Blast hole layout method based on crack propagation characteristics under coupling model

Abstract

The embodiment of the invention provides a blast hole layout method based on crack propagation characteristics under a coupling model, and relates to the field of blast hole position calculation and data processing. The method comprises the following steps: acquiring crustal stress data and rock mechanics data; coupling a stress field model by utilizing the explosion load, the crustal stress data and the rock mechanics data; acquiring blasting data under the stress of the infinitesimal point by utilizing the stress field model, wherein the blasting data comprises the radius of a crushing area and the radius of a fracture area of the rock; based on the blasting data, utilizing MATLAB to predict a crack propagation path under the stress of the infinitesimal point; and obtaining an optimized blast hole arrangement diagram by utilizing the crack propagation path. According to the scheme provided by the invention, the blasting effect can be predicted more accurately by accurately calculating, simulating and optimizing the blast hole arrangement diagram, so that unnecessary blast holes are reduced, and the efficiency of blasting operation is improved. The blast hole layout method based on the crack propagation characteristic can better control the damage range of the rock, the problem of excessive damage is avoided, and the stability of the rock around the tunnel is protected.

Description

Technical Field

[0001] The present application relates to the technical field of blasthole position calculation and data processing, and in particular to a blasthole layout method based on crack propagation characteristics under a coupling model. Background Art

[0002] The traditional drilling and blasting method arranges a large number of cut holes in the center of the tunnel excavation working face. Unreasonable arrangement of blasting holes may cause cracks in the rock around the tunnel, causing excessive damage to the mountain by blasting, causing extensive damage to the retained rock in the arch waist area, causing over-excavation, and seriously affecting the quality of blasting.

[0003] In order to improve the blasting efficiency and blasting quality, and effectively control the degree of rock damage, a scientific and efficient tunnel blasting hole layout method is proposed to solve the above problems. Summary of the invention

[0004] One purpose of the present application is to provide a blasthole layout method based on crack propagation characteristics under a coupled model to solve the problem of insufficient blasting quality of traditional drilling and blasting methods.

[0005] To achieve the above objectives, the present application provides a blasthole layout method based on crack propagation characteristics under a coupling model, comprising the following steps:

[0006] Step 1: Obtain geostress data and rock mechanics data;

[0007] Step 2: The stress field model is obtained by coupling the explosion load, ground stress data and rock mechanics data;

[0008] Step 3: Use the stress field model to obtain the blasting data under the micro-element point force, the blasting data includes the radius of the rock crushing zone and the radius of the fracture zone;

[0009] Step 4: Based on the blasting data, use MATLAB to predict the crack propagation path under the force of the micro-element point;

[0010] Step 5: Use the crack propagation path to obtain the optimized blasthole layout.

[0011] Furthermore, the geostress data include self-weight stress, tectonic stress and lateral pressure coefficient λ; the rock mechanics data include dynamic compressive strength σ of rock cd and the dynamic tensile strength of rock σ td .

[0012] Furthermore, the stress field model is expressed by the formula

[0013]

[0014] Radial stress in the coupled stress field; σ θis the tangential stress in the coupled stress field; τ rθ and τ θr are the shear stresses in the coupled stress field; σ v is the self-weight stress in the vertical direction; σ H is the horizontal deadweight stress; r0 is the radius of the blast hole; r is the distance from the calculation point to the explosion center; θ is the horizontal angle between any point in the rock and the center of the blast hole; P d is the uniform force of explosive on the blasting hole wall; α is the pressure attenuation coefficient; λ is the lateral pressure coefficient.

[0015] Furthermore, based on the Mohr-Coulomb failure criterion and stress field model, the radius of the crushing zone R is obtained. C The formula is:

[0016]

[0017] Among them, the pressure attenuation coefficient α is equal to 3, σ cd is the dynamic pressure strength of rock mass, A is the physical and mechanical performance parameter of rock;

[0018] According to the formula The radius of the crack area R T Solve, where σ td is the dynamic tensile strength of rock, m is the tensile strength enhancement coefficient of rock caused by ground stress; β is the characteristic failure parameter of rock.

