Tunnel blasting simulation method and system for karst area

Abstract

The invention discloses a tunnel blasting simulation method and system for a karst area, and relates to the field of tunnel blasting simulation, and the method comprises the steps: building a three-dimensional geologic model of the karst area, and generating an initial ground stress distribution rule through numerical simulation; generating refined initial crustal stress field data; calculating stress wave intensity and time sequence data generated by explosion; acquiring stress wave propagation data; calculating the surrounding rock damage degree and the crack initial position and direction; simulating the surrounding rock crack propagation process, and calculating the penetration probability and the propagation speed of the crack near the karst cave in combination with the karst cave characteristic parameters; analyzing the surrounding rock stability and damage evolution trend of the karst cave area; and optimizing explosive source item parameters and stress wave propagation boundary conditions, and generating a karst area tunnel blasting simulation result. According to the method, the influence of the karst cave on stress wave propagation is accurately simulated, powerful support is provided for optimizing a blasting scheme and improving construction safety and efficiency, and the method has important guiding significance on tunnel engineering under complex geological conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunnel blasting simulation, and particularly relates to a tunnel blasting simulation method and system for karst areas. Background Art

[0002] In the simulation of tunnel blasting in karst areas, applying the initial in-situ stress is a key step. The application of the initial in-situ stress needs to accurately reflect the stress state before tunnel excavation to ensure the accuracy of the simulation. However, the geological conditions in karst areas are complex, and the presence of karst caves makes the distribution of the initial in-situ stress non-uniform. Near the karst caves, the stress concentration phenomenon is significant, which leads to the need for more delicate treatment in applying the initial in-situ stress. If the initial in-situ stress is applied inaccurately, the subsequent blasting simulation results will deviate greatly and cannot truly reflect the stress wave propagation and surrounding rock damage during the blasting process. When simulating the explosion of explosives, setting the source term of the explosive explosion is a technical difficulty. The propagation process of the stress wave and the explosion-generated gas in the surrounding rock is significantly affected by the karst caves. The presence of karst caves changes the propagation path and intensity of the stress wave, resulting in reflection, refraction, and scattering of the stress wave near the karst caves. These phenomena make the propagation process of the stress wave complex and difficult to accurately simulate. In addition, the flow behavior of the explosion-generated gas in the karst caves is also different from that in the intact surrounding rock, which further increases the difficulty of the simulation. When simulating the stress wave propagation and surrounding rock damage, the influence of karst caves on the blasting process needs to be particularly concerned. The propagation of the stress wave near the karst caves will cause a stress concentration effect, significantly increasing the damage degree of the surrounding rock near the karst caves. However, the shape, size, and distribution of karst caves have different effects on the stress wave propagation and surrounding rock damage, which requires detailed analysis for different karst cave characteristics during the simulation process. In addition, the damage mechanism of the surrounding rock under the action of the stress wave is complex, including processes such as crack generation, propagation, and penetration, and these processes are more intense near the karst caves. Therefore, these damage mechanisms need to be accurately captured during the simulation process to ensure the reliability of the simulation results. Summary of the Invention

[0003] To solve the above technical problems, the present invention proposes a tunnel blasting simulation method and system for karst areas, which realizes high-precision simulation of the tunnel blasting process in karst areas by accurately simulating the influence of karst caves on the stress wave propagation, provides strong support for optimizing the blasting scheme, improving construction safety and efficiency, and has important guiding significance for tunnel engineering under complex geological conditions.

[0004] To achieve the above object, the present invention provides a tunnel blasting simulation method for karst areas, including: establishing a three-dimensional geological model of the karst area, extracting the characteristic parameters of the distribution, shape, and size of the karst caves, and generating the initial in-situ stress distribution law through numerical simulation;

[0005] Based on the initial in-situ stress distribution law, combined with the stress concentration correction factor and surrounding rock mechanical parameters in the karst cave area, refined initial in-situ stress field data is generated;

[0006] Set the explosive source term and calculate the stress wave intensity and time series data generated by the explosion;

[0007] Use the wave equation solver to simulate the reflection, refraction, and scattering of stress waves near the karst cave and obtain the stress wave propagation data;

[0008] According to the stress wave propagation data, combined with the surrounding rock damage mechanics model, calculate the degree of surrounding rock damage and the initial position and direction of cracks;

[0009] Simulate the process of surrounding rock crack propagation, and calculate the penetration probability and propagation speed of cracks near the karst cave in combination with the karst cave characteristic parameters;

[0010] Generate a surrounding rock damage distribution map, and analyze the stability and damage evolution trend of the surrounding rock in the karst cave area in combination with the initial in-situ stress field data;

[0011] Based on the damage evolution trend, optimize the explosive source term parameters and stress wave propagation boundary conditions to generate the tunnel blasting simulation results in the karst area.

