Rapid quantitative evaluation method for stability of deep tunnel surrounding rock in high tectonic stress area

Abstract

The invention provides a rapid quantitative evaluation method for stability of deep tunnel surrounding rocks in a high tectonic stress area, and belongs to the technical field of deep tunnel surrounding rocks. The method comprises the steps of providing a numerical value and analytical method for analyzing external stress distribution of a surrounding rock loose circle of a deep tunnel in a high tectonic stress area, then providing a surrounding rock loose circle range evaluation method fusing the numerical value and the analytical method, and finally rapidly predicting the maximum thickness of the surrounding rock loose circle through two dimensionless factors capable of reflecting high tectonic stress characteristics. According to the method, aiming at the deeply-buried tunnel in the high tectonic stress area of the Sichuan-Tibet railway, an analysis method considering engineering calculation precision and speed requirements is developed by taking deep rock mass engineering digital-numerical value integrated analysis as an idea and combining natural advantages of a prior analysis method in the aspect of rapid calculation; the important requirements of dynamic design of deep tunnel engineering and three-dimensional positive analysis of surrounding rock stability are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of surrounding rock of deep-buried tunnels, and particularly relates to a method for rapidly quantitatively evaluating the stability of surrounding rock of deep-buried tunnels in high tectonic stress areas. Background Technique

[0002] The Sichuan-Tibet Railway traverses the Qinghai-Tibet Plateau region formed by the collision and uplift of the Indian plate and the Eurasian plate. Most of the line is located in the area where the eastward lateral extrusion of the Qinghai-Tibet Plateau is the most intense. The strong and frequent geological tectonic actions have formed a geostress environment with particularly prominent horizontal tectonic stress, bringing unprecedented challenges to the construction of the Sichuan-Tibet Railway. The Sichuan-Tibet Railway has a large number of ultra-long deep-buried tunnels in high tectonic stress areas under construction and proposed construction. The excavation unloading of these tunnels is extremely likely to induce a series of engineering disasters such as sudden rock bursts, strong brittle failures, and continuous large deformations, and the geological safety risks brought to the construction and even the entire life cycle operation of the Sichuan-Tibet tunnels cannot be ignored. Therefore, scientifically evaluating the stability of the surrounding rock of deep-buried tunnels in high tectonic stress areas is not only a prerequisite for tunnel construction but also the basis for tunnel disaster prevention and control, and is of great significance to the Sichuan-Tibet Railway.

[0003] The thickness of the loosened zone of the surrounding rock after the excavation of a deep-buried tunnel can provide a quantitative reference basis for the evaluation of the stability of the surrounding rock. In tunnel design, the support structure design can be preliminarily given according to the pre-determined thickness of the loosened zone, and then during the construction process, the thickness of the loosened zone of the surrounding rock during the excavation of the tunnel face can be detected by using on-site measuring devices, which is conducive to realizing the dynamic design of the support structure. Rapidly and accurately determining the thickness of the loosened zone of unsupported surrounding rock in advance is the prerequisite for realizing the dynamic design of the support structure and is also a hot spot and difficult problem in the analysis of the stability of surrounding rock in tunnel engineering. The stability of the surrounding rock after tunnel excavation is directly related to the magnitude of the geostress, the strength of the rock, and the degree of joint development, etc. A large number of on-site measurements have shown that the range of the loosened zone of the surrounding rock of deep-buried tunnels is directly related to the magnitude of the geostress and the strength of the surrounding rock. When the tunnel burial depth increases, the loosened zone increases approximately linearly in a certain direction. In particular, in a high tectonic stress environment, the surrounding rock has significant non-uniform failure characteristics, and the morphological characteristics of the loosened zone show a strong correlation with the geostress field. The shape of the loosened zone is generally U-shaped or V-shaped.

[0004] By developing test equipment or improving test methods, the failure process of tunnel surrounding rock under high stress can be simulated indoors. However, this method is limited by equipment and time consumption. Numerical methods can greatly reduce test costs and conduct repetitive tests, reducing the errors caused by the discreteness of model test samples. However, at present, numerical methods have defects in rapid calculation and analysis and are difficult to meet the major requirements of the dynamic design of deep-buried tunnel projects. Analytical methods or semi-analytical and semi-numerical methods have the significant advantage of being able to quickly perform parameter analysis, but the existing methods are difficult to consider the influence of high tectonic stress on the stability of surrounding rock.

