An underground coal mine hydraulic cavity forming process simulation optimization method and system

Abstract

The application provides a coal mine underground hydraulic cavity forming process simulation optimization method and system, obtains target coal seam parameters, establishes a three-dimensional coal seam structure, performs model particle filling, and forms a coal numerical model; sets cavity forming parameters, establishes a model three-dimensional structure of the cavity forming system, generates abrasive particles and liquid particles according to a ratio, and sets boundary conditions; performs parameter calibration and balances the model among the particles of coal, water and abrasive; performs numerical simulation calculation of a hydraulic cavity forming process coupled with a discrete element method and computational fluid dynamics, simulates a hydraulic cavity forming operation process, and records the distribution of local stress, density and porosity in a target cavity forming area in the simulation process; according to multiple numerical simulation calculation results under different cavity forming parameters, the response relationship of pressure relief and permeability improvement effects to each hydraulic cavity forming parameter is analyzed, based on the analysis results, an optimization scheme of the hydraulic cavity forming parameters is determined, and a final hydraulic cavity forming process scheme is obtained. The application improves the accuracy and applicability of simulation.

Description

Technical Field

[0001] This invention belongs to the field of pressure relief and permeability enhancement technology for gas-bearing coal seams in underground coal mines, and relates to a simulation and optimization method and system for hydraulic cavity creation process in underground coal mines. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] With the gradual depletion of shallow-buried coal resources, many mines have now entered the deep mining stage. Deep mining is often accompanied by complex environments such as high ground stress, high geothermal radiation, high gas emission, and low coal seam permeability. In particular, in high-gas mines, the risk of gas accidents such as coal and gas outbursts and gas explosions poses a serious threat to mine safety.

[0004] Gas drainage is one of the most effective methods for controlling gas accidents in mines. Hydraulic cavity drilling, as a hydraulic coal seam decompression and permeability enhancement method based on gas drainage boreholes, can not only increase the permeability of coal seams and promote gas desorption, but also locally decompress the coal body and promote the development and connection of internal fractures in the coal body around the gas drainage borehole, thereby achieving more efficient gas drainage.

[0005] Currently, hydraulic cavity creation has been widely applied as a safe and effective pressure relief and permeability enhancement method in the gas control of high-gas and low-permeability coal seams. However, due to the lack of transparency of the coal body, it is impossible to accurately and intuitively judge the pressure relief and permeability enhancement effect of the current cavity creation operation in actual operation. The cavity creation parameters can only be adjusted by relying on indirect parameters such as coal output and the work experience of the operators. This often results in unsatisfactory cavity creation effects such as cross-holes and inadequate pressure relief, which cannot meet the requirements of efficient cavity creation in coal seams under complex occurrence environments. There is also a lack of theoretical guidance on the cavity creation process. Numerical simulation has the advantages of low cost, easy control, and high visualization, and has been widely used in the study of underground engineering problems. Existing hydraulic cavity creation simulations are mostly based on the FEM-CFD method, which ignores important parameters such as coal mass loss and fracture development caused by hydraulic impact. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a simulation and optimization method and system for hydraulic cavity creation technology in coal mines. This invention can overcome the shortcomings of existing numerical simulation methods for hydraulic cavity creation in characterizing parameters such as coal mass loss, abrasive particle impact, and fracture development.

[0007] According to some embodiments, the present invention adopts the following technical solution:

[0008] A simulation and optimization method for hydraulic cavity creation technology in coal mines includes the following steps:

[0009] Obtain the target coal seam parameters, establish a three-dimensional coal seam structure, fill the model with particles, and form a numerical model of the coal seam.

[0010] Set the cavity-forming parameters according to the actual cavity-forming scheme, establish the three-dimensional structure of the cavity-forming system model, generate abrasive particles and liquid particles according to the ratio, and set the boundary conditions.

[0011] The parameters of coal, water, and abrasive particles were calibrated and the model was balanced.

[0012] Numerical simulation of the hydraulic cavity-building process coupled with discrete element method and computational fluid dynamics is performed to simulate the hydraulic cavity-building operation process and record the distribution of local stress, density and porosity in the target cavity-building area during the simulation.

[0013] Based on the results of multiple numerical simulations under different cavity-forming parameters, the response relationship between the pressure relief and permeability enhancement effect and each hydraulic cavity-forming parameter was analyzed. Based on the analysis results, the optimization scheme of the hydraulic cavity-forming parameters was determined, and the final hydraulic cavity-forming process scheme was obtained.