[0012] Optionally, establishing a three-dimensional geological model of the karst area includes: based on geological exploration data, using Kriging interpolation method to construct a three-dimensional geological body model, extracting the karst cave boundary through threshold segmentation method, and dividing grid cells to establish a numerical simulation calculation domain.

[0013] Optionally, generating refined initial in-situ stress field data includes: applying a stress concentration correction factor to the initial in-situ stress in the area near the karst cave, and smoothing the stress values exceeding the threshold through an interpolation algorithm.

[0014] Optionally, setting the explosive source term includes: calculating the time series data of the stress wave intensity decay over time based on the explosive equivalent, initiation method, and flow characteristics of the explosion gas.

[0015] Optionally, simulating the stress wave propagation includes: defining the karst cave boundary conditions in the wave equation solver, and calculating the propagation paths of stress wave reflection, refraction, and scattering in combination with parameters such as elastic modulus, density, and Poisson's ratio.

[0016] Optionally, calculating the degree of surrounding rock damage includes: based on the time series data of stress wave intensity values, combined with the damage factor model, determining the initial position of cracks and extracting the propagation direction.

[0017] Optionally, simulating the process of surrounding rock crack propagation includes: analyzing the stress state at the crack tip using the maximum circumferential stress criterion, and predicting the penetration probability and propagation speed of cracks in combination with the karst cave spacing and shape parameters.

[0018] Optionally, analyzing the surrounding rock stability includes: superimposing the surrounding rock damage distribution map on the initial in-situ stress field, and combining the crack density and stress concentration area data to determine the risk level of surrounding rock instability.

[0019] Optionally, optimizing the explosive source term parameters includes: adjusting the charge amount and detonation timing according to the evolution trend of surrounding rock damage, and setting free boundary and fixed boundary conditions to correct the simulation results.

[0020] On the other hand, to achieve the above object, the present invention also provides a tunnel blasting simulation system for karst areas, including: a three-dimensional geological modeling module, an initial in-situ stress field generation module, an explosive explosion simulation module, a stress wave propagation simulation module, a surrounding rock damage calculation module, a crack propagation simulation module, a surrounding rock stability analysis module, and a blasting simulation optimization module;

[0021] The three-dimensional geological modeling module is used to establish a three-dimensional geological model of the karst area, extract the characteristic parameters of the distribution, shape and size of the karst caves, and generate the initial in-situ stress distribution law through numerical simulation;

[0022] The initial in-situ stress field generation module is used to generate refined initial in-situ stress field data based on the initial in-situ stress distribution law, combined with the stress concentration correction coefficient in the karst cave area and the mechanical parameters of the surrounding rock;

[0023] The explosive explosion simulation module is used to set the explosive source term and calculate the stress wave intensity and time series data generated by the explosion;

[0024] The stress wave propagation simulation module is used to simulate the reflection, refraction and scattering phenomena of stress waves near the karst caves by using a wave equation solver to obtain stress wave propagation data;

[0025] The surrounding rock damage calculation module is used to calculate the surrounding rock damage degree and the initial position and direction of cracks according to the stress wave propagation data, combined with the surrounding rock damage mechanics model;

[0026] The crack propagation simulation module is used to simulate the surrounding rock crack propagation process, and calculate the penetration probability and propagation speed of cracks near the karst caves in combination with the karst cave characteristic parameters;

[0027] The surrounding rock stability analysis module is used to generate a surrounding rock damage distribution map, and analyze the surrounding rock stability and damage evolution trend in the karst cave area in combination with the initial in-situ stress field data;

[0028] The blasting simulation optimization module is used to optimize the explosive source term parameters and the stress wave propagation boundary conditions based on the damage evolution trend, and generate the tunnel blasting simulation results in the karst area.

