Shallow-buried thick coal seam mining goaf boundary earth surface crack control method and system

Abstract

The invention provides a shallow-buried thick coal seam mining goaf boundary earth surface crack control method and system, and belongs to the field of mining area geological disaster prevention and control. The problems that an existing goaf boundary earth surface crack control method is high in cost and low in resource recovery rate are solved. The method comprises the following steps: acquiring geological mining parameters of a target mining area; based on the ground surface horizontal deformation model, obtaining a ground surface horizontal deformation value of a goaf boundary of a target mining area in a conventional strip mining reserved coal pillar mining mode, and determining a safe mining width and a mining height meeting ground surface deformation control requirements; analyzing the relationship between the safe mining width and the working face inclination length, and judging a mining mode; all the working faces are mined in sequence, after stoping of each working face is completed, an artificial roof is laid on the boundary of the goaf of the working face, mining is conducted on the boundary of the goaf, close to the previous working face, of the subsequent working face, and section coal pillars are not reserved; the method is applied to shallow-buried thick coal seam mining.

Description

Technical Field

[0001] This invention relates to the field of geological disaster prevention and control technology in mining areas, specifically to a method and system for controlling surface cracks at the boundary of mined-out areas in shallow-buried thick coal seams. Background Technology

[0002] Shallow-buried, thick coal seams are widely found in western my country's mining areas. Due to their shallow depth and thickness, these seams create extensive goaf areas after mining, leading to intense overburden movement and severe surface damage. In particular, step-like cracks and subsidence pits easily form at the boundaries of goaf areas, causing permanent damage that not only severely disrupts the ecological environment of the mining areas but also threatens surface buildings and the safety of people's lives and property. Therefore, implementing effective measures to control surface movement and deformation is crucial.

[0003] Currently, common methods for controlling surface subsidence mainly include strip mining, backfilling mining, and coordinated mining. Strip mining employs a "mine one, leave several branch roadways" approach, relying on the left-in coal pillars to support the overlying strata and reduce surface movement. Backfilling mining limits the overlying strata's movement space by filling the goaf with material, reducing surface deformation and improving resource recovery. Coordinated mining optimizes the layout of working faces so that deformations caused by adjacent working faces cancel each other out. However, all these methods have significant shortcomings:

[0004] 1. Strip mining requires leaving a large number of permanent coal pillars, resulting in low resource recovery rate. In addition, the high tunneling rate per 10,000 tons and frequent relocation of working faces seriously affect production efficiency.

[0005] 2. The initial investment in backfilling mining is large, the process is complex, and the material costs are high, which leads to limited production capacity, increased cost per ton of coal, and poor economic benefits.

[0006] 3. Coordinated mining has strict requirements on geological conditions and mining layout, and is complex to manage. In practice, it is often difficult to implement due to the limitation of mining space.

[0007] In summary, existing technologies generally suffer from problems such as high cost, low resource recovery rate, or limited applicability. There is an urgent need to provide a control method that can achieve efficient recovery of shallow buried thick coal seams and accurately suppress permanent cracks at the boundary of goaf while controlling costs. Summary of the Invention

[0008] To address the technical problems of high cost and low resource recovery rate of existing methods for controlling surface cracks at the boundary of mined-out areas, this invention proposes a method and system for controlling surface cracks at the boundary of mined-out areas in shallow-buried thick coal seam mining.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for controlling surface cracks at the boundary of a goaf area in shallow-buried thick coal seam mining, comprising the following steps:

[0010] Step S1: Obtain the geological and mining parameters of the target mining area. The geological and mining parameters include at least the working face dip length L, the total coal seam thickness M, the average mining depth H, and the overburden hardness coefficient f.

[0011] Step S2: Obtain the surface horizontal deformation value ε at the boundary of the goaf in the target mining area under the conventional strip mining with coal pillar retention mode based on the surface horizontal deformation model; determine the safe mining width d and mining height M1 that meet the surface deformation control requirements based on the surface horizontal deformation value ε.

