the zonal fracture evolution analysis of the surrounding rock are accurate and reliable , strong operability.

3. In view of the fact that the deformation of the surrounding rock tends to be stable after a period of excavation and support in deep caverns, the analysis model is established starting from the force analysis of the full-length anchor bolt used in the initial support construction of excavation, and by determining The radius of the neutral point of the bolt and its maximum axial force are analyzed separately for the surrounding rock partitions, and the results of the fracture analysis are very close to the actual engineering. Due to the redistribution of the surrounding rock stress after the excavation of the cavern, when the tensile stress generated by the rock mass on the elastic-plastic interface under the maximum tangential support pressure exceeds its ultimate tensile strength, the rock mass will produce radial cracking The phenomenon of alternate distribution of multiple fractured areas and non-fractured areas appears; the difference in rock mass displacement rate in the ruptured area and non-ruptured area will lead to multiple neutral points along the length of the bolt; moreover, the thickness of the ruptured area of the surrounding rock is approximately Decreasing trend in turn until the surrounding rock rupture stops. According to the force deformation characteristics of bolt tension-compression alternate distribution under the condition of partitioned fracture of surrounding rock, a new method of analyzing partitioned fracture of surrounding rock by inversion of force law of bolt is proposed. Based on the principle of coordinated deformation between the rod body and the surrounding rock, a mechanical model of the interaction between the full-length anchor rod and the surrounding rock is established, and the thickness of the cracked zone and the non-cracked zone of the surrounding rock in each zone of the surrounding rock are obtained through corresponding analysis. Based on Griffith's strength theory, the mechanical criterion (i.e., the basis for judging the fracture) of the elastic-plastic interface rock mass cracking after the stress redistribution of the surrounding rock is proposed, and then the total number of fractured areas of the surrounding rock (ie, M) is determined.

4. The use effect is good. Based on the principle of coordinated deformation of the anchor rod and the surrounding rock, the basic evolution law of the regional rupture of the surrounding rock is analyzed, and the thickness and quantity of the surrounding rock rupture area in the deep-buried cavern can be reasonably determined to be able to support the excavation and support of the cavern. provide an important theoretical basis. After analysis, it can be concluded that the thickness of each surrounding rock partition and the thickness of the rupture zone are in a decreasing trend from the cave wall to the depth of the surrounding rock. Determine the excavation scheme of the deep cavern and its surrounding rock support parameters, and provide a new idea for the study of the regional fracture of the surrounding rock in deep rock mass engineering.

To sum up, the present invention has simple steps, reasonable design, convenient implementation, and good application effect. The number of rupture areas outside the currently constructed cavern and the thickness and location of each rupture area can be obtained through the analysis of the fracture evolution of surrounding rock partitions. Provide a reliable basis for subsequent cavern excavation and surrounding rock support.

The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is a flow chart of the method of the present invention.

Fig. 2 is a schematic diagram of the distribution state of the rupture zone formed by the divisional rupture of the surrounding rock at the arch of the deeply buried cavern according to the present invention.

Explanation of reference signs:

1—deep buried cavern; 1-1—surrounding rock partition rupture area;

1-2—Non-rupture zone of surrounding rock division.

Detailed ways

As shown in Figure 1, a method for analyzing the fracture evolution of surrounding rock in deep caverns based on the force analysis of bolts includes the following steps:

Step 1, cavern excavation: excavate the cavern currently under construction;

Step 2. Determination of the basic mechanical parameters of the surrounding rock: through indoor tests on the rock samples taken from the site, the basic mechanical parameters of the surrounding caverns under construction are tested, and the test results are recorded synchronously;

Step 3. Fracture evolution analysis of surrounding rock partitions: According to the basic mechanical parameters of the surrounding rock determined in step 2, analyze the fracture evolution of the surrounding rock partitions for the currently constructed cavern, and analyze the current construction tunnel after the excavation is completed according to the analysis results. The number M of rupture zones existing on the surrounding rock of the chamber and the thickness of each rupture zone are determined respectively; where M is an integer and M≥0; when M=0, it means that there is no rupture zone on the surrounding rock of the currently constructed cavern ;

Combined with Figure 2, when analyzing the fracture evolution of the surrounding rock partitions for the currently constructed caverns, the surrounding rocks of the currently constructed caverns are divided into multiple surrounding rock partitions from the inside to the outside, and the multiple surrounding rock partitions are analyzed from the inside to the outside. Fracture analysis is carried out for rock divisions respectively, and the process is as follows:

Step 301. Fracture analysis of the first surrounding rock partition: performing a fracture analysis on the first surrounding rock partition outside the currently constructed cavern, including the following steps:

Step 3011, determining the thickness of the first surrounding rock partition: according to the formula The thickness of the first surrounding rock partition is calculated l ₀ , and the unit of _{l 0} is m _; The sum of the neutral point radius of the bolt in a surrounding rock partition and the equivalent excavation radius of the currently constructed cavern, the neutral point radius of the bolt in the first surrounding rock partition is the first The distance between the front end of the bolt and the neutral point in the surrounding rock partition; in U is the perimeter of the cross-section of the anchor used to support the cavern currently under construction, and its unit is m, A is the cross-sectional area of the anchor, and its unit is m ² , E _b is the anchor The modulus of elasticity and its unit is Pa, K is the shear stiffness coefficient on the unit length of the anchor rod body and its unit is Pa/m;