[0029] Technical effects of the present invention: The present invention discloses a tunnel blasting simulation method and system for karst areas. First, a three-dimensional geological model is established based on geological exploration data, characteristic parameters of karst caves are extracted, and non-uniform initial in-situ stress distribution is obtained through numerical simulation. Then, an explosive source term is set to simulate the propagation characteristics of stress waves near karst caves, and the degree of surrounding rock damage and the crack propagation process are calculated. By analyzing the stability of the surrounding rock and the damage evolution trend, the blasting parameter settings are optimized. The present invention realizes high-precision simulation of the tunnel blasting process in karst areas by accurately simulating the influence of karst caves on the propagation of stress waves, provides strong support for optimizing blasting schemes, improving construction safety and efficiency, and has important guiding significance for tunnel engineering under complex geological conditions. Description of the Drawings

[0030] The drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0031] Figure 1 It is a schematic flow chart of a tunnel blasting simulation method for karst areas according to an embodiment of the present invention;

[0032] Figure 2 It is a schematic structural diagram of a tunnel blasting simulation system for karst areas according to an embodiment of the present invention. Detailed Embodiments

[0033] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will refer to the drawings and combine the embodiments to detail this application.

[0034] It should be noted that the steps shown in the flowchart of the drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0035] As Figure 1 shown, this embodiment provides a tunnel blasting simulation method for karst areas, including:

[0036] Establish a three-dimensional geological model of the karst area, extract the characteristic parameters of the distribution, shape and size of karst caves, and generate the initial in-situ stress distribution law through numerical simulation;

[0037] Based on the initial in-situ stress distribution law, combined with the stress concentration correction coefficient in the karst cave area and the mechanical parameters of the surrounding rock, generate refined initial in-situ stress field data;

[0038] Set the explosive source term, and calculate the stress wave intensity and time series data generated by the explosion;

[0039] The wave equation solver is used to simulate the reflection, refraction and scattering of stress waves near the cave to obtain stress wave propagation data;

[0040] According to the stress wave propagation data, combined with the surrounding rock damage mechanics model, the surrounding rock damage degree and the initial position and direction of the crack are calculated;

[0041] Simulate the crack propagation process of the surrounding rock, and calculate the crack penetration probability and propagation speed near the cave in combination with the characteristic parameters of the cave;

[0042] Generate surrounding rock damage distribution map, and analyze the stability and damage evolution trend of surrounding rock in the cave area by combining initial geostress field data;

[0043] Based on the damage evolution trend, the explosive source term parameters and stress wave propagation boundary conditions are optimized to generate the simulation results of tunnel blasting in the karst area.

[0044] Furthermore, establishing a three-dimensional geological model of the karst area includes: constructing a three-dimensional geological body model based on geological exploration data using the Kriging interpolation method, extracting the cave boundaries through a threshold segmentation method, and dividing the grid units to establish a numerical simulation calculation domain.

[0045] Specifically, the Kriging interpolation method can be used to process discrete point data during three-dimensional modeling, and a geological body model can be constructed on this basis. Taking a limestone area as an example, a three-dimensional geological model containing multi-layer lithological structures was generated by processing 120 borehole data points, which clearly showed the spatial distribution law of the karst cave development zone. When identifying the boundaries of karst caves, the threshold segmentation method is often used to extract the contours of karst caves. In a certain engineering case, the density threshold method was used to successfully identify a group of karst caves with diameters ranging from 0.5 to 5 meters, and the shape parameters of the karst caves, including characteristic quantities such as the direction of the cave body and the extension length, were obtained. Meshing is a key link in numerical simulation. In a certain karst cave group area, tetrahedral meshes were used to segment the complex geological body, and the mesh was encrypted around the karst caves, generating a total of about 200,000 mesh units to ensure the calculation accuracy. In the calculation of non-uniform stress fields, the anisotropic characteristics of the rock mass need to be considered. In a certain case, finite element analysis found that stress concentration occurred at the top of the karst cave, and the maximum principal stress reached three times the original rock stress, indicating that there was a risk of instability in the area. The cubic spline interpolation method is used to deal with the abnormal values of stress distribution, which realizes the smooth transition of stress field. In a certain cave group example, the singular values in the calculation results are eliminated through interpolation correction, making the stress distribution more consistent with the actual situation.

[0046] Furthermore, generating refined initial geostress field data includes: applying a stress concentration correction coefficient to the initial geostress in the area near the cave, and smoothing the stress values exceeding the threshold value by an interpolation algorithm.

