Method for simulating stability disturbance of coal mining activity to root soil composite layer based on FLAC3D

Abstract

The invention discloses a method for simulating the stability disturbance of a root soil composite layer by a coal mining activity based on FLAC3D, and the method comprises the steps: building a plurality of reference numerical model plates through employing a Mohr-Coulomb criterion based on the geological data and mining data of a target mining area, carrying out the size calibration and grid division, carrying out the grid encryption of a coal seam plate and a root soil composite layer plate, and carrying out the simulation of the stability disturbance of the root soil composite layer. All the plates are combined to form an FLAC3D overall model, and mechanical parameters are given to the FLAC3D overall model; applying boundary displacement constraint and gravitational acceleration; anchoring units for simulating plant root systems are arranged on the root-soil composite layer plate, simulated mining is conducted on the coal seam plate, and a contact surface is arranged on the upper portion of a goaf; in the simulated mining process, the coal seam excavation stress transfer condition is analyzed according to the failure condition of the plastic zone of the root-soil composite layer. The change condition of a surrounding rock stress field in the underground coal mining process is simulated through FLAC3D numerical software, the influence of mining-induced stress on the stability of the root-soil composite layer is predicted, and the method has the advantages of being high in simulation precision, adjustable in parameter, low in cost and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of intersection of mine engineering and ecological environment protection, and particularly relates to a method for simulating disturbance of root-soil composite layer stability caused by coal mining activities based on FLAC3D. BACKGROUND

[0002] Root damage is a key ecological problem of plant damage in coal mining areas in arid and semi-arid well work, which is closely related to the special interface-related mechanical process of root and surrounding soil. However, due to the complex mechanical action mechanism of coal mining subsidence on root damage, the change factors are diversified and fuzzy, and the root grows in the soil, which has a "black box effect". It is difficult to carry out in-situ monitoring of plant root damage in the dynamic advancement of working face from self-opening cut to stop line in the field. The plant root damage mechanical model is an important means to explore the stress transmission mechanism of plant root damage and surrounding soil under different mining conditions. The existing numerical simulation researches are mostly focused on the deformation and failure mechanism of rock mass, and less on the response law of root-soil composite layer and root structure under the action of mining stress field (the root-soil composite layer refers to the special structure layer formed in the soil due to the existence of plant roots and the interaction between the plant roots and soil particles). For example, the Chinese invention patent with the patent publication number CN119720521A discloses a "surface mining subsidence dynamic prediction time function model and a parameter solving method thereof", which includes dynamic prediction of surface subsidence trajectory characteristics, total subsidence time characteristics, subsidence velocity characteristics and acceleration characteristics. The parameters used for parameter solving are all related prediction parameters of the commonly used surface mining subsidence static prediction model-probability integral method. The technical scheme disclosed by the patent fails to fully consider the all-round influence of mining activities on the ecological system of the ground, does not involve the discrimination of the disturbance of root-soil composite layer stability caused by coal mining stress, and has less functions. For another example, the Chinese invention patent with the patent publication number CN112197806A discloses a "method for installing a mining subsidence area movement deformation, hydrology and stress monitoring equipment", which includes: lowering the stress monitoring equipment, the inclinometer and the grouting pipe into the monitoring hole in the mining subsidence area; anchoring the stress monitoring equipment at the bottom through the grouting pipe; lowering and installing a plurality of fixed inclinometers in the inclinometer, and installing a osmometer at the bottom area in the inclinometer; connecting the data cables of the stress monitoring equipment, the fixed inclinometers and the osmometer with the ground data acquisition and transmission system. The technical scheme disclosed by the invention patent needs to use artificial installation of monitoring equipment, still has artificial operation error and cannot guarantee the safety of workers during installation, and fails to predict the disturbance of root-soil composite layer stability caused by well work coal mining activities and the possible stress condition of plant roots.

