Mining overburden strata separation simulation method and device based on FLAC3D

Abstract

The present disclosure relates to a FLAC3D-based simulation method and device for mining overburden separation. The method comprises obtaining stratum floor elevation data of a study area; establishing a three-dimensional engineering geological model; determining a constitutive model, yield criterion, boundary condition and calculation parameter for the engineering geological model in FLAC3D; determining a first grid group and a second grid group adjacent to each other in the engineering geological model, the first grid group corresponding to an upper stratum and the second grid group corresponding to a lower stratum, and the stiffness of the upper stratum being greater than that of the lower stratum; separating one or more nodes shared by the first grid group and the second grid group and filling interface elements; and simulating mining overburden separation in the engineering geological model by using a step-by-step mining method. In this way, discontinuous deformation can be achieved at the soft and hard stratum interface in the overburden stratum above the mining area, thereby simulating the generation and development process of the separation space, while maintaining continuous and coordinated deformation between other strata.

Description

Technical Field

[0001] This disclosure generally relates to the field of engineering geological simulation technology, and particularly to a method and apparatus for simulating mining-induced overburden separation based on FLAC3D. Background Technology

[0002] my country's fossil energy structure, characterized by abundant coal, scarce oil, and limited gas, dictates that coal will remain the primary energy source. Vast coal resources are located beneath buildings, water bodies, and railways, commonly known as "coal under the three layers." With the development and utilization of coal resources, these underground coal reserves require further development and utilization. However, surface subsidence induced by coal mining can adversely affect surface structures, thus necessitating scientific and rational methods for developing these "coal under the three layers." Overburden separation grouting technology is a new technique for reducing subsidence during mining operations targeting "coal under the three layers." This technology uses pre-designed grouting holes on the surface to fill the abscission spaces formed in the overburden during mining operations. The grouting solids control over overburden movement, thereby controlling surface subsidence.

[0003] The prerequisite for grouting overburden delamination is understanding the movement and development patterns of the overburden strata on the working face. Currently, scholars both domestically and internationally have conducted extensive theoretical research on the mechanisms and development patterns of delamination. However, a direct and effective method for simulating mining-induced overburden delamination is lacking. Current methods for delamination simulation mainly rely on similar physical model experiments and discrete element method (DEM) software numerical simulations (such as 3DEC). These methods have the following drawbacks: model experiments are time-consuming, labor-intensive, and costly. Building similar physical models requires significant manpower; experimental operations and data recording also require substantial time and manpower. Furthermore, model experiments require large experimental sites and a large amount of experimental materials, making preparation cumbersome and costly. Once the similar physical model is built, adjustments to the various rock strata are difficult to make during the experiment, making it hard to achieve good simulation results. If the simulation results are unsatisfactory, the experiment must be repeated. Discrete element method (DEM) numerical simulation software is generally used for simulations of small scales and simple working conditions, and its simulation effect is poor for large-scale and complex rock and soil deformation problems. Currently, scholars generally use discrete element method (DEM) software to simulate and calculate individual delamination layers, which only allows for theoretical research on the development process and mechanism of delamination layers, but cannot establish large-scale, detailed three-dimensional geological models that closely resemble engineering realities. Furthermore, DEM software generally has a slow computation speed.

[0004] Among numerous numerical simulation software programs, FLAC3D is currently widely used for simulating deformation of rock and soil masses in three dimensions. However, FLAC3D is developed based on continuum mechanics theory and explicit finite difference methods, making it unsuitable for discontinuous deformation problems such as fractures, collapses, and penetrations. Since the formation of delamination spaces in mining-induced overburden is due to the discontinuous deformation of rock strata with varying degrees of hardness within the overburden, resulting in the separation of soft and hard rock layers, the challenge in simulating the development of delamination in mining-induced overburden lies in simulating the discontinuity at the interface between hard and soft rock within FLAC3D software.

[0005] Therefore, there is an urgent need for a FLAC3D-based method for simulating mining-induced overburden separation, in order to at least partially solve the above problems. Summary of the Invention

[0006] The purpose of this disclosure is to provide a method and apparatus for simulating mining-induced overburden separation based on FLAC3D, so as to at least partially solve the above-mentioned problems existing in the prior art.