[0047] Specifically, taking a certain karst area as an example, when the surrounding rock is moderately weathered limestone, its elastic modulus is about twenty gigapascals, the Poisson's ratio is 0.28, and the uniaxial compressive strength is sixty megapascals. These parameters directly affect the stress distribution characteristics. For example, the larger the elastic modulus, the faster the stress transfer and the more obvious the stress concentration phenomenon. The determination of the stress threshold needs to combine the engineering practice and the safety factor. In the above case, 70% of the uniaxial compressive strength can be used as the stress threshold, that is, forty-two megapascals. When the calculated stress exceeds this value, stress field smoothing treatment is required. Using the Kriging interpolation algorithm to smooth the stress field can effectively eliminate stress mutations and make the stress distribution more reasonable. The determination of the non-uniform stress field distribution range needs to consider the influence area of the karst cave. Taking three times the diameter of the karst cave as the boundary of the influence range, for the aforementioned karst cave with a diameter of ten meters, its influence range is thirty meters. Grid division is carried out within this range, and the grid size is gradually refined from the outside to the inside. The grid size near the karst cave can be taken as 0.5 meters, and 2 meters can be taken for the periphery. In finite element calculations, the setting of boundary conditions is crucial. The gravitational stress can be applied in the vertical direction, and the corresponding stress can be applied in the horizontal direction according to the measured in-situ stress value. For a karst cave at a depth of one hundred meters, the vertical stress is about 2.7 megapascals, and the horizontal stress may reach 4 to 6 megapascals. The judgment of the stress concentration area needs to focus on the top and bottom of the karst cave.

[0048] Furthermore, setting the explosive source term includes: calculating the time-series data of the stress wave intensity decay over time based on the explosive equivalent, initiation method, and the flow characteristics of the explosion-generated gas flow.

[0049] Specifically, the stress wave distribution calculation uses the explicit dynamic finite element method. During the simulation, the time step is set to one microsecond to ensure calculation stability. Through the stress wave propagation law, the reflection, refraction, and superposition effects of the wave in different media are analyzed. For example, at the boundary of the karst cave, due to the difference in medium impedance, obvious stress wave reflection and diffraction phenomena will occur. The judgment of the stress wave concentration area is mainly based on the stress wave amplitude and duration. At characteristic positions such as the top and bottom of the karst cave, stress wave focusing often occurs, resulting in local stress concentration. For example, when the local stress exceeds twice the average value of the surrounding area, it can be determined as the stress concentration area. The time-series data of these areas need to be recorded and analyzed emphatically to provide a basis for engineering design and safety assessment.

[0050] Furthermore, simulating the stress wave propagation includes: defining the boundary conditions of the karst cave in the wave equation solver, and combining the parameters of elastic modulus, density, and Poisson's ratio to calculate the propagation paths of stress wave reflection, refraction, and scattering.

[0051] Specifically, when dividing the grid in the simulation domain, it is necessary to select an appropriate grid size according to the geometric characteristics of the karst cave. For a karst cave with a diameter of 10 meters, the grid size can be set to 0.5 meters, which can ensure the calculation accuracy while taking into account the calculation efficiency. The initial stress wave field is usually described by a Gaussian function, and the amplitude and frequency of the waveform need to match the actual engineering situation. The reflection and refraction phenomena of stress waves on the karst cave wall are the key research objects. When the incident wave reaches the surface of the karst cave, part of the energy is reflected, and part of the energy continues to propagate and undergoes multiple scatterings inside the karst cave. By recording the spatio-temporal evolution process of the wave field, the propagation path of stress waves around the karst cave can be obtained.

[0052] Furthermore, calculating the damage degree of the surrounding rock includes: based on the time series data of stress wave intensity values, combined with the damage factor model, determining the initial crack position and extracting the propagation direction.

