A numerical calculation method and system for stress deformation of mountain tunnel support and a terminal

Abstract

The application discloses a mountain tunnel support stress deformation numerical calculation method, system and terminal, and the method comprises the following steps: according to the rock hardness degree, rock mass integrity, buried depth and initial ground stress field of the mountain tunnel, surrounding rock classification and grading, buried depth grading and ground stress grading are carried out, then corresponding constitutive model and boundary conditions are selected according to the grading results; based on the constitutive model and the boundary conditions, according to the tunnel simulation parameters, a mountain tunnel support stress deformation numerical model is established for simulation calculation, and the stress and deformation of the support structure are obtained. The application is based on tunnel grading discrimination, adaptively matches the constitutive model and the boundary conditions, is used for the establishment of the numerical model, can effectively improve the accuracy of the stress simulation calculation of the support structure, realizes the differentiated calculation requirements of the same framework from shallow burying to super deep burying, is favorable for evaluating the safety and stability of the support structure, and is suitable for the optimization design and construction safety evaluation of the tunnel support structure under complex geological conditions.

Description

Technical Field

[0001] This invention relates to the field of mountain tunnel support design technology, specifically to a method, system, and terminal for numerical calculation of stress and deformation in mountain tunnel support. Background Technology

[0002] Numerical simulation, as an important tool for studying the stress-deformation characteristics of tunnel support, can simulate various complex working conditions, deformation and failure processes of surrounding rock, stress evolution, and post-failure properties. However, traditional numerical models have certain shortcomings in simulating the stress-deformation mechanisms of tunnels under coupled conditions such as different burial depths, in-situ stresses, and complex strata, and their adaptability and efficiency need further improvement. On the one hand, for tunnel engineering in complex geological environments such as deeply buried soft rock, ultra-deep buried (high in-situ stress) fractured zones, and altered hard rock, commonly used elastoplastic constitutive models (such as Mohr-Coulomb, Drucker-Prager, Hoek-Brown, etc.) have significant shortcomings, such as difficulty in accurately describing dilatational effects, strain softening, large deformation, structural deterioration, and creep behavior. They also have difficulty accurately simulating the progressive failure and surrounding rock deformation instability process induced by high in-situ stress, which limits their applicability under complex geological conditions. Therefore, it is necessary to introduce constitutive models with dilatational, strain softening, damage evolution, and rheological characteristics to improve simulation accuracy. On the other hand, the mechanical calculation models for tunnel support structures mainly include the stratum-structure model and the load-structure model. The former treats the surrounding rock and support structure as a whole, directly considering the bearing capacity of the surrounding rock, and is the model that is currently being sought after and is under development in the design and calculation of tunnel structural systems. In the numerical simulation process, the tunnel support structure and the surrounding rock mass interact, and the loads acting on the rock mass are mainly self-weight stress and tectonic stress. Therefore, the determination of the ground stress is the key to the suitability of the stratum-structure model. For shallow and deep buried soft rock tunnels, the load is usually determined according to the self-weight stress field, with the upper boundary being the ground line as the free boundary, and other boundaries usually subject to displacement constraints. When the burial depth is large, due to the soil arching effect and the existence of tectonic stress, the results calculated according to the self-weight stress often cannot reflect the actual engineering situation. Especially for high ground stress deep buried soft rock and ultra-deep buried tunnels (burial depth > 500m), if the entire stratum is simulated in the numerical modeling process, the calculation volume is large and the calculation cost is extremely high. Therefore, force boundary conditions can be used for simulation, that is, uniformly distributed surrounding rock stress (pressure) is set around the model, so how to calculate this stress value is crucial. For calculating the surrounding rock pressure in deeply buried tunnels, the commonly used railway (highway) tunnel design specifications are based on empirical formulas or Terzaghi formulas derived from extensive statistical analysis of the loosened surrounding rock pressure in deeply buried tunnels. However, the former calculates the surrounding rock pressure under deep burial conditions as independent of burial depth, while the latter calculates the surrounding rock pressure as the burial depth increases, tending to a constant value. Extensive field measurement data shows that the actual surrounding rock pressure in deeply or ultra-deeply buried tunnels is still affected by burial depth. Therefore, the standard methods lack rationality and accuracy, and it is urgent to consider incorporating factors such as burial depth and the rock mass strength-strain ratio to correct the surrounding rock pressure calculation, thereby applying stress boundary conditions that better fit engineering realities to improve the efficiency and accuracy of numerical calculations.

[0003] Therefore, this invention proposes a numerical calculation method, system and terminal for the stress and deformation of mountain tunnel support considering multiple geological factors, coupling the interaction effects of stratum properties, tunnel burial depth and ground stress state, and constructing a system to realize the same framework to meet the differentiated calculation needs from shallow burial to ultra-deep burial, for tunnel optimization design and construction safety assessment under complex geological conditions. Summary of the Invention

[0004] The purpose of this invention is to propose a numerical calculation method, system, and terminal for the stress and deformation of mountain tunnel support considering multiple geological factors. This solves the problem of calculation or prediction deviation of stress and deformation of mountain tunnel support caused by the failure of traditional numerical models to consider the coupling of multiple geological factors. It is used to evaluate the safety and stability of support structures and guide the optimal design of support structures.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] Firstly, this invention proposes a numerical calculation method for the stress and deformation of support in mountain tunnels, specifically including the following steps:

[0007] Step 1: Based on the rock hardness, rock mass integrity, burial depth, and initial geostress field of the mountain tunnel, classify and grade the surrounding rock, as well as the burial depth and geostress levels, and then select the corresponding constitutive model and boundary conditions.

