Mountain tunnel support stress deformation numerical calculation method, system and terminal

Abstract

The invention discloses a mountain tunnel support stress deformation numerical calculation method, system and terminal, and the method comprises the steps: carrying out the classification and grading of surrounding rock, the grading of the burial depth and the grading of the crustal stress according to the rock hardness degree, the rock mass integrity degree, the burial depth and the initial crustal stress field of a mountain tunnel; selecting a corresponding constitutive model and a boundary condition according to a grading result; and based on the constitutive model and the boundary conditions, according to the tunnel simulation parameters, establishing a mountain tunnel support stress deformation numerical model for simulation calculation, and obtaining the stress and deformation of the support structure. The method is used for establishing the numerical model based on tunnel grading judgment, adaptive matching of the constitutive model and the boundary conditions, the accuracy of stress simulation calculation of the supporting structure can be effectively improved, the differentiated calculation requirement that the same frame is compatible with shallow burying to ultra-deep burying is met, evaluation of the safety and stability of the supporting structure is facilitated, and the method is suitable for popularization and application. The method is suitable for tunnel supporting structure optimization design and construction safety evaluation under complex geological conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mountain tunnel support design, and particularly relates to a mountain tunnel support stress deformation numerical calculation method, system and terminal. BACKGROUND

[0002] Numerical simulation method is an important means to study the stress and deformation characteristics of tunnel support, which can simulate various complex conditions, deformation and failure process of surrounding rock, stress evolution, and post-failure behavior. However, the traditional numerical model has certain shortcomings in simulating the stress and deformation mechanism of tunnel under different coupling conditions such as different buried depths, ground stress, and complex strata. Its adaptability and efficiency need to be further improved. On the one hand, for deep-buried soft rock, super-deep-buried (high ground stress) fracture zone, and altered hard rock tunnel engineering in complex geological environment, the commonly used elastic-plastic constitutive model (such as Mohr-Coulomb, Drucker-Prager, Hoek-Brown, etc.) has significant defects in accurately describing shear dilatancy, strain softening, large deformation, structural degradation, and creep behavior, making it difficult to accurately simulate the progressive failure and surrounding rock deformation instability process induced by high ground stress, which limits its applicability in complex geological conditions. Therefore, a constitutive model with shear dilatancy, strain softening, damage evolution, and rheological characteristics needs to be introduced to improve the simulation accuracy. On the other hand, the mechanical calculation model of tunnel support structure mainly includes stratum-structure model and load-structure model. The former considers the bearing capacity of surrounding rock as a whole and directly considers the bearing capacity of surrounding rock, which is the model currently used and being developed in the design and calculation of tunnel structure system. In the process of numerical simulation, the tunnel support structure and its surrounding rock interact, and the load acting on the rock mass is mainly the self-weight stress and tectonic stress. Therefore, the determination of ground stress is the key to the suitability of stratum-structure model. For shallow and deep soft surrounding rock tunnels, the load is usually determined according to the self-weight stress field, and the upper boundary is free with ground line, while the other boundaries are usually subjected to displacement constraints. When the buried depth is large, due to the soil arching effect and the existence of stratum tectonic stress, the results calculated by the self-weight stress often cannot reflect the actual engineering. Especially for high ground stress deep-buried soft rock and super-deep-buried tunnels (buried depth > 500 m), if the entire stratum is simulated in the numerical modeling process, the calculation amount is large and the calculation cost is extremely high. Therefore, force boundary conditions can be used for simulation, i.e. uniform surrounding rock stress (pressure) is set on the four sides of the model. Therefore, how to calculate the stress value is crucial. For deep-buried tunnel surrounding rock pressure calculation, the commonly used highway and tunnel design specification is an empirical formula for deep-buried tunnel loose surrounding rock pressure or the Terzaghi formula based on a large amount of statistical analysis. However, the surrounding rock pressure calculated by the former is independent of the buried depth under deep-buried conditions, and the surrounding rock pressure calculated by the latter tends to a constant value as the buried depth increases. However, a large number of measured data show that the actual surrounding rock pressure of deep-buried or super-deep-buried tunnels is still affected by the buried depth. Therefore, the specification method lacks rationality and accuracy, and it is urgent to consider the correction of surrounding rock pressure calculation by introducing factors such as buried depth and rock mass strength-ground stress ratio, so as to apply more suitable stress boundary conditions to improve the numerical calculation efficiency and accuracy.

[0003] Therefore, the present invention proposes a numerical calculation method, system and terminal for the stress and deformation of mountain tunnel support that considers multiple geological factors, couples the interactive effects of stratum properties, tunnel burial depth and ground stress state, and constructs a system to achieve the same framework compatibility with differentiated calculation requirements from shallow to ultra-deep burial, which is used for tunnel optimization design and construction safety assessment under complex geological conditions. Summary of the Invention

[0004] The purpose of the present invention is to propose a numerical calculation method, system and terminal for the stress and deformation of mountain tunnel supports that takes into account multiple geological factors, so as to solve the problem of calculation or prediction deviation of the stress and deformation of mountain tunnel supports caused by the traditional numerical model not considering the coupling of multiple geological factors, and to evaluate the safety and stability of the support structure and guide the optimal design of the support structure.