[0003] The FLAC3D numerical simulation model has universal analysis capability in the field of continuum mechanics and has essential advantages in the aspect of processing discontinuous medium, is particularly suitable for analyzing the static and dynamic response problems of solid medium under load, can take into account the mining depth, advancing speed, coal seam depth, coal seam thickness and rock structure and other factors to simulate and analyze the mining-induced soil mechanical mechanism, and has a wide application in the field of mine rock mechanics and mine pressure research; the FLAC3D numerical simulation model is introduced into the simulation of the damage of the root-soil composite layer caused by the disturbance of underground mining, can more accurately reproduce the ground deformation propagation path and energy distribution characteristics caused by underground mining activities, and can realize the simulation and prediction of the damage degree of the root-soil composite layer and root system under different mining conditions by setting reasonable constitutive model and parameter combination. At present, there is no FLAC3D numerical software modeling method that systematically combines the interaction of root-soil and the response of mining stress field, and the traditional root-soil composite layer damage evaluation relies on field monitoring, has high cost and strong hysteresis, and lacks fine damage evaluation indexes for root system. Therefore, an effective method is needed to simulate and predict the influence of coal mining activities on the stability of the root-soil composite layer. SUMMARY

[0004] The purpose of the present application is to provide a method for simulating the disturbance of coal mining activities on the stability of the root-soil composite layer based on FLAC3D, which uses FLAC3D numerical software to simulate the change of stress field of surrounding rock in underground mining process, further analyzes the damage of root-soil composite layer and plant root system, has the advantages of high simulation accuracy, adjustable parameters and low cost, and can accurately predict and quantitatively analyze the influence of mining stress on the stability of root-soil composite layer.

[0005] To achieve the above purpose, the present application provides the following scheme:

[0006] A method for simulating the disturbance of coal mining activities on the stability of the root-soil composite layer based on FLAC3D, the method comprising the following steps:

[0007] S1, based on the geological data and mining data of the target mining area, a plurality of benchmark numerical model plates are constructed using Mohr-Coulomb criterion, the plurality of benchmark numerical model plates including a floor plate, a coal seam plate, a direct roof plate, a sandstone layer plate and a root-soil composite layer plate;

[0008] S2, the size of the benchmark numerical model plates is calibrated and meshed, a model plate to be analyzed is selected, and mesh encryption processing is performed, wherein the model plate to be analyzed includes the coal seam plate and the root-soil composite layer plate;

[0009] S3, all the benchmark numerical model plates are merged to form a FLAC3D whole model, and the corresponding mechanical parameters of each benchmark numerical model plate are respectively given, the mechanical parameters including density, bulk modulus, shear modulus, cohesion, tensile strength, internal friction angle, normal stiffness and shear stiffness;

[0010] S4, displacement constraints are performed on the model boundary, the x-axis and y-axis are fixed, the model bottom is fixed, the horizontal and vertical displacements are both 0, the model top is not provided with displacement constraints; meanwhile, the initial velocities of the x-axis, y-axis and z-axis are set to 0, and the gravity acceleration is applied to the whole model;

[0011] S5, the anchoring units simulating plant root systems are arranged on the root-soil composite layer plate, and the coal seam plate is simulated to be mined in the FLAC3D numerical software, a contact surface is arranged on the upper part of the goaf, and parameters are assigned to the contact surface;

[0012] S6, during the simulation of the mining process, the stress transmission of the coal seam excavation is analyzed according to the root-soil composite layer plastic zone damage.

[0013] Further, in S1, the geological data of the target mining area includes geological structure information, soil parameters, vegetation root system distribution information and coal seam information, wherein the geological structure information includes rock layer distribution and type, the soil parameters include soil density, cohesion and internal friction angle, and the coal seam information includes cohesion and internal friction angle.

[0014] The mining data includes mining depth and mining speed.

[0015] Further, in S2, the coal seam plate is located between the floor plate and the immediate roof, and the coal seam plate is divided into an encryption area and a non-encryption area according to the mining requirements, wherein the part that needs to be mined is grid-encrypted, and the part that does not need to be mined does not need to be encrypted.