[0008] Step 2: Based on the constitutive model and boundary conditions obtained in Step 1, and according to the tunnel simulation parameters, establish a numerical model of the stress and deformation of the mountain tunnel support for simulation calculation, and obtain the stress, deformation and distribution of the plastic zone of the surrounding rock of the support structure.

[0009] The constitutive model and boundary conditions are selected according to the following method:

[0010] For shallow-buried tunnels and deep-buried hard rock tunnels, a modified elastoplastic model and displacement boundary conditions are selected.

[0011] For deep-buried 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 ordinary, the strain softening model and displacement boundary conditions are selected.

[0012] For deep-buried cohesive soil tunnels, the Burgers rheological model and displacement boundary conditions are selected.

[0013] For ultra-deep buried tunnels with extremely high or high ground stress in fractured zones, a surrounding rock damage correction model and stress boundary conditions are selected.

[0014] For ultra-deep buried soft rock and altered rock tunnels with extremely high or high ground stress, the Burgers rheological model and stress boundary conditions are selected.

[0015] Furthermore, the burial depth classification includes:

[0016] Shallow burial: H < H p ;

[0017] Deep burial: H p ≤H≤500m;

[0018] Ultra-deep burial: H > 500m;

[0019] Among them, H p Determine according to formulas (1.1)-(1.3):

[0020] (1.1);

[0021] (1.2);

[0022] (1.3);

[0023] In the formula: H is the tunnel burial depth; H p h is the dividing depth between deep and shallow tunnels. q The equivalent load height is the coefficient value that corresponds to the worse the surrounding rock conditions (I→VI). s is the surrounding rock level, such as s=5 for Class V surrounding rock. B is the tunnel excavation width. ω is the tunnel width influence coefficient. i is a parameter related to the surrounding rock level. When B<5, i=0.2, and when B>5, i=0.1.

[0024] Furthermore, the geostress classification includes:

[0025] Extremely high ground stress: R c / σ1<4;

[0026] High ground stress: 4≤R c / σ1≤7;

[0027] Typical geostress: R c / σ1>7;

[0028] Among them, R c σ1 represents the uniaxial saturated compressive strength of the rock; σ1 represents the maximum principal stress.

[0029] Furthermore, the tunnel simulation parameters include: geological property parameters, groundwater, tunnel burial depth, initial geostress field, tunnel cross-section design parameters, and support structure design parameters;

[0030] Among them, the formation property parameters include uniaxial saturated compressive strength R c Rock mass unit weight, lateral pressure coefficient λ, surrounding rock elastic modulus, surrounding rock cohesion c, and internal friction angle φ.

[0031] Furthermore, the strain softening model is determined according to equations (2.1)-(2.3):

[0032] (2.1);

[0033] (2.2);

[0034] (2.3);

[0035] In the formula: The cohesion of the surrounding rock; φ0 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 A positive constant to control the softening rate; For shear plastic strain, the second invariant form of the strain tensor is used, and it can be obtained by incremental summation; c res Residual cohesion of the surrounding rock; φ res The residual internal friction angle of the surrounding rock; To achieve the critical shear plastic strain corresponding to the residual strength; t is the plastic strain rate tensor; t is time.

[0036] Furthermore, the surrounding rock damage correction model is determined according to equations (3.1)-(3.3):

[0037] (3.1);

[0038] (3.2);

[0039] (3.3);

[0040] In the formula: E damaged E0 is the elastic modulus after damage correction for the surrounding rock; E0 is the initial elastic modulus of the surrounding rock; c damaged c0 is the cohesion after damage correction of the surrounding rock; c0 is the initial cohesion of the surrounding rock; φ damaged φ is the internal friction angle after damage correction for the surrounding rock; φ0 is the initial internal friction angle of the surrounding rock; Δφ is the empirical attenuation coefficient; D is the damage factor;

[0041] The damage factor D is determined according to equation (3.4):

[0042] (3.4);

[0043] In the formula: k1 and k2 are the geostress sensitivity coefficient and the fragmentation sensitivity coefficient, respectively, which are calibrated by 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; RQD is the rock quality index.

[0044] Furthermore, for shallow-buried tunnels, rock samples can be obtained directly by drilling. The viscoelastic parameters of the Burgers rheological model can be obtained from the results of on-site direct shear rheological tests according to equations (4.1) and (4.2):

[0045] (4.1);

[0046] (4.2);

[0047] In the formula: γ is the shear strain; Shear stress; G1 is the time; G2 is the viscoelastic shear modulus; G1 and η2 are the viscosity coefficients; γ0 is the instantaneous shear strain; G1, η1, and η2 are obtained by regression analysis of the shear creep curve using the least squares method;

[0048] For deep and ultra-deep buried tunnels, due to the limited drilling depth, it is difficult to obtain rock samples at the desired tunnel burial depth H. Furthermore, the parameters of the Burgers rheological model are sensitive to burial depth, especially parameters η1 and G2. Therefore, multiple rheological tests on rock samples at different burial depths are required. The viscosity coefficients η1 and η2, and the shear moduli G1 and G2 can be uniformly corrected according to equations (4.3) and (4.4).

[0049] (4.3);

[0050] (4.4);

[0051] In the formula: η(H) and G(H) are the corrected viscosity coefficient and shear modulus, respectively, 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 For reference burial depth; η ref G ref Reference parameters for burial depth; n η α G α η n is a parameter to be determined. η Power-law fitting of rheological tests under stepped confining pressure on rock samples determined that the values ​​for α are typically 1.2–1.5 for hard rocks and 0.8–1.0 for soft rocks; G The values ​​were obtained through ultrasonic shear wave velocity measurements and logarithmic regression of rock samples at different burial depths, with a typical value of 0.08 ± 0.02; α ηThe viscosity coefficient and shear modulus data were obtained by regression analysis from multiple sets of rock sample tests at different burial depths.