[0019] Furthermore, the method of using MATLAB to predict the crack propagation path under the stress of the micro-element point includes the following steps:

[0020] Step 41: Create a MATLAB modeling environment using blasting data, ground stress data, and rock mechanics data;

[0021] Step 42: Import the initial blasthole layout into the modeling environment to create a geometric model;

[0022] Step 43: defining a crack extension criterion for the geometric model to obtain a crack expansion model;

[0023] Step 44: Use the crack growth model to simulate the crack growth process and obtain the predicted crack growth path.

[0024] Further, the step of defining the crack propagation criterion for the geometric model comprises the following steps:

[0025] Step 431: Experimentally determine the fracture toughness K of the rock IC ,

[0026] Step 432: Using the formula Calculation of stress intensity factor K I ,

[0027] Among them, σ is the far-field stress; a is the crack length; W is the width of the rock where the crack is located; is a geometric factor, which depends on the ratio of crack length to rock width;

[0028] Step 432: Compare stress intensity factors K I and fracture toughness K IC The size of the expansion result is obtained if K I >K IC , then the expansion result is that the crack will expand, otherwise, the expansion result is that the crack will not expand;

[0029] Step 433: define the crack propagation direction as the bisector direction of the angle between the direction of maximum shear stress and the direction of maximum energy release rate.

[0030] Furthermore, the method of simulating the crack propagation process using the crack growth model to obtain the predicted crack propagation path includes the following steps:

[0031] Step 441: Initializing the crack tip position according to the initial blasthole layout diagram;

[0032] Step 442: Divide the micro-points around the crack tip and calculate the stress intensity factor K of the micro-points I ;

[0033] Step 443: Compare the stress intensity factor K of the microelement point I and fracture toughness K IC The size of K I >K IC Then step 444 is executed, otherwise the crack stops expanding and a predicted crack expansion path is obtained;

[0034] Step 444: Use finite element analysis to track the development of the crack and update the crack tip position, and loop through steps 442 to 443 until the crack stops expanding, thereby obtaining a predicted crack expansion path.

[0035] Furthermore, the method of obtaining an optimized blasthole arrangement diagram using the crack propagation path includes the following steps:

[0036] Step 51: Setting the tunnel contour in the crack growth model;

[0037] Step 52: preparing a number of different initial blasthole layouts and simulating the crack propagation process using a crack propagation model;

[0038] Step 53: Select the initial blasthole arrangement diagram with a crushing zone radius that has a coincidence degree of greater than 90% with the tunnel contour and a shortest fracture zone radius as the optimized blasthole arrangement diagram.

[0039] Furthermore, the preparation of several different initial blasthole layouts comprises the following steps:

[0040] Step 521: Draw a basic blasthole layout diagram using a conventional design method;

[0041] Step 522: Set the blasthole spacing range and blasthole specifications, and control variables to generate several different initial blasthole layout diagrams based on the basic blasthole layout diagram.

[0042] Compared with the related art, the advantage of optimizing the blasthole layout diagram in the solution provided by the embodiment of the present application is that through precise calculation and simulation, the blasting effect can be predicted more accurately, thereby reducing unnecessary blastholes and improving the efficiency of blasting operations. The blasthole layout method based on crack propagation characteristics can better control the damage range of the rock, avoid the problem of excessive damage, and help protect the stability of the rock around the tunnel. The optimized blasthole layout can more effectively utilize the explosion energy and reduce the damage to the rocks retained outside the tunnel design outline, thereby improving the quality of tunnel construction. Scientific blasthole layout can reduce the risk of blasting caused by unreasonable layout and enhance the safety of tunnel construction.