[0016] Further, in S3, the FLAC3D whole model has a strike length of 300m, a tendency distance of 200m and a height of 83m.

[0017] Further, in S4, the displacement constraints are that the model periphery and bottom remain fixed in position during the simulation of the mining process.

[0018] Further, in S5, the anchoring unit simulating plant root systems is specifically: according to the quasi-cohesion theory and anchoring theory, a full-length anchoring unit is used to simulate the layout of plant root systems, wherein the row spacing of the root system is 2m and the column spacing is 3m.

[0019] Further, in S5, the mining area of the simulation mining has a strike length of 110m, a tendency length of 80m and a height of 6m.

[0020] Further, in S5, the contact surface arranged on the upper part of the goaf is assigned with parameters including normal stiffness, tangential stiffness and cohesion.

[0021] Further, in the S6, the root-soil composite layer plastic zone failure condition is divided into a tensile failure region, a shear failure region, and a region with both tensile failure and shear failure.

[0022] Further, in the S6, during simulation of the mining process, the coal seam excavation stress transmission is analyzed according to the root-soil composite layer plastic zone failure condition, including:

[0023] The maximum shear stress at different positions of the root-soil composite layer from the mining disturbance is obtained by using the maximum shear stress function of the FLAC3D numerical software, so as to analyze the stress condition of the root-soil composite layer at different positions.

[0024] According to the specific embodiments provided by the present application, the following technical effects are disclosed: the method for simulating the disturbance of coal mining activities on the stability of the root-soil composite layer based on FLAC3D provided by the present application, by constructing a three-dimensional geological model including rock strata, coal seams and root-soil composite layers, combining Mohr-Coulomb criterion and field geological data, simulating the damage effect of stress field transmission on the root-soil composite layer and surface vegetation root system during the mining process.

[0025] Compared with the traditional method, the present application has the following advantages: (1) high simulation accuracy, which can truly reflect the damage mechanism of the mining stress field on the root-soil composite layer; (2) using the powerful post-processing function of the FLAC3D numerical software, the spatial distribution characteristics of the damage region can be intuitively displayed, which is convenient for decision makers to intuitively understand the spatial distribution of the damage; (3) for different vegetation types and geological conditions, the parameter settings in the model can be flexibly adjusted to adapt to various complex natural environments; (4) good scalability, which can be used for the study of the influence of other underground engineering on the surface ecology; (5) a three-dimensional geomechanical model including coal seams, rock strata, overburden layers and plant root layers is established, and material parameters are set according to the actual geological conditions, which can accurately simulate the influence of underground mining activities on the structure of the root-soil composite layer; (6) combining advanced theories such as enhanced fiber model to simulate the contribution of root system to soil shear strength, the simulation result is closer to the actual situation, and the prediction accuracy is improved; (7) compared with the surface subsidence which focuses on the macroscopic level, the present method can deeply explore the stress-strain relationship of the root-soil composite layer at the microscopic level, which is helpful for formulating more effective ecological protection strategies; (8) compared with the traditional test method or empirical formula, the present application can greatly improve the prediction efficiency without increasing additional cost, and reduce the economic loss caused by misjudgment.

[0026] In conclusion, the present application firstly introduces plant roots into the numerical simulation system of the disturbance effect of well mining on coal, accurately predicts the influence of mining stress on the stability of root-soil composite layer through FLAC3D numerical software, solves the problem of micro-damage quantification of traditional methods, has the advantages of high simulation accuracy, adjustable parameters, low cost, and is suitable for ecological restoration evaluation and green mining planning in ecologically fragile mining areas. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0028] Figure 1 The flow chart of the method for simulating the disturbance of coal mining activities on the stability of root-soil composite layer based on FLAC3D of the present application;

[0029] Figure 2 The schematic diagram of the base numerical model plate in the FLAC3D numerical software of the present application;

[0030] Figure 3 The three-dimensional schematic diagram of the FLAC3D whole model of the present application;

[0031] Figure 4 The example diagram of the surface layer and the bottom layer of the root-soil composite layer and the monitoring line arrangement of the present application;