Step 3012, determination of fracture: compare the difference between |σ _{r0 -μ} (σ _θ0 +σ _z0 )| When |σ _r0 -μ(σ _θ0 +σ _z0 )|≥|σ _t |, it is judged that there is a fracture in the first surrounding rock partition and at this time the first surrounding rock partition is a fractured surrounding rock partition, and go to step 3013; otherwise , it is judged that there is no fracture zone on the surrounding rock of the currently constructed cavern and M=0, and the analysis process of the regional fracture evolution of the surrounding rock of the currently constructed cavern is completed;

The cracked surrounding rock partition is divided into a cracked zone and a non-cracked zone located outside the cracked zone;

Among them, |σ _t | is the absolute value of σ _t , and σ _t is the tensile strength of the surrounding rock of the currently constructed cavern, and its unit is Pa, Among them, m is the coefficient related to the rock type and integrity of the surrounding rock of the currently constructed cavern and m=0.001~25, s is the rock mass integrity coefficient of the surrounding rock of the currently constructed cavern, and σ _c is the current construction cavern The uniaxial compressive strength of the rock mass surrounding the chamber and its unit is Pa;

|σ _r0 -μ(σ _θ0 +σ _z0 )| is the absolute value of σ _r0 -μ(σ _θ0 +σ _z0 );

Among them, μ is the Poisson’s ratio of the surrounding rock mass of the cavern currently under construction, σ _r0 is the radial stress of the rock mass at the elastic-plastic boundary of the first surrounding rock partition under the peak support pressure, and its unit is Pa; in is the internal friction angle of the surrounding rock mass of the currently constructed cavern, and P0' is the supporting reaction force on the elastic-plastic interface of the first surrounding rock partition; is the outer diameter of the plastic zone of the surrounding rock in the first surrounding rock division and c is the cohesion of the surrounding rock mass of the cavern currently under construction, and its unit is Pa; A ₀ and t are coefficients, Among them, G is the shear modulus of the surrounding rock mass of the cavern currently under construction and its unit is Pa; b is the support coefficient, b is a constant and 0<b<1; is the displacement value of the surrounding rock on the surface of the currently constructed cavern before support and its unit is m, r _b0 is the distance from the outer end of the bolt in the first surrounding rock partition to the center of the currently constructed cavern and r _b0 = l ₀ +R ₀ ; N _max0 is the maximum axial force on the bolt at the neutral point of the bolt in the first surrounding rock partition and B is the coefficient related to the deformation of the surrounding rock of the currently constructed cavern and E _r is the comprehensive elastic modulus of the surrounding rock mass of the currently constructed cavern, and its unit is Pa; P ₀ is the original rock stress of the surrounding rock mass of the currently constructed cavern before excavation, and its unit is Pa; R _p0 is the plastic zone radius of the currently constructed cavern surrounding rock under elastic-plastic conditions after excavation, and its unit is m,

σ _θ0 is the tangential stress at the elastic-plastic boundary of the surrounding rock in the first surrounding rock partition and σ _z0 is the axial stress at the elastic-plastic boundary of the surrounding rock in the first surrounding rock partition and σ _z0 = (1+2μ)P ₀ , the units of σ _θ0 and σ _z0 are both Pa;

Step 3013, determine the thickness of the rupture zone in the first surrounding rock partition: according to the formula Determine the thickness d _s0 of the rupture zone in the first surrounding rock subregion;

in, is the outer diameter of the fracture zone in the first surrounding rock partition and Inner diameter of the rupture zone in the first wall rock subdivision

Step 302, Fracture Analysis of the Next Surrounding Rock Partition: Perform a crack analysis on the next surrounding rock partition outside the currently constructed cavern; in this step, the surrounding rock partition for crack analysis is the Kth outside the currently constructed cavern Surrounding rock partition, wherein K is a positive integer and K≥2, K=k+1, k is a positive integer and k≥1; in this step, the k surrounding rock partitions located inside the Kth surrounding rock partition are all The fracture analysis process has been completed;

When performing fracture analysis on the Kth surrounding rock partition, the following steps are included:

Step 3021, determining the thickness of the Kth surrounding rock partition: according to the formula Calculate the thickness l _k of the Kth surrounding rock partition, and the unit of l _k is m;

In formula (Ⅲ), ρ _k is the sum of the neutral point radius of the bolt in the Kth surrounding rock partition and the equivalent excavation radius of the cavern currently under construction, and the anchor in the Kth surrounding rock partition The neutral point radius of the rod is the distance between the front end of the anchor rod and the neutral point in the Kth surrounding rock partition; Wherein, Δl _kz is the sum of the partition thicknesses of the k surrounding rock partitions located inside the K-th surrounding rock partition and its unit is m;

Step 3022, determination of fracture: compare the difference between |σ _{rk -μ} (σ _θk +σ _zk )| When |σ _rk -μ(σ _θk +σ _zk )|≥|σ _t |, it is judged that there is a crack in the Kth surrounding rock partition and at this time the Kth surrounding rock partition is a fractured surrounding rock partition, and then go to step 3023; otherwise , it is judged that there is no fracture zone on the Kth surrounding rock partition and M=k, and the analysis process of the fracture evolution of the surrounding rock partition of the currently constructed cavern is completed;

Among them, |σ _rk -μ(σ _θk +σ _zk )| is the absolute value of σ _rk -μ(σ _θk +σ _zk );

