A three-dimensional finite element simulation method for underground caverns considering dynamic evolution of surrounding rock deformation parameters

Abstract

This invention discloses a three-dimensional finite element simulation method for underground caverns that considers the dynamic evolution of surrounding rock deformation parameters. Based on triaxial loading and unloading tests of the surrounding rock in an underground cavern, the method first obtains the evolution equations of the surrounding rock deformation parameters under different stress paths, then constructs a three-dimensional finite element calculation model of the underground cavern. Through secondary development technology of finite element software, the evolution equations are embedded into the simulation process, realizing real-time dynamic adjustment of the deformation modulus and Poisson's ratio of the surrounding rock as the stress state changes during excavation. During the simulation, the method cyclically executes "stress monitoring - path judgment - parameter calculation - model assignment - convergence calculation" according to the excavation step sequence until the cavern excavation is completed. This invention restores the deterioration law of surrounding rock parameters under unloading during underground cavern excavation, improves the fit between numerical simulation results and engineering reality, and provides a reliable basis for the stability analysis of the surrounding rock and the design of excavation and support schemes for underground caverns.

Description

Technical Field

[0001] This invention relates to the field of numerical simulation technology for underground caverns in geotechnical engineering, and in particular to a three-dimensional finite element simulation method for underground caverns that considers the dynamic evolution of surrounding rock deformation parameters. It is applicable to the three-dimensional finite element simulation of the entire process of excavation of deep underground caverns with complex geological conditions in fields such as hydropower, transportation, and mining, and provides technical support for the stability analysis of surrounding rock and the optimization of excavation and support schemes for underground caverns. Background Technology

[0002] In the construction of underground caverns, three-dimensional finite element simulation is a core technical means to analyze the stress, displacement distribution, and stability of the surrounding rock during cavern excavation. The accuracy of the simulation results directly determines the safety of engineering design and construction. In traditional three-dimensional finite element simulation methods for underground caverns, the deformation parameters (deformation modulus, Poisson's ratio) of the surrounding rock are set to constant values ​​and are not adjusted with changes in stress state throughout the entire excavation simulation process.

[0003] However, in actual engineering projects, the excavation of underground caverns causes a redistribution of stress in the surrounding rock, resulting in various unloading stress paths, such as rising axial pressure followed by unloading of confining pressure, and vice versa. Under unloading, the surrounding rock undergoes significant parameter deterioration; the deformation modulus decreases with decreasing confining pressure, while Poisson's ratio increases. Furthermore, the evolution of surrounding rock parameters differs significantly under different stress paths and initial stress states. Traditional simulation methods neglect the dynamic evolution characteristics of surrounding rock parameters, leading to significant deviations between simulation results and actual stress and displacement distributions in engineering projects. This results in an inaccurate reflection of the true stability of the surrounding rock under unloading during cavern excavation and may even provide incorrect references for engineering design.

[0004] Currently, existing studies have revealed the evolution law of deformation parameters under unloading of surrounding rock through indoor triaxial tests, but this evolution law has not yet been deeply integrated with three-dimensional finite element simulation. There is a lack of a standardized finite element simulation method that can realize real-time dynamic adjustment of surrounding rock parameters. Some existing methods only manually adjust the surrounding rock parameters in local areas and do not realize automatic dynamic adjustment of the entire model and the entire excavation sequence. They are inefficient and have poor accuracy, and cannot be applied to large underground cavern projects with complex structural surfaces.