[0043] In summary, the present invention can not only improve the blasting efficiency, but also effectively control rock destruction, reduce damage to retained rocks, and improve the quality and safety of blasting. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The present invention is an exemplary flow chart of the tunnel blasting hole layout method provided in the present application. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0046] like Figure 1 As shown in FIG. 1 , the blasthole arrangement method based on the crack propagation characteristics under the coupling model includes the following steps:

[0047] Step 1: Obtain geostress data and rock mechanics data;

[0048] Step 2: Couple the stress field model using blast load, ground stress data and rock mechanics data;

[0049] Step 3: Use the stress field model to obtain the blasting data under the micro-element point force, the blasting data includes the radius of the rock crushing zone and the radius of the fracture zone;

[0050] Step 4: Based on the blasting data, use MATLAB to predict the crack propagation path under the force of the micro-element point;

[0051] Step 5: Use the crack propagation path to obtain the optimized blasthole layout diagram.

[0052] The tunnel blasting blasthole layout method provided by the present invention optimizes the blasting process through scientific means to improve the blasting efficiency and quality. The whole process emphasizes the accurate prediction of the crack propagation path to guide the scientific layout of the blastholes, thereby reducing the consumption of explosives, improving the blasting efficiency, and effectively controlling the damage to the retained rock, ensuring the safety and efficiency of tunnel construction. Compared with the traditional drilling and blasting method, this method significantly improves the scientificity and accuracy of the blasting design, and provides strong technical support for tunnel construction.

[0053] Specifically, the geostress data include self-weight stress, tectonic stress and lateral pressure coefficient λ; among them, self-weight stress mainly depends on the density and burial depth of the rock, tectonic stress is the stress generated by geological tectonic movement, and the lateral pressure coefficient λ is the proportional relationship between lateral geostress and vertical geostress. All three can be obtained on-site through drilling measurement method.

[0054] Rock mechanics data include the dynamic compressive strength of rock σ cd and the dynamic tensile strength of rock σ td The dynamic compressive strength of rock is cd It is the ability of rock to resist compression failure under high-speed loading conditions, usually obtained by high-speed loading test using a split Hopkinson bar device; the dynamic tensile strength of rock σ td It is the ability of rock to resist tensile failure, obtained by the Brazilian splitting test or other specialized impact test methods.

[0055] Among them, the stress field model coupled in step 2 is expressed by the formula

[0056] It means that, where σ r is the radial stress in the coupled stress field; σ θ is the tangential stress in the coupled stress field; τ rθ and τ θr are the shear stresses in the coupled stress field; σ v is the self-weight stress in the vertical direction; σ H is the horizontal deadweight stress; r0 is the radius of the blast hole; r is the distance from the calculation point to the explosion center; θ is the horizontal angle between any point in the rock and the center of the blast hole; P dis the uniform force of explosive on the blasting hole wall; α is the pressure attenuation coefficient; λ is the lateral pressure coefficient.

[0057] The coupling of stress distribution expressions based on the coupling of blast load and ground stress is mainly based on the consideration that before tunnel excavation, the surrounding rock is already in a three-dimensional stress state due to the self-gravity stress of the overlying rock mass. Ground stress has an inhibitory effect on blast load, and the ground stress of the original rock and the dynamic stress field formed after the detonation of the explosive are superimposed on each other to form a secondary coupled stress field.

[0058] The specific coupling process is as follows:

[0059] Original geostress: Before tunnel excavation, the surrounding rock already has self-weight stress and tectonic stress. These stresses act on the rock to form an initial stress field.

[0060] Explosive load introduction: When the explosive explodes in the blast hole, extremely high pressure and temperature will be rapidly generated in the local area, forming a shock wave. The shock wave propagates outward, exerting strong compression and shearing effects on the surrounding rocks.

[0061] Stress superposition: The instantaneous stress field generated by the explosion is superimposed on the original ground stress field to form a new coupled stress field. In the coupled stress field, the original ground stress has a suppressive effect on the explosion load, affecting the rock fracture and energy transfer process.