[0012] Step S3: Analyze the relationship between the safe mining width d and the working face dip length L to determine the mining mode:

[0013] When the safe mining width d is not less than the working face dip length L, the thickness-limited mining mode is adopted, and multiple square working faces are arranged along the working face dip direction for mining. The mining width of the square working face is the working face dip length L, and the mining height is the mining height M1.

[0014] When the safe mining width d is less than the working face dip length L, a step-type connection pillarless mining mode is adopted. Multiple step-shaped working faces are arranged along the working face dip direction for staged mining. The step width of the step-shaped working face is the safe mining width d, and the step height of the step-shaped working face is the mining height M1.

[0015] Step S4: Mining each working face in sequence, and after each working face is mined out, laying an artificial false roof at the boundary of its goaf. Subsequent working faces are mined adjacent to the boundary of the goaf of the previous working face, without leaving any section coal pillars.

[0016] Furthermore, in step S2, the horizontal deformation value ε of the surface is obtained by constructing a surface horizontal deformation model using the probability integral method. The expression for the surface horizontal deformation model is:

[0017] ;

[0018] ;

[0019] ;

[0020] ;

[0021] In the formula, b is the horizontal movement coefficient, W0 is the maximum subsidence value, r is the main influence radius, M is the total thickness of the coal seam, and q is the subsidence coefficient. H represents the coal seam dip angle, and H represents the average mining depth. The tangent of the main influencing angle is C, and the depth ratio is C.

[0022] Furthermore, in step S2, the preliminary model for obtaining the safe mining width d is as follows:

[0023] ;

[0024] In the formula, k is the correction coefficient and f is the overlying rock hardness coefficient;

[0025] The final model for obtaining the safe mining width d, determined by combining the preliminary model and the surface horizontal deformation model, is as follows:

[0026] ;

[0027] when hour, ;

[0028] when hour, ;

[0029] when hour, .

[0030] Furthermore, in step S2, the model for obtaining the sampling height M1 is as follows:

[0031] .

[0032] Furthermore, the overburden hardness coefficient f is determined based on the Protodyakonov robustness coefficient:

[0033] When the rock mass is a hard overlying rock, f > 8;

[0034] When the rock mass is a medium-hard overburden, 3 ≥ f < 8;

[0035] When the rock mass is a weak overlying rock, f < 3.

[0036] Furthermore, when using the limited-thickness mining mode, the artificial false roof has a square structure; when using the stepped-connected pillarless mining mode, the artificial false roof has a stepped shape.

[0037] Stepped coal pillars are reserved on the side of the working face at both ends of the target mining area that is far away from its corresponding artificial false roof;

[0038] The step width of both the stepped artificial roof and the stepped coal pillar is the safe mining width d, and the step height is the mining height M1.

[0039] Furthermore, in step S4, the artificial false roof is a flexible support structure consisting of at least a combination of metal mesh and anchor bolts.

[0040] Furthermore, the process of laying the artificial false ceiling is as follows:

[0041] After the current working face is mined out, a metal mesh is installed at the cut-off line of the corresponding goaf boundary. One end of the metal mesh is fixedly connected to the roof rock layer corresponding to the current goaf, and the other end of the metal mesh extends and is fixed to the floor corresponding to the current goaf, so that the artificial false roof forms a flexible retaining wall.

[0042] Furthermore, adjacent metal meshes are connected by double-strand iron wires, and temporary support devices are installed at preset intervals along the inclined length direction to complete temporary reinforcement support.

[0043] A surface fracture control system for the boundary of a goaf in shallow-buried thick coal seam mining, used to implement the method described above, includes:

[0044] The parameter acquisition module is used to acquire the geological and mining parameters of the target mining area. The geological and mining parameters include at least the working face dip length L, the total coal seam thickness M, the average mining depth H, and the overburden hardness coefficient f.