[0005] To address the aforementioned technical issues, there is an urgent need to propose a three-dimensional finite element simulation method for underground caverns that considers the dynamic evolution of surrounding rock deformation parameters. This method combines the evolution equations of surrounding rock deformation parameters obtained from indoor triaxial loading and unloading tests with three-dimensional finite element simulation. Through secondary development, it enables real-time, automatic, and full-model dynamic adjustment of surrounding rock parameters during excavation, thereby improving the accuracy and engineering fit of numerical simulation and providing reliable numerical simulation support for the safe construction of underground cavern projects. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a three-dimensional finite element simulation method for underground caverns that considers the dynamic evolution of surrounding rock deformation parameters. This method solves the technical problems of constant surrounding rock parameters and large deviations from actual engineering conditions in traditional three-dimensional finite element simulations of underground caverns, and the inability of existing methods to achieve automatic dynamic adjustment of parameters across the entire model and excavation sequence. Based on the results of indoor triaxial loading and unloading tests, a finite element simulation process with dynamic parameter evolution is constructed to achieve real-time automatic adjustment of the deformation modulus and Poisson's ratio of the surrounding rock during excavation, thereby improving the accuracy of simulation results and providing a reliable basis for the stability analysis of surrounding rock in underground caverns.

[0007] The objective of this invention is achieved as follows: A three-dimensional finite element simulation method for underground caverns considering the dynamic evolution of surrounding rock deformation parameters is based on indoor triaxial loading and unloading tests of the surrounding rock in underground caverns, combined with three-dimensional finite element numerical simulation technology, to achieve real-time dynamic adjustment of the surrounding rock deformation parameters during excavation. The deformation parameters include deformation modulus and Poisson's ratio. The method specifically includes the following steps: S1. Triaxial loading and unloading test of surrounding rock and acquisition of deformation parameter evolution equation: standard samples were made from the original surrounding rock of the underground cavern, and triaxial loading and unloading tests were carried out under different confining pressures and stress paths. The evolution law of deformation modulus and Poisson's ratio of surrounding rock with confining pressure unloading was analyzed, and exponential evolution equations of deformation modulus and Poisson's ratio with confining pressure as the variable were constructed. S2. Construction of a three-dimensional finite element calculation model for underground caverns: Based on the engineering geological survey data, topography and structural surface distribution characteristics of underground caverns, a three-dimensional geometric model of the underground caverns is constructed, a finite element mesh is generated, the initial mechanical parameters and constitutive model of the rock mass are set, and the geostress boundary conditions and excavation sequence are determined. S3. Development of a dynamic parameter adjustment program for finite element simulation: Based on the secondary development language of finite element software, write a dynamic parameter adjustment program, embed the deformation modulus and Poisson's ratio evolution equations obtained in step S1 into the program, and realize the program's identification of the stress state of model elements, determination of stress path and automatic calculation of deformation parameters. S4. Dynamic adjustment of parameters and finite element simulation under the excavation sequence: According to the excavation sequence set in step S2, the underground cavern is simulated in stages. Each excavation step executes the following sub-steps: S41. Element stress monitoring: After a single excavation is completed, all elements of the finite element model are traversed to monitor and extract the real-time values ​​of the maximum principal stress and minimum principal stress of each element. S42. Stress path determination: Compare the changes in the maximum and minimum principal stresses of each unit before and after excavation to determine the stress path type of each unit. S43. Dynamic parameter calculation: Based on the stress path type and real-time confining pressure value of each element, call the program in step S3 to calculate the real-time deformation modulus and Poisson's ratio of each element through the evolution equation. S44. Model parameter assignment: The calculated real-time deformation modulus and Poisson's ratio are batch-assigned to each element of the finite element model to update the model's mechanical parameters. S45. Convergence Calculation: Perform calculations on the updated finite element model until the model reaches the stress-displacement convergence condition, thus completing the simulation of this excavation sequence. S5. Repeat step S4 to perform dynamic parameter adjustment and finite element simulation for all excavation steps of the underground cavern, and obtain the stress, displacement distribution law and stability evaluation results of the surrounding rock in the entire excavation process of the underground cavern considering the dynamic evolution of surrounding rock deformation parameters.

[0008] Preferably, in step S1, the stress path includes a constant confining pressure loading path with increasing axial pressure, a confining pressure unloading path with increasing axial pressure, and a confining pressure unloading path with decreasing axial pressure. The confining pressure value is set according to the actual ground stress test conditions, and the evolution equation is in the form of an exponential function, which respectively characterizes the variation law of deformation modulus and Poisson's ratio with confining pressure unloading.