σ _rk is the radial stress of the rock mass at the elastic-plastic boundary of the Kth surrounding rock partition under the action of the peak support pressure, and its unit is Pa; P _k is the supporting reaction force on the elastic-plastic interface in the Kth surrounding rock partition and its unit is Pa, τ _s is the residual shear strength of the surrounding rock of the currently constructed cavern and its unit is Pa, is the outer diameter of the rupture zone in the k-th surrounding rock zone located inside and adjacent to the K-th surrounding rock zone, is the inner diameter of the rupture zone in the kth surrounding rock partition; is the outer diameter of the plastic zone of the surrounding rock in the Kth surrounding rock partition and A _k is the coefficient and Where r _bk is the sum of the thickness of the rupture zone in the Kth surrounding rock subregion and the equivalent excavation radius of the currently constructed cavern and r _bk = l _k + R ₀ ; N _maxk is the sum of the Kth surrounding rock subregion The maximum axial force on the anchor rod at the neutral point of the anchor rod and

σ _θk is the tangential stress at the elastic-plastic boundary of the surrounding rock in the Kth surrounding rock partition and σ _zk is the axial stress at the elastic-plastic boundary of the surrounding rock in the Kth surrounding rock partition and σ _zk =(1+2μ)P ₀ , the unit of σ _θk and σ _zk is Pa;

Step 3023, determine the thickness of the rupture zone in the Kth surrounding rock partition: according to the formula Determining the thickness d _sk of the rupture zone in the Kth surrounding rock partition;

in, is the outer diameter of the fracture zone in the Kth surrounding rock partition and ΔR _k ＝R ₀ +Δl _kz ; the inner diameter of the rupture zone in the Kth surrounding rock partition

Step 303, repeating step 302 one or more times until the process of analyzing the fracture evolution of the surrounding rock partitions of the currently constructed cavern is completed.

In this embodiment, the cavern currently being constructed in step 1 is a deeply buried cavern 1 with a buried depth greater than 50 m.

The buried 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.

In this embodiment, when excavating the currently constructed cavern in step 1, excavate the currently constructed cavern from back to front along the longitudinal extension direction and the excavation length is not greater than 50m.

The cavern currently being constructed in step 1 is a deep buried tunnel or an underground coal mine roadway. In this embodiment, the currently constructed cavern is a deep buried tunnel.

During actual construction, the cavern currently under construction may also be a pipeline cavern for installation of underground pipelines.

As shown in Figure 2, the surrounding rock partitions in step 3 are located outside the currently constructed cavern, and the cross-sectional shapes of the surrounding rock partitions, the cracked area, and the non-cracked area are all consistent with those of the currently constructed cavern. The cross-sectional shape is the same.

That is to say, when the surrounding rock has zonal fractures, the surrounding rocks around the currently constructed caverns all have zonal fractures.

As shown in FIG. 2 , each of the fractured surrounding rock partitions is composed of a fractured zone and a non-fractured zone located outside the fractured zone. Wherein, the cracked area is the broken area 1-1 of the surrounding rock partition, and the non-cracked area is the non-cracked area 1-2 of the surrounding rock partition.

s=0~1 described in step 3012.

In this embodiment, m=0.01, s=1, and b=0.8 described in step 3012. During actual construction, the values of m, s and b can be adjusted accordingly according to specific needs.

The P ₀ ′ described in step 3012 is the same as the supporting reaction force on the surrounding rock at the wall of the currently constructed cavern when the bolt is used to support the currently constructed cavern. In this embodiment, for simplicity of calculation, the anchor rod is used as a non-prestressed anchor rod, and P ₀ ′=0 Pa. For the accuracy of the data, the test method can also be used to test the support reaction force of the surrounding rock at the wall of the currently constructed cavern during the current construction of the cavern support, and according to the support reaction force obtained from the test to P ₀ ' Make sure.

The neutral point radius of the bolt in the first surrounding rock partition is The neutral point radius of the bolt in the Kth surrounding rock partition is

ΔR _k described in step 3023 is the distance from the outer edge of the kth surrounding rock subregion to the center of the cavern.

The rock mass in the earth's crust that has not been affected by human engineering activities (such as tunneling, coal mine underground roadway, etc.) is called proto-rock mass, or proto-rock for short. The original rock stress mentioned in step 2012 refers to the natural stress existing in the formation without engineering disturbance, also known as initial stress of rock mass, absolute stress or ground stress.

At the initial stage of cavern excavation, the stress of surrounding rock occurs secondary distribution, the tangential compressive stress on surrounding rock of cavern wall increases sharply, and the cavern wall is in an elastic or elastoplastic state. Since the cave wall is a free surface, the surrounding rock can only produce transverse stretching and expansion into the cave under tangential pressure. When the tensile deformation of the surrounding rock under tangential pressure reaches its ultimate strain, the first rupture zone appears on the cave wall, that is, the "pseudo-face". For the shallow rock mass, due to the low stress level, it is impossible to produce the second rupture zone after the stress release; for the deep rock mass under the high ground stress condition, the outer boundary of the first crack zone produced after the stress release is equivalent to At the new excavation boundary, the stresses are redistributed again. When the redistributed stress field satisfies the failure conditions of the rock mass, the stress is released again, forming the second rupture zone. By analogy, this phenomenon will continue until the maximum radial tensile strain of the surrounding rock caused by the axial support pressure is less than the ultimate tensile strain of the rock mass, and finally a zonal fracture phenomenon will be formed inside the surrounding rock, and finally a zonal fracture phenomenon will be formed in the deep surrounding rock.