[0014] As an alternative implementation method, the specific process of obtaining target coal seam parameters includes obtaining coal samples from the target cavity-forming area, conducting physical experiments, and obtaining the sample's gangue content, compressive strength, shear strength, porosity, density, and bedding distribution.

[0015] The distribution of borehole periphery fractures was obtained using a scanning method, and their length, location, and direction were statistically analyzed.

[0016] As an alternative implementation method, the specific process of establishing a three-dimensional coal seam structure and filling the model with particles includes establishing a three-dimensional model based on the coal seam structure of the target area, and setting the density, particle size range, grouping and porosity parameters of the particles based on physical experimental results, and filling the model with particles.

[0017] As an alternative implementation method, the specific process of forming a coal seam numerical model includes adding bedding and joint information to the coal seam model based on the distribution of structural surface information obtained by scanning or electron microscopy, adding fracture distribution information to the coal seam model based on the fracture distribution, and completing the establishment of the coal seam numerical model.

[0018] As an alternative implementation method, in the specific process of setting the cavity-making parameters according to the actual cavity-making scheme and establishing the three-dimensional structure of the cavity-making system model, the hydraulic cavity-making model parameters are set, including: water pressure, abrasive group distribution ratio, abrasive properties, axial retraction speed, circumferential rotation speed, cavity-making length, cavity-making spacing, water-abrasive ratio and nozzle structure. After the parameters are set, the particle parameters are set and the boundary conditions are set.

[0019] As an alternative implementation method, the specific process for calibrating the parameters between coal, water, and abrasive particles includes:

[0020] A non-adhesive model was used between solid particles. Based on the dynamic and static angles of repose obtained from the material dropping experiment and the roller experiment, the static friction coefficient and rolling friction coefficient between particles were macroscopically calibrated.

[0021] Based on the elastic modulus, Poisson's ratio, friction coefficient, compressive strength, and tensile strength obtained from physical experiments, the elastic modulus, normal stiffness, tangential stiffness, normal bond strength, and tangential bond strength of parallel bonded bonds were calibrated using a trial-and-error method. This ensured that after the microscopic parameters of the model were calibrated, its macroscopic parameters remained consistent with the results of physical experiments.

[0022] As an alternative implementation method, the specific process of performing numerical simulation calculations of the hydraulic cavity-building process coupled with discrete element method and computational fluid dynamics includes:

[0023] A fluid domain is generated in the nozzle and liquid transport pipeline of the hydraulic cavity-forming system. The computational domain of the fluid is determined based on its distribution range. The fluid parameters in the computational domain are set according to the process characteristics of hydraulic cavity-forming. The direction and velocity of the ejected particles from the nozzle of the hydraulic cavity-forming system under the action of this flow field are calculated.

[0024] Based on the velocity and direction of the ejected particles, the changes in various physical and mechanical parameters of coal seam particles under the action of ejected particles are calculated.

[0025] Perform traversal and statistical analysis of particle location information and bonding information;

[0026] Place monitoring balls at key locations to monitor the surface properties of various parameters of particles in that area. Repeat the above steps until the cavity is created.

[0027] As an optional implementation method, the specific process of recording the distribution of local stress, density, and porosity within the target cavity area during the simulation includes:

[0028] Set the unit analysis window according to the analysis requirements, that is, set the size of the unit window space. Divide the calculation domain with the unit analysis window and calculate the stress, density and porosity in each unit analysis window respectively.

[0029] As an alternative implementation method, the parameters obtained from the simulation are analyzed using a multi-information fusion analysis method to characterize the pressure relief and cavity-forming effect of hydraulic cavity formation.

[0030] A simulation and optimization system for hydraulic cavity creation technology in coal mines includes:

[0031] The numerical model building module is configured to acquire target coal seam parameters, establish a three-dimensional coal seam structure, fill model particles, and form a coal seam numerical model.

[0032] The 3D model building module is configured to set the cavity-making parameters according to the actual cavity-making scheme, establish the 3D structure of the cavity-making system model, generate abrasive particles and liquid particles according to the ratio, and set boundary conditions.

[0033] The parameter calibration module is configured to calibrate the parameters between coal, water, and abrasive particles and balance the model.