[0053] Specifically, the stress wave propagation path data reflects the variation characteristics of stress waves in the karst cave area. By analyzing the amplitude and frequency characteristics of the waveform curve, the intensity value sequence at different times is obtained. Taking a certain karst cave project as an example, during the propagation of stress waves, the intensity value gradually decays from the initial 100 MPa to 50 MPa, showing typical exponential decay characteristics. The mechanical model of the surrounding rock mass needs to consider the anisotropy and inhomogeneity of the rock mass, and a damage factor is introduced into the model to characterize the degree of damage of the rock mass. Taking a certain limestone karst cave as an example, the compressive strength of the rock mass is 80 MPa. When the stress wave intensity exceeds 40 MPa, microscopic cracks begin to appear, and the damage degree increases non-linearly. The distribution of the damage degree is directly related to the crack initiation position, and the crack propagation direction is judged by the stress intensity factor. In actual engineering, the top and side walls of the karst cave are often stress concentration areas. When the damage degree exceeds 0.6, through-cracks are extremely likely to form in this area. The intensity value adjustment uses the cubic spline interpolation algorithm to ensure the stability of numerical calculations.

[0054] Furthermore, simulating the crack propagation process of the surrounding rock includes: using the maximum circumferential stress criterion to analyze the stress state at the crack tip, combined with the karst cave spacing and shape parameters, predicting the crack penetration probability and propagation speed.

[0055] Specifically, the crack propagation algorithm is an important tool for studying the development of surrounding rock cracks. Common methods include the maximum circumferential stress criterion and the maximum energy release rate criterion. Taking the maximum circumferential stress criterion as an example, when the circumferential stress at the crack tip reaches the critical value, the crack begins to propagate. In practical applications, stress monitoring points can be arranged at the crack tip to record the change process of stress over time and obtain crack propagation path data. The characteristic parameters of karst caves include the size, shape, distribution density, etc. of the karst caves. Taking a limestone area as an example, the average diameter of underground karst caves is 3 meters, showing an elliptical distribution, and the spacing between karst caves is about 15 meters. By analyzing the spatial position relationship between the crack propagation path and the karst caves, the crack penetration probability can be calculated. When it is found that the penetration probability in a dense area of a certain karst cave group reaches 0.8, exceeding the preset threshold of 0.6, it is necessary to interpolate and adjust the characteristic parameters of the karst caves in this area. The crack propagation speed is closely related to the stress state of the surrounding rock and the properties of the rock mass. Taking a mining area as an example, the surrounding rock is mainly composed of granite, and the initial crack length is 0.5 meters. Under the action of dynamic load, the crack propagation speed gradually increases from 0.1 meter per second to 0.5 meters per second. By drawing a speed distribution map, the fast and slow changes of crack propagation can be intuitively displayed.

[0056] Furthermore, analyzing the stability of the surrounding rock includes: superimposing the surrounding rock damage distribution map on the initial in-situ stress field, and combining the crack density and stress concentration area data to determine the risk level of surrounding rock instability.

[0057] Furthermore, optimizing the explosive source term parameters includes: adjusting the charge amount and detonation timing according to the surrounding rock damage evolution trend, and setting free boundary and fixed boundary conditions to correct the simulation results.

[0058] Specifically, under the complex geological conditions in karst areas, the millisecond delay initiation technology is adopted, and the initiation time difference between adjacent blast holes is set to 25 milliseconds, which can effectively control the vibration of the surrounding rock mass. In terms of boundary condition setting, a free boundary is set on the tunnel excavation face, and fixed constraints are adopted for the rest of the boundaries to simulate the real stratum conditions. In the analysis of stress wave propagation, the stress concentration areas of the surrounding rock mainly appear at the top and side walls of the karst cave. The actual case shows that the stress concentration coefficient at the top of the karst cave reaches 2.5, far exceeding the critical value of 1.8. Combining with the crack propagation data, it is found that when the stress concentration coefficient at the top exceeds 2.0, microcracks begin to expand and connect to form through cracks. The analysis of the surrounding rock characteristics shows that in the area where karst caves develop, the compressive strength of the rock mass generally decreases by 30%. During the stress wave propagation process, stress concentration is likely to occur in this weakened area. For example, in a tunnel karst cave area, the original compressive strength of the rock mass is 80 MPa, and it drops to 56 MPa under the influence of corrosion, resulting in the generation of new crack propagation under the action of stress waves. By optimizing the blasting parameters, the damage to the surrounding rock can be controlled while ensuring the excavation efficiency. Practice has proved that by adopting smooth blasting technology and reducing the charge amount of the perimeter holes by 40%, overbreak and disturbance of the surrounding rock can be effectively controlled. At the same time, adjusting the initiation network and adopting a two-way central delay initiation scheme can reduce the blasting vibration by 25%. The damage evolution analysis shows that the damage to the surrounding rock shows a trend of expanding from shallow to deep and from the perimeter to the inside. In the area where karst caves develop, the damage depth can reach 2 meters outside the excavation contour line. After adjusting the blasting parameters, the damage depth is controlled within 1 meter, and the self-stabilizing ability of the surrounding rock is significantly improved. The final simulation results show that the optimized blasting scheme not only ensures the excavation efficiency but also effectively controls the damage to the surrounding rock.