For a long time, full-length anchor bolts have been widely used in the surrounding rock support of caverns (especially in the initial support of caverns, such as the initial support of caverns). It is assumed that the surrounding rock is in an elastic-plastic state at the initial stage of cavern excavation, and the surface surrounding rock continues to deform into the cavern space under the action of vertical pressure to form a rupture zone. For the convenience of discussion, it is assumed that: first, the section of the cavern is equivalent to a circle, and its longitudinal length is much larger than the transverse width, which belongs to the plane strain problem; second, the rock mass around the anchor is simplified to be homogeneous, continuous and Third, there is no relative sliding between any point on the surface of the anchor rod and the surrounding rock mass; fourth, the tensile strength of the anchor rod is much greater than that of the surrounding rock mass, and its length is from the surface of the surrounding rock to The outer boundary of the elastic zone. In the present invention, by simplifying the surrounding rock of the cavern into an ideal elastic-plastic medium, a full-length anchor bolt is arranged in the surrounding rock of the cavern.

After the soft rock cavern is excavated, along the length direction of the arch wall support bolt 2, there are surrounding rock crushing zone, plastic zone and elastic zone in sequence from inside to outside. Since the rock mass in each zone has different radial deformation, the closer to the cave chamber surface, the greater the radial displacement rate of the surrounding rock. A section of the rod near the surface of the cavern has a tendency to prevent the rock mass in the crushing zone from deforming into the cavern, and its surface produces positive frictional resistance pointing to the cavern; because the displacement rate of the rock mass in the elastic-plastic zone is smaller than that in the crushing zone, the rest of the rod body Then, under the pulling effect of the rod body close to the surface of the cavern, negative frictional resistance pointing to the deep surrounding rock is generated. The interface between the positive and negative friction of the rod body is the neutral point of the anchor rod. The relative displacement and surface friction between the rod body and the surrounding rock mass at this point are zero, but its axial tension reaches the maximum value. Therefore, there is a demarcation point whose surface frictional resistance points to the opposite on the arch wall support anchor rod 2, and this demarcation point is the neutral point where the relative displacement between the arch wall support anchor rod 2 and its surrounding rock mass is zero. point friction is zero. But at this boundary point, the axial pulling force of the anchor rod 2 reaches the maximum, and the axial pulling force gradually decreases from the boundary point to both ends of the arch wall supporting anchor rod 2 and tends to zero.

In this way, the present invention is based on the principle of coordinated deformation of the anchor rod and the surrounding rock, and by establishing the mechanical interaction between the anchor rod body and the surrounding rock mass that supports the arch wall (i.e. the arch and the side wall) of the excavated cavern. Based on the model, the distribution law of frictional resistance and axial force on the surface of the bolt is analyzed, and according to the static equilibrium condition of the bolt body, the position of the neutral point where the relative displacement between the bolt body and the rock mass is zero and the maximum axial tension value are deduced.

Since the rock mass in each zone has different radial deformation, the closer to the cave wall, the greater the radial displacement rate of the surrounding rock. A section of the rod body close to the cave wall has the tendency to prevent the rock mass in the crushing zone from deforming into the cave, and its surface generates negative frictional resistance pointing into the cave; because the displacement rate of the rock mass in the elastoplastic zone is smaller than that in the crushing zone, the rest of the rod body is The positive friction resistance pointing to the deep surrounding rock is generated under the pulling effect of the rod body close to the cave wall. The positive and negative friction resistance interface of the rod body is the neutral point of the bolt body. The relative displacement between the rod body and the surrounding rock mass at this point and the surface of the rod body The frictional resistance is zero, but its axial pulling force reaches the maximum value.

The stress of the surrounding rock in the cavern is continuously transmitted to the deep part of the surrounding rock through multiple redistributions. In the process of zonal fracture in the surrounding rock, new neutral points appear continuously along the length direction of the bolt body. The inside of each neutral point is a crushing zone with a large deformation rate, and the negative frictional resistance acting on the rod body points to the inside of the hole. ; The outer side is a non-rupture zone with a small deformation rate, and the positive frictional resistance acting on the rod body points to the deep surrounding rock. Due to the ups and downs of the radial displacement and radial strain of the surrounding rock at the peak and trough, the full-length anchor bolt in the surrounding rock will be alternately distributed in tension-compression force. These phenomena fully indicate that there are zonal fractures in the surrounding rocks of deeply buried caverns, in which fractured areas and non-fractured areas alternate.

After analysis, it is concluded that there are multiple neutral points (also known as anchor rod neutral points) in the anchor rod stress in the surrounding rock of the deep buried cavern 1, and there are multiple rupture zones and The phenomenon that multiple non-ruptured regions are distributed at intervals, that is, the phenomenon of partition rupture. The multiple neutral points are respectively M ₁ , M ₂ , M ₃ , . . . from inside to outside. And, the distance between each neutral point and the center of the cavern is Wherein, O ₀ is the center of the cavern, M _i is the ith neutral point in the surrounding rock of the deep buried cavern 1, i is a positive integer and i=1, 2, 3, ...; O ₀ M _i is The distance between the i-th neutral point and the center of the cavern. In addition, there is a neutral point in each surrounding rock partition, when the surrounding rock partition ruptures, the axial force on the head and end of the bolt body in each surrounding rock partition along the length direction of the bolt is equal to zero, and the bolt bodies in the two adjacent surrounding rock partitions do not affect each other in terms of stress and deformation.