[0052] Furthermore, the displacement boundary conditions are as follows: the upper boundary of the two-dimensional plane numerical model is the ground line as the free boundary, the two side boundaries constrain the horizontal displacement, and the bottom boundary constrains the 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.

[0053] Furthermore, the stress boundary condition is as follows: a vertically uniformly distributed surrounding rock stress σ is set at the upper and lower boundaries of the numerical model. x The horizontally distributed surrounding rock stress σ is set at the left and right boundaries. y The horizontal and vertical boundary ranges of the model are typically set to 6-10 times the tunnel excavation span, relative to the tunnel dimensions.

[0054] For the aforementioned deep-buried soft rock and ultra-deep-buried tunnels with extremely high or high ground stress, the stress boundary value shall be the measured ground stress value from engineering projects; or, if there is no measured ground stress value from engineering projects, it shall be determined according to formulas (5.1) and (5.2):

[0055] (5.1);

[0056] (5.2);

[0057] In the formula: σ x The surrounding rock stress is evenly distributed horizontally; σ y B represents the vertically distributed surrounding rock stress; H represents the tunnel excavation width; G represents the tunnel burial depth; G represents the surrounding rock deformation level, which is initially determined based on the rock mass strength-stress ratio during the exploration stage and corrected based on the measured deformation during the construction stage; λ represents the lateral pressure coefficient.

[0058] Secondly, the present invention also provides a numerical calculation system for the stress and deformation of mountain tunnel support, used to implement the above-mentioned numerical calculation method for the stress and deformation of mountain tunnel support considering multiple geological factors, the system comprising:

[0059] Simulation parameter input module: used to input tunnel simulation parameters, including stratum property parameters, burial depth, groundwater, initial ground stress field, tunnel cross-section design parameters, and support structure design parameters;

[0060] Tunnel classification and discrimination module: used to classify and grade surrounding rock as well as tunnel burial depth and ground stress;

[0061] Simulation calculation module: Based on the tunnel classification results, it matches the corresponding constitutive model and boundary conditions for the numerical model of stress and deformation of mountain tunnel support, and performs simulation calculations based on the input simulation parameters;

[0062] Output early warning module: used to output the stress, deformation and distribution of the plastic zone of the surrounding rock of the support structure of the mountain tunnel, and to trigger an early warning of support structure failure when the displacement of the support structure exceeds the threshold.

[0063] Furthermore, the threshold for the displacement of the support structure is determined according to the standard "Technical Specification for Monitoring and Measurement of Railway Tunnels" Q / CR9218-2024.

[0064] Thirdly, the present invention also provides a terminal, the terminal including a processor and a memory for storing processor-executable programs, wherein when the processor executes the program stored in the memory, it implements the numerical calculation method for stress deformation of mountain tunnel support.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] 1) This invention classifies and distinguishes the surrounding rock, burial depth, and geostress of mountain tunnels based on rock hardness, rock mass integrity, burial depth, and initial geostress field. It couples the interaction effects of stratum properties, tunnel burial depth, and geostress state, and adaptively matches the corresponding constitutive model and boundary conditions for the establishment of numerical simulation models. This can effectively improve the accuracy of stress simulation calculation of mountain tunnel support structures, and is beneficial for evaluating the safety and stability of support structures and guiding the optimization design of support structures.

[0067] 2) Compared with traditional elastoplastic constitutive models (such as the Mohr-Coulomb model), the strain softening model, Burgers rheological model, and surrounding rock damage correction model can more accurately describe the dilatation effect, strain softening, structural deterioration and creep behavior, as well as simulate the progressive failure and surrounding rock deformation instability process induced by high ground stress.

[0068] 3) The stress boundary conditions adopted in this invention take into account the influence of factors such as burial depth and rock mass strength-ground stress ratio, which are more in line with engineering practice and are especially suitable for deep buried soft rock and ultra-deep buried tunnels with high ground stress.

[0069] 4) This invention can achieve accurate mechanical analysis of support structures, effectively solve the problem of deviation in the calculation or prediction of stress and deformation of mountain tunnel support caused by the failure of traditional numerical models to consider the coupling of multiple geological factors, and realize the same frame to meet the differentiated calculation needs from shallow burial to ultra-deep burial. It is suitable for tunnel optimization design and construction safety assessment under complex geological conditions. Attached Figure Description

[0070] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings.

[0071] Figure 1This is a schematic diagram of the boundary conditions for matching in Embodiment 1 of the present invention; wherein, σ x For horizontal stress boundary, σ y This represents the vertical stress boundary.

[0072] Figure 2 This is a schematic diagram of the boundary conditions matched in Embodiment 2 of the present invention.

[0073] Figure 3 These are the field test values ​​and fitting curves of the viscoelastic parameters of the Burgers rheological model in Embodiment 2 of the present invention.

[0074] Figure 4 This is a schematic diagram of the structure of Embodiment 3 of the present invention.

[0075] Figure 5 This is the output result of the support clearance convergence in Embodiment 1 of the present invention.

[0076] Figure 6 This is the output result of the plastic zone of the surrounding rock in Embodiment 1 of the present invention.

[0077] Figure 7 This is a comparison chart of the initial support force output results calculated using the Burgers rheological model and the Mohr-Coulomb model (MC model for short) in Embodiment 2 of the present invention.