[0034] The simulation module is configured to perform numerical simulation of the hydraulic cavity-building process coupled with discrete element method and computational fluid dynamics, simulate the hydraulic cavity-building operation process, and record the distribution of local stress, density and porosity in the target cavity-building area during the simulation.

[0035] The optimization module is configured to analyze the response relationship between the pressure relief and permeability enhancement effect and each hydraulic cavity-forming parameter based on the results of multiple numerical simulations under different cavity-forming parameters. Based on the analysis results, the optimization scheme of the hydraulic cavity-forming parameters is determined, and the final hydraulic cavity-forming process scheme is obtained.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] 1. This invention acquires the parameters of the target coal seam through various methods such as physical experiments and field experiments, establishes a three-dimensional coal seam structure based on geological exploration results, fills it with particles, and constructs structural surfaces of different scales based on coal seam information such as bedding and fractures, thereby achieving higher precision coal seam reconstruction in the pre-cavitation area.

[0038] 2. This invention achieves high-precision characterization of the liquid in a hydraulic cavity-forming system by using small-sized particles to simulate the liquid. It also achieves simultaneous characterization of water and abrasive by generating abrasive and water particles according to a specific ratio. Furthermore, it accurately simulates the interaction process between water particles, abrasive particles, and coal particles through DEM-CFD coupled simulation. By analyzing the interactions between different types of particles, the hydraulic cavity-forming process can be accurately simulated and analyzed, obtaining information such as particle collisions and rebounds. The acquisition and analysis of these parameters cannot be achieved by traditional FEM-CFD simulation methods.

[0039] 3. By monitoring and recording the changes in parameters such as local stress, density, and porosity of the coal seam during the simulation process, and by combining multi-information fusion analysis methods, a high-precision characterization of the pressure relief and permeability enhancement effect of hydraulic cavity creation is achieved. The above parameters are all calculated based on the parameters of the coal seam after cavity creation, which has higher accuracy than traditional equivalent parameter analysis. Attached Figure Description

[0040] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0041] Figure 1 This is a flowchart of the hydraulic cavity-building DEM-CFD simulation calculation of the present invention.

[0042] Figure 2 This is a schematic diagram of the optimized process of hydraulic cavity creation according to the present invention. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0044] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0045] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0046] Example 1

[0047] In one or more embodiments, a simulation and optimization method for hydraulic cavity creation technology in coal mines coupled with DEM-CFD is disclosed, which specifically includes the following steps:

[0048] Step 1: Obtain relevant parameters of the target cavity-forming coal seam based on methods such as physical experiments, field experiments, and geological data surveys, and model the coal seam.

[0049] Specifically, it includes the following processes:

[0050] Step 1.1: Obtain coal samples from the target cavity-forming area and conduct physical experiments such as industrial analysis, tensile-compressive-shear tests, and CT scans to obtain parameters such as gangue content, compressive strength, shear strength, porosity, density, and bedding distribution. Using borehole television and other scanning methods, obtain the distribution of borehole periphery fractures and statistically analyze their length, location, and direction.

[0051] Step 1.2: In this model, DEM establishes a three-dimensional model based on the coal seam structure of the target area, and imports the model into PFC software based on the physical experiment results, sets particle (group) parameters (density, particle size range, grouping, porosity, etc.), and fills the model with particles.

[0052] Step 1.3: Based on the distribution of structural surface information obtained from experiments such as CT scans and electron microscopy, add bedding and joint information to the coal seam model. Based on the fracture distribution obtained from methods such as borehole television, add fracture distribution information to the coal seam model to complete the establishment of the coal seam numerical model.

[0053] The coal seam model is mainly composed of particle and structural surface information. Its modeling process includes: establishing a three-dimensional coal seam structure based on coal seam geological information; generating particles in the model based on the microscopic physical parameters of coal samples obtained from physical experiments; and constructing structural surfaces in the model based on structural surface information of different scales such as joints, bedding, and fractures.

[0054] Step 2: Based on the hydraulic cavity-forming design scheme, establish a 3D model and import it into PFC software. Set the parameters of the hydraulic cavity-forming model, including: water pressure, abrasive group distribution ratio, abrasive properties, axial retraction speed, circumferential rotation speed, cavity length, cavity spacing, water-abrasive ratio, nozzle structure, etc. After setting the parameters, set the particle (group) parameters (density, particle size range, grouping, ratio, etc.), fill the model with particles, and set boundary conditions.