[0059] As Figure 2 shown, in this embodiment, a tunnel blasting simulation system for karst areas is further provided, including: a three-dimensional geological modeling module, an initial in-situ stress field generation module, an explosive explosion simulation module, a stress wave propagation simulation module, a surrounding rock damage calculation module, a crack propagation simulation module, a surrounding rock stability analysis module, and a blasting simulation optimization module;

[0060] The three-dimensional geological modeling module is used to establish a three-dimensional geological model of the karst area, extract the characteristic parameters of the distribution, shape, and size of the karst caves, and generate the initial in-situ stress distribution law through numerical simulation;

[0061] The initial in-situ stress field generation module is used to generate refined initial in-situ stress field data based on the initial in-situ stress distribution law, combined with the stress concentration correction coefficient in the karst cave area and the mechanical parameters of the surrounding rock;

[0062] The explosive explosion simulation module is used to set the explosive explosion source term and calculate the stress wave intensity and time series data generated by the explosion;

[0063] The stress wave propagation simulation module is used to simulate the reflection, refraction and scattering phenomena of stress waves near the karst cave by using a wave equation solver, and obtain stress wave propagation data;

[0064] The surrounding rock damage calculation module is used to calculate the degree of surrounding rock damage, the initial position and direction of cracks according to the stress wave propagation data and in combination with the surrounding rock damage mechanics model;

[0065] The crack propagation simulation module is used to simulate the process of surrounding rock crack propagation, and calculate the penetration probability and propagation speed of cracks near the karst cave in combination with the karst cave characteristic parameters;

[0066] The surrounding rock stability analysis module is used to generate a surrounding rock damage distribution map, and analyze the surrounding rock stability and damage evolution trend in the karst cave area in combination with the initial in-situ stress field data;

[0067] The blasting simulation optimization module is used to optimize the explosive source term parameters and stress wave propagation boundary conditions based on the damage evolution trend, and generate the tunnel blasting simulation results in the karst area.

[0068] The present invention discloses a tunnel blasting simulation method and system for a karst area. First, a three-dimensional geological model is established based on geological exploration data, karst cave characteristic parameters are extracted, and a non-uniform initial in-situ stress distribution is obtained through numerical simulation. Then, an explosive source term is set, the propagation characteristics of stress waves near the karst cave are simulated, and the degree of surrounding rock damage and the process of crack propagation are calculated. By analyzing the surrounding rock stability and damage evolution trend, the blasting parameter settings are optimized. The present invention realizes the high-precision simulation of the tunnel blasting process in the karst area by accurately simulating the influence of the karst cave on the stress wave propagation, provides strong support for optimizing the blasting scheme, improving the construction safety and efficiency, and has important guiding significance for tunnel engineering under complex geological conditions.

[0069] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A tunnel blasting simulation method for karst areas, characterized in that, Including: Establish a three-dimensional geological model of the karst area, extract the characteristic parameters of the distribution, shape and size of the karst caves, and generate the initial in-situ stress distribution law through numerical simulation; Based on the initial in-situ stress distribution law, combine the stress concentration correction factor in the karst cave area and the mechanical parameters of the surrounding rock to generate refined initial in-situ stress field data; Set the explosive source term, and calculate the stress wave intensity and time series data generated by the explosion; Use a wave equation solver to simulate the reflection, refraction and scattering phenomena of stress waves near the karst caves, and obtain stress wave propagation data; According to the stress wave propagation data, combine with the surrounding rock damage mechanics model to calculate the damage degree of the surrounding rock and the initial position and direction of the cracks; Simulate the process of surrounding rock crack propagation, and combine with the karst cave characteristic parameters to calculate the penetration probability and propagation speed of the cracks near the karst caves; Generate a surrounding rock damage distribution map, and combine with the initial in-situ stress field data to analyze the stability of the surrounding rock in the karst cave area and the damage evolution trend; Based on the damage evolution trend, optimize the explosive source term parameters and stress wave propagation boundary conditions to generate the tunnel blasting simulation results in the karst area.