[0078] Figure 8 This is a comparison chart of the stress output results of the secondary lining calculated using the Burgers rheological model and the Mohr-Coulomb model in Embodiment 2 of the present invention.

[0079] Figure 9 This is a structural diagram of the terminal in Embodiment 4 of the present invention; wherein: 10-processor; 20-memory; 30-display; 40-computing program. Detailed Implementation

[0080] To make the objectives, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Several embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be thorough and complete.

[0081] Example 1 and Example 2;

[0082] Please see Figure 1-3 The numerical calculation method for stress and deformation of mountain tunnel support according to an embodiment of the present invention includes the following steps:

[0083] Step 1: Based on the rock hardness, rock mass integrity, burial depth, and initial geostress field of the mountain tunnel, classify and grade the surrounding rock, burial depth, and geostress, and then select the corresponding constitutive model and boundary conditions.

[0084] The parameters involved in this embodiment are: geological properties, groundwater (distribution depth), tunnel depth H, initial in-situ stress field (maximum principal stress σ1, minimum principal stress σ3, etc.), tunnel cross-section design parameters, and support structure design parameters; geological properties include uniaxial saturated compressive strength R. c The parameters for the simulation of tunnels in Examples 1 and 2 are as follows: 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; tunnel cross-section design parameters include tunnel excavation width B and tunnel excavation height; support structure design parameters include density, elastic modulus, Poisson's ratio, and thickness of the primary support and secondary lining; and tunnel simulation parameters involved in Examples 1 and 2 are shown in Table 1.

[0085] .

[0086] Tunnel classification includes three aspects: surrounding rock classification and grading, burial depth grading, and in-situ stress grading. The surrounding rock type (soft rock, hard rock, cohesive soil, altered rock, fractured zone, etc.) and surrounding rock grade (Grade I-VI) are determined based on the rock hardness and rock mass integrity. Burial depth grading and in-situ stress grading are also performed simultaneously. See Table 2 below for details. The surrounding rock grading results are used for burial depth grading.

[0087] .

[0088] The burial depth classification includes:

[0089] Shallow burial: H < H p ;

[0090] Deep burial: H p ≤H≤500m;

[0091] Ultra-deep burial: H > 500m;

[0092] Among them, H p Determine according to formulas (1.1)-(1.3):

[0093] (1.1);

[0094] (1.2);

[0095] (1.3);

[0096] In the formula: H is the tunnel burial depth; H pThe depth is the dividing line between deep and shallow tunnels. The worse the surrounding rock conditions (Level I → VI), the larger the corresponding coefficient (2 → 2.5); s represents the surrounding rock level, such as s = 5 for Level V surrounding rock; h q ω is the equivalent load height value; B is the tunnel excavation width; ω is the tunnel width influence coefficient, i=0.2 when B<5, and i=0.1 when B>5.

[0097] The geostress classification includes:

[0098] Extremely high ground stress: R c / σ1<4;

[0099] High ground stress: 4≤R c / σ1≤7;

[0100] Typical geostress: R c / σ1>7;

[0101] Among them, R c σ1 represents the uniaxial saturated compressive strength of the rock; σ1 represents the maximum principal stress.

[0102] Based on the parameters in Table 1, the classification results for Example 1 and Example 2 are as follows:

[0103] In Example 1, the surrounding rock type is soft rock, and the surrounding rock grade is V; H p =21.96m, H p ≤H=225m≤500m, meaning the tunnel depth classification result is deep burial; σ1=6.87MPa, R c =1.0MPa, calculate R c / σ1=0.146MPa<4, meaning the geostress classification result is extremely high geostress.

[0104] In Example 2, the surrounding rock type is cohesive soil, and the surrounding rock grade is IV; H p =17.87m, H p ≤H=175m≤500m, meaning the tunnel depth classification result is deep burial; σ1=2.2MPa, R c =1.0MPa, calculate R c / σ1=0.45MPa<4, meaning the geostress classification result is extremely high geostress.

[0105] Based on the aforementioned tunnel classification results, the constitutive model and boundary conditions are selected using the following method:

[0106] For shallow-buried tunnels and deep-buried hard rock tunnels, a modified elastoplastic model and displacement boundary conditions are selected.

[0107] For deep-buried 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 ordinary, the strain softening model and displacement boundary conditions are selected.

[0108] For deeply buried cohesive soil tunnels, the Burgers rheological model and displacement boundary conditions are selected.

[0109] For ultra-deep buried tunnels with extremely high or high ground stress in fractured zones, a surrounding rock damage correction model and stress boundary conditions are selected.

[0110] For ultra-deep buried soft rock and altered rock tunnels with extremely high or high ground stress, the Burgers rheological model and stress boundary conditions are selected.

[0111] First, this embodiment provides a supplementary explanation of the displacement boundary conditions and stress boundary conditions.

[0112] The displacement boundary conditions are as follows: the upper boundary of the numerical model is the ground line as the free boundary, the two side boundaries constrain the horizontal displacement, and the bottom boundary constrains the vertical displacement and horizontal displacement. Relative to the tunnel size, the horizontal boundary range of the model is usually set to 6-10 times the tunnel excavation span, that is, about 3-5 times the width on the left and right sides of the tunnel. The vertical boundary is taken according to the calculated target burial depth.

[0113] The stress boundary condition is as follows: a vertically distributed surrounding rock stress σ is set at the upper and lower boundaries of the numerical model. x The horizontally distributed surrounding rock stress σ is set at the left and right boundaries. y Relative to the tunnel size, the horizontal and vertical boundary ranges of the model are usually set to 6-10 times the tunnel excavation span, that is, the tunnel width is set to approximately 3-5 times both vertically and horizontally.