[0032] Figure 5 The example diagram of the full-length anchoring unit and the monitoring line arrangement of the present application;

[0033] Figure 6 The schematic diagram of coal mining of the present application;

[0034] Figure 7 The schematic diagram of the disturbance characteristics of the stability of root-soil composite layer under different mining heights of the present application, wherein (a) is the surface layer characteristics of the root-soil composite layer, and (b) is the bottom layer characteristics of the root-soil composite layer;

[0035] Figure 8 The schematic diagram of the disturbance characteristics of the stability of root-soil composite layer under different mining speeds of the present application, wherein (a) is the surface layer characteristics of the root-soil composite layer, and (b) is the bottom layer characteristics of the root-soil composite layer;

[0036] Figure 9 The schematic diagram of the disturbance characteristics of the stability of root-soil composite layer under different buried depths of the present application, wherein (a) is the surface layer characteristics of the root-soil composite layer, and (b) is the bottom layer characteristics of the root-soil composite layer;

[0037] Explanation of reference signs: 1, floor plate; 2, coal seam plate; 3, immediate roof plate; 4, root-soil composite layer plate; 5, anchoring unit; 4-1, root-soil composite layer bottom layer; 4-2, root-soil composite layer surface layer; 5-1, lower part of root system; 5-2, upper part of root system; 5-3, monitoring line. DETAILED DESCRIPTION

[0038] Embodiments of the present application are described in detail below, which are intended to explain the present application, and cannot be understood as a limitation of the present application. If a specific technique or condition is not specified in the embodiments, the technique or condition described in the literature in the art or according to the product manual is used. If the manufacturer of the material or instrument is not specified, it is a conventional product that can be obtained by purchase.

[0039] The method for simulating disturbance of mining activities to stability of root-soil composite layer based on FLAC3D provided by the present application, by constructing a three-dimensional geological model comprising rock strata, coal seams and root-soil composite layers, combining field geological data and laboratory test data to set reasonable material parameters, using FLAC3D numerical software to simulate the change of stress field of surrounding rock in the process of underground mining, and further analyzing the damage of root-soil composite layer and plant root system. The present application reduces the consumption of manpower and material resources, and has the advantages of high simulation accuracy, adjustable parameters, low cost and the like. The influence of mining stress on the stability of root-soil composite layer is accurately predicted by FLAC3D numerical software.

[0040] As shown in Figure 1 The method for simulating disturbance of mining activities to stability of root-soil composite layer based on FLAC3D provided by the present application, comprising the following steps:

[0041] S1, based on the geological data and mining data of the target mining area, a plurality of benchmark numerical model plates are constructed using Mohr-Coulomb criterion, as shown in Figure 2 and Figure 3 The plurality of benchmark numerical model plates include floor plate 1, coal seam plate 2, immediate roof plate 3, sandstone layer plate and root-soil composite layer plate 4; wherein the geological data of the target mining area includes geological structure information, soil parameters, vegetation root system distribution information and coal seam information, etc., the geological structure information includes rock strata distribution and types, etc., the soil parameters include the density, cohesion and internal friction angle of soil, etc., and the coal seam information includes cohesion and internal friction angle; the mining data includes mining depth, mining speed, etc.

[0042] S2, size calibration and grid division are performed on the benchmark numerical model plates, as shown in Figure 6As shown, a selected model block to be analyzed is subjected to grid encryption processing, wherein the model block to be analyzed includes a coal seam block and a root-soil composite layer block; the coal mine area to be mined and the root-soil composite layer area to be analyzed are subjected to grid encryption, because in the underground mining simulation, the coal seam excavation area and the root-soil composite layer on the ground are the key areas of stress redistribution and deformation concentration, and grid encryption can more accurately capture the stress gradient, plastic zone expansion and failure mode of these areas. At the same time, in order to save calculation time, the non-key area does not need to be subjected to grid encryption, and different model blocks are named different rock stratum names.