[0005] Therefore, developing a design analysis method that can simultaneously meet the requirements of engineering accuracy and rapid calculation is an issue that needs further research in current tunnel engineering, especially for deep-buried tunnels in high tectonic stress areas of the Sichuan-Tibet Railway. Summary of the Invention

[0006] The purpose of the present invention is to provide a rapid quantitative evaluation method for the stability of surrounding rocks of deep-buried tunnels in high tectonic stress areas, which is characterized by including the following steps:

[0007] S1: Calculate the stress distribution within the loosened circle of the surrounding rocks of the deep-buried tunnel according to the engineering rock mass strength parameters;

[0008] S2: Calculate the stress distribution outside the loosened circle of the surrounding rocks of the deep-buried tunnel based on the in-situ stress parameters of the engineering geological area given in the geological exploration data;

[0009] S3: Provide a rapid calculation method for the range of the loosened circle of the surrounding rocks of the deep-buried tunnel considering the in-situ stress characteristics of the high tectonic stress area;

[0010] S4: Construct a database of the loosened circles of the surrounding rocks of the deep-buried tunnel under different in-situ stress conditions, and give a rapid evaluation formula for the maximum thickness of the loosened circle reflecting the influence of high tectonic stress.

[0011] Further, S1 specifically includes the following steps:

[0012] S11: Under the theoretical framework of the three-dimensional strength analysis of GZZ rock mass, the surrounding rock strength parameters include m b , s and a, and their calculation expressions are:

[0013]

[0014] In the formula, m i is the rock texture parameter, GSI is the geological strength index, and D is the excavation blasting disturbance coefficient.

[0015] First, use in-situ digital testing means such as mobile phone photography to quickly obtain the joint information of the surrounding rocks of the tunnel face and use 5G transmission technology to upload it to the cloud in real time. Then, remotely identify the GSI value of the current tunnel face according to the calculation formula recommended by Hoek. Finally, take the D value according to Hoek's recommendation and determine the m i value through on-site rebound dynamics tests or by looking up tables.

[0016] S12: Use the three-dimensional strength theory of GZZ rock mass to describe the failure behavior of the surrounding rocks within the loosened circle. The expression of the smooth GZZ criterion is:

[0017]

[0018] In the formula, σ c is the uniaxial compressive strength of intact rock, I1 is the first stress invariant, J2 is the second stress deviator invariant, θσ is the stress Lode angle.

[0019] The plastic stress in the loosened zone is solved by numerical method. The equilibrium equation in difference form is:

[0020]

[0021] where r is the radial coordinate of the tunnel surrounding rock, σ r is the minimum principal stress, σ α is the maximum principal stress, and the out-of-plane stress σ z in the loosened zone is the intermediate principal stress, and its expression is:

[0022]

[0023] Calculate the stress distribution of the surrounding rock loosened zone according to Eqs. (2), (3), and (4).

[0024] Furthermore, the calculation steps of the stress distribution of the surrounding rock loosened zone in S12 are as follows:

[0025] S121: According to the tunnel inner wall boundary condition and Eq. (1), use the fsolve function in Matlab software to solve the maximum principal stress σ α(1) ;

[0026] S122: According to Eqs. (2), (3), and (4), use the fsolve function in Matlab software to calculate the stress components σ (2) at r r(2) , σ z(2) , σ α(2) ;

[0027] S123: By analogy, use the fsolve function in Matlab software to calculate the stress components σ (j) at r r(j) , σ z(j) , σ α(j) , and obtain the stress distribution in the loosened zone.

[0028] Furthermore, S2 specifically includes the following steps:

[0029] S21: Use a set of mapping functions to describe the loosened zone range, which can be expressed by Taylor series as:

[0030]

[0031] where c1 and c -k are both m + 1 unknown coefficients, and ζ is a complex variable.