[0114] For deep-buried soft rock and ultra-deep-buried tunnels with extremely high or high ground stress, the stress boundary value shall be preferably adopted based on the measured ground stress value; or, if there is no measured ground stress value, it shall be determined according to the following formulas (5.1) and (5.2):

[0115] (5.1);

[0116] (5.2);

[0117] In the formula, σ x The surrounding rock stress is evenly distributed horizontally; σ y B represents the vertically distributed surrounding rock stress; H represents the tunnel excavation width; G represents the tunnel burial depth; G represents the surrounding rock deformation level, which is initially determined based on the rock mass strength-stress ratio during the exploration stage and corrected based on the measured deformation during the construction stage; λ represents the lateral pressure coefficient.

[0118] The numerical model established in this invention is a planar model. Because the 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 buried tunnels. Setting the model size at 6-10 times the tunnel size is a conventional technique in this field.

[0119] In Example 1, based on the tunnel classification results (ultra-high ground stress deep-buried soft rock tunnel), a strain softening model and stress boundary conditions were selected. Please refer to... Figure 1 Specifically, the stress boundary condition involves setting a vertically distributed surrounding rock stress σ at the upper and lower boundaries of the numerical model. x The horizontally distributed surrounding rock stress σ is set at the left and right boundaries. y Using the measured geostress values ​​from engineering projects, i.e., based on the geostress parameters in Table 1, σ can be obtained through three-dimensional calculation. x =5.90MPa, σ y =4.85MPa.

[0120] In Example 2, based on the tunnel classification results (deeply buried cohesive soil tunnel with extremely high ground stress), the Burgers rheological model and displacement boundary conditions were selected. Please refer to... Figure 2 The specific displacement boundary conditions are as follows: the upper boundary of the model is the ground line as the free boundary, the two side boundaries constrain the horizontal displacement, and the bottom boundary constrains the vertical and horizontal displacements.

[0121] Next, this embodiment will further elaborate on the constitutive models mentioned above. The constitutive models involved in this embodiment include the modified elastoplastic model, the strain softening model, the Burgers rheological model, and the surrounding rock damage correction model.

[0122] First, the modified elastoplastic model is an existing model. For the specific model and its derivation, please refer to the following reference (Jia Shanpo, Chen Weizhong, Yang Jianping, et al. Elastoplastic 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).

[0123] Second, the strain softening model expresses the strength of the surrounding rock through strain softening by introducing a functional relationship between the strength parameter and the equivalent plastic strain, as shown in equations (2.1)-(2.3):

[0124] (2.1);

[0125] (2.2);

[0126] (2.3);

[0127] In the formula: The cohesion of the surrounding rock; φ0 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 A positive constant to control the softening rate; For shear plastic strain, the second invariant form of the strain tensor is used, and it can be obtained by incremental summation; c res Residual cohesion of the surrounding rock; φ res The residual internal friction angle of the surrounding rock; To achieve the critical shear plastic strain corresponding to the residual strength; For plastic strain rate tensor; For time.

[0128] Therefore, based on the parameters in Table 1, the residual cohesion and internal friction angle of the surrounding rock in Example 1 were calculated to be 100 kPa and 25°, respectively.

[0129] Third, the surrounding rock damage correction model is determined according to equations (3.1)-(3.3):

[0130] (3.1);

[0131] (3.2);

[0132] (3.3);

[0133] In the formula: E damaged E0 is the elastic modulus after damage correction for the surrounding rock; E0 is the initial elastic modulus of the surrounding rock; c damaged c0 is the cohesion after damage correction of the surrounding rock; c0 is the initial cohesion of the surrounding rock; φ damaged φ is the internal friction angle after damage correction for the surrounding rock; φ0 is the initial internal friction angle of the surrounding rock; Δφ is the empirical attenuation coefficient; D is the damage factor;

[0134] The damage factor D is determined according to equation (3.4):

[0135] (3.4);

[0136] In the formula: k1 and k2 are the geostress sensitivity coefficient and the fragmentation sensitivity coefficient, respectively, which are calibrated by 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; RQD is the rock quality index.

[0137] Fourth, the Burgers rheological model involves two different cases:

[0138] (1) For shallow-buried tunnels, rock samples can be obtained directly by drilling. The viscoelastic parameters of the Burgers rheological model can be obtained from the results of the field direct shear rheological test according to equations (4.1) and (4.2):

[0139] (4.1);

[0140] (4.2);

[0141] In the formula: γ is the shear strain; Shear stress; G1 is the time; G2 is the viscoelastic shear modulus; G1 and η2 are the viscosity coefficients; γ0 is the instantaneous shear strain; G1, η1, and η2 are obtained by regression analysis of the shear creep curve using the least squares method;

[0142] (2) For deep and ultra-deep buried tunnels, due to the limited drilling depth, it is difficult to obtain rock samples at the desired tunnel burial depth H. Furthermore, the parameters of the Burgers rheological model are sensitive to burial depth, especially parameters η1 and G2. Therefore, multiple rheological tests on rock samples at different burial depths are required. The viscosity coefficients η1 and η2, and the shear moduli G1 and G2 can be uniformly corrected according to equations (4.3) and (4.4):

[0143] (4.3);

[0144] (4.4);

[0145] In the formula: η(H) and G(H) are the corrected viscosity coefficient and shear modulus, respectively, and η(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 For reference burial depth; η ref G ref Reference parameters for burial depth; n η α G α η n is a parameter to be determined. η Power-law fitting of rheological tests under stepped confining pressure on rock samples determined that the values ​​for α are typically 1.2–1.5 for hard rocks and 0.8–1.0 for soft rocks; G The values ​​were obtained through ultrasonic shear wave velocity measurements and logarithmic regression of rock samples at different burial depths, with a typical value of 0.08 ± 0.02; α η The viscosity coefficient and shear modulus data were obtained by regression analysis from multiple sets of rock sample tests at different burial depths.