[0009] Preferably, in step S1, the expressions for the deformation modulus evolution equation and the Poisson's ratio evolution equation are as follows:

[0010]

[0011] In the formula: μ is the real-time Poisson's ratio of the rock mass during the unloading process of confining pressure, μ0 is the initial Poisson's ratio of unloading, E is the real-time deformation modulus of the rock mass during the unloading process of confining pressure, E0 is the initial deformation modulus of unloading, σ3 is the real-time confining pressure value, and A1, A2, B1, and B2 are fitting parameters, which are obtained by fitting indoor triaxial loading and unloading test data.

[0012] Preferably, in step S2, the constitutive model adopts the strain softening / hardening Mohr-Coulomb model, and the excavation sequence is consistent with the layered and step-by-step excavation sequence of the actual construction of the underground cavern.

[0013] Preferably, in step S3, the finite element software is FLAC3D, ANSYS, or ABAQUS, the secondary development language is FISH, APDL, or Python, and the program has the functions of element traversal, stress extraction, path judgment, parameter calculation, and batch assignment.

[0014] Preferably, in step S42, the stress path type is determined based on the principal stress change characteristics: the lifting shaft pressure and unloading confining pressure path is characterized by an increase in the maximum principal stress and a decrease in the minimum principal stress; the unloading shaft pressure and unloading confining pressure path is characterized by a decrease in both the maximum and minimum principal stress; and the lifting shaft pressure and constant confining pressure path is characterized by an increase in the maximum principal stress and a change in the minimum principal stress.

[0015] Preferably, in step S4, stress monitoring and parameter updates are performed on the model elements after each time step calculation is completed, until the stress-displacement model of the current excavation step converges.

[0016] Preferably, the underground cavern is an underground cavern of different rock mass types.

[0017] Preferably, the underground cavern is a deep-buried or shallow-buried underground cavern project containing faults, joints, and blocks.

[0018] Preferably, the method also includes setting a control simulation condition with constant surrounding rock parameters, comparing the simulation results of the two conditions, and quantitatively analyzing the impact of the dynamic evolution of surrounding rock parameters on the stress, displacement and stability of the surrounding rock in the underground cavern.

[0019] Due to the adoption of the above technical solution, the present invention has the following beneficial effects: 1. This invention deeply integrates the deformation parameter evolution equation obtained from the triaxial loading and unloading test of the surrounding rock in the underground cavern with the three-dimensional finite element simulation, breaking through the technical limitation of constant surrounding rock parameters in traditional finite element simulation. It accurately restores the dynamic deterioration law of the deformation modulus and Poisson's ratio of the surrounding rock under the unloading of the underground cavern excavation, making the simulation results more in line with the actual engineering situation and effectively improving the accuracy and reliability of numerical simulation.

[0020] 2. This invention utilizes a dedicated program developed through secondary development of finite element software to achieve automated dynamic adjustment of surrounding rock parameters across the entire model and excavation sequence. This eliminates the need for manual intervention in the calculation and assignment of unit parameters, solving the problems of low efficiency and poor accuracy associated with manual adjustments in existing methods. It significantly improves the efficiency of finite element simulation of underground caverns and is suitable for large underground cavern projects with complex structural surfaces.

[0021] 3. This invention constructs a standardized dynamic parameter adjustment process of "stress monitoring - path judgment - parameter calculation - model assignment - convergence calculation". The steps are clear, logically coherent, and repeatable. Those skilled in the art can implement it independently by following the steps in the instruction manual. Moreover, the evolution equation fitting parameters can be flexibly adjusted according to different rock mass types and different engineering geological conditions, which has strong practicality and scalability.