[0045] The safety parameter determination module, connected to the parameter acquisition module, obtains the surface horizontal deformation value ε of the goaf boundary of the target mining area under the conventional strip mining with coal pillar retention mode based on the surface horizontal deformation model; and determines the safe mining width d and mining height M1 that meet the surface deformation control requirements based on the surface horizontal deformation value ε.

[0046] The mining mode determination module, connected to the safety parameter determination module, is configured as follows:

[0047] Analyze the relationship between the safe mining width d and the dip length L of the working face, and determine the mining mode: when the safe mining width d is not less than the dip length L of the working face, the thickness-limited mining mode is adopted; when the safe mining width d is less than the dip length L of the working face, the step-connected pillarless mining mode is adopted.

[0048] The mining execution module, connected to the mining mode determination module, is used to execute mining operations according to the determined mining mode.

[0049] When the mining mode is determined to be limited thickness, multiple square working faces are arranged along the dip direction of the working face for mining. The mining width of the square working face is the dip length L of the working face, and the mining height is the mining height M1.

[0050] When the mining mode is determined to be a stepped, pillarless mining mode, multiple stepped working faces are arranged along the dip direction of the working face for phased mining. The step width of the stepped working face is the safe mining width d, and the step height of the stepped working face is the mining height M1.

[0051] The advantages of this invention over the prior art are as follows:

[0052] 1. This invention adopts a step-type pillarless mining mode, which arranges multiple working faces with a step width of d and a step height of M1 along the dip direction of the working face for staged mining. Compared with the traditional strip mining mode with pillars, it significantly improves resource recovery efficiency and economic benefits. Compared with the traditional backfilling mining mode, it does not require a large amount of backfilling material. With lower engineering investment and simple construction technology, it effectively controls the surface cracks at the boundary of shallow buried thick coal seam goaf, and significantly reduces the cost of mining per ton of coal.

[0053] 2. This invention obtains the safe mining width d and mining height M1 of the mining face through a surface horizontal deformation model, and carries out step-by-step pillarless mining in stages according to the safe mining width d. This effectively alleviates the degree of surface movement and deformation at the boundary of the goaf, effectively reduces the number, opening amount and development depth of permanent cracks at the boundary of the goaf, effectively inhibits the formation of subsidence pits, and protects the surface ecology and the safety of structures.

[0054] 3. The method of the present invention is simple to implement, does not introduce complex new equipment or high-cost materials, is easy to promote and apply in existing production mines, and is convenient for on-site engineering technicians to design and implement according to specific conditions. It has universal applicability to shallow buried thick coal seam mining areas.

[0055] 4. By clearly defining the judgment thresholds for two mining modes, this invention can specifically address the contradiction between surface crack control and resource extraction under different working conditions. When d≥L, the thickness-limited mining mode is adopted, which simplifies the mining layout and improves mining efficiency while meeting the surface deformation control requirements. When d<L, the step-connected pillarless mining mode is adopted, which can effectively control the surface deformation at the boundary of the goaf through phased step mining, while eliminating the need for section pillars and improving the coal resource recovery rate. This invention achieves the coordinated advancement of safe mining of shallow buried thick coal seams and surface environmental protection, avoiding the subjectivity and experience dependence of traditional mining mode selection, and ensuring precise matching between the mining mode and the surface deformation control requirements and working face parameters of the target mining area. Attached Figure Description

[0056] The present invention will be further described below with reference to the accompanying drawings:

[0057] Figure 1 A working face layout diagram for conventional strip mining with coal pillars;

[0058] Figure 2 This is a working face layout diagram of the thickness-limited mining mode of the present invention;

[0059] Figure 3 This is a working face layout diagram of the stepped, pillarless mining mode of the present invention;

[0060] Figure 4Distribution map of surface damage under the conventional strip mining method with coal pillar retention;

[0061] Figure 5 This is a distribution map of surface damage under the step-connected pillarless mining mode of the present invention;

[0062] Figure 6 A schematic diagram of the surface subsidence curves corresponding to the stepped, pillarless mining mode of the present invention and the conventional strip mining mode with pillars.

