Well field boundary high-stress area working face low-impact-risk optimal arrangement determination method

Abstract

A well field boundary high-stress area working face low-impact-risk optimal arrangement determination method comprises the steps that at least two working face arrangement schemes are designed according to site conditions, corresponding numerical models are established for the designed working face arrangement schemes, mechanical parameters are given to all the numerical models according to coal rock stratum mechanical parameter measurement results, and the working face low-impact-risk optimal arrangement determination method is obtained. After model boundary conditions are set, the working face is excavated according to the actual mining sequence and different working face arrangement schemes, and finally the optimal working face arrangement scheme of the working face in the well field boundary high-stress area with the low impact risk is comprehensively determined by analyzing stress characteristics under each working face arrangement scheme. According to the method, the optimal layout scheme of the working face of the well field boundary high-stress area is determined through a numerical simulation method, a reference basis is provided for scientific and reasonable layout of the working face on site, and the impact risk in the working face mining process is reduced.

Description

Technical Field

[0001] The present invention relates to a method for determining the optimal layout of a working face with low impact risk in a high-stress area at the boundary of a mine field, belonging to the technical field of safe coal mining. Background Technique

[0002] Rock burst is one of the typical dynamic disasters of coal and rock masses occurring in the process of coal mining, and it is also a special form of manifestation of mine pressure. It is mainly manifested as the sudden and violent release of the elastic strain energy accumulated in the coal and rock masses, and its powerful destructiveness seriously threatens the safety production underground. There are many factors affecting the risk of rock burst, including whether the layout of the working face is reasonable. With the rapid development of computer technology and numerical simulation technology, the numerical simulation method is becoming an irreplaceable method for analyzing the impact hazard.

[0003] For the working faces with large areas of goaf on both sides of the mine field boundary, there is a high impact hazard during the mining process. If the working face can be reasonably arranged, the impact risk of the working face can be effectively reduced, and the safe mining of coal resources can be guaranteed. Therefore, a method for combining numerical simulation to analyze the impact hazard of working face mining and optimizing the optimal layout method for low-impact-risk mining of the working face is needed. Summary of the Invention

[0004] The invention aim of the present invention is to provide a method for determining the optimal layout of a working face with low impact risk in a high-stress area at the boundary of a mine field, which can scientifically and reasonably arrange the working face with large areas of goaf on both sides of the mine field boundary and reduce the impact risk during the working face mining process.

[0005] To achieve the above object, the present invention provides a method for determining the optimal layout of a working face with low impact risk in a high-stress area at the boundary of a mine field, including the following steps:

[0006] S1. According to the on-site situation, design at least two working face layout schemes. The more working face layout schemes are designed, the more likely an optimal layout scheme can be obtained;

[0007] S2. Establish corresponding numerical models for the working face layout schemes designed in S1. According to the determination results of the mechanical parameters of coal and rock strata, assign the mechanical parameters to each numerical model and set the model boundary conditions;

[0008] S3. Excavate the working face according to the actual mining sequence and different working face layout schemes;

[0009] S4. Analyze the stress characteristics under each working face layout scheme, and comprehensively determine the optimal working face layout scheme with low impact risk in the high-stress area at the boundary of the mine field.

[0010] Furthermore, the working face characteristics in the high-stress area at the wellfield boundary are as follows: ① A wellfield boundary protection coal pillar is left between the adjacent wellfields A and B; ② The coal seam belonging to wellfield A and close to the coal pillar on one side of the wellfield boundary protection coal pillar has been mined, forming a goaf; ③ The coal seam belonging to wellfield B and far away from the coal pillar on the other side of the wellfield boundary protection coal pillar has been mined, forming a goaf; the coal seam close to the coal pillar has not yet been arranged for mining, and the coal seams in this area are only arranged into working face A and working face B; ④ The mining order of the two working faces is to mine working face A first and then working face B, where working face B is closer to the wellfield boundary coal pillar.

[0011] Furthermore, the specific process of S2 is:

[0012] S2.1, according to the geological characteristics around the working face and the designed working face layout plan, use FLAC 3D The numerical software uses built-in modeling code commands to establish a three-dimensional numerical model, in which geological characteristics include coal seam dip and thickness, roof and floor strata lithology and thickness. The working face layout plan should design at least two working face dip lengths, and further design the cut-hole positions and stop-mining positions of the two working faces. The model size is determined based on the working face range in the high-stress zone at the wellfield boundary.

[0013] S2.2. Grid densification near the coal seam, with the grid size gradually increasing as it moves away from the coal seam;

[0014] S2.3. Group the models according to the actual occurrence of coal and rock strata, and divide the rock strata with the same lithology into the same group; and set different mechanical parameters for each group through the code;

[0015] S2.4. Set boundary conditions, including displacement boundary conditions and stress boundary conditions;

[0016] The displacement boundary conditions are: fixed support at the bottom of the model and hinged support around the model;

[0017] The stress boundary conditions are as follows: a confining pressure is applied according to the actual ground stress test value, and an equivalent load of the overlying rock stratum is applied above the model. The equivalent load is calculated as follows: σ = ρgh, where σ is the equivalent load, ρ is the average density of the overlying rock stratum, and g is the acceleration of gravity.