[0022] 4. This invention enables real-time dynamic adjustment of surrounding rock parameters throughout the entire underground cavern excavation process. It can accurately capture the dynamic evolution characteristics of surrounding rock stress and displacement under excavation unloading, and clearly reflect the degree and range of surrounding rock parameter deterioration in stress concentration areas such as the arch, sidewalls, floor, and near faults. This provides accurate numerical simulation basis for the zoning of surrounding rock stability in underground caverns, selection of excavation support timing, and optimization of support schemes.

[0023] 5. This invention supports control simulation conditions with constant parameters, and can quantitatively analyze the impact of the dynamic evolution of surrounding rock parameters on the stress, displacement and stability of the surrounding rock in underground caverns. It provides quantitative indicators for engineering technicians to assess the degree of impact of unloading effects, and further enhances the engineering application value of numerical simulation results. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the overall process of the method of the present invention. Figure 2 This is a schematic diagram of the three-dimensional finite element calculation model of the underground cavern of the Kala Hydropower Station in an embodiment of the present invention; Figure 3 This is a cloud map showing the distribution of surrounding rock deformation parameters during the excavation of an underground cavern in an embodiment of the present invention (considering the dynamic evolution of parameters). Detailed Implementation

[0025] A three-dimensional finite element simulation method for underground caverns considering the dynamic evolution of surrounding rock deformation parameters is proposed. Based on the indoor triaxial loading and unloading test of the surrounding rock in the underground cavern, and combined with three-dimensional finite element numerical simulation technology, the method realizes the real-time dynamic adjustment of the surrounding rock deformation parameters (deformation modulus, Poisson's ratio) during the excavation process. The method includes the following steps: S1. Triaxial loading and unloading test of surrounding rock and acquisition of deformation parameter evolution equations Standard cylindrical specimens with a diameter of 50 mm and a height of 100 mm were prepared from the original surrounding rock of the underground cavern. Triaxial loading and unloading tests were carried out under different confining pressures and different stress paths. The stress paths included the constant confining pressure loading path with increasing axial pressure, the unloading path with increasing axial pressure and unloading path with decreasing axial pressure and unloading path with decreasing confining pressure.

[0026] By processing experimental data, the evolution of the deformation modulus and Poisson's ratio of the surrounding rock under different stress paths and initial stress states with the unloading of confining pressure was analyzed. An exponential function was used to fit the experimental data, and exponential evolution equations for the deformation modulus and Poisson's ratio with confining pressure as variables were constructed. The expressions for the evolution equations are as follows:

[0027]

[0028] In the formula: μ is the real-time Poisson's ratio of the rock mass during the unloading process of confining pressure, μ0 is the initial Poisson's ratio of unloading, E is the real-time deformation modulus of the rock mass during the unloading process of confining pressure, E0 is the initial deformation modulus of unloading, σ3 is the real-time confining pressure value, and A1, A2, B1, and B2 are fitting parameters, which are obtained by fitting the data of indoor triaxial loading and unloading test. The values ​​of the fitting parameters are different under different stress paths and different confining pressures.

[0029] S2. Construction of a three-dimensional finite element calculation model of the underground cavern Based on the engineering geological survey data, topography, strata lithology and structural plane (faults, joints, controlling structural planes) distribution characteristics of the underground cavern, a three-dimensional geometric model of the underground cavern is constructed using three-dimensional modeling software, and a hexahedral finite element mesh is divided according to the engineering accuracy requirements.

[0030] Based on the results of indoor tests and geological survey data, the initial mechanical parameters of the rock mass (density, cohesion, internal friction angle, initial deformation modulus, initial Poisson's ratio, etc.) were set. The constitutive model adopted the strain softening / hardening Mohr-Coulomb model. Combined with the field measured data of geostress, the geostress boundary conditions and displacement boundary conditions of the model were set. According to the actual construction plan of the underground cavern, the layered and step-by-step excavation sequence of the model was determined, and the excavation sequence was consistent with the actual construction.

[0031] S3, Development of a program for dynamically adjusting finite element simulation parameters Based on the secondary development language of finite element software (such as FISH language of FLAC3D, APDL language of ANSYS, and Python language of ABAQUS), write a special program for dynamic parameter adjustment, and embed the deformation modulus and Poisson's ratio exponential evolution equation obtained in step S1 into the program code.