[0063] Figure 7 This is a schematic diagram of the system structure of the present invention.

[0064] In the diagram: 1 represents the coal pillar, 2 represents the working face, and 3 represents the artificial false roof. Detailed Implementation

[0065] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate relative orientations or positional relationships and are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0066] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0067] like Figures 1 to 7 As shown, this invention provides a method for controlling surface cracks at the boundary of a goaf area in shallow-buried thick coal seam mining, comprising the following steps:

[0068] Step S1: Obtain the geological and mining parameters of the target mining area. The geological and mining parameters include at least the working face dip length L, the total coal seam thickness M, the average mining depth H, and the overburden hardness coefficient f. The geological and mining parameters and the working face data n to be laid out are determined according to the geological and mining conditions of the target mining area.

[0069] Step S2: Obtain the surface horizontal deformation value ε at the boundary of the goaf in the target mining area under the conventional strip mining with coal pillar 1 mining mode based on the surface horizontal deformation model; determine the safe mining width d and mining height M1 that meet the surface deformation control requirements based on the surface horizontal deformation value ε.

[0070] Specifically, the horizontal deformation value ε of the land surface is obtained by constructing a horizontal deformation model using the probability integral method. The expression for the horizontal deformation model is as follows:

[0071] ;

[0072] ;

[0073] ;

[0074] ;

[0075] In the formula, b is the horizontal movement coefficient, W0 is the maximum subsidence value, r is the main influence radius, M is the total thickness of the coal seam, and q is the subsidence coefficient. H represents the coal seam dip angle, and H represents the average mining depth. The tangent of the main influencing angle is C, and the depth ratio is C.

[0076] The preliminary model for obtaining the safe mining width d is as follows:

[0077] ;

[0078] In the formula, k is the correction coefficient and f is the overlying rock hardness coefficient.

[0079] The overlying rock hardness coefficient f is determined based on the Protodyakonov strength coefficient:

[0080] When the rock mass is a hard overlying rock, f > 8;

[0081] When the rock mass is a medium-hard overburden, 3 ≥ f < 8;

[0082] When the rock mass is a weak overlying rock, f < 3.

[0083] The final model for obtaining the safe mining width d, determined by combining the preliminary model and the surface horizontal deformation model, is as follows:

[0084] ;

[0085] when hour, ;

[0086] when hour, ;

[0087] when hour, .

[0088] The model for obtaining the mining height M1 is as follows:

[0089] .

[0090] Step S3: Analyze the relationship between the safe mining width d and the working face dip length L to determine the mining mode:

[0091] When the safe mining width d is not less than the working face dip length L (d≥L), the limited thickness mining mode is adopted, and multiple square working faces 2 are arranged along the dip direction of the working face 2 for mining. The mining width of the square working face 2 is the working face dip length L, and the mining height is the mining height M1.

[0092] Specifically, when using the coal cutting actuator to cut coal in the target mining area, the cutting length of a single working face 2 is equal to the working face dip length L. Multiple working faces 2 are mined sequentially by adjusting the height of the coal shearer drum, strictly controlling the actual cutting height to not exceed the mining height M1. If the total coal seam thickness M is greater than the mining height M1, top coal or bottom coal is retained during mining, with the remaining coal thickness serving as a protective layer, and top coal caving is not performed. By limiting the vertical height of a single mining operation (mining height M1), the migration space and intensity of the overburden are reduced, thereby keeping the surface horizontal deformation value within the allowable range.

[0093] When the safe mining width d is less than the dip length L of the working face (d < L), a step-type pillarless mining mode is adopted. Multiple step-shaped working faces 2 are arranged along the dip direction of the working face 2 for staged mining. The step width of the step-shaped working face 2 is the safe mining width d, the step height of the step-shaped working face 2 is the mining height M1, and the total mining height is the total thickness of the coal seam M.

