Simulation method for stress recovery of goaf caving gangue

Abstract

The application discloses a kind of simulation methods of goaf caving gangue stress recovery, comprising the following steps: S1 collection parameter, by collecting mine drilling data, obtain rock mechanics parameters and each rock thickness data;S2 model is built, based on the existing parameter establishes three-dimensional geological model;S3 stress recovery calculation, the stress recovery state under different mining step is calculated;S4 load simulation, vertical load is applied to model, to simulate the vertical stress that caving coal gangue is applied to roof and floor surrounding rock in mining process;S5 simulation mining, model is simulated mining, and the dynamic process of stress recovery is observed.The application knows the dynamic change condition of caving coal gangue to roof and floor surrounding rock effect in mining process by calculation, and then equivalent vertical stress is applied to model, to simulate the effect of coal gangue to roof and floor surrounding rock, provides a new method and train of thought for goaf coal gangue caving stress recovery simulation.

Description

A simulation method for stress recovery of collapsed gangue in goaf. Technical Field

[0001] This invention relates to the field of numerical simulation technology for stress recovery in goaf areas, and in particular to a simulation method for stress recovery of collapsed gangue in goaf areas. Background Technology

[0002] Coal resources are my country's most important primary energy source. Research on stress recovery during mining can effectively reduce the risk of roof failure during mining. Currently, many scholars have made significant progress on stress recovery, but effective methods are still lacking in simulating the dynamic evolution of stress recovery during mining.

[0003] Current research on stress recovery mainly relies on in-situ stress testing and theoretical formula calculations. However, this method has several drawbacks: in-situ stress testing requires significant time and effort, places high demands on the rock mass, and is influenced by numerous factors; it also presents many limitations in practical application. Furthermore, theoretical formula calculations fail to intuitively reflect the dynamic process of stress recovery and cannot adequately depict the stress changes experienced by the rock mass during mining. Summary of the Invention

[0004] To address the technical problems mentioned in the background section, this invention provides a simulation method for stress recovery of collapsed gangue in goaf areas.

[0005] This invention is achieved using the following technical solution: a simulation method for stress recovery of collapsed gangue in a goaf, comprising the following steps:

[0006] S1. Collect parameters: Obtain rock mechanical parameters and thickness data of each rock layer by collecting borehole data in the mining area;

[0007] S2. Construct the model: Build a three-dimensional geological model based on existing parameters;

[0008] S3, Stress recovery calculation, calculates the stress recovery state under different mining step distances;

[0009] S4. Load simulation: Apply vertical loads to the model to simulate the vertical stress exerted on the roof and floor surrounding rock by the coal and gangue that collapses during mining.

[0010] S5. Simulated mining: Simulate mining using the model and observe the dynamic process of stress recovery.

[0011] As a further improvement to the above scheme, in step S3, the stress recovery calculation is performed on the stress recovery status of the overlying strata in the goaf under different mining steps. The calculation method includes the following steps:

[0012] S31. Divide the concentrated stress load in the mining support pressure into the limit equilibrium zone and the elastic zone;

[0013] The support pressure load in the ultimate equilibrium zone is divided into the post-peak stress reduction load and the pre-peak stress increase load; the load increase in the ultimate equilibrium zone is calculated based on the post-peak stress reduction load and the pre-peak stress increase load.

[0014] S32. Calculate the increase in load in the elastic zone;

[0015] S33. Calculate the load in the goaf stress release zone before and after coal seam mining based on the increase in load in the limit equilibrium zone and the increase in load in the elastic zone.

[0016] S34. Based on the load in the goaf stress release zone before and after coal seam mining, obtain the stress growth parameters of the goaf, and thus determine the stress growth function of the goaf.

[0017] As a further improvement to the above scheme, in step S31, the post-peak stress reduction load is expressed as S B The pre-peak stress increase load is expressed as S. C The increase in load in the limit equilibrium region is then expressed as:

[0018] ;

[0019] Where K is the bearing compressive stress concentration factor, x b σ0 represents the width of the limit equilibrium zone, and σ0 represents the original rock stress.