[0032] The program has five core functions: ① Model element traversal: traversing all elements of the finite element model one by one; ② Element stress extraction: real-time monitoring and extraction of the maximum and minimum principal stress values ​​of each element; ③ Stress path judgment: determining the element stress path type based on the change in principal stress before and after excavation; ④ Dynamic parameter calculation: calculating real-time parameters based on the stress path and real-time confining pressure value through evolution equations; ⑤ Batch parameter assignment: batch updating and assigning the calculated real-time parameters to the model elements.

[0033] S4. Dynamic parameter adjustment and finite element simulation under excavation sequence Following the excavation sequence set in step S2, a step-by-step excavation simulation of the underground cavern is performed. After each excavation step is completed, the following sub-steps are executed: stress monitoring, path determination, parameter calculation, model assignment, and convergence calculation. Specifically: S41. Unit stress monitoring: After completing a single excavation, pause the finite element model calculation, and use the procedure in step S3 to traverse all units of the model, monitor and extract the real-time values ​​of the maximum principal stress and minimum principal stress of each unit after excavation. S42. Stress path determination: Compare the initial principal stress value before excavation of each unit with the real-time principal stress value after excavation, calculate the change in principal stress, and determine the stress path type based on the change characteristics: The path of lifting axial pressure and unloading confining pressure is characterized by an increase in the maximum principal stress and a decrease in the minimum principal stress; the path of unloading axial pressure and unloading confining pressure is characterized by a decrease in both the maximum and minimum principal stresses; and the path of lifting axial pressure and constant confining pressure is characterized by an increase in the maximum principal stress and a constant minimum principal stress. S43. Dynamic parameter calculation: Based on the stress path type and real-time confining pressure value determined by each element, the evolution equation in the program is called to calculate the real-time deformation modulus and Poisson's ratio of each element respectively. The evolution equation of the corresponding fitting parameters is called for different stress paths. S44. Model parameter assignment: The program assigns the calculated real-time deformation modulus and Poisson's ratio to each element of the finite element model in batches, replacing the original initial parameters and completing the real-time update of the model's mechanical parameters. S45. Convergence Calculation: Continue to calculate the finite element model after parameter updates. Repeat steps S41-S44 after each time step calculation is completed until the model reaches the preset stress-displacement convergence condition, thus completing the finite element simulation of this excavation step sequence.

[0034] S5. Repeat the simulation until excavation is complete. Repeat step S4 to perform finite element simulations on each excavation step of the underground cavern in sequence, so as to realize the real-time dynamic adjustment and convergence calculation of the surrounding rock parameters after each excavation step, until the simulation of all excavation steps of the underground cavern is completed.

[0035] After the simulation is completed, the stress distribution cloud map, displacement distribution cloud map, and plastic zone distribution cloud map of the surrounding rock for each excavation step during the entire excavation process are extracted to obtain the stress and displacement evolution law and stability evaluation results of the underground cavern considering the dynamic evolution of surrounding rock deformation parameters.

[0036] This method can also set up a control simulation condition with constant surrounding rock parameters, that is, keep the deformation modulus and Poisson's ratio of the surrounding rock at initial constant values, and keep the other model parameters and excavation steps consistent with this method. The simulation results of the two conditions are compared to quantitatively analyze the impact of the dynamic evolution of surrounding rock parameters on the stress, displacement and stability of the surrounding rock of the underground cavern.

[0037] The method of this invention is applicable to underground caverns of different rock types such as sandy slate, granite, marble, and limestone. It is also applicable to deep and shallow underground cavern projects with complex structural surfaces such as faults, joints, and key blocks. It can be widely used in numerical simulation of underground caverns in fields such as hydropower, transportation, mining, and geological disposal of nuclear waste.