[0007] According to a first aspect of this disclosure, a method for simulating mining-induced overburden separation based on FLAC3D is provided. The method includes:

[0008] S1: Collect borehole data of the study area and, based on the collected borehole data, obtain the elevation data of the bottom of the rock strata in the study area;

[0009] S2: Based on the obtained elevation data, a three-dimensional engineering geological model is established in FLAC3D, wherein the engineering geological model is meshed in FLAC3D to form multiple mesh groups, each of the multiple mesh groups is associated with a corresponding rock layer in the rock layer and adjacent mesh groups share one or more nodes;

[0010] S3: Determine the constitutive model, yield criterion, boundary conditions, and calculation parameters for the engineering geological model in the FLAC3D;

[0011] S4: In the engineering geological model, a first grid group and a second grid group that are adjacent to each other are determined, wherein the first grid group corresponds to the upper rock layer, the second grid group corresponds to the lower rock layer, and the stiffness of the upper rock layer is greater than that of the lower rock layer.

[0012] S5: Separate the one or more nodes shared between the first mesh group and the second mesh group and fill the interface unit; and

[0013] S6: The step-by-step mining method is used in the engineering geological model to simulate the overlying layer separation caused by mining.

[0014] In some embodiments, nodes between the first grid group and the second grid group are separated and filled with interface cells to simulate delamination space caused by discontinuous deformation.

[0015] In some embodiments, obtaining the elevation data of the top of the rock strata floor in the study area may be done using the Kriging method and may include: generalizing the rock strata based on geological time; and further stratifying the rock strata within the geological time based on lithological differences.

[0016] In some embodiments, the engineering geological model being meshed in the FLAC3D to form multiple mesh groups may include: determining a working face between adjacent rock strata in the rock strata based on the actual location of the coal mining face; expanding the engineering geological model outwards from the working face as the center; and performing a first-size meshing outside the working face area and a second-size meshing within the working face area, wherein the first size is larger than the second size.

[0017] In some embodiments, determining the constitutive model, yield criterion, boundary conditions, and calculation parameters for the engineering geological model in FLAC3D may include: selecting the constitutive model, the yield criterion, and the boundary conditions in FLAC3D; and determining the initial calculation parameters of the engineering geological model based on field borehole core samples.

[0018] In some embodiments, the step-by-step mining method used in the engineering geological model to simulate the overburden separation during mining may include: selecting the mining step distance and using the step-by-step mining method to perform the mining simulation calculation of the working face.

[0019] In some embodiments, the mining step distance may be less than or equal to the second dimension.

[0020] In some embodiments, the method may further include: determining the location of key layers, the location of delamination development, the overburden movement pattern, the dynamic development pattern of delamination, and predicting surface subsidence based on the mining simulation calculation results of the working face.

[0021] In some embodiments, the key layer includes at least one of the following: a primary key layer; and one or more sub-key layers.

[0022] According to a second aspect of this disclosure, a FLAC3D-based apparatus for simulating mining-induced overburden separation is provided. The apparatus includes: one or more processors; and a storage device for storing FLAC3D, which, when executed by the one or more processors, causes the one or more processors to implement the method according to a first aspect of this disclosure.

[0023] In general, the various embodiments of this disclosure can achieve at least the following beneficial effects:

[0024] (1) The continuous-discontinuous coupling calculation method for simulating overburden delamination using FLAC3D software can achieve discontinuous deformation at the interface between soft and hard rock layers in the overburden of the mining area, thereby simulating the generation and development process of delamination space, while maintaining continuous and coordinated deformation between other rock layers. Engineering practice shows that this method has high simulation accuracy and strong applicability.

[0025] (2) The simulation method disclosed herein has a fast calculation speed, is suitable for handling large-scale and complex calculation models, and can establish large-scale three-dimensional refined geological models that are close to the actual engineering situation.

[0026] (3) This simulation method requires less manpower and material resources and has good economic practicality.

[0027] (4) The parameters of the numerical model are inverted based on the field measured data to obtain simulation results that fit the actual engineering situation.

[0028] (5) The simulation results of this method can effectively predict the location and process of delamination development in the overlying strata on the coal mining face, guide the selection of appropriate grouting layers and timing on site, and provide scientific guidance for delamination grouting projects.