[0094] Step S4: Mining each working face 2 sequentially, and after the mining of each working face 2 is completed, laying an artificial false roof 3 at the boundary of its corresponding goaf. Subsequent working faces 2 are mined adjacent to the goaf boundary of the previous working face 2, without leaving any section coal pillars 1. Specifically, when using the limited thickness mining mode, the artificial false roof 3 has a square structure; when using the stepped connection pillarless mining mode, the artificial false roof 3 has a stepped shape. At both ends of the target mining area, the working faces away from their corresponding artificial false roofs have stepped coal pillars reserved on the side. The step width of both the stepped artificial false roof 3 and the stepped coal pillar 1 is the safe mining width d, and the step height is the mining height M1.

[0095] The artificial false roof 3 is a flexible protective structure composed of at least a metal mesh combined with anchor bolts. The material of the artificial false roof 3 is a high-strength, corrosion-resistant steel wire mesh with a diameter of 4mm to 6mm.

[0096] The process of laying the artificial false ceiling 3 is as follows:

[0097] After the current working face 2 is mined out, a diamond-shaped metal mesh is installed at the roof cutting line of the corresponding goaf boundary. The upper end of the diamond-shaped metal mesh is fixedly connected to the roof strata corresponding to the current goaf by anchor bolts or anchor cables, and the lower end of the diamond-shaped metal mesh extends to the floor corresponding to the current goaf and is compacted or anchored with heavy objects. The artificial false roof 3 forms a flexible retaining wall to prevent the collapsed gangue from the current goaf from flowing into the mining space of the next adjacent working face 2, realizing continuous mining without coal pillars 1.

[0098] Adjacent diamond-shaped metal meshes are connected by double-strand iron wires, and temporary support devices are installed at predetermined intervals (e.g., 2-3m) along the inclined length direction to complete temporary reinforcement support. The temporary support devices are single hydraulic props or timber stacks.

[0099] To make the objectives, technical solutions, and advantages of the present invention clearer, a specific embodiment is now provided:

[0100] Taking the mining of working face 606 2 and working face 607 2 adjacent to working face 606 2 in a shallow-buried thick coal seam mining area as an example, the mining control method of the present invention is applied to the following steps:

[0101] Step S1: The working face dip length L of working face 2 of 606 is 170m, and the working face dip length L of working face 2 of 607 is 150m; the average mining depth H is 200m, which is a near-horizontal coal seam (α≈0°); the total coal seam thickness M is 12m;

[0102] Determined based on the geological and mining conditions of the target mining area:

[0103] The overlying rock is a medium-hard rock layer, and the hardness coefficient f of the overlying rock is 4.

[0104] The subsidence coefficient q = 0.6;

[0105] The main influencing angle is tangent tanβ = 2.0;

[0106] The horizontal movement coefficient b = 0.3;

[0107] The correction factor k=3.

[0108] Step S2: Obtain the surface horizontal deformation value ε at the boundary of the goaf in the target mining area under the conventional strip mining with coal pillar 1 mining mode based on the surface horizontal deformation model; determine the safe mining width d and mining height M1 that meet the surface deformation control requirements based on the surface horizontal deformation value ε.

[0109] The expression for the horizontal deformation model of the Earth's surface is:

[0110] ;

[0111] ;

[0112] ;

[0113] ;

[0114] The resulting horizontal surface deformation value ε was 0.032832m.

[0115] The final expression for the safe mining width d is:

[0116] ;

[0117] when hour, ;

[0118] when hour, ;

[0119] when hour, ;

[0120] Based on the final model of the safe mining width d, the safe mining width d is approximately 46m.

[0121] Based on the model of mining height M1 The mining height M1 was obtained as 6m.