[0005] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a numerical calculation method for the stress and deformation of mountain tunnel support, which specifically includes the following steps: Step 1: Based on the rock hardness, rock mass integrity, burial depth, and initial geostress field of the mountain tunnel, perform surrounding rock classification and grading, as well as burial depth classification and geostress classification, and then select the corresponding constitutive model and boundary conditions; Step 2: Based on the constitutive model and boundary conditions obtained in Step 1 and the tunnel simulation parameters, a numerical model of the stress and deformation of the mountain tunnel support is established and simulated to obtain the stress, deformation, and plastic zone distribution results of the support structure; The constitutive model and boundary conditions are selected according to the following method: For shallow tunnels and deep hard rock tunnels, the modified elastoplastic model and displacement boundary conditions are used; For deep soft rock tunnels, if the ground stress is extremely high or high, the strain softening model and stress boundary conditions are selected; if the ground stress is normal, the strain softening model and displacement boundary conditions are selected; For deep buried clay soil tunnels, the Burgers rheological model and displacement boundary conditions are used; For ultra-deep tunnels in fractured zones with extremely high or high ground stress, the surrounding rock damage correction model and stress boundary conditions are used; For ultra-deep soft rock and altered rock tunnels with extremely high or high ground stress, the Burgers rheological model and stress boundary conditions are selected.

[0006] Furthermore, the burial depth classification includes: Shallow burial: H<H p ; Deep burial: H p ≤H≤500m; Ultra-deep burial: H>500m; wherein H p are determined according to formula (1.1)-(1.3): (1.1); (1.2); (1.3); wherein: H is the tunnel depth; H p is the deep-shallow tunnel demarcation depth; h q is the equivalent load height, the worse the surrounding rock condition (I→VI grade), the greater the corresponding coefficient value (2→2.5); s is the surrounding rock grade, such as the V-grade surrounding rock, then s=5; B is the tunnel excavation width; ω is the tunnel width influence coefficient, and i is a parameter related to the surrounding rock grade, when B<5, i=0.2, and when B>5, i=0.1.

[0007] Further, the ground stress grading includes: extremely high ground stress: R c / σ1<4; high ground stress: 4≤R c / σ1≤7; general ground stress: R c / σ1>7; wherein R c is the rock uniaxial saturated compressive strength; and σ1 is the maximum principal stress.

[0008] Further, the tunnel simulation parameters include: stratum attribute parameters, underground water, tunnel depth, initial ground stress field, tunnel section design parameters, and supporting structure design parameters. Wherein the stratum attribute parameters include uniaxial saturated compressive strength R c , rock bulk density, lateral pressure coefficient λ, surrounding rock elastic modulus, surrounding rock cohesion c and internal friction angle φ.

[0009] Further, the strain softening model is determined according to formula (2.1)-(2.3): (2.1); (2.2); (2.3); wherein: is the cohesion of the surrounding rock; is the internal friction angle of the surrounding rock; c0 is the initial cohesion of the surrounding rock; φ0 is the initial internal friction angle of the surrounding rock; H c , H φ are positive constant values for controlling the softening rate. For the shear plastic strain, the second invariant form of strain tensor is adopted, and the increment summation can be obtained; c res For the residual cohesion of surrounding rock; φ res For the residual internal friction angle of surrounding rock; For the critical shear plastic strain corresponding to the residual strength; For the plastic strain rate tensor; t is time.

[0010] Further, the surrounding rock damage correction model is determined according to formula (3.1)-(3.3): (3.1); (3.2); (3.3); In the formula: E damaged For the elastic modulus of surrounding rock after damage correction; E0 is the initial elastic modulus of surrounding rock; c damaged For the cohesion of surrounding rock after damage correction; c0 is the initial cohesion of surrounding rock; φ damaged For the internal friction angle of surrounding rock after damage correction; φ0 is the initial internal friction angle of surrounding rock; Δφ is the empirical attenuation coefficient; D is the damage factor; Wherein, the damage factor D is determined according to formula (3.4): (3.4); In the formula: k1 and k2 are stress-sensitive coefficient and broken degree-sensitive coefficient respectively, which are calibrated by indoor triaxial test; σ1 is the maximum principal stress in the initial stress field; σ3 is the minimum principal stress in the initial stress field; RQD is the rock quality index.

[0011] Further, for shallow tunnel, rock sample conditions can be directly obtained by drilling, and the viscoelastic parameters of the Burgers rheological model can be obtained according to the results of field direct shear rheological test and according to formula (4.1), (4.2): (4.1); (4.2); In the formula: γ is shear strain; Is shear stress; Is time; G1 is viscoelastic shear modulus; G2 is instantaneous shear modulus; η1, η2 are viscous coefficients; γ0 is instantaneous shear strain; G1, η1, η2 are obtained by regression analysis of shear creep curve by least square method; For deep and ultra-deep tunnels, it is difficult to obtain rock samples at the required tunnel burial depth H due to the limited drilling sampling depth. The parameters of the Burgers rheological model are sensitive to the burial depth, especially the parameters η1 and G2. Therefore, it is necessary to carry out rheological tests on multiple groups of rock samples at different burial depths. The viscosity coefficients η1, η2 and the shear moduli G1, G2 can be uniformly corrected according to equations (4.3) and (4.4) to obtain: (4.3); (4.4); Where: η(H) and G(H) are the corrected viscosity coefficient and shear modulus, and n(H) corresponds to the viscosity coefficients η1 and η2, and G(H) corresponds to the viscoelastic shear modulus G1 and the instantaneous shear modulus G2; H ref is the reference burial depth; η ref , G ref is the reference parameter of the burial depth; n η , α G , α η is a parameter to be determined; n η Determined by power law fitting of rock sample step confining pressure rheological test, the value range of hard rock is usually 1.2-1.5, and the value range of soft rock is usually 0.8-1.0; α G The typical value is 0.08±0.02, which is obtained by ultrasonic shear wave velocity measurement and logarithmic regression of rock samples at different burial depths. η The viscosity coefficient and shear modulus data were obtained by regression analysis of multiple groups of rock sample tests at different burial depths.

[0012] Furthermore, the displacement boundary conditions are as follows: the ground line is used as the free boundary at the upper boundary of the two-dimensional plane numerical model, the boundaries on both sides constrain horizontal displacement, and the bottom boundary constrains vertical and horizontal displacements; relative to the tunnel size, the horizontal boundary range of the model is usually set to 6-10 times the tunnel excavation span, and the vertical boundary is taken according to the calculated target burial depth.