[0018] Furthermore, the specific process of S4 is as follows: the simulation results analysis content is the stress characteristics of each stage of working face mining under different mining schemes:

[0019] S4.1. Analyze the maximum advance stress during excavation of working face B under each scheme;

[0020] S4.2. Analyze the maximum advance stress during mining at working face B under each scheme;

[0021] S4.3. Compare the stress values obtained in steps S4.1 and S4.2 under each scheme, and determine that the scheme with the smallest stress value is the optimal working face layout scheme.

[0022] The present invention designs at least two working face layout schemes based on on-site conditions, establishes corresponding numerical models for the designed working face layout schemes, assigns mechanical parameters to each numerical model based on the results of coal and rock stratum mechanical parameter measurements, sets model boundary conditions, and then excavates the working face according to the actual mining sequence and different working face layout schemes. Finally, by analyzing the stress characteristics under each working face layout scheme, the optimal working face layout scheme with low impact risk for the working face in the high-stress area at the boundary of the well field is comprehensively determined. The present invention determines the optimal layout scheme for the working face in the high-stress area at the boundary of the well field through numerical simulation, providing a reference basis for the scientific and reasonable layout of the on-site working face, and reducing the impact risk during the working face mining process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a workflow diagram of the method of the present invention;

[0024] Figure 2 This is a schematic plan view of the mining engineering of the 250108-1 and 250109-1 working faces in an embodiment of the present invention;

[0025] Figure 3 1 is a numerical model diagram of three schemes in the embodiment of the present invention;

[0026] Figure 4 (a) is the maximum advance stress cloud diagram of the 250108-1 working face during excavation in the first embodiment of the present invention;

[0027] Figure 4 (b) is the maximum advance stress cloud diagram of the 250108-1 working face during mining in the first embodiment of the present invention;

[0028] Figure 5 (a) is the maximum advance stress cloud diagram of the 250108-1 working face during excavation in the second embodiment of the present invention;

[0029] Figure 5 (b) is the maximum advance stress cloud diagram of the 250108-1 working face during mining in the second embodiment of the present invention;

[0030] Figure 6 (a) is the maximum advance stress cloud diagram of the 250108-1 working face during excavation in the third embodiment of the present invention;

[0031] Figure 6 (b) is the maximum advance stress cloud diagram of the 250108-1 working face during mining in the third embodiment of the present invention;

[0032] Figure 7 It is a stress statistical histogram of the working face after mining under the three schemes of the embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the accompanying drawings.

[0034] like Figure 1 As shown, a method for determining the optimal layout of a working face with low impact risk in a high stress area at the boundary of a well field includes the following steps:

[0035] S1. Design at least two working face layout plans based on the site conditions. The more working face layout plans there are, the more likely it is to obtain the optimal layout plan;

[0036] S2. Establish a corresponding numerical model for the working face layout scheme designed in S1, assign mechanical parameters to each numerical model based on the results of the mechanical parameters of the coal and rock strata, and set the model boundary conditions;

[0037] S3. Excavate the working face according to the actual mining sequence and different working face layout plans;

[0038] S4. Analyze the stress characteristics of each working face layout scheme, and comprehensively determine the optimal working face layout scheme with low impact risk in the high stress area at the boundary of the well field.

[0039] Example: 250108-1 working face is the 8th working face in the upper layer of 2501 mining area of Huating Coal Mine. Its specific location underground is: the mine boundary in the north; the main roadway protection coal pillar in the south; and the 250109-1 working face in the west;

[0040] The 250109-1 working face is the 8th working face in the upper layer of the 2501 mining area of Huating Coal Mine. Its specific underground location is: to the west, it is adjacent to the 40m boundary coal pillar of the mine field and the large-scale goaf of Chenjiagou Coal Mine; to the east, it is adjacent to the 250101-1 to 250108-1 working faces. Figure 2 This is a schematic plan view of the mining project at the 250108-1 and 250109-1 working faces.

[0041] (1) According to the on-site conditions, three working face layout schemes were designed for comparison and optimization. The specific schemes are shown in Table 1:

[0042] Table 1 Working face layout scheme

[0043]

[0044]

[0045] (2) Using the continuum mechanics analysis software FLAC 3D Numerical models of the above 7 schemes are established, seeFigure 3 ; The model size is 776m×100m×258m (X×Y×Z). Without considering the influence of dip angle, the coal seam grid size is 1m×1m, and the grid size gradually increases in the direction away from the coal seam. During the simulation, the excavation length of the working face and the mining height of each layer are based on the actual length;

[0046] (3) The Mohr-Coulomb model is selected for the model, and the mechanical parameters of the model are determined as shown in Table 2:

[0047] Table 2 Mechanical parameters of coal and rock strata

[0048]