[0029] It should be understood that the description in the Summary of the Invention is not intended to limit the key or essential features of the embodiments of this disclosure, nor is it intended to restrict the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0030] The above and other objects, features, and advantages of embodiments of the present disclosure will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of the present disclosure are illustrated in the drawings by way of example and not limitation, in which:

[0031] Figure 1 This is a flowchart illustrating a FLAC3D-based method for simulating mining-induced overburden separation according to some embodiments of the present disclosure.

[0032] Figure 2 This is a schematic diagram illustrating the state of nodes to be separated between preset meshes in FLAC3D according to some embodiments of the present disclosure.

[0033] Figure 3 This is a schematic diagram showing the location of delamination development according to an embodiment of the present disclosure.

[0034] Figure 4 It shows the basis Figure 3 A schematic diagram of the subcritical layer three-layer delamination variation in the embodiment shown.

[0035] Figure 5 It shows the basis Figure 3 A schematic diagram of the development curve of the subcritical layer triple delamination in the embodiment shown.

[0036] Figure 6 It shows the basis Figure 3 The diagram shows the thickness curve of the delamination development when the working face is mined to 400m in the embodiment shown.

[0037] Figure 7 It shows the basis Figure 6 A schematic diagram of the cross-sectional lines of the model in the embodiment shown.

[0038] In the various figures, the same or corresponding reference numerals indicate the same or corresponding parts. Detailed Implementation

[0039] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0040] In the description of embodiments of this disclosure, the term "comprising" and similar terms should be understood as open-ended inclusion, i.e., "including but not limited to". The term "based on" should be understood as "at least partially based on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first", "second", etc., may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0041] It should be noted that in the various embodiments of this disclosure, "rock strata" and "strata" are the same or similar concepts. That is, in the context of this disclosure, the two can be used interchangeably.

[0042] As described above, this disclosure proposes a continuous-discontinuous coupling calculation method for simulating mining-induced overburden delamination in FLAC3D software. FLAC3D is a numerical simulation software based on continuum mechanics and is generally not used to simulate the mechanical behavior of discontinuous media exhibiting interlayer separation. Its inability to simulate discontinuous media mechanical behavior limits its application in simulating mining-induced overburden delamination. To simulate the process of delamination space formation due to the separation of soft and hard rock layers in FLAC3D software, this disclosure proposes a method of separating the nodes between soft and hard rock layers and adding interface elements, creating conditions for the formation of delamination space and achieving the goal of completing continuous-discontinuous coupling calculations in FLAC3D software. Through the method proposed in this disclosure, mining-induced overburden delamination simulation calculations can be completed in FLAC3D, providing a new, effective, and economical method for studying the dynamic development law of delamination. Engineering practice shows that this method can achieve good simulation results.

[0043] In addition, the simulation method disclosed herein has a fast calculation speed, is suitable for handling large-scale and complex calculation models, and can establish large-scale three-dimensional refined geological models that are close to the actual engineering situation. The simulation method consumes less manpower and material resources and has good economic practicality. The parameters of the numerical model can be adjusted at any time during the simulation process and inverted based on the field measured data, so as to obtain simulation results that fit the actual engineering situation.

[0044] The following will be combined with the appendix Figure 1 To be continued Figure 7 The embodiments of this disclosure will be described in detail.

[0045] Figure 1 This is a flowchart illustrating a FLAC3D-based method 100 for simulating mining-induced overburden separation according to some embodiments of the present disclosure. In some embodiments, reference is made to... Figure 1Method 100 includes the following steps: S1: Collecting borehole data of the study area and obtaining the elevation data of the rock strata floor of the study area based on the collected borehole data; S2: Establishing a three-dimensional engineering geological model in FLAC3D based on the obtained elevation data, wherein the engineering geological model is meshed in FLAC3D to form multiple mesh groups, each mesh group being associated with a corresponding rock stratum in the rock strata and adjacent mesh groups sharing one or more nodes; S3: Determining the constitutive model, yield criterion, boundary conditions, and calculation parameters for the engineering geological model in FLAC3D; S4: Determining a first mesh group and a second mesh group that are adjacent to each other in the engineering geological model, wherein the first mesh group corresponds to the upper rock stratum, the second mesh group corresponds to the lower rock stratum, and the stiffness of the upper rock stratum is greater than that of the lower rock stratum; S5: Separating one or more nodes shared between the first mesh group and the second mesh group and filling the interface elements; and S6: Simulating the overburden separation by a step-by-step mining method in the engineering geological model.