[0013] Furthermore, the stress boundary condition is: setting the vertical uniformly distributed surrounding rock stress σ at the upper and lower boundaries of the numerical model x , the left and right boundaries are set to average the surrounding rock stress σ y ; Relative to the tunnel size, the model horizontal and vertical boundary range is usually set to 6-10 times the tunnel excavation span; For tunnels buried in soft rock or ultra-deep tunnels with extremely high or high in-situ stress, the stress boundary value shall be the measured in-situ stress value; or, if the measured in-situ stress value is unavailable, it shall be determined according to formulas (5.1) and (5.2): (5.1); (5.2); In the formula: σ x σ is the horizontal uniform surrounding rock stress; σ y σ is the vertical uniform surrounding rock stress; B is the tunnel excavation width; H is the tunnel burial depth; G is the surrounding rock deformation grade, which is preliminarily determined according to the rock mass strength stress ratio in the survey stage, and is corrected according to the measured deformation in the construction stage; and λ is the lateral pressure coefficient.

[0014] In a second aspect, the present application further provides a mountain tunnel support stress deformation numerical calculation system for implementing the above-mentioned mountain tunnel support stress deformation numerical calculation method considering multiple geological factors, and the system comprises: A simulation parameter input module is configured to input tunnel simulation parameters, including stratum attribute parameters, burial depth, underground water, initial ground stress field, tunnel cross-section design parameters, and support structure design parameters. A tunnel grading discrimination module is configured to classify and grade the surrounding rock and grade the tunnel burial depth and ground stress. A simulation calculation module is configured to match corresponding constitutive models and boundary conditions for the mountain tunnel support stress deformation numerical model according to the tunnel grading discrimination results, and perform simulation calculation according to the input simulation parameters. An output warning module is configured to output the stress, deformation and surrounding rock plastic zone distribution of the mountain tunnel support structure, and trigger a support structure failure warning when the support structure displacement exceeds a threshold value.

[0015] Further, the threshold value of the support structure displacement is determined according to the specification “Railway Tunnel Monitoring Measurement Technical Specification” Q / CR9218-2024.

[0016] In a third aspect, the present application further provides a terminal comprising a processor and a memory for storing a processor-executable program, wherein the processor implements the above-mentioned mountain tunnel support stress deformation numerical calculation method when executing the program stored in the memory.

[0017] Compared with the prior art, the present application has the following beneficial effects: 1) The present application classifies and discriminates the mountain tunnel surrounding rock, burial depth and ground stress based on the hardness of rock, the integrity of rock mass, the burial depth and the initial ground stress field, couples the interactive effects of stratum attributes, tunnel burial depth and ground stress state, adaptively matches corresponding constitutive models and boundary conditions, and is used for establishing a numerical simulation model, which can effectively improve the accuracy of mountain tunnel support structure stress simulation calculation, is conducive to evaluating the safety and stability of the support structure and guiding the optimization design of the support structure. 2) Compared with the traditional elastic-plastic constitutive model (such as Mohr-Coulomb model), the strain softening model, Burgers rheological model and surrounding rock damage correction model can more accurately describe the dilatancy effect, strain softening, structural deterioration and creep behavior, and simulate the progressive failure and surrounding rock deformation instability process induced by high ground stress; 3) The stress boundary condition adopted in the application considers the influence of factors such as buried depth, rock mass strength-ground stress ratio, and is more in line with engineering practice, and is especially suitable for high ground stress deep buried soft rock and super deep buried tunnel; 4) The application can realize accurate mechanical analysis of the supporting structure, effectively solve the deviation problem of mountain tunnel support stress and deformation calculation or prediction caused by not considering the coupling of multiple geological factors in the traditional numerical model, and realize the differentiated calculation demand of the same framework from shallow to super deep, and is suitable for tunnel optimization design and construction safety evaluation under complex geological conditions. BRIEF DESCRIPTION OF DRAWINGS

[0018] The above and / or additional aspects and advantages of the application will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings.

[0019] Figure 1 is a schematic diagram of the boundary condition matched by the first embodiment of the application; wherein σ x is a horizontal stress boundary, and σ y is a vertical stress boundary.

[0020] Figure 2 is a schematic diagram of the boundary condition matched by the second embodiment of the application.

[0021] Figure 3 is the Burgers rheological model viscoelasticity parameter field test value and fitting curve of the second embodiment of the application.

[0022] Figure 4 is a structural schematic diagram of the third embodiment of the application.

[0023] Figure 5 is the output result of the support clearance convergence of the first embodiment of the application.

[0024] Figure 6 is the output result of the plastic zone of the surrounding rock of the first embodiment of the application.

[0025] Figure 7 is a comparison diagram of the primary support stress output results calculated by the Burgers rheological model and the Mohr-Coulomb model (referred to as M-C model) in the second embodiment of the application.

[0026] Figure 8Figure is a comparison chart of force output results of the secondary lining calculated by the Burgers rheological model and the Mohr-Coulomb model in the second embodiment of the present application.