[0055] Numerical modeling of the hydraulic cavity-forming system includes: establishing a three-dimensional numerical model structure based on the structure of the hydraulic cavity-forming system; generating abrasive particles according to the proportions of each abrasive component; and generating liquid (particles) according to the water-abrasive ratio.

[0056] The liquid is characterized by small particles with a particle size much smaller than that of abrasive particles; the liquid particles have surface tension after agglomeration, and the surface tension is characterized by the viscous bonding between the outer surface particles.

[0057] Step 3: Based on the macroscopic parameters obtained from indoor experiments, and combined with relevant existing data from the field, parameter calibration is performed between particle types such as liquid particles-abrasive particles, liquid particles-wall, liquid particles-coal particles, coal particles-abrasive particles, and coal particles-wall.

[0058] Specifically, including:

[0059] Step 3.1: Calibration of Unbonded Solid Particle Parameters. An unbonded model is used for the solid particles, meaning the adhesive effects between abrasive and coal seam particles are not considered. Macroscopic and microscopic parameters are calibrated. The static friction coefficient μ between particles is macroscopically calibrated based on the dynamic and static angles of repose α and β obtained from the drop test and drum test. s and rolling friction coefficient μ r .

[0060] Step 3.2: Parallel bond parameter calibration.

[0061] Based on the elastic modulus E, Poisson's ratio v, coefficient of friction c, and compressive strength σ obtained from the physical experiment in step 1 tTensile strength σ l The elastic modulus E of the parallel bond was determined using a trial-and-error method, taking parameters such as [parameter 1] and [parameter 2]. c Normal stiffness k n Tangential stiffness k s Normal bond strength σ c Tangential bond strength τ c This ensures that the macroscopic parameters of the model remain consistent with the experimental results after the microscopic parameters are calibrated. After parameter calibration, the coal seam model is rebalanced.

[0062] Step 4: Record the distribution of particles, the distribution of bonding bonds, and the stress conditions in the current model, and then place test balls.

[0063] Step 5: Perform DEM-CFD coupled simulation numerical calculations for the hydraulic cavity-forming process in coal mines, and statistically analyze the particle location information, stress, porosity, and other parameters for each step, as well as the bonding parameters for each step, until the predetermined cavity-forming steps are completed.

[0064] Specifically, the following steps are included:

[0065] Step 5.1: Generate and calculate the fluid domain.

[0066] The fluid is mainly used to drive the small balls in the cavity-making system. The fluid domain is mainly distributed in the nozzles and liquid transport pipes of the hydraulic cavity-making system. The computational domain of the fluid is determined based on its distribution range, and the fluid parameters in the computational domain are set according to the process characteristics of hydraulic cavity making. The direction, velocity and other parameters of the ejected particles from the nozzles of the hydraulic cavity-making system under the action of this flow field are calculated.

[0067] Step 5.2: Solid domain calculation.

[0068] Assign the velocity and direction of the ejected particles obtained in step 5.1 to the discrete element module to calculate the changes in various physical and mechanical parameters of the coal seam particles under the action of the ejected particles.

[0069] Step 5.3: Traverse and statistically analyze particle location information and bonding bond information;

[0070] Using the traversal command in PFC, we can collect the position information of all particles in the computational domain at that time, and at the same time, we can collect the information of all bonding bonds.

[0071] Step 5.4: Place monitoring balls at important locations to monitor the surface properties of various parameters of particles in that area.

[0072] Step 5.5: Repeat steps 5.1-5.4 until the predetermined hole-making steps are completed.

[0073] In the cavity-forming system, the particles are driven by the flow field in the CFD model. Both liquid particles and abrasive particles are driven by the flow field. After the particles are ejected from the nozzle, they are no longer affected by the flow field.

[0074] There are bonding bonds between a large number of particles that make up the coal seam structure. During the simulation, some coal particles are impacted by liquid particles and abrasive particles, causing the bonding bonds to break and detach from the coal seam structure. This causes changes in parameters such as local strength, stress, density, and porosity of the coal seam. The corresponding parameters can be statistically calculated based on the changes in the number of particles and bonding bonds.

[0075] Step 6: Obtain the particle parameter values ​​at different time steps through the coupled calculation process, set the unit analysis window according to the analysis requirements, that is, set the size of the unit window space, divide the calculation domain with the unit analysis window, and calculate the parameters such as stress, density, and porosity in each unit analysis window respectively. The calculation method is shown in the following formula.