[0020] As a further improvement to the above scheme, in step S32, the increase in the load on the elastic zone is expressed as:

[0021] ;

[0022] Where K is the bearing compressive stress concentration factor, x b σ0 is the width of the limit equilibrium zone, σ0 is the original rock stress, C is the range of the elastic zone, and l is the distance between the side of the elastic zone and the coal wall.

[0023] As a further improvement to the above scheme, in step S33, based on the principle of balancing the stress release in the goaf and the incremental load of the support pressure in front of the coal face, the sum of the increase in load in the ultimate equilibrium zone and the increase in load in the elastic zone is taken as the stress increase in the goaf:

[0024] .

[0025] As a further improvement to the above scheme, in step S34, the load in the stress release zone of the goaf before and after mining is expressed as:

[0026] ;

[0027] Where σ0 is the original rock stress, L C σ represents the stress recovery distance in the goaf. c This is the stress growth function in the goaf.

[0028] Based on the stress growth S in the goaf area in step S33 A The stress growth function σ is calculated. c The value;

[0029] The stress growth function σ c Defined as an exponential function and expressed as:

[0030] ;

[0031] Where σ0 is the original rock stress, x is the distance between the goaf side and the coal face, and L C denoted as the stress recovery distance in the goaf, and n is the stress growth parameter in the goaf.

[0032] According to the stress growth function σ c The value of n is used to calculate the stress growth parameter n in the goaf.

[0033] The stress growth parameter n in the goaf is taken as a constant to redefine the stress growth function equation in the goaf, and the stress during the mining process is recovered in the form of this equation.

[0034] As a further improvement to the above scheme, in step S4, the load simulation also includes the following steps:

[0035] S41. When the roof collapses for the first time, the stress recovery at the bottom of the goaf is considered to be the same as that at the top, based on the stress recovery calculation results in step S3.

[0036] The magnitude and range of the force are represented by the time step.

[0037] When the excavation is completed, the vertical stress acting on the model is the same as the force exerted by the falling coal gangue on the roof and floor surrounding rock.

[0038] S42. In the subsequent mining process, repeat the steps in S41, always keeping the magnitude and range of the vertical stress applied to the model related to the time step.

[0039] The present invention also provides an apparatus for simulating stress recovery of collapsed gangue in goaf areas as described in any of the above-mentioned methods, the apparatus comprising:

[0040] The parameter collection module is used to obtain rock mechanical parameters and thickness data of each rock layer by collecting borehole data in the mining area;

[0041] The model building module is used to build three-dimensional geological models based on existing parameters.

[0042] The calculation module is used to calculate the stress recovery state under different mining steps;

[0043] The load simulation module applies vertical loads to the model to simulate the vertical stress exerted on the roof and floor surrounding rock by falling coal and gangue during mining operations; and

[0044] The mining simulation module is used to simulate mining operations on a model and observe the dynamic process of stress recovery.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] This invention calculates the dynamic changes in the effect of coal gangue falling on the roof and floor surrounding rocks during mining, and then applies an equivalent vertical stress to the model to simulate the effect of coal gangue on the roof and floor surrounding rocks. It is simple to operate and easy to apply in practice, providing a new method and approach for simulating the stress recovery of coal gangue falling in goaf areas. Attached Figure Description

[0047] Figure 1 is a flowchart of the stress recovery technology for collapsed gangue in the goaf area according to the present invention;

[0048] Figure 2 is a flowchart of the FISH command execution process;

[0049] Figure 3 shows the load distribution around the mining area;

[0050] Figure 4 is a schematic diagram of vertical stress application under different mining step distances;

[0051] Figure 5 is a schematic diagram of the numerical model;

[0052] Figure 6 shows the final vertical stress distribution in the caving method mining;

[0053] Figure 7 shows the final vertical stress distribution after the reaction force is applied. Detailed Implementation

[0054] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0055] Example 1

[0056] Referring to Figure 1, the simulation method for stress recovery of collapsed gangue in the goaf includes the following steps:

[0057] S1. Collect borehole data in the mining area. By collecting borehole data in the mining area, we can obtain data such as rock mechanical parameters and the thickness of each rock layer.