[0027] Figure 9 Figure is a structure diagram of the terminal in the fourth embodiment of the present application; wherein: 10 is a processor; 20 is a memory; 30 is a display; 40 is a calculation program. DETAILED DESCRIPTION

[0028] In order to make the objects, features and advantages of the present application more apparent, the specific embodiments of the present application are described in detail below with reference to the drawings. The present application is shown in several embodiments in the drawings. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0029] Embodiment one and embodiment two; Please see Figures 1-3 The numerical calculation method for stress deformation of mountain tunnel support according to the embodiment of the present application comprises the following steps: Step one: according to the rock hardness, rock mass integrity, buried depth and initial ground stress field of the mountain tunnel, the surrounding rock classification and grading, buried depth grading and ground stress grading are carried out, and then the corresponding constitutive model and boundary conditions are selected; The parameters involved in the present embodiment are: stratum attribute parameters, underground water (distribution depth), tunnel buried depth H, initial ground stress field (maximum principal stress σ1, minimum principal stress σ3, etc.), tunnel cross-section design parameters and support structure design parameters; the stratum attribute parameters include uniaxial saturated compressive strength R c , rock hardness, rock mass integrity, rock mass unit weight γ, lateral pressure coefficient λ, surrounding rock elastic modulus, surrounding rock cohesion c and internal friction angle φ; the tunnel cross-section design parameters include tunnel excavation width B and tunnel excavation height; the support structure design parameters include the density, elastic modulus, Poisson's ratio and thickness of the primary support and the secondary lining; the tunnel simulation parameters involved in embodiment one and embodiment two are shown in Table 1.

[0030] .

[0031] The tunnel grading includes three aspects, which are the surrounding rock classification and grading, buried depth grading and ground stress grading. The rock type (soft rock, hard rock, cohesive soil, altered rock, fracture zone, etc.) and rock grade (grade I- VI) are determined according to the rock hardness and rock mass integrity, and the buried depth grading and ground stress grading are carried out at the same time. For reference, Table 2 is shown below. The surrounding rock grading result is used for buried depth grading.

[0032] .

[0033] The buried depth classification includes: shallow buried: H p ; deep buried: H p ≤H≤500m; ultra-deep buried: H>500m; wherein, H p is determined according to formula (1.1)-(1.3): (1.1); (1.2); (1.3); wherein: H is the buried depth of the tunnel; H p is the deep and shallow buried tunnel demarcation depth, wherein the worse the surrounding rock condition (I→VI grade), the greater the corresponding coefficient value (2→2.5); s is the surrounding rock grade, such as the V grade surrounding rock, then s=5; h q is the equivalent load height value; B is the tunnel excavation width; ω is the tunnel width influence coefficient, when B<5, i=0.2, and when B>5, i=0.1.

[0034] The ground stress classification includes: extremely high ground stress: R c / σ1<4; high ground stress: 4≤R c / σ1≤7; general ground stress: R c / σ1>7; wherein, R c is the uniaxial saturated compressive strength of the rock; σ1 is the maximum principal stress.

[0035] According to the parameters in Table 1, the classification determination results of Example One and Example Two are: In Example One, the surrounding rock type is soft rock, the surrounding rock grade is V grade; H p =21.96m, H p ≤H=225m≤500m, that is, the buried depth classification result of the tunnel is deep buried; σ1=6.87MPa, R c =1.0MPa, R c / σ1=0.146MPa<4, that is, the ground stress classification result is extremely high ground stress.

[0036] In Example Two, the surrounding rock type is clay, the surrounding rock grade is IV grade; H p =17.87m, H p ≤H=175m≤500m, that is, the buried depth classification result of the tunnel is deep buried; σ1=2.2MPa, R c= 1.0 MPa, R c / σ1=0.45 MPa < 4, i.e. the ground stress classification result is extremely high ground stress.

[0037] According to the aforementioned tunnel classification discrimination result, the constitutive model and boundary condition are selected by the following method: For shallow-buried tunnels and deep-buried hard rock tunnels, a modified elastic-plastic model and a displacement boundary condition are selected; For deep-buried soft rock tunnels, if it is extremely high or high ground stress, a strain softening model and a stress boundary condition are selected, and if it is general ground stress, a strain softening model and a displacement boundary condition are selected; For deep-buried clay tunnels, a Burgers rheological model and a displacement boundary condition are selected; For super-deep-buried and extremely high or high ground stress fracture zone tunnels, a surrounding rock damage correction model and a stress boundary condition are selected; For super-deep-buried and extremely high or high ground stress soft rock and altered rock tunnels, a Burgers rheological model and a stress boundary condition are selected.

[0038] First, the displacement boundary condition and the stress boundary condition are first explained.

[0039] The displacement boundary condition is that the ground line is a free boundary on the upper boundary of the numerical model, the horizontal displacement is constrained on the two side boundaries, and the vertical displacement and the horizontal displacement are constrained on the bottom boundary; relative to the tunnel size, the model horizontal boundary range is usually set to 6-10 times the tunnel excavation span, i.e. about 3-5 times the width on the left and right of the tunnel, and the vertical boundary is valued according to the calculated target burial depth.

[0040] The stress boundary condition is that the vertical uniform surrounding rock stress σ x is set on the upper and lower boundaries of the numerical model, and the horizontal uniform surrounding rock stress σ y is set on the left and right boundaries; relative to the tunnel size, the model horizontal and vertical boundary range is usually set to 6-10 times the tunnel excavation span, i.e. about 3-5 times the width on the top and bottom and on the left and right of the tunnel; For extremely high or high ground stress deep-buried soft rock and super-deep-buried tunnels, the stress boundary value is preferably the engineering measured ground stress value; or, if there is no engineering measured ground stress value, it is determined according to the following formulas (5.1) and (5.2): (5.1); (5.2); In the formula, σ x is the horizontal uniform surrounding rock stress; and σ yis the vertical uniformly distributed surrounding rock stress; B is the tunnel excavation width; H is the tunnel burial depth; G is the surrounding rock deformation grade, which is preliminarily determined based on the rock strength-stress ratio during the survey phase and corrected based on the measured deformation during the construction phase; λ is the lateral pressure coefficient.

[0041] The numerical model established in this paper is a planar model. Because stress boundary conditions are also set at 6-10 times the tunnel excavation span in the vertical direction of the model, the model size is significantly reduced compared to displacement boundary conditions, especially for deep and ultra-deep tunnels. Setting the model size at 6-10 times the tunnel span is a conventional technique in this field.