[0032] S22: According to Eq. (5), use two analytical functions to represent the stress distribution outside the surrounding rock loosened zone:

[0033]

[0034] Among them, the coefficients of the analytic function are 2n, and B1 and B2 are related to the self-weight stress σ v and the horizontal tectonic stress σ h , and their expressions are as follows:

[0035]

[0036] The stress components outside the surrounding rock loosening zone can be expressed as:

[0037] σ x +σ y = 4Re[Φ(ζ)] (10)

[0038]

[0039] In the formula

[0040] S23: According to the stress boundary conditions on the boundary of the surrounding rock loosening zone, the equation for solving the analytic function is:

[0041]

[0042] In the formula, X n and Y n are the surface force components along the horizontal and self-weight directions, and can be calculated by the following formula:

[0043]

[0044] In the formula, σ x and σ y are the normal stress components along the x and y directions in the rectangular coordinate system respectively, τ xy is the shear stress component, and l and m are the direction cosines of the unit outer normal of the boundary point under discussion with the horizontal and self-weight directions.

[0045] Furthermore, the solution steps of the analytic function in S23 are as follows:

[0046] S231: Based on the stress distribution of the loosening zone determined in S12, calculate the surface force components X n and Y n ;

[0047] S232: Expand the line integral term on the right side of equation (12) into a Fourier series as follows:

[0048]

[0049] Let ζ take 2n + 1 different boundary values in Equation (14), and directly determine the 2n + 1 coefficients in Equation (14) using the linear equation solver of Matlab software;

[0050] S233: Expand the fraction on the left - hand side of Equation (12) with respect to the mapping function into a Fourier series as follows:

[0051]

[0052] Let ζ take 2n + 1 different boundary values in Equation (15), and directly determine the 2n + 1 coefficients in Equation (15) using the linear equation solver of Matlab software;

[0053] S234: Substitute Equations (14) and (15) into Equation (12), and obtain a linear equation system for the coefficients a k and b k by comparing the terms with the same power of ζ. Then directly determine a k and b k .

[0054] Furthermore, S3 specifically includes the following steps:

[0055] S31: Use the damage proximity function FAI GZZ to quantitatively evaluate the yield or damage degree of a point. In the principal stress space, FAI GZZ represents the ratio of the distance from the stress state of any point to the hydrostatic stress axis to the distance from the corresponding limit stress state of this point to the hydrostatic stress axis , and its expression is:

[0056]

[0057] According to the stress contact condition on the boundary of the loose circle, construct the definite - solution equation for the boundary of the loose circle as:

[0058]

[0059] where r1 and r2 are penalty factors.

[0060] S32: Take Equation (17) as the objective function, take the coefficients of the mapping function in Equation (5) as design variables, and use an optimization algorithm to seek the optimal value of the objective function.

[0061] S33: After optimizing using the particle swarm algorithm, check whether the static equilibrium condition on the boundary of the loose circle meets the accuracy requirements according to Equation (12). If so, the calculation terminates and the optimal individual is output; if not, appropriately increase the number of particles and the number of iterations and continue the calculation until the requirements are met.

[0062] S34: Substitute the optimal individual into Equation (5) to output the range of the surrounding rock loosening zone.

[0063] Furthermore, S4 specifically includes the following steps:

[0064] S41: Calculate the surrounding rock loosening zone of deep-buried tunnels under different tectonic stress environments according to the processes in S1 - S3 and construct its database.

[0065] S42: Use the ratio K of the average value of the horizontal tectonic stress and the self-weight geostress to the uniaxial compressive strength of the rock σ to evaluate the influence of the geostress level on the stability of the tunnel surrounding rock, and its expression is:

[0066]

[0067] Use the stress concentration factor K determined by the horizontal tectonic stress and the self-weight geostress SCF to evaluate the influence of the geostress difference on the stability of the tunnel surrounding rock, and its expression is:

[0068]

[0069] According to the database constructed in S41, statistically analyze the maximum thickness r of the loosening zone max and the corresponding relationship with two dimensionless factors K σ and K SCF to establish a linear evaluation expression of r max with respect to K <~ σ and K SCF and use the least squares method to determine the slope coefficient and intercept coefficient in the linear expression.

[0070] S43: Establish a piecewise correction evaluation expression for the maximum thickness of the surrounding rock loosening zone during the dynamic excavation process of the tunnel.