[0046] In step S1, borehole data of the study area can be collected, and based on the collected borehole data, the elevation data of the rock strata floor of the study area can be obtained. In this way, the rock strata or formations can be generalized.

[0047] In some embodiments, borehole data of the study area can be collected, and the rock strata of the study area can be generalized based on the borehole data. Specifically, the rock strata can be generalized according to different geological ages, and then further stratified according to different lithologies within each geological age. Here, lithology refers to some attributes reflecting the characteristics of rocks, such as color, composition, structure, cement and cement type, special minerals, etc. It should be understood that any method of stratification using lithology in the art can be used to implement the above steps, and this disclosure does not impose any limitations on it. It should be noted that the study area can be a study area of ​​any soil or rock strata, and this disclosure does not impose any limitations on it.

[0048] Furthermore, the elevation data of the floor strata can be obtained from borehole data using Kriging interpolation. Kriging is a regression algorithm that uses the covariance function to spatially model and predict (interpolate) stochastic processes / random fields. For specific stochastic processes, such as intrinsically stationary processes, Kriging can provide the optimal linear unbiased estimate; therefore, it is also known as the spatially optimal unbiased estimator in geostatistics. If the covariance functions are equivalent in form and the modeling object is a stationary Gaussian process, the output of ordinary Kriging has the same mean and confidence interval as the output of Gaussian process regression under normal likelihood, demonstrating stable predictive performance.

[0049] In step S2, a three-dimensional engineering geological model is established in FLAC3D based on the obtained elevation data. The engineering geological model is meshed in FLAC3D to form multiple mesh groups. Each mesh group is associated with a corresponding rock stratum, and adjacent mesh groups share one or more nodes. In this way, a refined three-dimensional engineering geological model can be established.

[0050] Those skilled in the art will understand that the delamination height decreases with distance from the working surface. Therefore, in some embodiments, to obtain good simulation results, the model should be appropriately expanded outwards from the working surface as the center. In FLAC3D, the mesh is divided; to ensure calculation speed, a large-size mesh can be performed outside the working surface area, while a more refined mesh is performed within the working surface area.

[0051] In step S3, the constitutive model, yield criterion, boundary conditions, and calculation parameters for the engineering geological model are determined in FLAC3D.

[0052] In some embodiments, FLAC3D software can be configured with multiple constitutive models and yield criteria. Appropriate constitutive models, yield criteria, and boundary conditions can be selected based on the actual simulation requirements. Regarding calculation parameters, in some embodiments, core samples obtained from field boreholes can be used for laboratory tests to obtain the initial parameters required for model calculations, including the elastic modulus, Poisson's ratio, cohesion, internal friction angle, unit weight, and tensile strength of each rock stratum. Parameter inversion can then be performed during subsequent calculations.

[0053] In steps S4 and S5, in the engineering geological model, a first grid group and a second grid group are identified that are adjacent to each other. The first grid group corresponds to the upper rock layer, and the second grid group corresponds to the lower rock layer, with the upper rock layer having a higher stiffness than the lower rock layer. Then, one or more nodes shared between the first and second grid groups are separated and interface elements are filled. Depending on the lithology, when the hardness of adjacent rock layers differs significantly throughout the model, the method described in steps S4 and S5 is used for processing. This allows for the simulation of delamination spaces caused by discontinuous deformation in continuously deforming rock layers.

[0054] In the field of mining-induced overburden technology, the key stratum refers to the rock stratum that controls the activity of the overburden strata locally or even to the entire surface. A key stratum typically includes one or more sub-key strata and a main key stratum. According to the key stratum theory, the delamination space in mining-induced overburden is caused by discontinuous deformation between soft and hard rock strata, with one to several thick, hard rock strata playing a major controlling role in the activity of the overburden strata in the stope. The key stratum is relatively thicker than other similar rock strata and is also relatively harder, meaning it has a higher elastic modulus and strength. Generally, when the key stratum bends and deforms, the bending deformation of all or part of its overlying rock strata is synchronized and coordinated, while discontinuous deformation occurs between the key stratum and the underlying rock strata. Therefore, the delamination space often develops below the harder rock strata. Simulating the development of the delamination space below the harder rock strata is crucial for calculating mining-induced overburden delamination and predicting surface subsidence.