[0042] In Example 1, based on the tunnel classification results (very high ground stress deep buried soft rock tunnel), the strain softening model and stress boundary conditions are selected. Figure 1 The stress boundary condition is to set the vertical uniformly distributed surrounding rock stress σ at the upper and lower boundaries of the numerical model. x , the left and right boundaries are set to average the surrounding rock stress σ y , using the measured ground stress values ​​of the project, that is, based on the ground stress parameters in Table 1, σ can be obtained through three-dimensional calculation x =5.90MPa,σ y =4.85MPa.

[0043] In Example 2, based on the tunnel classification results (very high ground stress deep buried clay soil tunnel), the Burgers rheological model and displacement boundary conditions are selected. Figure 2 ,The displacement boundary conditions are specifically as follows: the upper boundary of the model takes the ground line as the free boundary, the two side boundaries constrain horizontal displacement, and the bottom boundary constrains vertical and horizontal displacement.

[0044] Next, this embodiment further elaborates on the constitutive models mentioned above. The constitutive models involved in this embodiment include a modified elastic-plastic model, a strain softening model, a Burgers rheological model, and a surrounding rock damage correction model.

[0045] First, the modified elastic-plastic model is an existing model. The specific model and its derivation can be referred to the literature (Jia Shanpo, Chen Weizhong, Yang Jianping, et al. Elastic-plastic constitutive model based on modified Mohr-Coulomb criterion and its numerical implementation [J]. Rock and Soil Mechanics, 2010, 31(07): 2051-2058. DOI: 10.16285 or j.rsm.2010.07.041.).

[0046] Second, the strain softening model is to express the strain softening of the surrounding rock strength by introducing the functional relationship between the strength parameter and the equivalent plastic strain evolution, as shown in Equations (2.1)-(2.3): (2.1); (2.2); (2.3); wherein: is the cohesion of the surrounding rock; is the internal friction angle of the surrounding rock; c0 is the initial cohesion of the surrounding rock; φ0 is the initial internal friction angle of the surrounding rock; H c , H φ is a positive constant for controlling the softening rate; is the shear plastic strain, which is obtained by increment summation in the form of the second invariant of the strain tensor; c res is the residual cohesion of the surrounding rock; φ res is the residual internal friction angle of the surrounding rock; is the critical shear plastic strain corresponding to the residual strength; is the plastic strain rate tensor; is the time.

[0047] Therefore, the residual cohesion and the residual internal friction angle of the surrounding rock in the first embodiment are 100 kPa and 25°, respectively, which are calculated based on the parameters in Table 1.

[0048] Thirdly, the surrounding rock damage correction model is determined according to formulae (3.1)-(3.3): (3.1); (3.2); (3.3); wherein: E damaged is the elastic modulus of the surrounding rock after damage correction; E0 is the initial elastic modulus of the surrounding rock; c damaged is the cohesion of the surrounding rock after damage correction; c0 is the initial cohesion of the surrounding rock; φ damaged is the internal friction angle of the surrounding rock after damage correction; φ0 is the initial internal friction angle of the surrounding rock; Δφ is an empirical attenuation coefficient; D is a damage factor; wherein, the damage factor D is determined according to formula (3.4): (3.4); wherein: k1 and k2 are the ground stress sensitivity coefficient and the broken degree sensitivity coefficient, respectively, which are calibrated by indoor triaxial test; σ1 is the maximum principal stress in the initial ground stress field; σ3 is the minimum principal stress in the initial ground stress field; RQD is the rock quality index.

[0049] Fourthly, the Burgers rheological model involves two different cases: (1) For shallow tunnel, rock samples can be directly drilled to obtain the situation, Burgers rheological model viscoelastic parameters can be obtained according to the results of field direct shear rheological test and according to formula (4.1), (4.2): (4.1); (4.2); In the formula: γ is the shear strain; is the shear stress; is the time; G1 is the viscoelastic shear modulus; G2 is the instantaneous shear modulus; η1, η2 are the viscosity coefficients; γ0 is the instantaneous shear strain; G1, η1, η2 are obtained by regression analysis of shear creep curve by least square method; (2) For deep and super deep buried tunnel, due to the limited depth of drilling sampling, it is difficult to obtain the rock sample at the depth H of the tunnel, and the Burgers rheological model parameters are sensitive to the depth, especially the parameters η1 and G2. Therefore, a plurality of rheological tests of rock samples at different depths need to be carried out, and the viscosity coefficients η1, η2 and shear modulus G1, G2 can be obtained by correction according to formula (4.3), (4.4): (4.3); (4.4); In the formula: η(H), G(H) are the corrected viscosity coefficients and shear modulus, and η(H) corresponds to the viscosity coefficients η1, η2, and G(H) corresponds to the viscoelastic shear modulus G1 and the instantaneous shear modulus G2; H ref is the reference depth; η ref , G ref are the reference parameters of the reference depth; n η , α G , α η are the undetermined parameters; n η Determined by power law fitting of rock sample step confining pressure rheological test, the value range of hard rock is usually 1.2-1.5, and the value range of soft rock is usually 0.8-1.0; α G Obtained by ultrasonic transverse wave velocity measurement of rock samples at different depths and logarithmic regression, and the typical value is 0.08±0.02; α η Obtained by regression analysis of viscosity coefficients and shear modulus data obtained by a plurality of rheological tests of rock samples at different depths.