[0071] Furthermore, the establishment process of the piecewise correction evaluation expression in S43 is as follows:

[0072] S431: Utilize the surrounding rock information revealed by the tunnel face during the tunnel excavation process to establish a database of the maximum thickness of the loosening zone of the current tunnel with the variation of engineering geological conditions according to the measured results of the loosening zone thickness;

[0073] S432: Utilize the surrounding rock information revealed by the tunnel face during the tunnel excavation process to quickly evaluate the maximum thickness of the loosening zone according to the prediction formula obtained in S42;

[0074] S433: Based on the surrounding rock information revealed by the tunnel face during the tunnel excavation process, dynamically segment (classify) the engineering geological conditions of the tunnel. According to the measured results in S431 and the predicted results in S432, establish a sectional correction evaluation expression for the maximum thickness of the loosening zone of the tunnel surrounding rock.

[0075] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0076] 1. A rapid quantitative evaluation method for the stability of surrounding rock in deep-buried tunnels in high tectonic stress areas proposed by the present invention integrates an elastic analytical solution for the outer domain of a loosening zone with a complex shape and a plastic stress numerical solution for the loosening zone of a circular tunnel, realizing the rapid evaluation of the stability of surrounding rock.

[0077] 2. The present invention uses two dimensionless factors to reflect the in-situ stress environment to which the deep-buried tunnel is subjected, and can be used to rapidly predict the maximum thickness of the loosening zone of the surrounding rock.

[0078] 3. All the rock mass parameters required for the evaluation method described in the present invention can be quickly obtained on-site through digital measurement means or on-site tests, and three-dimensional forward analysis of the stability of the surrounding rock of the tunnel project can be realized. Description of the Drawings

[0079] Figure 1 It is a flow chart of a rapid quantitative evaluation method for the stability of surrounding rock in deep-buried tunnels in high tectonic stress areas provided by the present invention.

[0080] Figure 2 It is a schematic diagram of the numerical model for calculating the stress of the loosening zone of the surrounding rock S1 in a rapid quantitative evaluation method for the stability of surrounding rock in deep-buried tunnels in high tectonic stress areas provided by the present invention.

[0081] Figure 3 It is a schematic diagram of the analytical model for calculating the external stress of the loosening zone of the surrounding rock in step S2 in a rapid quantitative evaluation method for the stability of surrounding rock in deep-buried tunnels in high tectonic stress areas provided by the present invention.

[0082] Figure 4 It is a flow chart of the rapid calculation method for the range of the loosening zone of the surrounding rock in step S3 in a rapid quantitative evaluation method for the stability of surrounding rock in deep-buried tunnels in high tectonic stress areas provided by the present invention. Detailed Embodiments

[0083] The following will describe in more detail a rapid quantitative evaluation method for the stability of surrounding rock in deep-buried tunnels in high tectonic stress areas of the present invention with reference to the schematic diagrams, in which the preferred embodiments of the present invention are shown. It should be understood that those skilled in the art can modify the present invention described herein while still achieving the beneficial effects of the present invention. Therefore, the following description should be understood as a broad guidance for those skilled in the art and not as a limitation to the present invention.

[0084] AsFigure 1 As shown in the figure, a method for quickly quantifying and evaluating the stability of surrounding rock in a deep-buried tunnel in a high tectonic stress area includes the following steps:

[0085] Step 1: Refer to Figure 2 , and calculate the stress distribution in the loosened circle of the surrounding rock of the deep-buried tunnel according to the strength parameters of the engineering rock mass.

[0086] Step 1 specifically includes:

[0087] Step 11: Under the theoretical framework of the three-dimensional strength analysis of GZZ rock mass, the surrounding rock strength parameters include m b , s, and a, and their calculation expressions are:

[0088]

[0089] In the formula, m i is the rock texture parameter, GSI is the geological strength index, and D is the excavation blasting disturbance coefficient.

[0090] First, use in-situ digital testing methods such as mobile phone photography to quickly obtain the joint information of the surrounding rock of the working face and use 5G transmission technology to upload it to the cloud in real time. Then, remotely identify the GSI value of the current working face according to the calculation formula recommended by Hoek. Finally, take the D value according to Hoek's recommendation, and determine the m i value through on-site rebound dynamics tests or by looking up tables.