[0055] In FLAC3D software, preset mesh groups (such as the first mesh group and the second mesh group) are typically used to simulate various rock strata. The preset mesh groups share nodes, which are also referred to as nodes to be separated in the embodiments of this disclosure. The specific technical methods of representing rock strata with mesh groups in FLAC3D software will not be elaborated in this disclosure. Figure 2 This is a schematic diagram illustrating the state of nodes to be separated between preset meshes in FLAC3D according to some embodiments of the present disclosure.

[0056] like Figure 2 As shown, the nodes at the interface between mesh group 1 and mesh group 2 are either in a shared state or in a state to be separated. In this state, only continuous deformation of the two mesh groups can be achieved, but discontinuous deformation between the two mesh groups cannot be generated, thus preventing the separation of the two mesh groups and making it impossible to simulate the development of delamination space. In other words, this state of nodes to be separated makes FLAC3D unable to simulate the situation where delamination space is generated.

[0057] Therefore, according to some embodiments of this disclosure, by comprehensively analyzing the physical and mechanical parameters of each rock stratum, the nodes between rock strata in the model where the upper layer is hard rock and the lower layer is soft rock can be separated and set to a dual-node state. That is, in strata where delamination conditions may develop, the shared nodes of the connecting layers of the two grid groups are divided into two, with each using its own separate node. In this way, there is no connection between the upper and lower grid groups, that is, they lose their interaction with each other.

[0058] Subsequently, interface elements can be set at the layer where the two nodes are set. Due to the positional relationship of the two nodes, the upper and lower mesh layers have no connection and lose their interaction relationship. Applying interface elements re-establishes the connection between these two mesh layers. In FLAC3D software, interface elements are the connection between separable sub-mesh layers during the calculation process, which can be used to represent physical discontinuities, such as faults, structural planes, or contact surfaces between two different materials. Specifically, in this method, after separating the shared node into two nodes, the transmission of physical quantities such as force and displacement between the upper and lower layers disappears. Adding interface elements enables the transmission of physical quantities such as force and displacement, so that discontinuous deformation at this location does not affect the movement of the overlying strata.

[0059] In this way, by separating the nodes at the junction of soft and hard rock layers and adding interface units, discontinuous deformation can be generated between the soft and hard rock layers, thus creating the preconditions for the generation of delamination space between these layers, and this method does not interfere with overburden movement.

[0060] In step S6, a step-by-step mining method is used to simulate overburden separation in the engineering geological model. Specifically, an appropriate mining step distance can be selected, and the working face mining simulation calculation is performed using the step-by-step mining method. To obtain good simulation results, the smallest grid size can be selected as the mining step distance. During the calculation process, the calculation parameters can be inverted based on field measurement data to make the calculation results more consistent with engineering reality.

[0061] In one embodiment, a working face between adjacent rock strata can be determined, and then the engineering geological model can be expanded outwards from the working face. A first-size grid is then created outside the working face area, and a second-size grid is created within the working face area, where the first grid size is larger than the second size. This allows the mining step distance to be selected using the second size, or, more precisely, a mining step distance smaller than the second size can be used to obtain more accurate results.

[0062] In addition, method 100 may optionally include determining the location of key layers, the location of delamination development, the movement law of overburden and the dynamic development law of delamination based on the mining simulation calculation results, and making surface subsidence prediction.

[0063] In one specific embodiment, after the model calculation is completed, all data such as the location of key layers, the location of delamination development, the movement pattern of overlying strata, and the dynamic development pattern of delamination can be derived from the calculation results through induction, and surface subsidence prediction can be performed. In this embodiment, the prediction method that considers multiple factors yields more accurate results.

[0064] The exemplary embodiments of this disclosure will be further described below with reference to exemplary engineering examples. This example embodiment performs numerical simulation calculations on the dynamic development law of overburden delamination in a coal mine working face in Shanxi Province, and can further predict surface subsidence based on the calculation results.

[0065] In this embodiment, lithological data from 34 boreholes near the coal mine study area were collected, and the strata or formations of the study area were generalized based on the borehole data. Specifically, the strata were first generalized based on different geological ages. In the three-dimensional geological model, the strata were divided from top to bottom as follows: Quaternary surface soil, Upper Permian Shiqianfeng Formation, Upper Permian Shihezi Formation, Lower Permian Shihezi Formation, Permian Shanxi Formation, Upper Carboniferous Taiyuan Formation, and Ordovician Fengfeng Formation. Secondly, within each geological age, the strata were further refined according to different lithologies. In this case, the strata of the study area were divided into 17 layers. In this way, the generalization of the strata or formations was completed, and a detailed stratification of the strata in the study area was obtained.