[0058] S2. Construct the model: Based on the existing parameters, establish a FLAC3D three-dimensional geological model and assign it the correct constitutive relations, boundary conditions, parameters, and other conditions.

[0059] S3. Stress recovery calculation: The stress recovery status of the overlying strata in the goaf is calculated using theoretical formulas under different mining step distances, and the vertical stress value at the origin of the model coordinate system is obtained.

[0060] S4. Referring to Figure 2, write a command flow based on the FISH language built into the FLAC3D5.0 mining model so that the dynamic change of vertical stress is always related to the time step. After each excavation, the magnitude and distribution of vertical stress are the results obtained according to the theoretical formula.

[0061] Vertical loads were applied to the model to simulate the vertical stress exerted on the roof and floor surrounding rock by the coal and gangue that collapsed during mining.

[0062] In this embodiment, a timestep refers to a time interval discretized in time, used to describe the evolution of a system or process. In many fields such as physics, engineering, and computer science, timesteps are used to describe the evolution of simulated systems over time. In numerical computation, a timestep typically refers to the discretization of time, dividing a continuous time interval into several discrete time intervals, each called a timestep. This division allows us to approximate a continuous time evolution process using numerical methods, thereby obtaining more accurate numerical results.

[0063] S5. Simulated mining: Simulate mining on the model and observe the dynamic process of stress recovery. That is, mine the model with equal step distances and observe the dynamic process of stress recovery.

[0064] In step S3, the calculation method for the stress recovery status of the overlying strata in the goaf under different mining steps includes the following steps:

[0065] S31. In the direction of face advancement, based on the stress state of the rock strata, the concentrated stress load support pressure in the mining area is divided into a limit equilibrium zone, an elastic zone, and a stress recovery zone. The stress recovery in the goaf is closely related to the stress concentration in front of the coal face, and it is a dynamic equilibrium process that continues to increase as the mining space increases.

[0066] The support pressure load in the ultimate equilibrium zone is divided into the post-peak stress reduction load and the pre-peak stress increase load; the load increase in the ultimate equilibrium zone is calculated based on the post-peak stress reduction load and the pre-peak stress increase load.

[0067] S32. Calculate the increase in load in the elastic zone;

[0068] S33. Calculate the load in the goaf stress release zone before and after coal seam mining based on the increase in load in the limit equilibrium zone and the increase in load in the elastic zone.

[0069] S34. Based on the load in the goaf stress release zone before and after coal seam mining, obtain the stress growth parameters of the goaf, and thus determine the stress growth function of the goaf.

[0070] Referring to Figure 3, in step S31, the post-peak stress reduction load is represented as S. B (Region B in Figure 3), the pre-peak stress increase load is represented by S. C (Region C in Figure 3), the increase in load in the limit equilibrium region is expressed as:

[0071] ;

[0072] Where K is the bearing compressive stress concentration factor, x b σ0 represents the width of the limit equilibrium zone, and σ0 represents the original rock stress.

[0073] Referring to Figure 3, in step S32, the increase in load on the elastic zone is expressed as follows:

[0074] (Region D in Figure 3).

[0075] Where K is the bearing compressive stress concentration factor, x b σ0 is the width of the limit equilibrium zone, σ0 is the original rock stress, C is the range of the elastic zone, and l is the distance between the side of the elastic zone and the coal wall.

[0076] In step S33, based on the principle of balancing the stress release in the goaf and the incremental load of the support pressure in front of the coal face, the sum of the load increase in the ultimate equilibrium zone and the load increase in the elastic zone is taken as the stress increase in the goaf.