[0122] Step S3: Analyze the relationship between the safe mining width d and the working face dip length L to determine the mining mode:

[0123] The safe mining width d (46m) is less than the working face dip length L (170m). A bench-type, pillarless mining mode is adopted. Multiple benches, each 46m wide and 6m high, are arranged along the dip direction of working face 2, with a total mining height of 12m, for phased mining. The sequential mining of each working face 2 includes the following processes:

[0124] The first working face 2 was mined according to the mining specifications of a bench width of 46m, a bench height of 6m, and a total mining height of 12m. After the first working face 2 was mined out, at the boundary of the first goaf formed after the first working face 2 was mined out (corresponding to...) Figure 3 At locations A1B1 and B1C1, a first artificial false roof 3 in a stepped shape, made of high-strength, corrosion-resistant steel wire mesh, is laid. A coal pillar 1 is reserved on the side of the first goaf away from the first artificial false roof 3. The coal pillar 1, the first artificial false roof 3, and the boundary of the first goaf away from the coal pillar 1 are all stepped. The step width of the stepped artificial false roof 3 and the step height of the stepped coal pillar 1 are both 46m and 6m respectively.

[0125] A second working face 2 is mined on the side of the first artificial false roof 3 away from the first goaf. The mining specifications of the second working face 2 are the same as those of the first working face 2. After the second working face 2 is mined out, a second goaf is formed on the side of the first artificial false roof 3 away from the first goaf. The boundary of the second goaf away from the first artificial false roof 3 (corresponding to...) Figure 3 A high-strength second artificial roof 3 is laid at A2B2 and B2C2; the boundary of the second goaf away from the second artificial roof 3 is adjacent to and fits the first artificial roof 3; the boundary of the second goaf away from the first artificial roof 3 is stepped, and the second artificial roof 3 is stepped.

[0126] This process continues until all n working faces 2 are mined, with a total of n-1 artificial false roofs 3 laid. When mining the nth working face 2, ensure that a coal pillar 1 is reserved at the boundary of the nth goaf formed after the nth working face 2 is mined, away from the boundary of the (n-1)th artificial false roof 3. This coal pillar 1 is also stepped. The boundary of the nth goaf away from the boundary of the (n-1)th artificial false roof 3 is stepped.

[0127] A model measuring 750m × 232m was established using PFC2D numerical simulation software, and compared with the conventional strip mining mode with one coal pillar (see [link to PFC2D model]). Figure 1 This invention employs a stepped, pillarless mining mode (see [link]). Figure 3 The mining effect.

[0128] like Figure 4 and Figure 6As shown, conventional strip mining with coal pillar 1 was adopted for mining. A total of six permanent cracks were developed at the boundary of the goaf, with a maximum opening of 6.9m and a maximum depth of 95.7m. The surface subsidence curve drops sharply at the boundary, and the surface is severely damaged.

[0129] like Figure 5 and Figure 6 As shown, this invention employs a stepped, pillarless mining mode. Four permanent fractures developed at the boundary of the goaf, with the maximum opening reduced to 2.0m (a 70.4% decrease) and the maximum depth reduced to 75.3m (a 21.3% decrease). The surface subsidence curve is relatively gentle at the boundary, with a significant reduction in boundary subsidence. Furthermore, a rebound occurs at the location corresponding to the stepped coal pillar 1, indicating that surface deformation has been effectively mitigated, achieving the goal of controlling the development of surface fractures.

[0130] This invention provides a surface fracture control system for the boundary of a goaf in shallow-buried thick coal seam mining, used to implement the method described above, comprising:

[0131] The parameter acquisition module is used to acquire the geological and mining parameters of the target mining area. The geological and mining parameters include at least the working face dip length L, the total coal seam thickness M, the average mining depth H, and the overburden hardness coefficient f.

[0132] The safety parameter determination module is connected to the parameter acquisition module. Based on the surface horizontal deformation model, it obtains the surface horizontal deformation value ε of the goaf boundary of the target mining area under the conventional strip mining with coal pillar 1 mining mode. Based on the surface horizontal deformation value ε, it determines the safe mining width d and mining height M1 that meet the surface deformation control requirements.

[0133] The mining mode determination module, connected to the safety parameter determination module, is configured as follows:

[0134] Analyze the relationship between the safe mining width d and the dip length L of the working face, and determine the mining mode: when the safe mining width d is not less than the dip length L of the working face, the thickness-limited mining mode is adopted; when the safe mining width d is less than the dip length L of the working face, the step-connected pillarless mining mode is adopted.