[0066] It should be noted that the number of boreholes, the method of layering, and the number of layers mentioned above are merely exemplary. Those skilled in the art can perform other layering according to the specific area to be studied, and this disclosure does not impose any restrictions on this.

[0067] Next, a detailed three-dimensional engineering geological model can be established as follows: The working face is 1140m long in the mining direction, which can be used as the x-axis of the three-dimensional geological model, with the mining direction being the positive x-axis. The y-axis of the three-dimensional geological model can be taken as perpendicular to the mining direction of the working face, with the positive z-axis pointing from low altitude to high altitude. The model extends outward by 1000m along the mining boundary of the working face on the positive and negative x-axis and y-axis, respectively, serving as the model boundary of this three-dimensional geological model. The model is 3140m long in the x-axis direction, 2280m long in the y-axis direction, and has an average thickness of approximately 850m in the z-axis direction.

[0068] In FLAC3D, the model can be meshed using triangular prism elements, or any other suitable element, as long as the desired effect is achieved; this disclosure does not impose any restrictions. Furthermore, within the working surface area, the mesh size can be set to 10m × 10m × 10m, which is the second size mentioned earlier. Outside the working surface, towards locations further away from it, the model mesh size can be increased, for example, to 30m × 30m × 30m, which is the first size mentioned earlier. In this way, the 3D geological model can be meshed into over 2.65 million elements, each with approximately 1.34 million nodes.

[0069] The determination of the constitutive model, yield criterion, boundary conditions, and calculation parameters can be achieved using the following exemplary method: the calculation boundary is a displacement-constrained boundary condition, the X-axis and Y-axis directions are normal displacement constraints, and the bottom of the Z-axis direction is a full constraint. The model boundary conditions can be set as follows:

[0070] (1) Single-factor horizontal constraint boundaries are set at the front, back, left and right boundaries of the model;

[0071] (2) The bottom boundary and vertical direction of the model are set to fully constrained bottom and vertical boundaries, and the initial acceleration is set to zero.

[0072] (3) The top of the model is set to free, without any constraints;

[0073] In some embodiments, an ideal elastoplastic model can be selected as the constitutive model, and the Mohr-Coulomb criterion can be used as the yield criterion. The selection of physical and mechanical parameters is based on the collected laboratory test results of borehole cores in the study area and numerical simulation experience.

[0074] It should be understood that the selection of the Mohr-Coulomb yield criterion is exemplary, and other yield criteria such as the Tresca yield criterion, the Mises yield criterion, or others may be used as yield criteria as needed, without limitation in this disclosure.

[0075] Subsequently, before the model's step-by-step mining simulation calculations, nodes were separated between rock strata where the upper layer was hard rock and the lower layer was soft rock, setting them to a dual-node state. Then, interface elements were set at the rock strata locations with dual nodes. After the interface elements were set, model calculations could be performed. The model calculations required step-by-step mining of the working face. To more closely approximate reality, in this embodiment, the mining step distance for the working face was set to 10m per step, consistent with the grid size of 10m×10m×10m within the working face area. In this embodiment, with a working face mining length of 1140m, a total of 114 mining steps were required.

[0076] In this particular embodiment, such as Figure 3 As shown, after the model calculation was completed, the numerical simulation results showed that four key layers were obtained in the overlying strata of the working face in the study area. They were named as the main key layer, sub-key layer one, sub-key layer two, and sub-key layer three from top to bottom. Delamination was developed under all four key layers, and the development conditions were different.

[0077] The following will take the third sub-critical layer as an example, combined with... Figure 4 and Figure 5 This paper introduces the changes in the subcritical layer 3 delamination layer and the development curve of the subcritical layer 3 delamination layer, so as to derive the dynamic evolution law of the subcritical layer 3.

[0078] In this embodiment, reference Figure 4 and Figure 5 When the working face is mined to 200m, by Figure 4 Part a and Figure 5 Part a is visible. At this point, with the mining of the working face, the subsidence of the overlying stratum has been transferred to the third subcritical layer. This layer exhibits significant delamination, which begins approximately at the opening of the working face and extends within 200 meters of the opening. Along the mining direction, the delamination exhibits a parabolic shape, with the largest delamination in the middle and smaller delamination at the edges. The maximum thickness of the delamination is approximately 0.7 meters, with the center of development located approximately 85 meters from the opening.