[0077] .

[0078] Referring to Figure 3, in step S34, the load of the stress release zone in the goaf before and after mining is expressed as (i.e., the area of ​​region A):

[0079] ;

[0080] Where σ0 is the original rock stress, L C σ represents the stress recovery distance in the goaf. c This is the stress growth function in the goaf.

[0081] Based on the stress growth S in the goaf area in step S33 A The stress growth function σ is calculated. c The value;

[0082] The stress growth function σ c Defined as an exponential function and expressed as:

[0083] ;

[0084] Where σ0 is the original rock stress, x is the distance between the goaf side and the coal face, and L C Let be the stress recovery distance in the goaf, and n be the stress growth parameter in the goaf. Then, we need to determine the stress growth function σ in the goaf. c That is, we only need to determine n.

[0085] Therefore, according to the stress growth function σ c The value of can be used to calculate the stress growth parameter n in the goaf;

[0086] The stress growth parameter n in the goaf is taken as a constant to redefine the stress growth function equation in the goaf, and the stress during the mining process is recovered in the form of this equation.

[0087] Therefore, when using FLAC3D5.0 numerical simulation software to perform full caving mining, the above parameters can be obtained relatively easily. Substituting them into the above formula, n can be calculated, and thus the stress growth function σ in the goaf can be obtained. c Based on the relationship, and by analyzing the theory, the stress recovery equations for different mining steps can be obtained.

[0088] In addition, due to the logic of the FLAC3D5.0 software command flow, it is also necessary to use the above function formula to calculate the vertical stress value at the origin of the model coordinate system.

[0089] In step S4, based on the FLAC3D5.0 mining model, dynamically changing vertical stress is applied to the goaf using the FISH language built into FLAC3D5.0, including the following steps:

[0090] S41. When the roof collapses for the first time, based on the stress recovery status of the overlying strata in the goaf under different mining steps and the vertical stress value at the origin of the model coordinates obtained in step S3, the stress recovery at the bottom of the goaf is regarded as the same as that of the roof.

[0091] The code is written using the FISH language, and the time step is used to represent the magnitude and range of the force. When the current excavation ends, the vertical stress acting on the model is consistent with the force exerted by the falling coal gangue on the roof and floor surrounding rock.

[0092] S42. In the subsequent mining process, repeat the steps in S41, always keeping the magnitude and range of the vertical stress applied to the model related to the time step.

[0093] When the working face advances to a certain distance, some of the coal gangue is compacted. At this time, the force exerted by this part of the coal gangue on the surrounding rock of the roof and floor is a constant value, so it is manifested as a uniformly distributed load at the corresponding position of the model.

[0094] Example 2

[0095] The method of Example 1 is applied to a specific working face in a coal mine. In this example, the theory of Example 1 is used as a basis, and it is simplified to a certain extent. The specific steps include the following:

[0096] S1. Based on the basic geological conditions of the working face, the model dimensions are determined to be 600*400*500m, the total excavation length of the working face is 300m, and the mining step distance is 15m. The original rock stress σ0 at the coal seam is approximately 7MPa. The rock mechanical parameters are shown in Table 1 below:

[0097] Rock layer thickness / m density / kg·m -3 Elastic modulus / Gpa Poisson's ratio Cohesion / MPa Tensile strength / MPa Angle of internal friction / ° coal5 139010.341.070.0421 rock1252576110.226.260.9829.4 rock220261470.201.390.8329.3 rock3102640110.207.341.0430.9 rock455286960.181.360.8722 rock545279870.191.210.7929.3 rock6652859100.247.361.0721 rock7802785110.226.250.9629.9 surface

[0098] Table 1 shows the mechanical parameters of the rock strata at the top and bottom of the coal seam.

[0099] S2. Referring to Figure 4, collect geological data for the mining area, including strata lithology, thickness, and rock mechanical parameters. Based on the corresponding geological conditions, generalize it into a FLAC3D5.0 model, select an appropriate mesh size, and assign it the correct constitutive relations, boundary conditions, and rock mass parameters.