[0062] Mathematical expression: The stress distribution expression is obtained based on the coupling effect of explosion load and ground stress.

[0063] Numerical simulation and experimental verification: The correctness and practicality of theoretical calculation results are verified through numerical simulation and field tests. These tests include static and dynamic tests to determine the critical crushing dissipation value of rock under different stress states.

[0064] Through the above process, a relatively accurate coupled stress field model can be obtained to guide the scientific layout of tunnel blasting holes and ensure that the energy transfer and rock fracture behavior during the blasting process are effectively controlled.

[0065] Based on the Mohr-Cou l omb failure criterion and stress field model, the radius R of the crushing zone is obtained. C The formula is:

[0066] Among them, the pressure attenuation coefficient α is equal to 3, σ cdis the dynamic pressure strength of rock mass, and A is the physical and mechanical performance parameter of rock; in blasting engineering, the selection of pressure attenuation coefficient α depends on the propagation characteristics of shock waves generated by blasting in rock. When α is selected to be equal to 3, it is usually because it is suitable for the pressure attenuation law in the shock wave zone. This selection makes the model simple and can well reflect the actual situation, which is convenient for engineering calculation and design.

[0067] According to the formula The radius of the crack area R T Solve, where σ td is the dynamic tensile strength of rock, m is the tensile strength enhancement coefficient of rock caused by ground stress; β is the characteristic failure parameter of rock.

[0068] Combining the two concepts of failure criterion and strain energy release rate can better understand and predict the fracture behavior of rock under explosive load. The critical conditions of rock fracture can be determined by the Mohr-Cou l omb failure criterion; the energy loss in the fracture process can be quantified by the strain energy release rate. The two together determine the scope and degree of rock fracture. In practical applications, these theories and formulas can help engineers design reasonable blasting schemes, such as determining the optimal blasting hole location, charge amount and detonation sequence. This scheme uses the charge amount and detonation sequence to control the variables to simulate the effect of blasting, so as to obtain the relationship between the blasthole location and the explosion effect. The advantage is that this method can scientifically predict and control the effect of blasting, improve blasting efficiency, and also ensure construction safety. The internal principle is based on the knowledge of rock mechanics and explosion physics. Through theoretical modeling and numerical simulation, the complex physical process is simplified into an easy-to-handle form for application in engineering practice.

[0069] The following steps are used to predict the crack propagation path under the load of micro-element points using MATLAB:

[0070] Step 41: Use blasting data, geostress data, and rock mechanics data to create a MATLAB modeling environment; at this stage, the blasting data, geostress data, and rock mechanics data acquired in the early stage need to be integrated. Use these data to build a digital model environment that can run in MATLAB and simulate real blasting scenarios. The creation of the modeling environment needs to consider factors such as rock material properties and geostress field distribution to ensure the authenticity of subsequent simulations.

[0071] Step 42: Import the initial blasthole layout into the modeling environment to create a geometric model; Import the initial blasthole layout into the constructed MATLAB modeling environment and convert it into a digital model. This process involves converting the two-dimensional or three-dimensional blasthole layout drawings into a geometric model so that the crack growth criteria can be applied in the next step. The geometric model should accurately reflect the location, depth, and direction of the blastholes, providing a basis for subsequent crack growth simulation.

[0072] Step 43: Define the crack propagation criterion for the geometric model to obtain the crack propagation model; This step is critical because it involves how to define how cracks propagate in rocks. The crack propagation criterion is usually based on the maximum shear stress theory or the energy release rate theory. In this method, the direction of the angle bisector between the maximum shear stress direction and the maximum energy release rate direction is defined as the crack propagation direction. Such a definition ensures that the crack propagation path is consistent with the internal stress distribution of the rock during the actual blasting process. By establishing a crack propagation model, the crack propagation criterion can be applied to a specific geometric model.