2. The tunnel blasting simulation method for the karst area according to claim 1, characterized in that Establishing a three-dimensional geological model of the karst area includes: based on geological exploration data, using Kriging interpolation method to construct a three-dimensional geological body model, extracting the karst cave boundary through threshold segmentation method, and dividing grid units to establish a numerical simulation calculation domain.

3. The tunnel blasting simulation method for the karst area according to claim 1, characterized in that Generating refined initial in-situ stress field data includes: applying a stress concentration correction factor to the initial in-situ stress in the area near the karst cave, and smoothing the stress values exceeding the threshold through an interpolation algorithm.

4. The tunnel blasting simulation method for the karst area according to claim 1, characterized in that Setting the explosive source term includes: based on the explosive equivalent, initiation method and flow characteristics of the explosion gas, calculating the time series data of the stress wave intensity decay over time.

5. The tunnel blasting simulation method for the karst area according to claim 1, characterized in that Simulating stress wave propagation includes: defining the karst cave boundary conditions in the wave equation solver, and combining with parameters such as elastic modulus, density and Poisson's ratio to calculate the propagation paths of stress wave reflection, refraction and scattering.

6. The tunnel blasting simulation method for the karst area according to claim 1, characterized in that Calculating the damage degree of the surrounding rock includes: based on the time series data of the stress wave intensity values, combining with the damage factor model, judging the initial position of the crack and extracting the propagation direction.

7. The tunnel blasting simulation method for the karst area according to claim 1, characterized in that Simulating the process of surrounding rock crack propagation includes: using the maximum circumferential stress criterion to analyze the stress state at the crack tip, and combining with the karst cave spacing and shape parameters to predict the penetration probability and propagation speed of the cracks.

8. The tunnel blasting simulation method for the karst area according to claim 1, characterized in that Analyzing the stability of the surrounding rock includes: superimposing the surrounding rock damage distribution map on the initial in-situ stress field, and combining with the crack density and stress concentration area data to determine the risk level of surrounding rock instability.

9. The tunnel blasting simulation method for karst areas according to claim 1, characterized in that Optimizing the parameters of the explosive source term includes: adjusting the charge amount and initiation timing according to the evolution trend of surrounding rock damage, and setting free boundary and fixed boundary conditions to correct the simulation results.

10. A system for the tunnel blasting simulation method for karst areas according to any one of claims 1-9, characterized in that, It includes: A three-dimensional geological modeling module, an initial in-situ stress field generation module, an explosive explosion simulation module, a stress wave propagation simulation module, a surrounding rock damage calculation module, a crack propagation simulation module, a surrounding rock stability analysis module, and a blasting simulation optimization module; The three-dimensional geological modeling module is used to establish a three-dimensional geological model of the karst area, extract the characteristic parameters of the distribution, shape, and size of the karst caves, and generate the initial in-situ stress distribution law through numerical simulation; The initial in-situ stress field generation module is used to generate refined initial in-situ stress field data based on the initial in-situ stress distribution law, combined with the stress concentration correction factor in the karst cave area and the mechanical parameters of the surrounding rock; The explosive explosion simulation module is used to set the explosive source term and calculate the stress wave intensity and time series data generated by the explosion; The stress wave propagation simulation module is used to simulate the reflection, refraction, and scattering phenomena of stress waves near the karst caves by using a wave equation solver to obtain stress wave propagation data; The surrounding rock damage calculation module is used to calculate the degree of surrounding rock damage and the initial position and direction of cracks according to the stress wave propagation data, combined with the surrounding rock damage mechanics model; The crack propagation simulation module is used to simulate the process of surrounding rock crack propagation, and calculate the penetration probability and propagation speed of cracks near the karst caves in combination with the karst cave characteristic parameters; The surrounding rock stability analysis module is used to generate a surrounding rock damage distribution map, and analyze the surrounding rock stability and damage evolution trend in the karst cave area in combination with the initial in-situ stress field data; The blasting simulation optimization module is used to optimize the parameters of the explosive source term and the stress wave propagation boundary conditions based on the damage evolution trend, and generate the tunnel blasting simulation results in the karst area.

Images