[0100] S3. Analyze the effect of coal and gangue falling during mining on the roof and floor surrounding rock based on theoretical formulas, and calculate the vertical stress at the origin of the model coordinate system. Taking the completion of mining as an example, the length of the goaf is 300m, the original rock stress σ0 = 7MPa, the bearing pressure concentration factor K = 2.61, and the width of the limit equilibrium zone X. b =12m, elastic zone range C=60m, stress recovery distance L in goaf C =105m.

[0101] S4. Substitute the parameters from step S3 into the functions in Example 1 to obtain the following results:

[0102] S41, Increase in load in the ultimate equilibrium zone S C-B =25.62 MPa·m;

[0103] S42, Increase in load in the elastic zone S D =2160.12 MPa·m;

[0104] S43, Load S in the stress release zone of the goaf before and after coal seam mining A =S C-B +S D =2185.74 MPa·m;

[0105] S44, according to S A The stress growth function σ was calculated numerically. c The value; then according to the stress growth function σ c The value of n was used to calculate the stress growth parameter n=0.65 in the goaf.

[0106] S45. Taking the stress growth parameter n in the goaf as a constant, the stress growth function equation in the goaf is determined as: σ c =σ0(x / L c ) 0.65 That is, the stress during the mining process is recovered in the form of this equation.

[0107] S5. Based on the three-dimensional geological model established in step S1, the theoretical formula in step S2 is simplified, and the power function is simplified into a function that changes linearly with a fixed gradient until the stress is restored to the original rock stress.

[0108] When the working face advanced to 45m, the roof collapsed. At this point, vertical stress was applied, maintaining a distance of 30m between the leading edge of the vertical stress and the working face. When the working face advanced to 120m, compaction zones began to appear in the goaf. The specific application method is as follows:

[0109] Using the software's built-in FISH language, a command flow is written to apply dynamically changing vertical loads to the model. The magnitude and range of these loads are related to the time step. Taking the completion of mining as an example, the specific steps are as follows:

[0110] (1) The vertical stress value at the origin of the model coordinate system obtained in step S3 is represented by a time step (see detailed code attached in Example 4 for specific code).

[0111] (2) As the program runs, the range of vertical stress gradually increases. The x-coordinate of the foremost vertical stress (i.e. the position where the collapse just begins) is expressed by time step (see detailed code attached below).

[0112] (3) As the working face continues to advance, the same principle applies. When the working face advances to 120m, the coal gangue begins to show signs of compaction, and at this time the magnitude of the force on this part is constant.

[0113] (4) Referring to Figure 5, the force applied by this method can more easily reflect the stress recovery process of the collapsed coal gangue in the goaf. The magnitude of the force is what is required in step (1), and the range of action of the force is what is required in step (2).

[0114] (5) Please refer to Figure 6 and embed the FISH language into the FLAC3D model. The vertical stress effect is shown in Figure 6. Please refer to Figure 7 and use the full collapse method to simulate mining and compare it. The effect is shown in Figure 7.

[0115] Example 3

[0116] This embodiment provides an apparatus for use in the simulation method of Embodiment 1 described above, the apparatus comprising:

[0117] The parameter collection module is used to obtain rock mechanical parameters and thickness data of each rock layer by collecting borehole data in the mining area;

[0118] The model building module is used to build three-dimensional geological models based on existing parameters.

[0119] The calculation module is used to calculate the stress recovery state under different mining steps;

[0120] The load simulation module applies vertical loads to the model to simulate the vertical stress exerted on the roof and floor surrounding rock by falling coal and gangue during mining operations; and

[0121] The mining simulation module is used to simulate mining operations on a model and observe the dynamic process of stress recovery.