[0146] Wherein, the undetermined parameter n η The calibration test procedure is as follows:

[0147] 1) Stepped confining pressure rheological test: For the same rock sample (e.g., altered granite), under a fixed axial pressure σ, the confining pressure is gradually increased (e.g., 5 MPa → 10 MPa → 15 MPa), and each group is maintained until steady-state creep; the steady-state creep rate ε is recorded. steady The equivalent viscosity coefficient η1 is calculated as σ axial compression / 3ε. steady；

[0148] 2) Data fitting: The coefficient n can be obtained by fitting η1 and confining pressure according to a power law relationship (linear regression on logarithmic scale). η .

[0149] Wherein, the undetermined parameter α G The calibration test procedure is as follows:

[0150] 1) Ultrasonic testing: Measuring the shear wave velocity V of rock samples at different burial depths (e.g., 50m, 100m, or 150m). s ; Calculate dynamic shear modulus (ρ is the density of the rock sample);

[0151] 2) Data fitting: The coefficient n can be obtained by fitting G2 and the burial depth H according to the logarithmic relationship. η .

[0152] Wherein, the undetermined parameter α η The calibration test procedure is as follows:

[0153] 1) Stepped loading rheological test: Drill cores (Φ50mm×100mm) were taken from the target strata (e.g., altered granite), grouped according to different burial depths (50m, 100m, or 150m); confining pressure was applied using a triaxial rheological testing machine (with long-term monitoring of confining pressure and axial displacement), followed by axial pressure applied in stages, each stage lasting 7-30 days, and strain-time curves were recorded; Burgers parameters were inverted by curve fitting using the least squares method (example data are shown in Table 3):

[0154] ;

[0155] 2) Coefficient determination: Based on the obtained coefficient n η For example, if we take a reference burial depth of 100m, we can substitute it into the aforementioned correction formula to calculate the coefficient α. η as follows: .

[0156] In-situ direct shear rheological tests were conducted using a self-developed on-site direct shear rheological device (patent number: ZL201210374780.7) to obtain experimental values ​​and fitting curves. Please refer to [the relevant documentation / reference]. Figure 3 As shown.

[0157] Further, through least squares regression analysis, the viscoelastic parameters of the Burgers rheological model used in Example 2 (a deep-buried cohesive soil tunnel with extremely high ground stress, obtained by correcting according to formulas (4.3) and (4.4)) are shown in Table 4 below.

[0158] .

[0159] Step 2: Based on the constitutive model and boundary conditions obtained in Step 1, and according to the tunnel simulation parameters, establish a numerical model of the stress and deformation of the mountain tunnel support for simulation calculation to obtain the stress, deformation and distribution of the plastic zone of the surrounding rock of the support structure.

[0160] The tunnel simulation parameters have been mentioned above, and the numerical model is established using software such as finite element method and finite difference method, for example, ABAQUS and FLAC. 2D The process of modeling and analysis using finite element and finite difference software is a conventional technique in this field and will not be elaborated here. Finally, the stress and deformation of the support structure are obtained, and the distribution results of the plastic zone of the surrounding rock and other relevant simulation results can also be obtained as needed. The stress can provide the safety factor of the support structure; the plastic zone can provide pre-support or reinforcement optimization measures; based on the stress and deformation of the support structure, the safety and stability of the support structure can be evaluated. Then, if the support structure exceeds the specified threshold, the support structure can be optimized based on the simulation results until the support structure meets the design requirements, and optimization suggestions for the support structure are provided.

[0161] Example 3;

[0162] Please refer to Figure 4 As shown, the present invention also provides a numerical calculation system for the stress and deformation of mountain tunnel support, used for a method of numerical calculation of the stress and deformation of mountain tunnel support, the numerical calculation system for the stress and deformation of mountain tunnel support includes:

[0163] Simulation parameter input module: used to input tunnel simulation parameters, including stratum property parameters, burial depth, groundwater, initial ground stress field, tunnel cross-section design parameters, and support structure design parameters;

[0164] Tunnel classification and discrimination module: used to classify and grade surrounding rock as well as tunnel burial depth and ground stress;

[0165] Simulation calculation module: Based on the tunnel classification results, it matches the corresponding constitutive model and boundary conditions for the numerical model of stress and deformation of mountain tunnel support, and performs simulation calculations based on the input simulation parameters;

[0166] Output early warning module: used to output the stress and deformation of the support structure of mountain tunnel and the plastic zone of the surrounding rock, and to trigger an early warning of support structure failure when the displacement of the support structure exceeds the threshold.

[0167] The threshold for the displacement of the support structure is determined according to the standard "Technical Specification for Monitoring and Measurement of Railway Tunnels" Q / CR 9218-2024, as shown in Tables 5 and 6.

[0168] The simulation calculation module also includes the process of building the simulation model. However, the model needs to be built manually by the user based on the tunnel classification results and tunnel simulation parameters. Simulation can only be performed after the model is completed. The tunnel classification module can be implemented using MATLAB or Python.

[0169] .

[0170] .