[0038] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] This embodiment uses the deep underground cavern of the Kala Hydropower Station on the Yalong River as the engineering background. The surrounding rock of the underground cavern is sandy slate, containing complex structural surfaces such as the F75 and F152 faults and the Jn119 joint. The total height of the main powerhouse is 75.77m. The method of this invention is used to carry out a three-dimensional finite element simulation of the underground cavern. The specific implementation steps are as follows: S1. Triaxial loading and unloading test of sandy slate and acquisition of deformation parameter evolution equations The original sandy slate rock of the exploration tunnel of the underground powerhouse of the Kala Hydropower Station was selected, and standard cylindrical specimens with a diameter of 50 mm and a height of 100 mm were made. Triaxial loading and unloading tests were carried out under confining pressures of 3 MPa, 6 MPa, 9 MPa and 12 MPa, with the unloading points set at 50%, 70% and 90% of the peak stress.

[0040] By organizing the experimental data, the evolution of the deformation modulus and Poisson's ratio of sandy slate with the unloading of confining pressure was analyzed. The evolution equations of deformation modulus and Poisson's ratio were obtained by fitting an exponential function:

[0041]

[0042] Among them, when the confining pressure is 6MPa and the peak stress at the unloading point is 70% under the lifting shaft pressure unloading path, the fitting parameters are A1=22.01, A2=0.87, B1=0.19, and B2=1.34; when the confining pressure is 6MPa and the peak stress at the unloading point is 70% under the unloading shaft pressure unloading path, the fitting parameters are A1=2.13, A2=2.42, B1=0.24, and B2=1.31. The values ​​of the fitting parameters under different working conditions are determined by experimental data.

[0043] S2. Construction of a three-dimensional finite element calculation model of the underground cavern of the Kala Hydropower Station Based on the engineering geological survey data, topography, and fault and joint distribution characteristics of the underground caverns of the Kala Hydropower Station, a three-dimensional geometric model was constructed. The model is 500m long and 500m wide, and the bottom elevation differs from the bottom elevation of the main and auxiliary powerhouses by 200m. A hexahedral finite element mesh was then created.

[0044] Initial mechanical parameters of sandy slate: density 2650 kg / m³ 3 Initial deformation modulus 27.45 GPa, initial Poisson's ratio 0.27, cohesion 16.99 MPa, internal friction angle 49.96°; fault F 75 F 152 Density 2300 kg / m³ 3 The deformation modulus is 1.0 GPa and the Poisson's ratio is 0.22. The constitutive model adopts the strain softening / hardening Mohr-Coulomb model, and the ground stress boundary conditions are set by combining the measured ground stress data (σ1=5.68~11.30MPa, σ3=4.24~5.50MPa).

[0045] S3, Development of a program for dynamically adjusting finite element simulation parameters Based on the FISH language of FLAC3D finite element software, a dedicated program for dynamic parameter adjustment was written. The exponential evolution equations of deformation modulus and Poisson's ratio obtained in step S1 were embedded into the program code. The program performs the following functions: ① Traverses all elements of the model; ② Extracts the real-time values ​​of the maximum and minimum principal stresses of each element; ③ Determines stress paths such as lifting the axial pressure and unloading the confining pressure, and unloading the axial pressure and unloading the confining pressure, based on the change in principal stress; ④ Calls the corresponding evolution equations to calculate the real-time deformation modulus and Poisson's ratio; ⑤ Assigns batch parameter values ​​to the model elements.