[0122] This embodiment has the same beneficial effects as Embodiment 1. By calculating the dynamic changes in the effect of the coal gangue falling during the mining process on the roof and floor surrounding rocks, an equivalent vertical stress is applied to the model to simulate the effect of the coal gangue on the roof and floor surrounding rocks. The operation is simple and easy to apply in practice.

[0123] Example 4

[0124] The source code used in this embodiment for stress recovery simulation when the working face advances to 300m, as an example, is as follows:

[0125] model null range x 435 450 group coal

[0126] def get_step; Get the current step number

[0127] step3 = step

[0128] end

[0129] @get_step

[0130] define apply1

[0131] The loop `nn(1,20);` demonstrates that each mining segment requires 20,000 steps to ensure computational balance.

[0132] Step 2 = Step - Step 1; Step 1 is the time step required before any collapse occurs in the first 30m of mining, and Step 2 is the time step required for mining this section. Since this section represents the 18th applied reaction force, its value is between 17*20000 and 18*20000.

[0133] stress1 = -1 * (step2 * 0.0525e3 + 0.07e6 * 150) - 0.7e6; stress1 is the vertical stress value at the origin of the model coordinate system. In this example, it is assumed that after 20,000 steps, the stress at the cut-in point recovers from 0.85σ0 to 1.0σ0, and the minimum stress recovery value generated by the collapse section is 0.1σ0, i.e., 0.7e6. From the initial and final values ​​of the stress on both sides of the collapse section, and the stress change gradient, the range of stress variation at the origin can be calculated. 0.0525e3 is the coefficient between step2 and stress1. 0.07e6 is the stress change gradient, 0.07e6 * 150, which represents the stress change within the distance from the cut-in point to the origin of the model.

[0134] stress2 = -1.75e7 + 0.07e6 * 150 = -7e6; This represents the load at the origin of the coordinate system, ensuring that the applied force is a uniformly distributed load with a magnitude equal to 1.0σ0.

[0135] x1 = 150 + 0.00075 * (step2); x1 is the coordinate of the foremost point of the stress point, i.e., the position where the coal gangue begins to collapse; 0.00075 is the additional collapse distance of the coal gangue per step, i.e., the collapse range is 15m every 20,000 steps.

[0136] step4 = step - step3; step4 is between 0 and 20000.

[0137] x2 = 150 + 0.0165 (step4); Ensure the uniformly distributed load and the triangular load are applied synchronously. 0.0165 represents the additional collapse distance of the coal gangue per step.

[0138] command

[0139] The command `apply szz @stress1 grad 0.07e6 0 0 range x 330 @x1 z 199.9200.1 y -300 -100;` applies vertical stress to the surrounding rock of the goaf roof, with 0.07e6 as the stress gradient and an application range of 330 to x1.

[0140] `apply szz @stress2 grad 0 0 0 range x 150 @x2 z 199.9 200.1 y -300 -100;` applies a uniformly distributed load to this section.

[0141] apply szz @stress1 grad 0.07e6 0 0 range x 330 @x1 z 194.9195.1 y -300 -100

[0142] apply szz @stress2 grad 0 0 0 range x 150 @x2 z 199.9 200.1 y -300 -100

[0143] step 1000

[0144] endcommand

[0145] endloop

[0146] end

[0147] @apply1

[0148] set mech ratio 1e-5

[0149] so

[0150] sav excavation300.sav .