[0043] As shown, the coal seam block is located between the floor block and the immediate roof, and the coal seam block is divided into an encryption area and a non-encryption area according to the mining requirements, wherein the part to be mined is subjected to grid encryption, and the part not to be mined does not need to be encrypted.

[0044] S3, merge all reference numerical model blocks to form a FLAC3D overall model, as shown in Figure 3 As shown, the mechanical parameters of each reference numerical model block are respectively assigned, including density, bulk modulus, shear modulus, cohesion, tensile strength, internal friction angle, normal stiffness and tangential stiffness;

[0045] The strike length of the FLAC3D overall model is 300m, the inclination distance is 200m, and the height is 83m.

[0046] Based on the relevant rock mechanical parameters, a FLAC3D overall model is established, and a txt text design command stream file is used. The theoretical calculation formula of the bulk modulus K and the shear modulus G in the rock mechanical parameters includes the following formula:

[0047]

[0048] Wherein, E is the elastic modulus, and υ is the Poisson's ratio.

[0049] S4, the displacement constraint of the model boundary is performed, the x-axis and y-axis are fixed, the bottom of the model is fixed, the horizontal and vertical displacements are both 0, and the top of the model is not provided with displacement constraint; at the same time, the initial velocities of the x-axis, y-axis and z-axis are set to 0, and the gravity acceleration (10m / s 2 ) is applied to the overall model;

[0050] The displacement constraint is that the four sides and the bottom of the model remain fixed in position during the simulation of mining, and will not move during the program running, which helps to stabilize the model and makes the simulation result more reliable.

[0051] S5, the root soil composite layer plate is laid out to simulate the anchoring unit of the plant root system, and the coal seam plate in the FLAC3D numerical software is simulated to be mined, the contact surface is arranged at the upper part of the goaf, and the parameters of the contact surface are valued (including normal stiffness, tangential stiffness and cohesion, etc.);

[0052] The anchoring unit simulating the plant root system is specifically: according to the quasi-cohesion theory and the anchoring theory, the full-length anchoring unit is used as the plant root system to be laid out, and the length of the anchoring unit in the model is determined according to the depth at which the vertical main roots of plants in different regions mainly concentrate in the soil. The row spacing of the root system is 2m, and the column spacing is 3m. The anchoring units are sequentially numbered, and in the result analysis, the stress values borne by the corresponding anchoring units are recorded as needed.

[0053] According to the designed anchoring unit, the anchoring unit is valued with corresponding parameters, such as elastic modulus, tensile strength, cross-sectional area, contact surface adhesion, and contact surface stiffness. Then, the model null command is used to mine the area to be mined, and the range command is used to determine the mining range. The model after mining is shown in Figure 6 . The strike length of the mining area in the simulation mining is 110m, the tendency length is 80m, and the height is 6m.

[0054] S6, during the simulation of mining, the stress transmission of coal seam excavation is analyzed according to the plastic zone damage of root soil composite layer.

[0055] The plastic zone damage of root soil composite layer is divided into tensile failure area, shear failure area and tensile failure area with shear failure area.

[0056] In the simulation of mining result analysis, the maximum shear stress function of the FLAC3D numerical software is used to obtain the maximum shear stress borne by the root soil composite layer at different positions from the mining disturbance, so as to analyze the stress condition of the root soil composite layer at different positions.

[0057] Figure 4 The monitoring line arrangement method for obtaining the maximum shear stress data of the root soil composite layer surface / bottom layer after mining at y = 15m is exemplified. According to these data, the maximum shear stress stress law of the root soil composite layer is analyzed, and the maximum shear strength of the root soil composite layer, i.e. the maximum shear stress that can be borne, is obtained from the model. According to the stress condition of the anchor rod, the stress distribution law of the vertical root system of the plant in the coal seam excavation in reality can also be predicted. Figure 5 The monitoring line arrangement method for obtaining the stress data of the upper and lower parts of the vertical main root after mining at y = 15m is exemplified.