[0076] σ v = f(σ1,σ2,…,σ n )

[0077] ρ v =f(m1,m2,…,m n ,V) (1)

[0078] ε v =f(v1,v2,…v n ,V)

[0079] In the formula σ v ρ v ε v σ represents stress, density, and porosity per unit analysis window, respectively. n Let m be the stress parameter for the connecting key n. n Let v be the mass of the nth particle. n Let V be the volume of the nth particle, and V be the volume of the unit analysis window.

[0080] Step 7: Based on Step 6, by recording the distribution of local stress, density, porosity, and other parameters within the target cavity-forming area during the simulation process, different weights are set, and a multi-information fusion analysis method is used to analyze the simulated parameters to characterize the pressure relief cavity-forming effect of hydraulic cavity formation. The numerical relationship is shown in Equation 2.

[0081] S=f(σ v ,ρ v ,ε v (2)

[0082] Step 8: Based on the results of multiple numerical simulations under different cavity-forming parameters, analyze the response relationship between the pressure relief and permeability enhancement effect and each hydraulic cavity-forming parameter. Based on the analysis results, propose an optimization scheme for the hydraulic cavity-forming parameters, and optimize the model through numerical calculation analysis to finally obtain an optimized hydraulic cavity-forming process scheme that is suitable for actual operating conditions.

[0083] Example 2

[0084] A simulation and optimization system for hydraulic cavity creation technology in coal mines includes:

[0085] The numerical model building module is configured to acquire target coal seam parameters, establish a three-dimensional coal seam structure, fill model particles, and form a coal seam numerical model.

[0086] The 3D model building module is configured to set the cavity-making parameters according to the actual cavity-making scheme, establish the 3D structure of the cavity-making system model, generate abrasive particles and liquid particles according to the ratio, and set boundary conditions.

[0087] The parameter calibration module is configured to calibrate the parameters between coal, water, and abrasive particles and balance the model.

[0088] The simulation module is configured to perform numerical simulation of the hydraulic cavity-building process coupled with discrete element method and computational fluid dynamics, simulate the hydraulic cavity-building operation process, and record the distribution of local stress, density and porosity in the target cavity-building area during the simulation.

[0089] The optimization module is configured to analyze the response relationship between the pressure relief and permeability enhancement effect and each hydraulic cavity-forming parameter based on the results of multiple numerical simulations under different cavity-forming parameters. Based on the analysis results, the optimization scheme of the hydraulic cavity-forming parameters is determined, and the final hydraulic cavity-forming process scheme is obtained.

[0090] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A simulation and optimization method for hydraulic cavity creation technology in coal mines, characterized in that, Includes the following steps: Obtain the target coal seam parameters, establish a three-dimensional coal seam structure, fill the model with particles, and form a numerical model of the coal seam. Set the cavity-forming parameters according to the actual cavity-forming scheme, establish the three-dimensional structure of the cavity-forming system model, generate abrasive particles and liquid particles according to the ratio, and set the boundary conditions. The parameters of coal, water, and abrasive particles were calibrated and the model was balanced. Numerical simulations of the hydraulic cavity-building process, which are coupled with discrete element method and computational fluid dynamics, are performed to simulate the hydraulic cavity-building operation and record the distribution of local stress, density and porosity in the target cavity-building area during the simulation. Based on the results of multiple numerical simulations under different cavity-forming parameters, the response relationship between the pressure relief and permeability enhancement effect and each hydraulic cavity-forming parameter was analyzed. Based on the analysis results, the optimization scheme of the hydraulic cavity-forming parameters was determined, and the final hydraulic cavity-forming process scheme was obtained. The specific process for calibrating the parameters between coal, water, and abrasive particles includes: The solid particles are modeled without adhesion, and the adhesion between abrasive and coal seam particles is not considered. Macroscopic and microscopic parameters are calibrated. Based on the dynamic and static angles of repose obtained from the material drop test and the roller test, the static friction coefficient and rolling friction coefficient between particles are macroscopically calibrated. Based on the elastic modulus, Poisson's ratio, friction coefficient, compressive strength, and tensile strength obtained from physical experiments, the elastic modulus, normal stiffness, tangential stiffness, normal bond strength, and tangential bond strength of the parallel bond were calibrated using a trial-and-error method, so that after the microscopic parameters of the model were calibrated, its macroscopic parameters were still consistent with the results of physical experiments. The specific process of numerical simulation of the hydraulic cavity-building process coupled with discrete element method and computational fluid dynamics includes: A fluid domain is generated in the nozzle and liquid transport pipeline of the hydraulic cavity-forming system. The computational domain of the fluid is determined based on its distribution range. The fluid parameters in the computational domain are set according to the process characteristics of hydraulic cavity-forming. The direction and velocity of the ejected particles from the nozzle of the hydraulic cavity-forming system are calculated under the action of this flow field. Based on the velocity and direction of the ejected particles, the changes in various physical and mechanical parameters of coal seam particles under the action of ejected particles are calculated. Perform traversal and statistical analysis of particle location information and bonding information; Place monitoring balls at key locations to monitor the surface properties of various parameters of particles in that area. Repeat the above steps until the cavity is created.