[0073] Step 44: Use the crack growth model to simulate the crack growth process and obtain the predicted crack growth path; The last step is to simulate the crack growth process based on the crack growth model. This step uses finite element analysis to track the development of the crack and update the crack tip position until the crack stops growing. After multiple iterations of simulation, the predicted crack growth path is finally obtained. This process can not only show how cracks propagate in the rock, but also help determine the optimal blasthole layout to achieve the best blasting effect.

[0074] Defining the crack growth criterion for a geometry model involves the following steps:

[0075] Step 431: Experimentally determine the fracture toughness K of the rock IC In this step, fracture toughness refers to the ability of rock to resist crack propagation, which reflects the ability of rock to resist fracture under external force. Experiments can determine K by loading the specimen and measuring the force required when it fractures. IC This step is crucial for the subsequent crack growth prediction because it is the key threshold for determining whether the crack will grow.

[0076] Step 432: Using the formula Calculation of stress intensity factor K I , where σ is the far-field stress; a is the crack length; W is the rock width where the crack is located; is a geometric factor, which depends on the ratio of crack length to rock width; the stress intensity factor takes into account the influence of crack shape, making the calculation result more consistent with the actual situation. I >K IC, it means that the crack may continue to expand; otherwise, the crack may not expand.

[0077] Step 432: Compare stress intensity factors K I and fracture toughness K IC The size of the expansion result is obtained if K I >K IC , the expansion result is that the crack will expand, otherwise, the expansion result is that the crack will not expand; this comparison provides a criterion for judging whether the crack expands or not, which helps to decide when to take measures to prevent crack expansion or promote crack expansion.

[0078] Step 433: Define the crack propagation direction along the bisector of the angle between the maximum shear stress direction and the maximum energy release rate direction; This step is to define the crack propagation direction. The crack propagates along the bisector of the angle between the maximum shear stress direction and the maximum energy release rate direction. This means that the crack propagation follows the principle of minimum resistance, that is, it develops in the direction that is easiest to propagate. This step ensures the accuracy of the crack propagation path and is also convenient for subsequent blasting design.

[0079] Using the crack growth model to simulate the crack growth process and obtain the predicted crack growth path includes the following steps:

[0080] Step 441: Initialize the crack tip position according to the initial blasthole layout diagram; determine the crack starting position, i.e. the initial position of the crack tip, according to the initial blasthole layout diagram. This step is the basis of the simulation and ensures that the starting point of the crack extension is accurate.

[0081] Step 442: Divide the micro-points around the crack tip and calculate the stress intensity factor K of the micro-points I ; The stress intensity factor is a key parameter used to measure the degree of stress concentration at the crack tip, and its size directly affects whether the crack will continue to expand.

[0082] Step 443: Compare the stress intensity factor K of the microelement point I and fracture toughness K IC The size of K I >K IC Then execute step 444, otherwise the crack stops expanding and the predicted crack expansion path is obtained; in this way, it can be determined whether the crack will continue to develop forward and verify whether the simulated crack terminal is the real terminal. If not, continue to expand the crack until the crack terminal is found.

[0083] Step 444: Use finite element analysis to track the development of the crack, update the crack tip position, and loop through steps 442 to 443 until the crack stops expanding, and obtain a predicted crack expansion path; by using finite element analysis to track the development of the crack, a complete crack expansion path can be obtained.

[0084] The process of obtaining the optimized blasthole layout using the crack propagation path includes the following steps:

[0085] Step 51: Set the tunnel contour in the crack growth model; This step requires the tunnel design contour to be clearly defined in the crack growth model. This involves determining the size, shape, and expected boundaries of the tunnel. The design contour is set to ensure that all subsequent blasthole arrangements and crack growth simulations are carried out around this design goal, thereby ensuring that the final blasting effect meets engineering requirements.