[0046] S4. Dynamic parameter adjustment and finite element simulation under excavation sequence Following the pre-defined excavation sequence, a step-by-step excavation simulation of the underground caverns of the Kala Hydropower Station was conducted. Taking the second layer of excavation as an example, the following sub-steps were executed: S41, Unit stress monitoring: After the second layer of excavation is completed, the model calculation is paused. The FISH program is used to traverse all units of the model and extract the real-time values ​​of the maximum principal stress and minimum principal stress of each unit after excavation. S42. Stress path determination: By comparing the changes in principal stress before and after excavation, the top arch unit is determined to be a lifting axial pressure unloading path (maximum principal stress increases, minimum principal stress decreases), and the middle sidewall unit is a unloading axial pressure unloading path (both maximum and minimum principal stresses decrease). S43. Dynamic parameter calculation: The evolution equation is called to calculate based on the stress path type and real-time confining pressure value of each element. S44. Model parameter assignment: The calculated real-time deformation modulus and Poisson's ratio are batch-assigned to each element of the model through the FISH program to update the mechanical parameters of the model. S45. Convergence Calculation: Continue the calculation on the model after parameter updates. Repeat the above steps after each time step is completed until the model converges and the simulation of the second layer of excavation is completed.

[0047] S5. Repeat the simulation until excavation is complete. Repeat step S4 to complete the dynamic adjustment of parameters and finite element simulation of the excavation sequence of the underground cavern of the Kala Hydropower Station. At the same time, set up a control condition with constant surrounding rock parameters and compare the simulation results of the two conditions.

[0048] The results show that, after considering the dynamic evolution of the surrounding rock deformation parameters, the deformation modulus decreased by a maximum of 16.99%, and the Poisson's ratio increased by a maximum of 48.15%, which accurately reflects the parameter deterioration characteristics of the surrounding rock under excavation unloading and provides a reliable basis for the stability analysis of the underground cavern of the hydropower station.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A three-dimensional finite element simulation method for underground caverns considering the dynamic evolution of surrounding rock deformation parameters, characterized in that, Based on the triaxial loading and unloading test of the surrounding rock in the underground cavern, and combined with three-dimensional finite element numerical simulation technology, the deformation parameters of the surrounding rock during excavation are dynamically adjusted in real time. The deformation parameters include the deformation modulus and Poisson's ratio. The specific steps are as follows: S1. Triaxial loading and unloading test of surrounding rock and acquisition of deformation parameter evolution equation: standard samples were made from the original surrounding rock of the underground cavern, and triaxial loading and unloading tests were carried out under different confining pressures and stress paths. The evolution law of deformation modulus and Poisson's ratio of surrounding rock with confining pressure unloading was analyzed, and exponential evolution equations of deformation modulus and Poisson's ratio with confining pressure as the variable were constructed. S2. Construction of a three-dimensional finite element calculation model for underground caverns: Based on the engineering geological survey data, topography and structural surface distribution characteristics of underground caverns, a three-dimensional geometric model of the underground caverns is constructed, a finite element mesh is generated, the initial mechanical parameters and constitutive model of the rock mass are set, and the geostress boundary conditions and excavation sequence are determined. S3. Development of a dynamic parameter adjustment program for finite element simulation: Based on the secondary development language of finite element software, write a dynamic parameter adjustment program, embed the deformation modulus and Poisson's ratio evolution equations obtained in step S1 into the program, and realize the program's identification of the stress state of model elements, determination of stress path and automatic calculation of deformation parameters. S4. Dynamic adjustment of parameters and finite element simulation under the excavation sequence: According to the excavation sequence set in step S2, the underground cavern is simulated in stages. Each excavation step executes the following sub-steps: S41. Element stress monitoring: After a single excavation is completed, all elements of the finite element model are traversed to monitor and extract the real-time values ​​of the maximum principal stress and minimum principal stress of each element. S42. Stress path determination: Compare the changes in the maximum and minimum principal stresses of each unit before and after excavation to determine the stress path type of each unit. S43. Dynamic parameter calculation: Based on the stress path type and real-time confining pressure value of each element, call the program in step S3 to calculate the real-time deformation modulus and Poisson's ratio of each element through the evolution equation. S44. Model parameter assignment: The calculated real-time deformation modulus and Poisson's ratio are batch-assigned to each element of the finite element model to update the model's mechanical parameters. S45. Convergence Calculation: Perform calculations on the updated finite element model until the model reaches the stress-displacement convergence condition, thus completing the simulation of this excavation sequence. S5. Repeat step S4 to perform dynamic parameter adjustment and finite element simulation for all excavation steps of the underground cavern, and obtain the stress, displacement distribution law and stability evaluation results of the surrounding rock in the entire excavation process of the underground cavern considering the dynamic evolution of surrounding rock deformation parameters.