2. The method for simulating and optimizing hydraulic cavity-forming technology in coal mines as described in claim 1, characterized in that, The specific process of obtaining target coal seam parameters includes obtaining coal samples from the target cavity-forming area, conducting physical experiments, and obtaining the sample's gangue content, compressive strength, shear strength, porosity, density, and bedding distribution. The distribution of borehole periphery fractures was obtained using a scanning method, and their length, location, and direction were statistically analyzed.

3. The simulation and optimization method for hydraulic cavity creation technology in coal mines as described in claim 1 or 2, characterized in that, The specific process of establishing a three-dimensional coal seam structure and filling the model with particles includes establishing a three-dimensional model based on the coal seam structure of the target area, and setting the density, particle size range, grouping and porosity parameters of the particles based on physical experimental results, and filling the model with particles.

4. The simulation and optimization method for hydraulic cavity creation technology in coal mines as described in claim 1 or 2, characterized in that, The specific process of forming a coal seam numerical model includes adding bedding and joint information to the coal seam model based on the distribution of structural surface information obtained by scanning or electron microscopy, adding fracture distribution information to the coal seam model based on the fracture distribution, and completing the establishment of the coal seam numerical model.

5. The simulation and optimization method for hydraulic cavity creation technology in coal mines as described in claim 1, characterized in that, In the specific process of setting the cavity-making parameters according to the actual cavity-making scheme and establishing the three-dimensional structure of the cavity-making system model, the hydraulic cavity-making model parameters are set, including: water pressure, abrasive group distribution ratio, abrasive properties, axial retraction speed, circumferential rotation speed, cavity-making length, cavity-making spacing, water-abrasive ratio and nozzle structure. After the parameters are set, the particle parameters are set and the boundary conditions are set.

6. The simulation and optimization method for hydraulic cavity creation technology in coal mines as described in claim 1, characterized in that, The specific process of recording the distribution of local stress, density, and porosity within the target cavity-forming area during the simulation includes: Set the unit analysis window according to the analysis requirements, that is, set the size of the unit window space. Divide the calculation domain with the unit analysis window and calculate the stress, density and porosity in each unit analysis window respectively.

7. The simulation and optimization method for hydraulic cavity creation technology in coal mines as described in claim 1, characterized in that, The parameters obtained from the simulation were analyzed using a multi-information fusion analysis method to characterize the pressure relief and cavity-forming effect of hydraulic cavity formation.

8. A simulation and optimization system for hydraulic cavity creation technology in coal mines, using the method described in claim 1, characterized in that it comprises: The numerical model building module is configured to acquire target coal seam parameters, establish a three-dimensional coal seam structure, fill model particles, and form a coal seam numerical model. The 3D model building module is configured to set the cavity-making parameters according to the actual cavity-making scheme, establish the 3D structure of the cavity-making system model, generate abrasive particles and liquid particles according to the ratio, and set boundary conditions. The parameter calibration module is configured to calibrate the parameters between coal, water, and abrasive particles and balance the model. The simulation module is configured to perform numerical simulation of the hydraulic cavity-building process coupled with discrete element method and computational fluid dynamics, simulate the hydraulic cavity-building operation process, and record the distribution of local stress, density and porosity in the target cavity-building area during the simulation. The optimization module is configured to analyze the response relationship between the pressure relief and permeability enhancement effect and each hydraulic cavity-forming parameter based on the results of multiple numerical simulations under different cavity-forming parameters. Based on the analysis results, the optimization scheme of the hydraulic cavity-forming parameters is determined, and the final hydraulic cavity-forming process scheme is obtained.

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