[0079] Continue to refer to Figure 4 and Figure 5 When the working face is mined to 400m, by Figure 4 Part b and Figure 5 As can be seen in section b, the maximum thickness of the abscission layer is about 0.34m, located about 300m from the opening eye. At this time, the abscission layer mainly develops in the section 240-400m from the opening eye.

[0080] Furthermore, such as Figure 4 and Figure 5 As shown, when the working face is mined to 600m, by Figure 4 Part C and Figure 5 In section c, the maximum thickness of the abscission layer is about 0.34m. It can also be observed that there are still some unclosed abscission layers in the 200m to 400m section. The abscission layer development in this layer has a long duration and a long development length.

[0081] Subsequently, when the working face was mined to 800m, by Figure 4 The middle part d and Figure 5 In the middle d section, the maximum thickness of the abscission layer is about 0.3m. The development range is located in the section about 680 to 1000m from the opening eye. The thickness of the abscission layer shows a significant decreasing trend in the section from 600 to 700m, and then gradually increases again.

[0082] When the working face is mined to 1000m, by Figure 4 Part e and Figure 5 As can be seen in section e, the maximum thickness of the abscission layer is about 0.1m, and the development range is located within a section of about 400 to 800m from the opening eye, where the abscission space is relatively small.

[0083] In this embodiment, when the working face advances to 1140m, i.e., after mining is completed, it is... Figure 4 The middle f part and Figure 5As can be seen in section f, near the stop line of the working face mining area, there is a delamination space with a maximum thickness of less than 0.25m that is not completely closed. The delamination in other locations is well developed and closed after development.

[0084] Thus, this embodiment shows that the delamination at the three subcritical layers developed earliest, with a maximum delamination thickness of 2m. After the mining of the working face ended, except for a small section of unclosed delamination near the stop line, the other locations were well closed.

[0085] The following will combine Figure 6 and Figure 7 Taking the delamination development at a working face depth of 400m as an example, this study analyzes the overall dynamic development pattern of delamination in the overlying strata of the research area. Figure 6 It shows the basis Figure 3 The diagram shows the thickness curve of the delamination development when the working face reaches 400m in the illustrated embodiment. Figure 7 It shows the basis Figure 6 A cross-sectional view of the embodiment shown.

[0086] In this embodiment, such as Figure 6 As shown, the lowest key layer, namely subkey layer three, is where delamination first occurs. At this level, subkey layer three controls the bending deformation of the overlying rock strata up to subkey layer two. The thickness of the delamination below subkey layer three gradually increases until subkey layer three breaks, initiating bending deformation. The rock strata it controls also undergo bending deformation along with subkey layer three. At this point, the thickness of the delamination at subkey layer three begins to decrease, while delamination at subkey layer two gradually develops.

[0087] Continue to refer to Figure 6 The remaining key layers follow a similar pattern. In this embodiment, when the second subcritical layer breaks, the second subcritical layer and the overburden it controls undergo synchronous bending deformation. The thickness of the delamination at the second subcritical layer gradually decreases, and delamination at the first subcritical layer gradually begins to form. When the first subcritical layer breaks, delamination below the main key layer begins to develop. With the breaking of the main key layer, significant surface subsidence will occur. Thus, by simulating continuous-discontinuous coupling calculations of overburden delamination during mining and performing comprehensive analysis, surface subsidence can be predicted.

[0088] Figure 7 The cross-sectional view of the working surface is shown in detail. In this embodiment, reference is made to... Figure 7 , Figures 3-5 The cross-sections shown are all based on Figure 7 The aa section line in the middle.

[0089] According to some embodiments, a FLAC3D-based device for simulating mining-induced overburden separation is also provided. This device includes one or more processors and a storage device. The processor can be any suitable processor in the art, such as a CPU. The storage device can be used to store FLAC3D software. Furthermore, when FLAC3D is executed by the one or more processors, the one or more processors perform the methods described above.