[0171] Please refer to Figure 5 , Figure 5 This is the tunnel support deformation result for Example 1. The calculated maximum support displacement is 0.474m, located in the lower right part of the tunnel, with a relative clearance convergence of 3.61%, which clearly exceeds the warning threshold (Class V surrounding rock, deep burial, arch foot horizontal relative clearance convergence threshold 2.00%). Further analysis is needed, combined with the output results of the surrounding rock plastic zone (please refer to...). Figure 6 Example 1 proposed two treatment schemes: adding anchor cables and deepening the invert arch. The latter was selected at the construction site, which optimized the structural stress, improved the structural bearing capacity, and ensured that the maximum stress of the secondary lining concrete was much lower than the ultimate bending tensile strength, thus ensuring the safety of the support structure.

[0172] Please refer to Figure 7 and Figure 8 , Figure 7 and Figure 8 This document presents the stress results for the tunnel support (initial support and secondary lining) in Example 2. To highlight the advantages of the Burgers rheological model used in Example 2, it compares the results with those calculated using the Mohr-Coulomb model (MC model). It should be noted that in Example 2, localized cracking and even large-scale spalling of the shotcrete in the arch ring and sidewalls occurred during the initial construction phase of the tunnel. Therefore, the comparison shows that neglecting the rheological characteristics of the surrounding rock in deeply buried cohesive soil strata can easily lead to unsafe calculations of structural stress and deformation, posing design risks. This demonstrates that the Burgers rheological model used in Example 2 and the obtained model parameters can effectively reflect the rheological characteristics of the strata and can be used for long-term safety evaluation of tunnel support structures. Based on the output results, Example 2 proposes an optimized support scheme that appropriately increases the support stiffness and the allowable deformation.

[0173] Example 4;

[0174] Please see Figure 9Based on the above-mentioned numerical calculation method and system for stress and deformation of mountain tunnel support, the present invention also provides a terminal, which includes a processor 10, a memory 20 and a display 30. Figure 9 Only some of the terminal components are shown; however, it should be understood that it is not required to implement all of the components shown, and more or fewer components may be implemented instead.

[0175] In some embodiments, the memory 20 may be an internal storage unit of the terminal, such as the terminal's hard drive or memory. In other embodiments, the memory 20 may be an external storage device of the terminal, such as a plug-in hard drive, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the terminal. Furthermore, the memory 20 may include both internal and external storage units of the terminal. The memory 20 is used to store application software and various types of data installed on the terminal, such as the program code for installing the terminal. The memory 20 may also be used to temporarily store data that has been output or will be output. In one embodiment, the memory 20 stores a calculation program 40 for a numerical calculation method of stress and deformation of mountain tunnel support, which can be executed by the processor 10 to implement the numerical calculation method of stress and deformation of mountain tunnel support according to the present invention.

[0176] In some embodiments, processor 10 may be a central processing unit (CPU), microprocessor or other data processing chip, used to run program code stored in memory 20 or process data, such as executing a numerical calculation method for stress and deformation of support in mountain tunnels.

[0177] In some embodiments, the display 30 may be an LED display, a liquid crystal display, a touch-screen liquid crystal display, or an OLED (Organic Light-Emitting Diode) touchscreen. The display 30 is used to display information from the terminal and a user interface for displaying visualizations. This user interface includes a display window for the stress and deformation of the support structure, a display window for the confining compression plastic zone (range, deformation amount, etc.), and a warning prompt window. It can at least display the stress and deformation at characteristic locations such as the tunnel arch foot and arch crown, and preferably allows for button presses. Figure 7-8 The system displays the stress and deformation at any location on the tunnel outline and labels the values. If the deformation exceeds the threshold, a warning is issued, such as by displaying a flashing window or text prompts. It can even be connected to an external buzzer or flashing light for warning purposes.

[0178] In one embodiment, when the processor 10 executes the calculation program 40 of a numerical calculation method for stress and deformation of mountain tunnel support stored in the memory 20, the steps of the numerical calculation method for stress and deformation of mountain tunnel support described above are implemented.

[0179] In summary, this invention proposes a numerical calculation method, system, and terminal for the stress and deformation of mountain tunnel support. Based on rock hardness, rock mass integrity, burial depth, and initial in-situ stress field, it classifies the surrounding rock, burial depth, and low stress of mountain tunnels. By coupling the interaction effects of strata properties, tunnel burial depth, and in-situ stress state, it adaptively selects corresponding constitutive models and boundary conditions. Furthermore, it creatively improves some constitutive models and boundary conditions, enabling some models to more accurately describe dilatation effects, strain softening, structural degradation, creep behavior, and simulate progressive failure induced by high in-situ stress. The deformation and instability process of the surrounding rock enables precise mechanical analysis of the support structure. The constitutive model and boundary conditions selected according to the tunnel classification are used to establish the numerical simulation model. This can effectively solve the problem of deviation in the calculation or prediction of stress and deformation of mountain tunnel support caused by the failure of traditional numerical models to consider the coupling of multiple geological factors. It realizes the compatibility of the same framework with the differentiated calculation needs from shallow to ultra-deep burial. It can effectively improve the accuracy of stress simulation calculation of mountain tunnel support structure, which is conducive to assessing the safety and stability of support structure and guiding the optimization design of support structure. It is applicable to the optimization design and construction safety assessment of tunnels under complex geological conditions.

[0180] It should be noted that, in this invention, the term "comprising" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal that includes that element.