[0058] If the maximum shear strength of the soil and the maximum shear strength of the root-soil composite layer are compared to analyze whether the plant roots can increase the shear strength of the soil, the command stream with the anchor rod and the command stream without the anchor rod can be respectively run in the FLAC3D numerical software, and finally the maximum shear strength of the soil and the maximum shear strength of the root-soil composite layer are analyzed according to the method described in step S6. According to the Mohr-Coulomb law, the maximum shear strength of the soil and the maximum shear strength of the root-soil composite layer formulae include the following formulae:

[0059]

[0060] Δs=τ'-τ

[0061] In the formulae, τ is the maximum shear strength of the soil, τ' is the maximum shear strength of the root-soil composite layer, c is the cohesion of the soil itself, σ is the normal stress perpendicular to the shear plane, is the internal friction angle of the soil, and Δs is the shear strength of the soil increased by the vertical main root.

[0062] According to the above formulae, it can be clearly known that the root-soil composite layer has stronger shear capacity than the soil.

[0063] Example 1

[0064] Under the condition of different coal seam mining heights (mining height (Mh)), the root-soil composite layer stability disturbance analysis method is used, which includes the following steps:

[0065] Step 1: Using the collected detailed geological structure information of the target mining area, a benchmark numerical model plate is constructed based on the Mohr-Coulomb criterion.

[0066] Step 2: Set the strike mining distance of the coal seam to 110m, the inclination mining distance to 80m, and the coal seam burial depth to 56m, and set different coal seam mining heights. (In this embodiment, the coal seam mining heights are set to 1m, 2m, 3m, 4m, 5m, and 6m)

[0067] Step 3: Using the established numerical model, different coal seam mining heights are simulated until the automatic running ends.

[0068] Step 4: According to the model obtained in step 3, it is analyzed as needed. The maximum shear stress data of the root-soil composite layer surface layer and the bottom layer can be obtained.

[0069] Figure 7 The shear stress curve trend graphs of the root-soil composite layer surface layer and the bottom layer at y=15m are shown, and the plastic zone distribution graphs of the root-soil composite layer surface layer and the bottom layer are shown, wherein None represents no damage, shear-p represents shear damage, and tension-p represents tensile damage. From the shear stress curve trend graphs of the root-soil composite layer surface layer and the bottom layer at y=15m, it can be seen that the shear stress of the root-soil composite layer surface layer is smaller than that of the root-soil composite layer bottom layer, and the shear stress of the root-soil composite layer surface layer is smaller than that of the root-soil composite layer bottom layer. Figure 7It can be seen from the figure that with the increase of the mining height of the coal seam, the maximum shear stress of the root-soil composite layer increases, the area of the shear failure of the surface and bottom layers of the root-soil composite layer increases with the increase of the mining height, the plastic zone of the surface layer of the root-soil composite layer is mainly tensile failure, and the plastic zone of the bottom layer is mainly shear failure.

[0070] Embodiment two:

[0071] Under the condition of different mining speeds (mining speed (Mv)) of the coal seam, the method for analyzing the stability disturbance of the root-soil composite layer by using the method of the present application comprises the following steps:

[0072] Step 1: Based on the Mohr-Coulomb criterion, a reference numerical model plate is constructed by using the collected detailed geological structure information of the target mining area.

[0073] Step 2: The thickness of the coal seam is set to 6m, the inclined mining distance is set to 80m, the buried depth of the coal seam is set to 56m, and different mining speeds of the coal seam are used to advance to the strike distance of 110m. (In this embodiment, the mining speed of the coal seam is set to 5m / time, 10m / time, 20m / time and 40m / time)

[0074] Step 3: The established numerical model is used to simulate the mining of the coal seam at different mining speeds until the automatic running ends.

[0075] Step 4: According to the model obtained in step 3, it is analyzed as needed. The maximum shear stress data of the surface layer and the bottom layer of the root-soil composite layer can be obtained.