[0091] Step 12: Use the three-dimensional strength theory of GZZ rock mass to describe the failure behavior of the surrounding rock in the loosened circle. The expression of the smooth GZZ criterion is:

[0092]

[0093] In the formula, σ c is the uniaxial compressive strength of intact rock, I1 is the first stress invariant, J2 is the second stress deviator invariant, and θ σ is the stress Lode angle.

[0094] Use numerical methods to solve the plastic stress in the loosened circle. Use the balance equation in differential form:

[0095]

[0096] In the formula, r is the radial coordinate of the tunnel surrounding rock, σ r is the minimum principal stress, σ α is the maximum principal stress, and the out-of-plane stress σ z in the loosened circle is the intermediate principal stress, and its expression is:

[0097]

[0098] Calculate the stress distribution of the surrounding rock loose circle according to formulas (2), (3), and (4).

[0099] Among them, the solution of the stress distribution of the surrounding rock loose circle can be realized according to the following steps, including:

[0100] Step 121: According to the tunnel inner wall boundary condition and formula (2), use the fsolve function in Matlab software to solve the maximum principal stress σ at the inner wall α(1) ;

[0101] Step 122: According to formulas (2), (3), and (4), use the fsolve function in Matlab software to calculate the stress components σ (2) at r r(2) , σ z(2) , σ α(2) ;

[0102] Step 123: By analogy, use the fsolve function in Matlab software to calculate the stress components σ (j) at r r(j) , σ z(j) , σ α(j) , and obtain the stress distribution within the loose circle.

[0103] Step 2, refer to Figure 3 , and calculate the stress distribution outside the surrounding rock loose circle of the deep-buried tunnel based on the in-situ stress parameters given in the geological exploration data.

[0104] Step 2 specifically includes:

[0105] Step 21: Use a set of mapping functions to describe the loose circle range, which can be expressed by the Taylor series as:

[0106]

[0107] In the formula, c1, c -k are both m + 1 unknown coefficients, and ζ is a complex variable.

[0108] Step 22: According to formula (5), use two analytical functions to represent the stress distribution outside the surrounding rock loose circle:

[0109]

[0110] In the formula, there are 2n analytical function coefficients, and B1 and B2 are related to the self-weight stress σ v and the horizontal tectonic stress σ h , and their expressions are:

[0111]

[0112] The stress components outside the surrounding rock loose circle can be expressed as:

[0113] σ x +σ y =4Re[Φ(ζ)] (10)

[0114]

[0115] wherein

[0116] Step 23, according to the stress boundary conditions on the boundary of the surrounding rock loosening zone, the equation for solving the analytic function is as follows:

[0117]

[0118] wherein, X n and Y n are the surface force components along the horizontal and self-weight directions, and can be calculated by the following formula:

[0119]

[0120] wherein, σ x and σ y are the normal stress components along the x and y directions in the rectangular coordinate system respectively, τ xy is the shear stress component, and l and m are the direction cosines of the unit outer normal of the boundary point under discussion with the horizontal and self-weight directions.

[0121] Among them, the solution of the analytic function is realized through the following steps:

[0122] Step 231: Based on the stress distribution of the loosening zone determined in Step 12, calculate the surface force components X n and Y n ;

[0123] Step 232: Expand the line integral term on the right side of Equation (12) into a Fourier series as follows:

[0124]

[0125] Let ζ in Equation (12) take 2n + 1 different boundary values, and directly determine the 2n + 1 coefficients in Equation (14) using the linear equation solver of Matlab software;

[0126] Step 233: Expand the fraction of the mapping function on the left side of Equation (12) into a Fourier series as follows:

[0127]

[0128] Let ζ take 2n + 1 different boundary values in Equation (12), and directly determine the 2n + 1 coefficients in Equation (15) using the linear equation solver of Matlab software;

[0129] Step 234: Substitute Equations (14) and (15) into Equation (12), and obtain a linear equation system for the coefficients a k and b k of the analytic function by comparing the terms with the same power of ζ, and directly determine a k and b k using the linear equation solver of Matlab software.

[0130] Step 3: Refer to Figure 4 to give a rapid calculation method for the range of the loosening zone of the surrounding rock of a deep-buried tunnel considering the in-situ stress characteristics in the high tectonic stress area.