[0135] The mining execution module, connected to the mining mode determination module, is used to execute mining operations according to the determined mining mode.

[0136] When the mining mode is determined to be limited thickness, multiple square working faces 2 are arranged along the dip direction of the working face 2 for mining. The mining width of the square working face 2 is the dip length L of the working face, and the mining height is the mining height M1.

[0137] When the mining mode is determined to be a stepped connection pillarless mining mode, multiple stepped working faces 2 are arranged along the dip direction of the working face 2 for staged mining. The step width of the stepped working face 2 is the safe mining width d, and the step height of the stepped working face 2 is the mining height M1.

[0138] Regarding the specific structure of this invention, it should be noted that the connection relationships between the various component modules used in this invention are definite and achievable. Except as specifically described in the embodiments, their specific connection relationships can bring about corresponding technical effects and solve the technical problems proposed by this invention without relying on the execution of corresponding software programs. The models of the components, modules, and specific components appearing in this invention, the connection methods between them, and the conventional usage methods and expected technical effects brought about by the above technical features, unless specifically described, are all publicly disclosed content in patents, journal articles, technical manuals, technical dictionaries, and textbooks that can be obtained by those skilled in the art before the application date, or belong to conventional technology, common knowledge, and other existing technologies in this field. There is no need to elaborate, which makes the technical solution provided in this case clear, complete, and achievable, and can reproduce or obtain corresponding physical products based on this technical means.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling surface cracks at the boundary of a goaf area in shallow-buried thick coal seam mining, characterized in that, Includes the following steps: Step S1: Obtain the geological and mining parameters of the target mining area. The geological and mining parameters include at least the working face dip length L, the total coal seam thickness M, the average mining depth H, and the overburden hardness coefficient f. Step S2: Based on the surface horizontal deformation model, obtain the surface horizontal deformation value ε of the goaf boundary of the target mining area under the conventional strip mining with coal pillar (1) mining mode; based on the surface horizontal deformation value ε, determine the safe mining width d and mining height M1 that meet the surface deformation control requirements; Step S3: Analyze the relationship between the safe mining width d and the working face dip length L to determine the mining mode: When the safe mining width d is not less than the working face inclination length L, the limited thickness mining mode is adopted, and multiple square working faces (2) are arranged along the inclination direction of the working face (2) for mining. The mining width of the square working face (2) is the working face inclination length L, and the mining height is the mining height M1. When the safe mining width d is less than the working face dip length L, a step-type connection pillarless mining mode is adopted. Multiple step-shaped working faces (2) are arranged along the dip direction of the working face (2) for staged mining. The step width of the step-shaped working face (2) is the safe mining width d, and the step height of the step-shaped working face (2) is the mining height M1. Step S4: Mining each working face (2) in sequence, and after each working face (2) is mined, laying an artificial false roof (3) at the boundary of its goaf. Subsequent working faces (2) are mined close to the boundary of the goaf of the previous working face (2), without leaving section coal pillars (1).

2. The method for controlling surface cracks at the boundary of the goaf in shallow-buried thick coal seam mining according to claim 1, characterized in that, In step S2, the horizontal deformation value ε of the land surface is obtained by constructing a horizontal deformation model using the probability integral method. The expression for the horizontal deformation model is: ； ； ； ； In the formula, b is the horizontal movement coefficient, W0 is the maximum subsidence value, r is the main influence radius, M is the total thickness of the coal seam, and q is the subsidence coefficient. H represents the coal seam dip angle, and H represents the average mining depth. The tangent of the main influencing angle is C, and the depth ratio is C.

3. The method for controlling surface cracks at the boundary of the goaf in shallow-buried thick coal seam mining according to claim 2, characterized in that, In step S2, the preliminary model for obtaining the safe mining width d is as follows: ； In the formula, k is the correction coefficient and f is the overlying rock hardness coefficient; The final model for obtaining the safe mining width d, determined by combining the preliminary model and the surface horizontal deformation model, is as follows: ； when hour, ; when hour, ; when hour, .