[0086] Step 52: Prepare several different initial blasthole layouts and use the crack growth model to simulate the crack growth process; at this stage, it is necessary to prepare a variety of different blasthole layout schemes. These layout schemes are usually based on certain experience and design rules, taking into account parameters such as blasthole spacing, depth, angle, etc. Each layout scheme will be imported into the crack growth model for simulation to observe its crack growth under specific conditions. By comparing the performance of different schemes, those designs that better meet the expected results can be selected.

[0087] Step 53: Select the initial blasthole arrangement diagram with a crushing zone radius that coincides with the tunnel contour line greater than 90% and a shortest fracture zone radius as the optimized blasthole arrangement diagram; finally, by comparing the simulation results of various arrangement schemes, select those arrangements with a crushing zone radius that coincides with the tunnel contour line greater than 90% and a shortest fracture zone radius as the optimized scheme. The coincidence here refers to the degree of matching between the crushing zone formed after the actual blasting and the design contour line, and the shortest fracture zone radius means that while achieving the expected blasting effect, the additional damage to the surrounding rocks is minimized.

[0088] The preparation of several different initial blasthole layouts includes the following steps:

[0089] Step 521: Draw a basic blasthole layout diagram using conventional design methods: First, draw a basic blasthole layout diagram based on past experience and actual requirements of tunnel engineering. This basic diagram will include key parameters such as the initial set blasthole location, quantity, spacing, depth and angle.

[0090] Step 522: Set the blasthole spacing range and blasthole specifications, and control the variables to generate several different initial blasthole layouts based on the basic blasthole layout diagram. In order to explore more possibilities, it is necessary to adjust the basic blasthole layout diagram and generate multiple versions of the layout diagram. Specifically, blasthole spacing range: set a reasonable blasthole spacing range based on the rock properties and the expected blasting effect. For example, from the minimum spacing to the maximum spacing, a new set of blasthole layout diagrams is generated at a certain increment; or the blastholes on both sides are equidistantly moved outward along the central axis of the blasthole arrangement. In this way, the effect of the blasthole arrangement spacing on the blasting effect can be tested.

[0091] Through the above steps, multiple different initial blasthole layouts can be generated. Each layout is obtained by changing the basic blasthole layout. This method can not only help us find the optimal blasthole layout, but also provide diverse inputs for subsequent crack propagation simulations, and then evaluate the impact of different design schemes on blasting effects. Finally, the layouts that can achieve the expected blasting effect and cause the least damage to the surrounding rocks are selected as the optimal solutions.

[0092] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily mention changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims, and the above embodiments should be regarded as exemplary and non-restrictive.

Claims

1. A blasthole layout method based on crack propagation characteristics under a coupling model, characterized in that: The following steps are involved: Step 1: Obtain geostress data and rock mechanics data; Step 2: The stress field model is obtained by coupling the explosion load, ground stress data and rock mechanics data; Step 3: Use the stress field model to obtain the blasting data under the micro-element point force, the blasting data includes the radius of the rock crushing zone and the radius of the fracture zone; Step 4: Based on the blasting data, use MATLAB to predict the crack propagation path under the force of the micro-element point; Step 5: Use the crack propagation path to obtain the optimized blasthole layout.

2. The method for blasthole layout based on crack propagation characteristics under a coupling model according to claim 1 is characterized in that: The geostress data include self-weight stress, tectonic stress and lateral pressure coefficient λ; the rock mechanics data include dynamic compressive strength σ of rock cd and the dynamic tensile strength of rock σ td .

3. The method for blasthole arrangement based on crack propagation characteristics under a coupling model according to claim 2 is characterized in that: The stress field model is expressed by It means that, where σ r is the radial stress in the coupled stress field; σ θ is the tangential stress in the coupled stress field; τ rθ and τ θr are the shear stresses in the coupled stress field; σ v is the self-weight stress in the vertical direction; σ H is the horizontal deadweight stress; r0 is the radius of the blast hole; r is the distance from the calculation point to the explosion center; θ is the horizontal angle between any point in the rock and the center of the blast hole; P d is the uniform force of explosive on the blasting hole wall; α is the pressure attenuation coefficient; λ is the lateral pressure coefficient.