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

In this embodiment, in step 3013, it is also necessary to calculate the thickness d _ns0 of the non-ruptured zone in the first surrounding rock subregion according to the formula d _ns0 = l ₀ -d _s0 ;

In step 3023, the thickness d _nsk of the non-ruptured zone in the K th surrounding rock partition needs to be calculated according to the formula d _nsk =l _k −d _sk .

In this embodiment, after the excavation of the cavern in step 1 is completed, a section is selected from the excavated cavern as the test section.

When determining the basic mechanical parameters of the surrounding rock in step 2, rock samples are taken from the test section for indoor testing, and the obtained test results are the basic mechanical parameters of the surrounding rock in the test section after excavation. In this way, the determined mechanical parameters need to be determined on the basis of experiments, which can effectively ensure the accuracy and reliability of data and reduce calculation errors.

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 tunnel, and when the cavern is excavated in step 1, the full-section excavation method or the step method is used for excavation.

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

In this embodiment, when determining the basic mechanical parameters of the surrounding rock in step 2, the determined basic mechanical parameters of the surrounding rock should at least include the original rock stress P ₀ of the surrounding rock mass of the currently constructed cavern before excavation, the current construction The internal friction angle of the surrounding rock mass of the cavern The Poisson's ratio μ of the surrounding rock mass of the cavern currently under construction, the support reaction force P ₀ ' on the elastic-plastic interface of the first surrounding rock section, the cohesion c of the surrounding rock mass of the currently constructed cavern, and the current The shear modulus G of the surrounding rock mass of the construction cavern, the displacement value of the surrounding rock on the surface of the currently constructed cavern before support The comprehensive elastic modulus E _r of the surrounding rock mass of the currently constructed cavern, the residual shear strength τ _s of the surrounding rock mass of the currently constructed cavern, and the uniaxial compressive strength σ _c of the surrounding rock mass of the currently constructed cavern.

In addition, the equivalent excavation radius R ₀ of the currently constructed cavern, the cross-sectional perimeter U of the anchor rod used for supporting the currently constructed cavern, the cross-sectional area A of the anchor rod, The elastic modulus E _b of the anchor rod and the shear stiffness coefficient K per unit length of the anchor rod body. Among them, the shear stiffness coefficient refers to the ratio of the corresponding shear stress to shear displacement of the rock specimen under certain normal stress and shear stress.

In this embodiment, the surrounding rock of the currently constructed cavern in step 2 is the surrounding rock where the arch or the left and right side walls of the currently constructed cavern are located.

Inner diameter of the rupture zone in the first surrounding rock subregion described in step 3013 is the distance from the inner boundary line of the rupture zone in the first surrounding rock division to the center of the currently constructed cavern, and the outer diameter of the rupture zone in the first surrounding rock division is the distance from the outer boundary line of the rupture zone in the first surrounding rock division to the center of the currently constructed cavern;

Inner diameter of the rupture zone in the Kth surrounding rock subregion described in step 3023 is the distance from the inner boundary line of the rupture zone in the Kth surrounding rock division to the center of the currently constructed cavern, and the outer diameter of the rupture zone in the Kth surrounding rock division It is the distance from the outer boundary line of the rupture zone in the Kth surrounding rock division to the center of the currently constructed cavern.

τ _s =τ _p -c described in step 3022, where τ _p is the peak shear strength (also referred to as peak strength) of the surrounding rock of the currently constructed cavern.

In this embodiment, a plurality of surrounding rock subregions are arranged radially from the inside to the outside of the cavern, and the multiple surrounding rock subregions are all located on the same cross-section of the currently constructed cavern.

In this example, the cavern currently being constructed is a straight-walled vaulted cavern, with an equivalent excavation radius R ₀ =2.0m, Poisson’s ratio μ=0.25, uniaxial compressive strength σ _c =37.7MPa, and the original rock Stress P ₀ =22.8MPa, cohesion c=12MPa, internal friction angle The comprehensive elastic modulus E _r of the rock mass = 4.2GPa, the shear modulus G = 1.68GPa, and the peak shear strength τ _p = 48MPa. After the cavern is excavated, a full-length non-prestressed bolt with a diameter of φ25mm is laid in the surrounding rock. Assuming that the length of the bolt body meets the calculation requirements, the cross-sectional circumference U=0.08m, and the cross-sectional area A=4.91×10 ^{- 4} m ² , the elastic modulus E _b of the anchor rod = 40GPa, the displacement value of the surrounding rock on the surface of the currently constructed cavern before support Shear stiffness coefficient K=360MPa/m.

In this example,

According to the formula When calculating the thickness l ₀ of the first surrounding rock partition, according to This yields l ₀ =3.07m.