[0076] Figure 8 The trend graph of the shear stress of the surface layer and the bottom layer of the root-soil composite layer at y=15m is shown, and the plastic zone distribution graph of the surface layer and the bottom layer of the root-soil composite layer is shown. Figure 8 It can be seen from the figure that the maximum shear stress of the surface and bottom layers of the root-soil composite layer under different mining speeds of the coal seam has basically the same change trend, the plastic zone of the surface layer of the root-soil composite layer is mainly tensile failure, and the plastic zone of the bottom layer is mainly shear failure.

[0077] Embodiment three:

[0078] Under the condition of different buried depths (buried depth (Md)) of the coal seam, the method for analyzing the stability disturbance of the root-soil composite layer by using the method of the present application comprises the following steps:

[0079] Step 1: Based on the Mohr-Coulomb criterion, a reference numerical model plate is constructed by using the collected detailed geological structure information of the target mining area.

[0080] Step 2: Set the strike mining distance of the coal seam to be 110m, the inclined mining distance to be 80m, the thickness of the coal seam to be 6m, and set different burial depths of the coal seam (in this embodiment, the burial depths of the coal seam are set to be 56m, 59m, 62m, 65m, 68m and 71m respectively).

[0081] Step 3: Simulate the mining of the coal seams with different burial depths by using the established numerical model until the automatic running is ended.

[0082] Step 4: According to the model obtained in step 3, analyze it as needed. The maximum shear stress data of the surface layer and the bottom layer of the root-soil composite layer can be obtained.

[0083] Figure 9 The trend graph of the shear stress suffered by the surface layer and the bottom layer of the root-soil composite layer at y=15m is illustrated, as well as the plastic zone distribution graph of the surface layer and the bottom layer of the root-soil composite layer. Figure 9 It can be seen from the above that, as the burial depth of the coal seam decreases, the maximum shear stress suffered by the root-soil composite layer increases significantly, and as the burial depth decreases, the plastic zone shear failure area of the surface layer of the root-soil composite layer and the plastic zone shear failure area of the bottom layer of the root-soil composite layer both gradually increase.

[0084] The present application uses numerical simulation technology to obtain the influence of the underground coal mining activity on the stability of the root-soil composite layer, and uses the anchor rod to replace the vertical main root of the typical plant, so as to obtain the influence of the stress disturbance caused by the mining activity on the plant root system, and verify the effect of the plant root system on the stability of the soil body.

[0085] In addition, the present application also provides a computer readable storage medium, which stores a computer program, and the computer program is executed to realize the method for simulating the disturbance of the root-soil composite layer stability caused by the coal mining activity based on FLAC3D.

[0086] The details of the present application are known technologies.

[0087] Through the above description of the embodiments, those skilled in the art can clearly understand that the embodiments can be realized by means of software and the necessary general hardware platform, and of course, can also be realized by hardware. Based on such understanding, the above technical solutions or the essential part of the prior art can be embodied in the form of a software product, which can be stored in a computer readable storage medium such as ROM / RAM, magnetic disk, optical disk, etc., and includes a plurality of instructions for making a computer device (which can be a personal computer, a server, or a network device, etc.) execute the method described in each embodiment or some part of the embodiment.