[0050] In which, the calibration test process of the undetermined parameter n η is as follows: 1) Step confining pressure rheological test: for the same rock sample (such as altered granite), under the condition of fixed axial pressure σ, the confining pressure is gradually increased (such as 5 MPa→10 MPa→15 MPa), and each group is maintained to steady creep; record the steady creep rate ε steady, back-calculation of equivalent viscous coefficient η1= σconfining pressure / 3ε steady； 2) Data fitting: η1and confining pressure are fitted by power law (linear regression in logarithmic coordinates) to obtain coefficient n η .

[0051] wherein, the undetermined parameter α G The calibration test procedure is as follows: 1) Ultrasonic testing: measure the transverse wave velocity V s of rock samples at different burial depths (such as 50 m or 100 m or 150 m); calculate the dynamic shear modulus G2 (ρ is the density of the rock sample); 2) Data fitting: fit G2and burial depth H by logarithmic relationship to obtain coefficient n η .

[0052] wherein, the undetermined parameter α η The calibration test procedure is as follows: 1) Step loading rheological test: take the drill core (Φ50 mm x 100 mm) from the target stratum (such as altered granite), and divide it into groups corresponding to different burial depths (50 m or 100 m or 150 m); apply confining pressure using a triaxial rheological testing machine (with long-term monitoring of confining pressure and axial displacement), and then apply axial pressure in stages, maintaining each stage for 7-30 days and recording the strain-time curve; use the least squares method to invert the Burgers parameters by curve fitting (example data are shown in Table 3): ; 2) Coefficient determination: based on the obtained coefficient n η , such as taking the reference burial depth as 100 m, substituting it into the aforementioned correction formula to obtain the coefficient α η as follows: .

[0053] Use the self-developed in-situ direct shear rheological device (patent number: ZL201210374780.7) to carry out in-situ direct shear rheological test to obtain test values and fitting curves, please refer to Figure 3 .

[0054] Further regression analysis by the least squares method obtains the viscoelastic parameters of the Burgers rheological model used in Example Two (extremely high ground stress deep-buried clayey soil tunnel, modified according to formula (4.3), (4.4)) as shown in Table 4.

[0055] .

[0056] Step two: based on the constitutive model and boundary conditions obtained in step one, according to the tunnel simulation parameters, a numerical model of the stress and deformation of the mountain tunnel support is established for simulation calculation, and the stress, deformation and plastic zone distribution of the support structure are obtained.

[0057] Wherein, the tunnel simulation parameters have been mentioned in the foregoing, the numerical model is established by finite element, finite difference and other software, such as ABAQUS, FLAC 2D and the like, the process of finite element and finite difference software modeling and analysis is a conventional technical means in the art, which will not be repeated here, and finally the stress and deformation of the support structure, the plastic zone distribution of the surrounding rock and other related simulation results can also be obtained as needed. The stress can obtain the safety factor of the support structure; the plastic zone can give the pre-supporting or reinforcement optimization measures; according to the stress and deformation of the support structure, the safety and stability of the support structure can be evaluated, and then if the support structure exceeds the specified threshold, the support structure can be optimized according to the simulation results until the support structure meets the design requirements, and the optimization suggestions of the support structure are provided.

[0058] Example three; Please refer to Figure 4 The present application also correspondingly provides a mountain tunnel support stress and deformation numerical calculation system for a mountain tunnel support stress and deformation numerical calculation method, the mountain tunnel support stress and deformation numerical calculation system comprises: Simulation parameter input module: for inputting tunnel simulation parameters, including stratum attribute parameters, burial depth, underground water, initial ground stress field, tunnel section design parameters, support structure design parameters; Tunnel grading discrimination module: for classifying and grading the surrounding rock and grading the tunnel burial depth and ground stress; Simulation calculation module: for matching corresponding constitutive model and boundary conditions for the mountain tunnel support stress and deformation numerical model according to the tunnel grading discrimination results, and performing simulation calculation according to the input simulation parameters; Output warning module: for outputting the stress and deformation of the mountain tunnel support structure and the plastic zone of the surrounding rock, and for triggering the support structure failure warning when the support structure displacement exceeds the threshold.

[0059] The threshold of the support structure displacement is determined according to the specification "Railway Tunnel Monitoring Measurement Technical Specification" Q / CR 9218-2024, as shown in Tables 5 and 6.

[0060] The simulation calculation module also includes the establishment process of the simulation model, but the establishment of the simulation model needs to be completed manually by the user according to the tunnel grading discrimination results and the tunnel simulation parameters, and the simulation can be performed after the modeling is completed. The tunnel grading discrimination module can be realized by MATLAB or PYTHON.

[0061] .

[0062] .

[0063] Please refer to Figure 5 , Figure 5 The maximum displacement of the support obtained by calculation is 0.474 m, which is located at the lower right part of the tunnel, and the relative clearance convergence reaches 3.61%, which has obviously exceeded the early warning threshold (Class V surrounding rock, deep burial, and the threshold of horizontal relative clearance convergence at the arch foot is 2.00%). Further combined with the output results of the plastic zone of the surrounding rock (please refer to Figure 6 ), two remediation schemes of adding anchor cables and deepening the inverted arch are proposed in Example One. The latter is selected in the construction site, the structure stress is optimized, the structure bearing capacity is improved, and the maximum stress of the secondary lining concrete is much smaller than the ultimate bending tensile strength, which ensures the safety of the support structure.

[0064] Please refer to Figure 7 and Figure 8 , Figure 7 and Figure 8 The stress results of the tunnel support (primary support and secondary lining) of Example Two are shown, and in order to highlight the advantages of the Burgers rheological model used in Example Two, the results are compared with those calculated by using the Mohr-Coulomb model (M-C model). It needs to be explained that in Example Two, the sprayed concrete of the arch ring and the side wall cracked locally or even peeled off in large areas at the initial stage of the construction of the site tunnel. Therefore, the comparison shows that if the rheological properties of the surrounding rock are ignored in deep buried clay strata, the structure stress and deformation calculation may be unsafe, and there is a design risk. That is, the Burgers rheological model used in Example Two and the model parameters obtained can better reflect the rheological properties of the strata and can be used for long-term safety evaluation of the tunnel support structure. Based on the output results, the support optimization scheme of appropriately increasing the support stiffness and increasing the reserved deformation is proposed in Example Two.