τ _s ＝τ _p -c＝48×10 ⁶ -12×10 ⁶ ＝36MPa;

σ _z0 ＝(1+2μ)P ₀ ＝＝(1+2×0.25)×22.8×10 ⁶ ＝34.2MPa;

σ _r0 -μ(σ _θ0 +σ _z0 )=(-31.24×10 ⁶ )-0.25×(92.04×10 ⁶ +34.2×10 ⁶ )=-62.80MPa;

The comparison shows that: |σ _r0 -μ(σ _θ0 +σ _z0 )|＞|σ _t |, so there is a fracture in the first surrounding rock partition and at this time the first surrounding rock partition is a fractured surrounding rock partition, and the first The cave wall rock mass in the surrounding rock partition will enter the brittle cracking state from the plastic state, and the first fracture zone of the surrounding rock will be formed after the cave wall becomes unstable.

In the initial stage of cavern excavation, the secondary distribution of stress in the surrounding rock occurs, and the distribution of the surrounding rock is elastic. It can be seen from the theory of elastic mechanics that when the concentrated stress on the surrounding rock at the cave wall exceeds its ultimate strength, the surrounding rock at the cave wall will first enter a state of plastic tension.

When the surrounding rock of the cave wall enters the fractured state from the plastic state, the stress of the surrounding rock is distributed three times;

Calculated

Shear modulus

Correspondingly, the outer diameter of the plastic zone in the first surrounding rock partition formed after the stress of the surrounding rock of the cave wall is distributed three times after the instability is calculated:

Corresponding calculations give: the thickness d _s0 of the rupture zone in the first surrounding rock division = 2.49-2.0 = 0.49m, and the thickness d _ns0 of the non-rupture zone in the first surrounding rock division = 3.07-0.49 = 2.58m;

Similarly, according to the method described in step 3021 to step 3023, the thickness of the cracked zone and the non-cracked zone in the Kth surrounding rock partition can be obtained, and according to the determined thickness of the cracked zone and the non-cracked zone in each surrounding rock partition The location of the fracture zone and non-crack zone in each surrounding rock partition is determined accordingly.

In this embodiment, according to the method described in step 3021 to step 3023, the thicknesses of the cracked zone and the non-cracked zone in the second surrounding rock subregion, the third surrounding rock subregion and the fourth surrounding rock subregion can be obtained.

Among them, the thickness of the second surrounding rock subregion l ₁ =1.84m, the thickness of the cracked zone within the second surrounding rock subregion d _s1 =0.34m, the thickness of the non-ruptured zone within the second surrounding rock subregion d _ns1 = 1.50m;

Thickness l ₂ of the third surrounding rock partition = 3.83m, thickness d _s2 of the cracked zone within the third surrounding rock partition = 0.57m, thickness d _ns2 of the non-ruptured zone in the third surrounding rock partition = 3.26m ;

Thickness l ₃ of the fourth surrounding rock division = 0.69m, thickness d s3 of the cracked zone within the fourth surrounding rock division d _s3 = 0.19m, thickness d ns3 of the non-ruptured zone within the fourth surrounding rock division d _ns3 = 0.50m .

Similarly, when performing fracture analysis on the fifth surrounding rock partition, Δl _4z =l ₀ +l ₁ +l ₂ +l ₃ =3.07+1.84+3.83+0.69=9.43m.

according to It is calculated that l ₄ =5.77m;

Correspondingly, the outer diameter of the plastic zone in the fifth surrounding rock partition formed by five stress distributions after the wall rock is unstable is:

The support reaction force on the elastic-plastic interface in the fifth surrounding rock division

σ _z4 ＝(1+2×0.25)×22.8×10 ⁶ ＝34.2MPa;

σ _r4 -μ(σ _θ4 +σ _z4 )＝-7.78×10 ⁶ -0.25×(68.58×106+34.2×106)＝-33.47MPa;

After comparison, it is concluded that: |σ _r4 -μ(σ _θ4 +σ _z4 )|<|σ _t |, it is judged that there is no rupture zone on the 5th (ie K) surrounding rock partition and M=4 (ie k), Complete the analysis process of the fracture evolution of the surrounding rock partition in the cavern currently under construction. At this time, the currently constructed cavern includes a total of 4 rupture zones, as shown in Figure 2 for details.

From the above content, it can be seen that the calculation results of the partitioned fracture of the surrounding rock of the cavern are shown in Table 1:

Table 1

In summary, according to the analysis of the fracture evolution of the surrounding rock partitions, the thickness and position of all the fracture zones outside the currently constructed cavern can be obtained, which can provide accurate and reliable basis for the determination of the surrounding rock support scheme after the excavation is completed, and is practical Very good value.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any way. All simple modifications, changes and equivalent structural changes made to the above embodiments according to the technical essence of the present invention still belong to the technical aspects of the present invention. within the scope of protection of the scheme.

Claims (7)