[0090] The various embodiments of this disclosure utilize the FLAC3D software to simulate a continuous-discontinuous coupling calculation method for overburden delamination during mining. This method enables discontinuous deformation at the interface between soft and hard rock layers in the overburden of the mining area, thereby simulating the generation and development process of delamination space, while maintaining continuous and coordinated deformation between other rock layers. Engineering practice shows that this method has high simulation accuracy and strong applicability. Moreover, the simulation method of this disclosure has a fast calculation speed, making it suitable for handling large-scale, complex calculation models, and can establish large-scale, refined three-dimensional geological models that closely resemble engineering realities. This simulation method requires less manpower and material resources, demonstrating good economic practicality. Furthermore, the parameters of the numerical model can be adjusted at any time during the simulation process and inverted based on field measurement data, thereby obtaining simulation results that closely match engineering realities.

[0091] While several specific implementation details are included in the foregoing discussion, these should not be construed as limiting the scope of this disclosure. Certain features described in the context of individual embodiments may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented individually or in any suitable sub-combination in multiple implementations.

[0092] Furthermore, although the operations are described in a specific order, this should be understood as requiring that such operations be performed in the specific order shown or in sequential order, or requiring that all illustrated operations be performed to achieve the desired result. In certain environments, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of this disclosure. Certain features described in the context of individual embodiments may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented individually or in any suitable sub-combination in multiple implementations.

[0093] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A FLAC3D-based mining overburden rock separation simulation method, characterized in that, include: S1: Collect borehole data of the study area and, based on the collected borehole data, obtain the elevation data of the bottom of the rock strata in the study area; S2: Based on the obtained elevation data, a three-dimensional engineering geological model is established in FLAC3D, wherein the engineering geological model is meshed in FLAC3D to form multiple mesh groups, each of the multiple mesh groups is associated with a corresponding rock layer in the rock layer and adjacent mesh groups share one or more nodes; S3: Determine the constitutive model, yield criterion, boundary conditions, and calculation parameters for the engineering geological model in the FLAC3D; S4: In the engineering geological model, a first grid group and a second grid group that are adjacent to each other are determined, wherein the first grid group corresponds to the upper rock layer, the second grid group corresponds to the lower rock layer, and the stiffness of the upper rock layer is greater than that of the lower rock layer. S5: Separate the one or more nodes shared between the first mesh group and the second mesh group, and fill the interface unit; and S6: The step-by-step mining method is used in the engineering geological model to simulate the overlying layer separation caused by mining.

2. The method of claim 1, wherein, The nodes between the first and second mesh groups are separated and filled with interface elements to simulate the delamination space caused by discontinuous deformation.

3. The method of claim 1, wherein, The elevation data of the rock strata floor in the study area were obtained using the Kriging method and included: The rock strata are generalized based on geological age; and Based on differences in lithology, the rock strata are further layered within the geological age.

4. The method of claim 1, wherein, The engineering geological model is meshed in FLAC3D to form multiple mesh groups, including: The working face between adjacent rock strata is determined based on the actual location of the coal mining face. With the working face as the center, the engineering geological model is expanded outwards in all directions; and A first-size mesh is performed outside the working surface area, and a second-size mesh is performed within the working surface area, wherein the second size is smaller than the first size.

5. The method of claim 1, wherein, The constitutive model, yield criterion, boundary conditions, and calculation parameters for the engineering geological model are determined in FLAC3D, including: In the FLAC3D, select the constitutive model, the yield criterion, and the boundary conditions; and Based on the borehole core samples, the initial calculation parameters of the engineering geological model were determined.

6. The method of claim 4, wherein, The simulation of mining-induced overburden separation using a step-by-step mining method in the engineering geological model includes: The mining step distance was selected, and the working face mining simulation calculation was carried out using the step mining method.

7. The method of claim 6, wherein, The mining step distance is less than or equal to the second dimension.

8. The method of claim 6, wherein, Also includes: Based on the simulation calculation results of the working face mining, the location of key layers, the location of delamination development, the movement law of overburden and the dynamic development law of delamination are determined, and surface subsidence is predicted.

9. The method of claim 8, wherein, The key layer includes at least one of the following: The primary key layer; and One or more sub-key layers.

10. A FLAC3D-based simulation device for mining-induced overburden separation, comprising: One or more processors; as well as a storage device for storing the FLAC3D that, when executed by the one or more processors, causes the one or more processors to implement the method of any one of claims 1-9.

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