[0131] Step 3 specifically includes:

[0132] Step 31: Use the failure proximity function FAIGZZ to quantitatively evaluate the yield or failure degree of a point. In the principal stress space, FAIGZZ represents the ratio of the distance from the stress state of any point to the hydrostatic stress axis to the distance from the corresponding limit stress state of this point to the hydrostatic stress axis , and its expression is:

[0133]

[0134] According to the stress contact condition on the boundary of the loosening zone, construct the definite solution equation for the boundary of the loosening zone as:

[0135]

[0136] where r1 and r2 are penalty factors.

[0137] In this embodiment, they are both taken as 100, R0 is the tunnel radius, the definite solution condition for the soft rock tunnel is to make the value of F(X) equal to 0, and the definite solution condition for the hard rock tunnel is to make the value of F(X) as close to 0 as possible.

[0138] Step 32: Take Equation (17) as the objective function, take the mapping function coefficients in Equation (5) as the design variables, and use the optimization algorithm to seek the optimal value of the objective function.

[0139] In this embodiment, the particle swarm optimization algorithm toolbox written in Matlab programming language is used. Set the range of the design variable c1 to [0, 5R0], and the rest of the c -k are all [-R0, R0], the number of particles is 20, the inertia constant is 0.6, the acceleration constants are all 1, the maximum flying speed is 10% of the maximum speed, and the maximum number of iterations is 400.

[0140] Step 33: After optimizing using the particle swarm algorithm, check whether the static equilibrium condition on the boundary of the loosened zone meets the accuracy requirements according to Equation (12). If so, terminate the calculation and output the optimal individual; if not, appropriately increase the number of particles and the number of iterations and continue the calculation until the requirements are met.

[0141] Step 34: Substitute the optimal individual into Equation (5) to output the range of the surrounding rock loosened zone.

[0142] Step 4: Construct a database of the surrounding rock loosened zones of deep-buried tunnels under different in-situ stress conditions, and give a rapid evaluation formula for the maximum thickness of the loosened zone reflecting the influence of high tectonic stress.

[0143] Step 4 specifically includes:

[0144] Step 41: Calculate the surrounding rock loosened zones of deep-buried tunnels under different tectonic stress environments according to the processes in Steps 1 to 3 and construct their database.

[0145] Step 42: Use the ratio K of the average value of the horizontal tectonic stress and the self-weight in-situ stress to the uniaxial compressive strength of the rock σ to evaluate the influence of the in-situ stress level on the stability of the tunnel surrounding rock, and its expression is:

[0146]

[0147] Use the stress concentration factor K determined by the horizontal tectonic stress and the self-weight in-situ stress SCF to evaluate the influence of the in-situ stress difference on the stability of the tunnel surrounding rock, and its expression is:

[0148]

[0149] According to the database constructed in Step 41, statistically analyze the corresponding relationship between the maximum thickness r of the loosened zone max and the two dimensionless factors K σ and K SCF , establish a linear evaluation expression of r max with respect to K σ and K SCF , and use the least squares method to determine the slope coefficient and intercept coefficient in the linear expression.

[0150] Step 43: Establish a piecewise correction evaluation expression for the maximum thickness of the surrounding rock loosened zone during the dynamic excavation process of the tunnel.

[0151] Among them, Step 43 can be implemented according to the following steps, including:

[0152] Step 431: Utilize the surrounding rock information revealed by the tunnel face during the tunnel excavation process to establish a database of the maximum thickness of the loosened zone of the current tunnel with the variation of the engineering geological conditions according to the measured results of the loosened zone thickness.

[0153] Step 432: Utilize the surrounding rock information revealed by the tunnel face during the tunnel excavation process, and quickly evaluate the maximum thickness of the loosening zone according to the prediction formula obtained in Step 42;

[0154] Step 433: Utilize the surrounding rock information revealed by the tunnel face during the tunnel excavation process to dynamically segment (classify) the engineering geological conditions of the tunnel. According to the measured results in Step 431 and the prediction results in Step 432, establish a sectional correction evaluation expression for the maximum thickness of the tunnel surrounding rock loosening zone, and complete the rapid quantitative evaluation of the stability of the surrounding rock of the deep-buried tunnel in the high tectonic stress area.