1. A method for analyzing the regional fracture evolution of the surrounding rock of a deeply buried cavern based on the force analysis of the bolt, characterized in that the method comprises the following steps: Step 1, cavern excavation: excavate the cavern currently under construction; Step 2. Determination of the basic mechanical parameters of the surrounding rock: the basic mechanical parameters of the surrounding rock of the currently constructed cavern are tested through indoor tests on the rock samples taken from the site, and the test results are recorded synchronously; Step 3. Fracture evolution analysis of surrounding rock partitions: According to the basic mechanical parameters of the surrounding rock determined in step 2, analyze the fracture evolution of the surrounding rock partitions for the currently constructed cavern, and analyze the current construction tunnel after the excavation is completed according to the analysis results. The number M of rupture zones existing on the surrounding rock of the chamber and the thickness of each rupture zone are determined respectively; where M is an integer and M≥0; when M=0, it means that there is no rupture zone on the surrounding rock of the currently constructed cavern ; When analyzing the fracture evolution of surrounding rock partitions for the currently constructed caverns, the surrounding rocks of the currently constructed caverns are divided into multiple surrounding rock partitions from the inside to the outside, and the multiple surrounding rock partitions are analyzed from the inside to the outside. Fracture analysis, the process is as follows: Step 301. Fracture analysis of the first surrounding rock partition: performing a fracture analysis on the first surrounding rock partition outside the currently constructed cavern, including the following steps: Step 3011, determining the thickness of the first surrounding rock partition: according to the formula (I), calculate the thickness l ₀ of the first surrounding rock partition, and the unit of l ₀ is m; in the formula (I), R ₀ is the equivalent excavation radius of the cavern currently under construction and its unit is m; _ρ0 is the sum of the neutral point radius of the bolt in the first surrounding rock subregion and the equivalent excavation radius of the currently constructed cavern, and the neutral point radius of the bolt in the first surrounding rock subregion is the distance between the front end of the bolt and the neutral point in the first surrounding rock partition; in U is the perimeter of the cross-section of the anchor used to support the cavern currently under construction, and its unit is m, A is the cross-sectional area of the anchor, and its unit is m ² , E _b is the anchor The modulus of elasticity and its unit is Pa, K is the shear stiffness coefficient on the unit length of the anchor rod body and its unit is Pa/m; Step 3012, determination of fracture: compare the difference between |σ _{r0 -μ} (σ _θ0 +σ _z0 )| When |σ _r0 -μ(σ _θ0 +σ _z0 )|≥|σ _t |, it is judged that there is a fracture in the first surrounding rock partition and at this time the first surrounding rock partition is a fractured surrounding rock partition, and go to step 3013; otherwise , it is judged that there is no fracture zone on the surrounding rock of the currently constructed cavern and M=0, and the analysis process of the regional fracture evolution of the surrounding rock of the currently constructed cavern is completed; The cracked surrounding rock partition is divided into a cracked zone and a non-cracked zone located outside the cracked zone; Among them, |σ _t | is the absolute value of σ _t , and σ _t is the tensile strength of the surrounding rock of the currently constructed cavern, and its unit is Pa, Among them, m is the coefficient related to the rock type and integrity of the surrounding rock of the currently constructed cavern and m=0.001~25, s is the rock mass integrity coefficient of the surrounding rock of the currently constructed cavern, and σ _c is the current construction cavern The uniaxial compressive strength of the rock mass surrounding the chamber and its unit is Pa; |σ _r0 -μ(σ _θ0 +σ _z0 )| is the absolute value of σ _r0 -μ(σ _θ0 +σ _z0 ); Among them, μ is the Poisson’s ratio of the surrounding rock mass of the cavern currently under construction, σ _r0 is the radial stress of the rock mass at the elastic-plastic boundary of the first surrounding rock partition under the peak support pressure, and its unit is Pa; in is the internal friction angle of the surrounding rock mass of the currently constructed cavern, and P0' is the supporting reaction force on the elastic-plastic interface of the first surrounding rock partition; is the outer diameter of the plastic zone of the surrounding rock in the first surrounding rock division and c is the cohesion of the surrounding rock mass of the cavern currently under construction, and its unit is Pa; A ₀ and t are coefficients, Among them, G is the shear modulus of the surrounding rock mass of the cavern currently under construction and its unit is Pa; b is the support coefficient, b is a constant and 0<b<1; is the displacement value of the surrounding rock on the surface of the currently constructed cavern before support and its unit is m, r _b0 is the distance from the outer end of the bolt in the first surrounding rock partition to the center of the currently constructed cavern and r _b0 = l ₀ +R ₀ ; N _max0 is the maximum axial force on the bolt at the neutral point of the bolt in the first surrounding rock partition and B is the coefficient related to the deformation of the surrounding rock of the currently constructed cavern and EE _r is the comprehensive elastic modulus of the surrounding rock mass of the currently constructed cavern, and its unit is Pa; P ₀ is the original rock stress of the surrounding rock mass of the currently constructed cavern before excavation, and its unit is Pa; R _p0 is the plastic zone radius of the currently constructed cavern surrounding rock under elastic-plastic conditions after excavation, and its unit is m, σ _θ0 is the tangential stress at the elastic-plastic boundary of the surrounding rock in the first surrounding rock partition and σ _z0 is the axial stress at the elastic-plastic boundary of the surrounding rock in the first surrounding rock partition and σ _z0 = (1+2μ)P ₀ , the units of σ _θ0 and σ _z0 are both Pa; Step 3013, determine the thickness of the rupture zone in the first surrounding rock partition: according to the formula (II), determine the thickness d _s0 of the rupture zone in the first surrounding rock subregion; in, is the outer diameter of the fracture zone in the