2. The three-dimensional finite element simulation method for underground caverns considering the dynamic evolution of surrounding rock deformation parameters according to claim 1, characterized in that, In step S1, the stress path includes the axial pressure constant confining pressure loading path, the axial pressure unloading confining pressure unloading path, and the axial pressure unloading confining pressure unloading path. The confining pressure value is set according to the actual ground stress test conditions. The evolution equation is in the form of an exponential function, which respectively characterizes the variation law of deformation modulus and Poisson's ratio with confining pressure unloading.

3. The three-dimensional finite element simulation method for underground caverns considering the dynamic evolution of surrounding rock deformation parameters according to claim 1, characterized in that, In step S1, the expressions for the deformation modulus evolution equation and the Poisson's ratio evolution equation are as follows: ； ； In the formula: μ is the real-time Poisson's ratio of the rock mass during the unloading process of confining pressure, μ0 is the initial Poisson's ratio of unloading, E is the real-time deformation modulus of the rock mass during the unloading process of confining pressure, E0 is the initial deformation modulus of unloading, σ3 is the real-time confining pressure value, and A1, A2, B1, and B2 are fitting parameters, which are obtained by fitting indoor triaxial loading and unloading test data.

4. The three-dimensional finite element simulation method for underground caverns considering the dynamic evolution of surrounding rock deformation parameters according to claim 1, characterized in that, In step S2, the constitutive model adopts the strain softening / hardening Mohr-Coulomb model, and the excavation sequence is consistent with the layered and step-by-step excavation sequence of the actual construction of the underground cavern.

5. The three-dimensional finite element simulation method for underground caverns considering the dynamic evolution of surrounding rock deformation parameters according to claim 1, characterized in that, In step S3, the finite element software is FLAC3D, ANSYS, or ABAQUS, and the secondary development language is FISH, APDL, or Python. The program has the functions of element traversal, stress extraction, path judgment, parameter calculation, and batch assignment.

6. The three-dimensional finite element simulation method for underground caverns considering the dynamic evolution of surrounding rock deformation parameters according to claim 1, characterized in that, In step S42, the stress path type is determined based on the principal stress change characteristics: the lifting shaft pressure and unloading confining pressure path is characterized by an increase in the maximum principal stress and a decrease in the minimum principal stress; the unloading shaft pressure and unloading confining pressure path is characterized by a decrease in both the maximum and minimum principal stresses; and the lifting shaft pressure and constant confining pressure path is characterized by an increase in the maximum principal stress and a change in the minimum principal stress.

7. The three-dimensional finite element simulation method for underground caverns considering the dynamic evolution of surrounding rock deformation parameters according to claim 1, characterized in that, In step S4, stress monitoring and parameter updates are performed on the model elements after each time step calculation is completed, until the stress-displacement model of this excavation step converges.

8. The three-dimensional finite element simulation method for underground caverns considering the dynamic evolution of surrounding rock deformation parameters according to any one of claims 1-7, characterized in that, The underground caverns are underground caverns of different rock mass types.

9. The three-dimensional finite element simulation method for underground caverns considering the dynamic evolution of surrounding rock deformation parameters according to any one of claims 1-7, characterized in that, Underground caverns are deep-buried or shallow-buried underground cavern projects containing faults, joints, and blocks.

10. The three-dimensional finite element simulation method for underground caverns considering the dynamic evolution of surrounding rock deformation parameters according to any one of claims 1-7, characterized in that, It also includes a control simulation with constant surrounding rock parameters, comparing the simulation results of the two conditions, and quantitatively analyzing the impact of the dynamic evolution of surrounding rock parameters on the stress, displacement and stability of the surrounding rock in underground caverns.

Images