[0155] The above is only the preferred embodiment of the present invention, and it does not play any limiting role on the present invention. Any person skilled in the art within the technical field, without departing from the technical solution of the present invention, makes any form of equivalent replacement or modification and other changes to the technical solution and technical content disclosed by the present invention, all of which belong to the content of not departing from the technical solution of the present invention and still fall within the protection scope of the present invention.

Claims

1. A rapid quantitative evaluation method for the stability of surrounding rock in deep-buried tunnels in high tectonic stress areas, characterized in that, It includes the following steps: S1: Calculate the stress distribution within the loosened zone of the surrounding rock of a deep-buried tunnel based on the strength parameters of engineering rock masses; S2: Calculate the stress distribution outside the loosened zone of the surrounding rock of a deep-buried tunnel based on the in-situ stress parameters of the engineering geological area given in the geological exploration data; S3: Present a rapid calculation method for the range of the loosened zone of the surrounding rock of a deep-buried tunnel considering the in-situ stress characteristics of the high tectonic stress area; S4: Construct a database of the loosened zone of the surrounding rock of a deep-buried tunnel under different in-situ stress conditions, and present a rapid evaluation formula for the maximum thickness of the loosened zone reflecting the influence of high tectonic stress.

2. The rapid quantitative evaluation method for the surrounding rock stability of a deep-buried tunnel in a high tectonic stress area according to claim 1, characterized in that The specific steps of S1 include the following: S11: Under the theoretical framework of the three-dimensional strength analysis of the GZZ rock mass, the surrounding rock strength parameters required include m b , s, and a; S12: Use the GZZ three-dimensional strength theory of rock masses to describe the failure behavior of the surrounding rock within the loosened zone. The smooth GZZ criterion expression is: In the GZZ criterion, σ c is the uniaxial compressive strength of intact rock, I1 is the first stress invariant, J2 is the second stress deviator invariant, and θ σ is the stress Lode angle; Combine the GZZ criterion, the relationship between the out-of-plane stress component and the in-plane stress component of the loosened zone surface of the surrounding rock, and the equilibrium equation in differential form to calculate the stress distribution of the loosened zone of the surrounding rock.

3. The rapid quantitative evaluation method for the surrounding rock stability of a deep-buried tunnel in a high tectonic stress area according to claim 2, characterized in that, The method for determining the surrounding rock strength parameters is as follows: First, use in-situ digital testing methods such as mobile phone photography to quickly obtain the joint information of the surrounding rock of the heading face and use 5G transmission technology to upload it to the cloud in real time. Then, remotely identify the GSI value of the current heading face according to the calculation formula recommended by Hoek. Finally, take the D value according to Hoek's suggestion and determine the m i value through on-site rebound dynamics tests or by looking up tables.

4. The rapid quantitative evaluation method for the surrounding rock stability of deep-buried tunnels in high tectonic stress areas according to claim 3, characterized in that, In S12, the solution of the stress distribution of the loosened zone of the surrounding rock includes the following steps: S121: Solve for the maximum principal stress σ at the inner wall using the fsolve function in Matlab software according to the boundary conditions of the tunnel inner wall and the GZZ strength criterion a(1) ; S122: Calculate according to the GZZ strength criterion, the relationship between the out-of-plane stress component and the in-plane stress component of the surrounding rock loosening circle, and the equilibrium equation in differential form. Use the fsolve function in Matlab software to calculate the stress components σ (2) at r r(2) , σ z(2) , σ a(2) ; S123: Use the fsolve function in Matlab software to calculate the stress components σ (j) at r r(j) , σ z(j) , σ a(j) , and obtain the stress distribution within the loosened zone.

5. The rapid quantitative evaluation method for the surrounding rock stability of a deep-buried tunnel in a high tectonic stress area according to claim 4, characterized in that The specific steps of S2 include the following: S21: Use a set of mapping functions to describe the range of the loosened zone. The mapping function is expressed by the Taylor series; S22: Based on the mapping function expressed by the Taylor series, use two analytical functions to represent the stress distribution outside the loosened zone of the surrounding rock; S23: Solve the analytical functions according to the stress boundary conditions on the boundary of the loosened zone of the surrounding rock.