first surrounding rock partition and The inner diameter of the rupture zone in the first wall rock division Step 302, Fracture Analysis of the Next Surrounding Rock Partition: Perform a crack analysis on the next surrounding rock partition outside the currently constructed cavern; in this step, the surrounding rock partition for crack analysis is the Kth outside the currently constructed cavern Surrounding rock partition, wherein K is a positive integer and K≥2, K=k+1, k is a positive integer and k≥1; in this step, the k surrounding rock partitions located inside the Kth surrounding rock partition are all The fracture analysis process has been completed; When performing fracture analysis on the Kth surrounding rock partition, the following steps are included: Step 3021, determining the thickness of the Kth surrounding rock partition: according to the formula Calculate the thickness l _k of the Kth surrounding rock partition, and the unit of l _k is m; In formula (Ⅲ), ρ _k is the sum of the neutral point radius of the bolt in the Kth surrounding rock partition and the equivalent excavation radius of the cavern currently under construction, and the anchor in the Kth surrounding rock partition The neutral point radius of the rod is the distance between the front end of the anchor rod and the neutral point in the Kth surrounding rock partition; Wherein, Δl _kz is the sum of the partition thicknesses of the k surrounding rock partitions located inside the K-th surrounding rock partition and its unit is m; Step 3022, determination of fracture: compare the difference between |σ _{rk -μ} (σ _θk +σ _zk )| When |σ _rk -μ(σ _θk +σ _zk )|≥|σ _t |, it is judged that there is a crack in the Kth surrounding rock partition and at this time the Kth surrounding rock partition is a fractured surrounding rock partition, and then go to step 3023; otherwise , it is judged that there is no fracture zone on the Kth surrounding rock partition and M=k, and the analysis process of the fracture evolution of the surrounding rock partition of the currently constructed cavern is completed; Among them, |σ _rk -μ(σ _θk +σ _zk )| is the absolute value of σ _rk -μ(σ _θk +σ _zk ); σ _rk is the radial stress of the rock mass at the elastic-plastic boundary of the Kth surrounding rock partition under the action of the peak support pressure, and its unit is Pa; P _k is the supporting reaction force on the elastic-plastic interface in the Kth surrounding rock partition and its unit is Pa, τ _s is the residual shear strength of the surrounding rock of the currently constructed cavern and its unit is Pa, is the outer diameter of the rupture zone in the k-th surrounding rock zone located inside and adjacent to the K-th surrounding rock zone, is the inner diameter of the rupture zone in the kth surrounding rock partition; is the outer diameter of the plastic zone of the surrounding rock in the Kth surrounding rock partition and A _k is the coefficient and Where r _bk is the sum of the thickness of the rupture zone in the Kth surrounding rock subregion and the equivalent excavation radius of the currently constructed cavern and r _bk = l _k + R ₀ ; N _maxk is the sum of the Kth surrounding rock subregion The maximum axial force on the anchor rod at the neutral point of the anchor rod and σ _θk is the tangential stress at the elastic-plastic boundary of the surrounding rock in the Kth surrounding rock partition and σ _zk is the axial stress at the elastic-plastic boundary of the surrounding rock in the Kth surrounding rock partition and σ _zk =(1+2μ)P ₀ , the unit of σ _θk and σ _zk is Pa; Step 3023, determine the thickness of the rupture zone in the Kth surrounding rock partition: according to the formula Determining the thickness d _sk of the rupture zone in the Kth surrounding rock partition; in, is the outer diameter of the fracture zone in the Kth surrounding rock partition and ΔR _k ＝R ₀ +Δl _kz ; the inner diameter of the rupture zone in the Kth surrounding rock partition Step 303, repeating step 302 one or more times until the process of analyzing the fracture evolution of the surrounding rock partitions of the currently constructed cavern is completed. 2. According to the method for analyzing the fracture evolution of the surrounding rock of the deep-buried cavern based on the force analysis of the bolt according to claim 1, it is characterized in that: when the cavern currently under construction is excavated in the step 1, along the longitudinal extension direction Excavate the cavern currently under construction from back to front and the excavation length shall not exceed 50m. 3. According to claim 1 or 2, the method for analyzing the fracture evolution of the surrounding rock in the deeply buried cavern based on the force analysis of the anchor rod is characterized in that: the surrounding rock in the step 3 is located outside the currently constructed cavern, The cross-sectional shapes of the surrounding rock partition, the cracked zone and the non-cracked zone are all the same as the cross-sectional shape of the currently constructed cavern. 4. According to claim 1 or 2, the method for analyzing the fracture evolution of surrounding rock in deep caverns based on stress analysis of rock bolts, is characterized in that: in step 3013, the formula d _ns0 =l ₀ -d _s0 is also required, Calculate the thickness d _ns0 of the non-cracked zone in the first surrounding rock partition; In step 3023, the thickness d _nsk of the non-ruptured zone in the K th surrounding rock partition needs to be calculated according to the formula d _nsk =l _k −d _sk . 5. According to claim 1 or 2, the method for analyzing the fracture evolution of the surrounding rock of the deep cavern based on the force analysis of the rock bolt, is characterized in that: m=0.01, s=0-1 described in step 3012, b=0.8. 6. According to claim 1 or 2, the method for analyzing the fracture evolution of surrounding rock in deep buried caverns based on stress analysis of rock bolts, is characterized in that: after the excavation of the cavern in step 1 is completed, the Select a section in the cavern as the test section; when determining the basic mechanical parameters of the surrounding rock in step 2, take rock samples from the test section for indoor testing, and the obtained test results are the results of the test section after excavation. Basic mechanical parameters of surrounding rock. 7. According to claim 1 or 2, the method for analyzing the fracture evolution of surrounding rock in deep buried caverns based on the force analysis of rock bolts, is characterized in that: in step 1, the cavern currently under construction is a deep buried tunnel or a coal mine underground roadway .