[0065] Example Four; Please refer to Figure 9 , based on the above-mentioned numerical calculation method and system for the stress and deformation of the mountain tunnel support, the application also correspondingly provides a terminal, which includes a processor 10, a memory 20 and a display 30. Figure 9 Only part of the components of the terminal are shown, but it should be understood that it is not required to implement all the shown components, and more or fewer components can be alternatively implemented.

[0066] The memory 20 can be an internal storage unit of the terminal in some embodiments, such as a hard disk or a memory of the terminal. The memory 20 can also be an external storage device of the terminal in other embodiments, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. equipped on the terminal. Further, the memory 20 can include both the internal storage unit and the external storage device of the terminal. The memory 20 is used to store application software and various data installed on the terminal, such as program codes installed on the terminal. The memory 20 can also be used to temporarily store data that has been output or will be output. In an embodiment, the memory 20 stores a calculation program 40 of a stress and deformation numerical calculation method of a mountain tunnel support, which can be executed by the processor 10 to implement the stress and deformation numerical calculation method of the mountain tunnel support.

[0067] The processor 10 can be a Central Processing Unit (CPU), a microprocessor or other data processing chip in some embodiments, which is used to run program codes or process data stored in the memory 20, such as to implement the stress and deformation numerical calculation method of the mountain tunnel support.

[0068] The display 30 can be an LED display, a liquid crystal display, a touch liquid crystal display, an Organic Light-Emitting Diode (OLED) touch, etc. in some embodiments. The display 30 is used to display information on the terminal and to display a visualized user interface, which has a display window of stress and deformation of the support structure, a display window (range, deformation, etc.) of the plastic zone of the confining pressure, and a window of early warning, and can at least display the stress and deformation of the characteristic positions such as the arch foot and the arch top of the tunnel, and preferably can display the stress and deformation of any position of the tunnel contour in the form of Figures 7-8 , and can mark the values. If the deformation exceeds the threshold, early warning is performed, such as flashing of the display window or text prompt, or even external buzzer and flashing light for early warning.

[0069] In an embodiment, when the processor 10 executes the calculation program 40 of the stress and deformation numerical calculation method of the mountain tunnel support in the memory 20, the steps of the above stress and deformation numerical calculation method of the mountain tunnel support are implemented.

[0070] In summary, the mountain tunnel support stress deformation numerical calculation method, system and terminal provided by the present application, based on the hardness of rock, the integrity of rock mass, the buried depth, the initial ground stress field, carries out the grading discrimination of mountain tunnel surrounding rock, buried depth and low stress, through the interaction effect of coupling stratum attribute, tunnel buried depth and ground stress state, adaptively selects the corresponding constitutive model and boundary condition, and makes creative improvement to part of the constitutive model and boundary condition, so that part of the constitutive model can more accurately describe the dilatancy effect, strain softening, structure degradation and creep behavior, and simulate the progressive failure and surrounding rock deformation instability process induced by high ground stress, realize accurate mechanical analysis of supporting structure, and the constitutive model and boundary condition selected according to the tunnel grading are used for the establishment of numerical simulation model, which can effectively solve the calculation or prediction deviation problem of mountain tunnel support stress deformation caused by the fact that the traditional numerical model does not consider the coupling of multiple geological factors, realize the differentiated calculation requirement from shallow burial to super deep burial in the same framework, effectively improve the accuracy of mountain tunnel support structure stress simulation calculation, and is beneficial to the evaluation of support structure safety and stability and the optimization design of support structure, and is suitable for the optimization design and construction safety evaluation of tunnel under complex geological conditions.

[0071] It should be noted that in the present application, the term "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or terminal including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or terminal. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of another identical element in the process, method, article or terminal including the element.

[0072] The above-described embodiments only express several embodiments of the present application, which are described in detail and specifically, but should not be understood as limiting the scope of the present application. It should be noted that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, which are all within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A numerical calculation method for stress and deformation of mountain tunnel support, characterized by: The following steps are involved: Step 1: Based on the rock hardness, rock mass integrity, burial depth, and initial geostress field of the mountain tunnel, perform surrounding rock classification and grading, as well as burial depth classification and geostress classification, and then select the corresponding constitutive model and boundary conditions; Step 2: Based on the constitutive model and boundary conditions obtained in Step 1 and the tunnel simulation parameters, a numerical model of the stress and deformation of the mountain tunnel support is established for simulation calculation to obtain the stress, deformation, and plastic zone distribution of the surrounding rock. The constitutive model and boundary conditions are selected as follows: For shallow tunnels and deep hard rock tunnels, the modified elastoplastic model and displacement boundary conditions are used; For deep soft rock tunnels, if the ground stress is extremely high or high, the strain softening model and stress boundary conditions are selected; if the ground stress is normal, the strain softening model and displacement boundary conditions are selected; For deep cohesive soil tunnels, the Burgers rheological model and displacement boundary conditions are used; For ultra-deep tunnels in fractured zones with extremely high or high ground stress, the surrounding rock damage correction model and stress boundary conditions are used; For ultra-deep soft rock and altered rock tunnels with extremely high or high ground stress, the Burgers rheological model and stress boundary conditions are selected.