4. The method for controlling surface cracks at the boundary of the goaf in shallow-buried thick coal seam mining according to claim 2, characterized in that, In step S2, the model for obtaining the sampling height M1 is as follows: 。 5. The method for controlling surface cracks at the boundary of the goaf in shallow-buried thick coal seam mining according to claim 3, characterized in that, The overlying rock hardness coefficient f is determined based on the Protodyakonov strength coefficient: When the rock mass is a hard overlying rock, f > 8; When the rock mass is a medium-hard overburden, 3 ≥ f < 8; When the rock mass is a weak overlying rock, f < 3.

6. The method for controlling surface cracks at the boundary of the goaf in shallow-buried thick coal seam mining according to claim 1, characterized in that, When the limited thickness mining mode is adopted, the artificial false roof (3) has a square structure; when the step-type connection pillarless mining mode is adopted, the artificial false roof (3) has a stepped shape. A stepped coal pillar (1) is reserved on the side of the working face at both ends of the target mining area away from its corresponding artificial false roof (3). The step width of the stepped artificial false roof (3) and the stepped coal pillar (1) are both safe mining widths d, and the step height is both mining height M1.

7. The method for controlling surface cracks at the boundary of the goaf in shallow-buried thick coal seam mining according to claim 1, characterized in that, In step S4, the artificial false roof (3) is a flexible support structure consisting of at least a metal mesh and anchor rods.

8. The method for controlling surface cracks at the boundary of the goaf in shallow-buried thick coal seam mining according to claim 1, characterized in that, The process of laying the artificial false ceiling (3) is as follows: After the current working face (2) is mined out, a metal mesh is hung at the top cutting line of the corresponding goaf boundary. One end of the metal mesh is fixedly connected to the roof rock layer corresponding to the current goaf, and the other end of the metal mesh extends and is fixed to the bottom plate corresponding to the current goaf, so that the artificial false roof (3) forms a flexible retaining wall.

9. The method for controlling surface cracks at the boundary of the goaf in shallow-buried thick coal seam mining according to claim 8, characterized in that, Adjacent metal meshes are connected by double-strand iron wires, and temporary support devices are installed at preset intervals along the inclined length direction to complete temporary reinforcement support.

10. A surface fracture control system for the boundary of a goaf in shallow-buried thick coal seam mining for implementing the method described in any one of claims 1-9, characterized in that, include: The parameter acquisition module is used to acquire the geological and mining parameters of the target mining area. The geological and mining parameters include at least the working face dip length L, the total coal seam thickness M, the average mining depth H, and the overburden hardness coefficient f. The safety parameter determination module is connected to the parameter acquisition module. Based on the surface horizontal deformation model, it obtains the surface horizontal deformation value ε of the goaf boundary of the target mining area under the conventional strip mining with coal pillar (1) mining mode. Based on the surface horizontal deformation value ε, it determines the safe mining width d and mining height M1 that meet the surface deformation control requirements. The mining mode determination module, connected to the safety parameter determination module, is configured as follows: Analyze the relationship between the safe mining width d and the dip length L of the working face, and determine the mining mode: when the safe mining width d is not less than the dip length L of the working face, the thickness-limited mining mode is adopted; when the safe mining width d is less than the dip length L of the working face, the step-connected pillarless mining mode is adopted. The mining execution module, connected to the mining mode determination module, is used to execute mining operations according to the determined mining mode. When the limited thickness mining mode is determined, multiple square working faces (2) are arranged along the dip direction of the working face (2) for mining. The mining width of the square working face (2) is the dip length L of the working face, and the mining height is the mining height M1. When it is determined to be a step-type connection pillarless mining mode, multiple step-shaped working faces (2) are arranged along the dip direction of the working face (2) for staged mining. The step width of the step-shaped working face (2) is the safe mining width d, and the step height of the step-shaped working face (2) is the mining height M1.

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