4. The method for blasthole layout based on crack propagation characteristics under a coupling model according to claim 3 is characterized in that: Based on the Mohr-Coulomb failure criterion and stress field model, the radius R of the crushing zone is obtained. C The formula is: Among them, the pressure attenuation coefficient α is equal to 3, σ cd is the dynamic pressure strength of rock mass, A is the physical and mechanical performance parameter of rock; According to the formula The radius of the crack area R T Solve, where σ td is the dynamic tensile strength of rock, m is the tensile strength enhancement coefficient of rock caused by ground stress; β is the characteristic failure parameter of rock.

5. The method for blasthole arrangement based on crack propagation characteristics under a coupling model according to claim 4 is characterized in that: The method of using MATLAB to predict the crack propagation path under the stress of the micro-element point includes the following steps: Step 41: Create a MATLAB modeling environment using blasting data, ground stress data, and rock mechanics data; Step 42: Import the initial blasthole layout into the modeling environment to create a geometric model; Step 43: defining a crack extension criterion for the geometric model to obtain a crack expansion model; Step 44: Use the crack growth model to simulate the crack growth process and obtain the predicted crack growth path.

6. The method for blasthole layout based on crack propagation characteristics under a coupling model according to claim 5 is characterized in that: Defining a crack growth criterion for a geometric model comprises the following steps: Step 431: Experimentally determine the fracture toughness K of the rock IC , Step 432: Using the formula Calculation of stress intensity factor K I , Among them, σ is the far-field stress; a is the crack length; W is the width of the rock where the crack is located; is a geometric factor, which depends on the ratio of crack length to rock width; Step 432: Compare stress intensity factors K I and fracture toughness K IC The size of the expansion result is obtained if K I >K IC , then the expansion result is that the crack will expand, otherwise, the expansion result is that the crack will not expand; Step 433: define the crack propagation direction as the bisector direction of the angle between the direction of maximum shear stress and the direction of maximum energy release rate.

7. The method for blasthole layout based on crack propagation characteristics under a coupling model according to claim 6, characterized in that: The method of simulating the crack propagation process using the crack propagation model to obtain a predicted crack propagation path comprises the following steps: Step 441: Initializing the crack tip position according to the initial blasthole layout diagram; Step 442: Divide the micro-points around the crack tip and calculate the stress intensity factor K of the micro-points I ; Step 443: Compare the stress intensity factor K of the microelement point I and fracture toughness K IC The size of K I >K IC Then step 444 is executed, otherwise the crack stops expanding and a predicted crack expansion path is obtained; Step 444: Use finite element analysis to track the development of the crack and update the crack tip position, and loop through steps 442 to 443 until the crack stops expanding, thereby obtaining a predicted crack expansion path.

8. The method for blasthole layout based on crack propagation characteristics under a coupling model according to claim 7 is characterized in that: The method of obtaining an optimized blasthole arrangement diagram using the crack propagation path comprises the following steps: Step 51: Setting the tunnel contour in the crack growth model; Step 52: preparing a number of different initial blasthole layouts and simulating the crack propagation process using a crack propagation model; Step 53: Select the initial blasthole arrangement diagram with a crushing zone radius that has a coincidence degree of greater than 90% with the tunnel contour and a shortest fracture zone radius as the optimized blasthole arrangement diagram.

9. The method for blasthole layout based on crack propagation characteristics under a coupling model according to claim 8, characterized in that: The preparation of several different initial blasthole layouts comprises the following steps: Step 521: Draw a basic blasthole layout diagram using a conventional design method; Step 522: Set the blasthole spacing range and blasthole specifications, and control variables to generate several different initial blasthole layout diagrams based on the basic blasthole layout diagram.

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