2. The numerical calculation method for stress and deformation of mountain tunnel support according to claim 1 is characterized in that: The burial depth classification includes: Shallow burial: H<H p ; Deep burial: H p ≤H≤500m; Ultra-deep burial: H>500m; Among them, H p Determine according to formula (1.1)-(1.3): （1.1）； （1.2）； （1.3）； Where: H is the tunnel depth; H p The boundary depth between deep and shallow tunnels; h q is the equivalent load height; s is the surrounding rock grade; B is the tunnel excavation width; ω is the tunnel width influence coefficient; i is a parameter related to the surrounding rock grade.

3. The numerical calculation method for stress and deformation of mountain tunnel support according to claim 1 is characterized in that: The in-situ stress classification includes: Extremely high ground stress: R c / σ1<4; High ground stress: 4≤R c / σ1≤7; General ground stress: R c / σ1>7; Among them, R c is the uniaxial saturated compressive strength of rock; σ1 is the maximum principal stress.

4. The numerical calculation method for stress and deformation of mountain tunnel support according to claim 1 is characterized in that: The tunnel simulation parameters include: stratum attribute parameters, groundwater, tunnel depth, initial ground stress field, tunnel section design parameters, and support structure design parameters; Among them, the formation attribute parameters include uniaxial saturated compressive strength, rock density, lateral pressure coefficient, surrounding rock elastic modulus, surrounding rock cohesion and internal friction angle.

5. The numerical calculation method for stress and deformation of mountain tunnel support according to claim 1 is characterized in that: The strain softening model is determined according to formulas (2.1)-(2.3): （2.1）； （2.2）； （2.3）； Where: is the cohesion of the surrounding rock; is the internal friction angle of the surrounding rock; c0 is the initial cohesion of the surrounding rock; φ0 is the initial internal friction angle of the surrounding rock; H c 、H φ is a positive constant that controls the softening rate; is the shear plastic strain; c res is the residual cohesion of surrounding rock; res is the residual internal friction angle of the surrounding rock; To achieve the critical shear plastic strain corresponding to the residual strength; is the plastic strain rate tensor; t is time.

6. The numerical calculation method for stress and deformation of mountain tunnel support according to claim 1 is characterized in that: The surrounding rock damage correction model is determined according to formulas (3.1)-(3.3): （3.1）； （3.2）； （3.3）； Where, E damaged is the elastic modulus after correction of surrounding rock damage; c damaged is the cohesion after correction of surrounding rock damage; φ damaged is the internal friction angle after surrounding rock damage correction; E0 is the initial elastic modulus of surrounding rock; c0 is the initial cohesion of surrounding rock; φ0 is the initial internal friction angle of surrounding rock; Δφ is the empirical attenuation coefficient; D is the damage factor; Among them, the damage factor D is determined according to formula (3.4): （3.4）； Where: k1 and k2 are the sensitivity coefficients of geostress and fragmentation, respectively, which are calibrated through indoor triaxial tests; σ1 is the maximum principal stress in the initial geostress field; σ3 is the minimum principal stress in the initial geostress field; and RQD is the rock quality index.

7. The numerical calculation method for stress and deformation of mountain tunnel support according to claim 1 is characterized in that: For shallow tunnels, the viscoelastic parameters of the Burgers rheological model are obtained based on the results of on-site direct shear rheological tests and according to equations (4.1) and (4.2): （4.1）； （4.2）； Where γ is the shear strain; is the shear stress; is time; G1 is the viscoelastic shear modulus; G2 is the instantaneous shear modulus; η1 and η2 are viscosity coefficients; γ0 is the instantaneous shear strain; For deep and ultra-deep tunnels, η1, η2, G1, and G2 are uniformly modified according to equations (4.3) and (4.4) to obtain: （4.3）； （4.4）； Where η(H) and G(H) are the corrected viscosity coefficient and shear modulus, η(H) corresponds to η1 and η2, and G(H) corresponds to G1 and G2; H is the tunnel depth; H ref is the reference burial depth; η ref , G ref is the reference parameter of the burial depth; n η , α G , α η To be determined parameters.

8. The numerical calculation method for stress and deformation of mountain tunnel support according to claim 1 is characterized in that: The displacement boundary conditions are as follows: the ground line is used as a free boundary at the upper boundary of the numerical model, the boundaries on both sides constrain horizontal displacement, and the bottom boundary constrains vertical and horizontal displacements; The stress boundary condition is: setting the horizontal average surrounding rock stress σ at the upper and lower boundaries of the numerical model x , vertical uniformly distributed surrounding rock stress σ is set on the left and right boundaries y ; For tunnels buried in soft rock or ultra-deep tunnels with extremely high or high in-situ stress, the stress boundary value shall be the measured in-situ stress value; or, if the measured in-situ stress value is unavailable, it shall be determined according to formulas (5.1) and (5.2): （5.1）； （5.2）； Where, σ x is the horizontal average stress of surrounding rock; y is the vertical uniformly distributed surrounding rock stress; B is the tunnel excavation width; H is the tunnel burial depth; G is the surrounding rock deformation grade; λ is the lateral pressure coefficient.

9. A numerical calculation system for the stress and deformation of mountain tunnel support, used to implement the numerical calculation method for the stress and deformation of mountain tunnel support according to any one of claims 1 to 8, characterized in that: include: Simulation parameter input module: used to input tunnel simulation parameters; Tunnel classification and identification module: used to classify and grade surrounding rock, as well as to classify tunnel burial depth and ground stress; Simulation calculation module: used to match the corresponding constitutive model and boundary conditions for the mountain tunnel support stress and deformation numerical model based on the tunnel classification results, and perform simulation calculations based on the input simulation parameters; Output warning module: used to output the deformation of the mountain tunnel support structure and trigger the support structure damage warning when the support structure displacement exceeds the threshold.

10. A terminal, characterized in that: The terminal includes a processor and a memory storing a program executable by the processor. When the processor executes the program stored in the memory, the numerical calculation method for stress and deformation of mountain tunnel support according to any one of claims 1 to 8 is implemented.

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