6. The rapid quantitative evaluation method for the surrounding rock stability of a deep-buried tunnel in a high tectonic stress area according to claim 5, characterized in that, In S23, the solution of the analytical functions includes the following steps: S231: Calculate the surface force components X n and Y n ; S232: Expand the integral terms of the surface force components X n and Y n into Fourier series; Let the independent variable in the series take 2n + 1 different boundary values, and use the linear equation solver in Matlab software to directly determine the 2n + 1 coefficients in the series; S233: Expand the fraction about the mapping function in S21 into a Fourier series; Let the independent variable in the series take 2n + 1 different boundary values, and use the linear equation solver in Matlab software to directly determine the 2n + 1 coefficients in the series; S234: Substitute the two Fourier series into the stress boundary conditions, and obtain a system of linear equations about the coefficients of the analytical functions by comparing the terms of the same power of the independent variable. Use the linear equation solver in Matlab software to directly determine the analytical functions.

7. The rapid quantitative evaluation method for the surrounding rock stability of deep-buried tunnels in high tectonic stress areas according to claim 6, characterized in that The specific steps of S3 include the following: S31: Use the damage proximity function FAI GZZ Quantitatively evaluate the yield or damage degree of any point. In the principal stress space, FAI GZZ represents the distance from the stress state of this point to the hydrostatic stress axis and the distance from the corresponding limit stress state of this point to the hydrostatic stress axis ratio; According to the stress contact conditions on the boundary of the loosened zone, construct a definite equation for the boundary of the loosened zone; S32: Use the definite equation to construct an objective function, take the coefficients of the mapping function as design variables, and use an optimization algorithm to seek the optimal value of the objective function; After using the particle swarm algorithm for optimization, check whether the static equilibrium conditions on the boundary of the loosened zone meet the accuracy requirements. If so, the calculation terminates and the optimal individual is output; if not, appropriately increase the number of particles and the number of iterations and continue the calculation until the requirements are met; S34: Output the range of the loosened zone of the surrounding rock according to the optimal individual.

8. The rapid quantitative evaluation method for the surrounding rock stability of deep-buried tunnels in high tectonic stress areas according to claim 7, characterized in that The specific steps of S4 include the following: S41: Calculate the loosened zone of the surrounding rock of a deep-buried tunnel under different tectonic stress environments through S1 - S3 and construct its database; S42: Use the ratio K of the average value of the horizontal tectonic stress and the in-situ stress due to self-weight to the uniaxial compressive strength of the rock σ to evaluate the influence of the in-situ stress level on the stability of the tunnel surrounding rock, and use the stress concentration factor K determined by the horizontal tectonic stress and the in-situ stress due to self-weight SCF to evaluate the influence of the in-situ stress difference on the stability of the tunnel surrounding rock. Based on the database constructed in S41, statistically analyze the maximum thickness r of the loosened zone max and the correspondence relationship with the two dimensionless factors K σ and K SCF to establish a linear evaluation expression of r max with respect to K σ and K SCF and use the least squares method to determine the slope coefficient and intercept coefficient in the linear expression; S43: Establish a piecewise correction evaluation expression for the maximum thickness of the loosened zone of the surrounding rock during the dynamic excavation process of the tunnel.

9. The rapid quantitative evaluation method for the surrounding rock stability of a deep-buried tunnel in a high tectonic stress area according to claim 8, characterized in that In S43, the establishment of the piecewise correction evaluation expression includes the following steps: S431: Utilize the surrounding rock information revealed by the heading face during the tunnel excavation process, and establish a database of the maximum thickness of the loosened zone that varies with the engineering geological conditions of the current tunnel according to the measured results of the thickness of the loosened zone; S432: Utilize the surrounding rock information revealed by the heading face during the tunnel excavation process, and quickly evaluate the maximum thickness of the loosened zone according to the prediction formula obtained in S42; S433: Utilize the surrounding rock information revealed by the heading face during the tunnel excavation process, dynamically segment the engineering geological conditions of the tunnel, and establish a sectional correction evaluation expression for the maximum thickness of the loosened zone of the tunnel surrounding rock according to the measured results in S431 and the prediction results in S432.

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