[0151] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A simulation method for stress recovery of collapsed gangue in a goaf, characterized in that, The process includes the following steps: S1. Parameter collection: Obtain rock mechanics parameters and thickness data of each stratum by collecting borehole data from the mining area; S2. Model construction: Establish a three-dimensional geological model based on existing parameters; S3. Stress recovery calculation: Calculate the stress recovery state under different mining steps; S4. Load simulation: Apply vertical loads to the model to simulate the vertical stress exerted on the roof and floor surrounding rocks by the coal and gangue that collapses during mining; S5. Simulated mining: Simulate mining on the model and observe the dynamic process of stress recovery; In step S3, the stress recovery calculation is performed on the stress recovery status of the overlying strata in the goaf under different mining steps, and the calculation method includes the following steps: S31 The concentrated stress load in the mining area is divided into a limit equilibrium zone and an elastic zone; the support pressure load in the limit equilibrium zone is further divided into a post-peak stress reduction load and a pre-peak stress increase load; the load increase in the limit equilibrium zone is calculated based on the post-peak stress reduction load and the pre-peak stress increase load; S32, the load increase in the elastic zone is calculated; S33, the stress release zone load in the goaf before and after coal seam mining is calculated based on the load increase in the limit equilibrium zone and the load increase in the elastic zone; S34, the stress growth parameter in the goaf is obtained based on the stress release zone load before and after coal seam mining, thereby determining the stress growth function in the goaf; in step S34, the stress release zone load in the goaf before and after mining is expressed as: Where σ0 is the original rock stress, and L C σ represents the stress recovery distance in the goaf. c The stress growth function in the goaf; based on the stress growth S in the goaf in step S33. A The stress growth function σ is calculated. c The value of the stress growth function σ; c Defined as an exponential function and expressed as: Where σ0 is the original rock stress, x is the distance between the goaf side and the coal face, and L C Where σ is the stress recovery distance in the goaf, and n is the stress growth parameter in the goaf; according to the stress growth function σ c The value of is used to calculate the stress growth parameter n in the goaf; the stress growth parameter n in the goaf is taken as a constant to redetermine the stress growth function equation in the goaf, and the stress during the mining process is recovered in the form of this equation.

2. The simulation method for stress recovery of collapsed gangue in a goaf as described in claim 1, characterized in that, In step S31, the post-peak stress reduction load is represented as S B The pre-peak stress increase load is expressed as S. C The increase in load in the limit equilibrium region is then expressed as: Where K is the bearing compressive stress concentration factor, and x b σ0 represents the width of the limit equilibrium zone, and σ0 represents the original rock stress.

3. The simulation method for stress recovery of collapsed gangue in a goaf as described in claim 2, characterized in that, In step S32, the increase in load on the elastic zone is expressed as: Where K is the bearing compressive stress concentration factor, and x b σ0 is the width of the limit equilibrium zone, σ0 is the original rock stress, C is the range of the elastic zone, and l is the distance between the side of the elastic zone and the coal wall.

4. The simulation method for stress recovery of collapsed gangue in a goaf as described in claim 3, characterized in that, In step S33, based on the principle of balancing the stress release in the goaf and the incremental load of the support pressure in front of the coal face, the sum of the load increase in the ultimate equilibrium zone and the load increase in the elastic zone is taken as the stress increase in the goaf. 。 5. The simulation method for stress recovery of collapsed gangue in a goaf as described in claim 2, characterized in that, In step S4, the load simulation also includes the following steps: S41, when the roof collapses for the first time, based on the stress recovery calculation results in step S3, the stress recovery at the bottom of the goaf is regarded as the same as that of the roof; the time step is used to represent the magnitude and range of the force; when the current excavation ends, the vertical stress acting on the model is consistent with the force of the collapsed coal gangue on the roof and bottom surrounding rock; S42, in the subsequent mining process, the steps in step S41 are repeated, and the magnitude and range of the vertical stress applied to the model are always related to the time step.

6. An apparatus for simulating stress recovery of collapsed gangue in a goaf area as described in any one of claims 1-5, characterized in that, The device includes: a parameter collection module for acquiring rock mechanics parameters and thickness data of each stratum by collecting borehole data from the mining area; a model construction module for establishing a three-dimensional geological model based on existing parameters; a calculation module for calculating the stress recovery state under different mining steps; a load simulation module for applying vertical loads to the model to simulate the vertical stress exerted on the roof and floor surrounding rocks by the coal gangue that falls during mining; and a mining simulation module for simulating mining on the model and observing the dynamic process of stress recovery.

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