[0181] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A numerical calculation method for the stress and deformation of support in mountain tunnels, characterized in that, Includes the following steps: Step 1: Based on the rock hardness, rock mass integrity, burial depth, and initial geostress field of the mountain tunnel, classify and grade the surrounding rock, as well as the burial depth and geostress levels, 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 according to the tunnel simulation parameters, establish a numerical model of the stress and deformation of the mountain tunnel support for simulation calculation to obtain the stress, deformation and distribution of the plastic zone of the surrounding rock of the support structure. The constitutive model and boundary conditions are selected according to the following method: For shallow-buried tunnels and deep-buried hard rock tunnels, a modified elastoplastic model and displacement boundary conditions are selected. For deep-buried 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 ordinary, the strain softening model and displacement boundary conditions are selected. For deeply buried cohesive soil tunnels, the Burgers rheological model and displacement boundary conditions are selected. For ultra-deep buried tunnels with extremely high or high ground stress in fractured zones, a surrounding rock damage correction model and stress boundary conditions are selected. For ultra-deep buried soft rock and altered rock tunnels with extremely high or high ground stress, the Burgers rheological model and stress boundary conditions are selected. For shallow-buried tunnels, the viscoelastic parameters of the Burgers rheological model are obtained based on the results of field direct shear rheological tests and according to equations (4.1) and (4.2): （4.1）； （4.2）； In the formula, γ is the shear strain; Shear stress; G1 is time; G2 is viscoelastic shear modulus; G1 is instantaneous shear modulus; η1 and η2 are viscosity coefficients; γ0 is instantaneous shear strain. For deep and ultra-deep buried tunnels, η1, η2, G1, and G2 are uniformly corrected according to equations (4.3) and (4.4) to obtain: （4.3）； （4.4）； In the formula, η(H) and G(H) are the corrected viscosity coefficient and shear modulus, respectively, with η(H) corresponding to η1 and η2, and G(H) corresponding to G1 and G2; H is the tunnel burial depth; H ref For reference burial depth; η ref G ref Reference parameters for burial depth; n η α G α η These are parameters to be determined.

2. The numerical calculation method for stress and deformation of mountain tunnel support according to claim 1, 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 formulas (1.1)-(1.3): （1.1）； （1.2）； （1.3）； In the formula: H is the tunnel burial depth; H p h is the dividing depth between deep and shallow tunnels. q denoted as equivalent load height; s as surrounding rock grade; B as tunnel excavation width; ω as tunnel width influence coefficient; and i as a parameter related to surrounding rock grade.

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

4. The numerical calculation method for stress and deformation of mountain tunnel support according to claim 1, characterized in that, The tunnel simulation parameters include: geological properties, groundwater, tunnel depth, initial stress field, tunnel cross-section design parameters, and support structure design parameters. Among them, the formation property parameters include uniaxial saturated compressive strength, rock mass unit weight, 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, characterized in that, The strain softening model is determined according to equations (2.1)-(2.3): （2.1）； （2.2）； （2.3）； In the formula: The cohesion of the surrounding rock; φ0 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 A positive constant to control the softening rate; c represents shear plastic strain; res Residual cohesion of the surrounding rock; φ res The residual internal friction angle of the surrounding rock; To achieve the critical shear plastic strain corresponding to the residual strength; t 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, characterized in that, The surrounding rock damage correction model is determined according to equations (3.1)-(3.3): （3.1）； （3.2）； （3.3）； In the formula, E damaged c is the elastic modulus after correction for surrounding rock damage; damaged Cohesion after damage correction of the surrounding rock; φ damaged φ0 is the internal friction angle after damage correction for the surrounding rock; E0 is the initial elastic modulus of the surrounding rock; c0 is the initial cohesion of the surrounding rock; φ0 is the initial internal friction angle of the surrounding rock; Δφ is the empirical attenuation coefficient; D is the damage factor. The damage factor D is determined according to equation (3.4): （3.4）； In the formula: k1 and k2 are the geostress sensitivity coefficient and the fragmentation sensitivity coefficient, respectively, which are calibrated by 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; RQD is the rock quality index.

7. The numerical calculation method for stress and deformation of mountain tunnel support according to claim 1, characterized in that, The displacement boundary conditions are as follows: the upper boundary of the numerical model is the ground line as the free boundary, the two side boundaries constrain the horizontal displacement, and the bottom boundary constrains the vertical and horizontal displacements. The stress boundary condition is as follows: a horizontally distributed surrounding rock stress σ is set at the upper and lower boundaries of the numerical model. x Vertically distributed surrounding rock stress σ is set at the left and right boundaries. y ; For deep-buried soft rock and ultra-deep-buried tunnels with extremely high or high ground stress, the stress boundary value shall be the measured ground stress value; or, if there is no measured ground stress value, it shall be determined according to formulas (5.1) and (5.2): （5.1）； （5.2）； In the formula, σ x The surrounding rock stress is evenly distributed horizontally; σ y λ represents the vertically distributed surrounding rock stress; B represents the tunnel excavation width; H represents the tunnel burial depth; G represents the surrounding rock deformation grade; and λ represents the lateral pressure coefficient.

8. 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 as described in any one of claims 1-7, characterized in that, include: Simulation parameter input module: used to input tunnel simulation parameters; Tunnel classification and discrimination module: used to classify and grade surrounding rock as well as tunnel burial depth and ground stress; Simulation calculation module: Based on the tunnel classification results, it matches the corresponding constitutive model and boundary conditions for the numerical model of stress and deformation of mountain tunnel support, and performs simulation calculations based on the input simulation parameters; Output early warning module: used to output the deformation of the support structure of mountain tunnel, and to trigger an early warning of support structure failure when the displacement of the support structure exceeds the threshold.

9. A terminal, characterized in that, The terminal includes a processor and a memory that stores executable programs. When the processor executes the program stored in the memory, it implements the numerical calculation method for stress and deformation of mountain tunnel support as described in any one of claims 1-7.

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