[0088] Having described various embodiments of the application, it is to be understood that the above description is meant to be illustrative only and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art, without departing from the scope and spirit of the described embodiments. The choice of words in this document is intended to best explain the principles of the embodiments, the practical application, or improvement over the technology in the art, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for simulating the disturbance of root-soil composite layer stability by coal mining activities based on FLAC3D, characterized in that, The method comprises the following steps: S1, based on the geological data and mining data of the target mining area, a plurality of benchmark numerical model plates are constructed using Mohr-Coulomb criterion, and the plurality of benchmark numerical model plates include a floor plate, a coal seam plate, a direct roof plate, a sandstone layer plate and a root-soil composite layer plate; S2, the size of the benchmark numerical model plate is calibrated and meshed, and a model plate to be analyzed is selected, and the mesh is encrypted, wherein the model plate to be analyzed includes the coal seam plate and the root-soil composite layer plate; S3, all the benchmark numerical model plates are merged to form a FLAC3D overall model, and the corresponding mechanical parameters of each benchmark numerical model plate are respectively given, and the mechanical parameters include density, bulk modulus, shear modulus, cohesion, tensile strength, internal friction angle, normal stiffness and tangential stiffness; S4, the displacement constraint of the model boundary is performed, the x-axis and y-axis are fixed, the bottom of the model is fixed, the horizontal and vertical displacements are both 0, and the top of the model is not provided with displacement constraint; meanwhile, the initial velocities of the x-axis, y-axis and z-axis are set to 0, and the gravity acceleration is applied to the overall model; S5, the anchoring unit simulating the plant root system is arranged in the root-soil composite layer plate, and the coal seam plate in the FLAC3D numerical software is simulated to be mined, a contact surface is arranged in the upper part of the goaf, and the parameters of the contact surface are valued; S6, in the process of simulating mining, the stress transmission condition of the coal seam excavation is analyzed according to the plastic zone damage condition of the root-soil composite layer.

2. The method for simulating the disturbance of root-soil composite layer stability by coal mining activities based on FLAC3D according to claim 1, characterized in that, In the S1, the geological data of the target mining area includes geological structure information, soil parameters, vegetation root system distribution information and coal seam information, wherein the geological structure information includes rock layer distribution and type, the soil parameters include soil density, cohesion and internal friction angle, and the coal seam information includes cohesion and internal friction angle; The mining data includes mining depth and mining speed.

3. The method for simulating the disturbance of root-soil composite layer stability by coal mining activities based on FLAC3D in accordance with claim 1, characterized in that, In the S2, the coal seam plate is located between the floor plate and the direct roof, and the coal seam plate is divided into an encrypted region and a non-encrypted region according to the mining requirement, wherein the part needing to be mined is meshed, and the part not needing to be mined does not need to be meshed.

4. The method for simulating the disturbance of root-soil composite layer stability by coal mining activities based on FLAC3D in claim 1, characterized in that, In the S3, the FLAC3D overall model has a length of 300m, a distance of 200m and a height of 83m.

5. The method for simulating the disturbance of root-soil composite layer stability by coal mining activities based on FLAC3D in accordance with claim 1, characterized in that, In the S4, the displacement constraint is that the model periphery and the bottom keep fixed positions in the process of simulating mining.

6. The method for simulating the disturbance of root-soil composite layer stability by coal mining activities based on FLAC3D in accordance with claim 1, characterized in that, In the S5, the anchoring unit simulating the plant root system is specifically: according to the quasi-cohesion theory and the anchoring theory, the full-length anchoring unit is used to simulate the plant root system and is arranged, wherein the row spacing of the root system is 2m, and the column spacing is 3m.

7. The method for simulating the disturbance of root-soil composite layer stability by coal mining activities based on FLAC3D in accordance with claim 1, characterized by, In the S5, the mining area of the simulated mining has a length of 110m, a distance of 80m and a height of 6m.

8. The method for simulating the disturbance of root-soil composite layer stability by coal mining activities based on FLAC3D in claim 1, characterized in that, In the S5, the contact surface arranged in the upper part of the goaf is valued with normal stiffness, tangential stiffness and cohesion.

9. The method for simulating the disturbance of root-soil composite layer stability by coal mining activities based on FLAC3D in accordance with claim 1, characterized by, In the S6, the plastic zone damage condition of the root-soil composite layer includes a tensile failure region, a shear failure region and a region with both tensile failure and shear failure.

10. The method for simulating the disturbance of root-soil composite layer stability by coal mining activities based on FLAC3D in accordance with claim 1, characterized by, In the S6, in the process of simulating mining, the stress transmission condition of the coal seam excavation is analyzed according to the plastic zone damage condition of the root-soil composite layer, which comprises: The maximum shear stress from mining disturbance at different positions of the root-soil composite layer is obtained by using the function of obtaining maximum shear stress in FLAC3D, and the stress conditions at different positions of the root-soil composite layer are analyzed.

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