[0049] (4) The top of the model is 270m from the ground surface. Therefore, the equivalent load can be calculated according to the formula σ = ρgh as 2500*10*270 = 6.75MPa; the horizontal stress coefficient is 2 times the vertical stress, and the equilibrium is calculated under this boundary condition; the working face is excavated according to the actual mining sequence and different layout schemes;

[0050] (5) Analyze the stress characteristics under each mining scheme, and the specific analysis is as follows:

[0051] a. Stress characteristics of Scheme 1:

[0052] As Figure 4 (a) shows, the maximum advanced stress during the driving of the 250108-1 working face is 35.24MPa;

[0053] As Figure 4 (b) shows, the maximum advanced stress during the coal mining of the 250108-1 working face is 54.51MPa;

[0054] b. Stress characteristics of Scheme 2:

[0055] As Figure 5 (a) shows, the maximum advanced stress during the driving of the 250108-1 working face is 31.87MPa;

[0056] As Figure 5 (b) shows, the maximum advanced stress during the coal mining of the 250108-1 working face is 53.24MPa;

[0057] c. Stress characteristics of Scheme 3:

[0058] As Figure 6 (a) shows, the maximum advanced stress during the driving of the 250108-1 working face is 39.44MPa;

[0059] As Figure 6 (b) shows, the maximum advanced stress during the coal mining of the 250108-1 working face is 57.30MPa;

[0060] (6) As Figure 7 shown, according to the stress statistical histogram after the mining of the above three working faces, it can be seen that the maximum advanced stress during the driving and coal caving of the 250108-1 working face in Scheme II is the lowest. Therefore, the optimal layout scheme for the working face with low impact risk in the high stress area of the mine field boundary is determined to be Scheme II.

Claims

1. An optimal layout determination method for low impact risk of working face in high stress area at the mine field boundary, characterized in that, It includes the following steps: S1. Design at least two working face layout schemes according to the on-site situation; S2. Establish corresponding numerical models for the working face layout schemes designed in S1. According to the determination results of the mechanical parameters of coal and rock strata, assign mechanical parameters to each numerical model and set the model boundary conditions; S3. Excavate the working face according to the actual mining sequence and different working face layout schemes; S4. Analyze the stress characteristics under each working face layout scheme, and comprehensively determine the optimal working face layout scheme with low impact risk for the working face in the high-stress area of the mine field boundary.

2. The optimal layout determination method for low impact risk of the working face in the high stress area at the minefield boundary according to claim 1, characterized in that, The characteristics of the working face in the high-stress area of the mine field boundary are as follows: ① There is a coal pillar for mine field boundary protection left between the adjacent mine fields A and B; ② The coal seam on the side of mine field A and close to the coal pillar of the coal pillar for mine field boundary protection has been mined, forming a goaf; ③ The coal seam on the other side of the coal pillar for mine field boundary protection and far from the coal pillar of mine field B has been mined, forming a goaf; The coal seam close to the coal pillar has not been arranged for working face mining, and only working face A and working face B are arranged in this area of the coal seam; ④ The mining sequence of the two working faces is to mine working face A first and then working face B, where working face B is closer to the coal pillar of the mine field boundary.

3. The optimal layout determination method for low impact risk of the working face in the high stress area at the well field boundary according to claim 1, characterized in that The specific process of S2 is as follows: S2.

1. According to the geological characteristics around the working face and the designed working face layout plan, use the built-in modeling code commands of FLAC 3D numerical software to establish a three-dimensional numerical model. The geological characteristics include the dip angle and thickness of the coal seam, and the lithology and thickness of the roof and floor rock strata. The working face layout plan should at least design two dip lengths of the working face, and further design the cutting eye positions and end positions of the two working faces. Determine the model size according to the working face range in the high-stress area at the mine field boundary; S2.

2. Conduct grid densification treatment near the coal seam, and the grid size gradually increases with the direction away from the coal seam; S2.

3. Group the model according to the actual occurrence of coal and rock strata, and divide the strata with the same lithology into the same group; and set different mechanical parameters for each group through codes; S2.

4. Set boundary conditions, including displacement boundary conditions and stress boundary conditions; Among them, the displacement boundary condition is: the bottom of the model is fixed support, and the four sides of the model are hinged support; The stress boundary condition is: apply confining pressure according to the actual in-situ stress test value, and apply the equivalent load of overlying strata above the model. The calculation method of the equivalent load is: σ = ρgh, where σ is the equivalent load, ρ is the average density of the overlying strata, and g is the acceleration of gravity.

4. The optimal layout determination method for low impact risk of the working face in the high stress area at the minefield boundary according to claim 1, characterized in that, The specific process of S4 is as follows: The content of the simulation result analysis is the stress characteristics at each stage of working face mining under different mining schemes: S4.

1. Analyze the maximum advanced stress during the driving of working face B under each scheme; S4.

2. Analyze the maximum advanced stress during the mining of working face B under each scheme; S4.

3. Compare the stress values obtained in steps S4.1 and S4.2 under each scheme, and determine the scheme with the minimum stress value as the optimal working face layout scheme.

Images