A numerical simulation method for the whole-area pressure relief characteristics of goaf with roof cutting

Abstract

The present invention discloses a numerical simulation research method for the global pressure relief characteristics of a goaf with top cutting and pressure relief. A numerical model is established by using FLAC3D simulation software, and simulation data under a traditional mining mode, a single-side top cutting and pressure relief mining mode, and a double-side top cutting and pressure relief mining mode are extracted and analyzed and compared respectively to obtain the global pressure relief characteristics of the goaf with top cutting and pressure relief. The stress distribution of the tunnel roof and the side of the tunnel and the internal stress distribution of the goaf which is difficult to monitor on site can be obtained. By comparing the pressure relief ranges in the horizontal and vertical directions under different mining modes, the pressure relief characteristics of the goaf under the top cutting and pressure relief mining mode are obtained. The wind flow migration and gas migration characteristics of the goaf can be clarified, and according to the wind flow migration law, the main air leakage areas of the working face and the goaf can be grasped, so as to carry out targeted air leakage prevention and sealing.

Description

Technical Field

[0001] The invention belongs to the technical field of safe mining of coal mines, and in particular relates to a numerical simulation research method for the global pressure relief characteristics of a goaf area with top cutting and pressure relief. Background Art

[0002] The traditional longwall mining method requires two drift tunnels to recover a working face, and a coal pillar is left to support the roof of the goaf. Therefore, there are problems such as tight connection of the working face and serious waste of coal pillars. The traditional coal-pillar-free mining technology includes two types: goaf-side tunneling and goaf-side tunneling. Although the goaf-side tunneling technology improves the coal recovery rate, it still requires tunneling, which is difficult to effectively solve the tense situation of mine excavation succession. Although the goaf-side tunneling technology reduces the amount of tunnel excavation, it is difficult to maintain the tunnel when mining deep coal seams. Therefore, the traditional coal-pillar-free mining technology has not been widely promoted.

[0003] The top-cutting and pressure-relieving mining mode only requires excavating one working face drift (another drift is automatically formed) to recover a working face, leaving zero coal pillars. The top-cutting and pressure-relieving automatic lane-forming and coal-pillar-free mining technology cuts off the connection between the laneway and the roof of the goaf through the directional pre-splitting and slitting technology of the roof, weakening the mechanical constraints between the two, so that the roof of the goaf can collapse in time to form the lane wall after the working face is pushed through, and the side of the lane is supported by gangue, and the gangue forms an effective support for the overlying rock layer, thereby eliminating the side of the lane filling and realizing coal-pillar-free mining. Compared with the traditional mining mode, the top-cutting and pressure-relieving mining technology has certain advantages.

[0004] The pressure relief characteristics of the goaf roof under different mining modes are bound to be different, and the difference in pressure relief characteristics will inevitably bring about changes in the stress field and fracture field inside the rock formation, thereby changing the permeability characteristics of the goaf, and further affecting the air flow migration and gas distribution in the goaf. Therefore, a numerical simulation research method for the global pressure relief characteristics of the goaf under the top cutting pressure relief mining mode is proposed as a prerequisite for clarifying the characteristics of air flow migration and gas migration in the goaf. Summary of the invention

[0005] The purpose of the present invention is to provide a numerical simulation research method for the global pressure relief characteristics of the goaf with top cutting and pressure relief in view of the deficiencies of the above-mentioned prior art, so as to provide basic support for preventing air leakage in the goaf and accurately extracting gas from the goaf under the top cutting and pressure relief mining mode.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for numerical simulation of the global pressure relief characteristics of a goaf with top cutting and pressure relief comprises the following steps:

[0008] (1) Collect, organize and analyze mine data and relevant geological conditions of the working face;

[0009] (2) According to the rock property parameters of the top and bottom plates of the working face, the numerical model was established using FLAC3D simulation software;

[0010] (3) The simulation adopts the Mohr-Coulomb constitutive model, and the strength criterion formula is:

[0011]

[0012] Among them, σ 1 is the maximum principal stress, MPa; σ 3 is the minimum principal stress, MPa; is the internal friction angle of rock, °; c is the cohesion, MPa; when f s When <0, the material will be destroyed;

[0013] (4) Horizontal displacement constraint boundaries are set on the front, back, left, and right surfaces of the model. At the same time, a vertical displacement constraint boundary is set on the lower surface, while the upper surface is set as a free boundary and self-weight stress is uniformly applied;

[0014] (5) Performing initial ground stress balance, the balance condition is that the maximum balance ratio is less than 1e-5;

[0015] (6) Excavate the tunnel and perform calculations, and the equilibrium condition is that the maximum equilibrium ratio is less than 1e-5;

[0016] (7) Using an empty model to excavate the working face, opening the large deformation mode, calculating the equilibrium condition with the maximum equilibrium ratio less than 1e-5, obtaining the simulation results of the goaf under the traditional mining mode, saving and extracting the data;

[0017] (8) calling the data file calculated in step (6), using an empty model to cut the top of the tunnel according to the cutting height and angle, and performing calculations, and the balance condition is that the maximum balance ratio is less than 1e-5;

[0018] The traditional mining model does not require this operation;

[0019] (9) Using an empty model to excavate the working face, opening the large deformation mode, and allowing the goaf roof to collapse, the calculation equilibrium condition is that the maximum equilibrium ratio is less than 1e-5, and the goaf simulation results under the top cutting and pressure relief mining mode are obtained, and the data are saved and extracted;

[0020] (10) The simulation data of the traditional mining mode, the single-side cutting-top pressure relief mining mode, and the double-side cutting-top pressure relief mining mode were extracted and analyzed and compared, and the overall pressure relief characteristics of the cutting-top pressure relief goaf were obtained.

[0021] In step (1), the mine data and geological conditions related to the working face include: working face burial depth, working face length and advancement distance, coal seam inclination, distribution of rock layers on the top and bottom plates of the working face, physical and mechanical properties of coal and rock mass, and top cutting height and angle.

[0022] The physical and mechanical properties of the coal rock mass include rock layer thickness, density, bulk modulus, shear modulus, cohesion, internal friction angle and tensile strength.

[0023] In step (9), the simulation data includes the stress distribution of the roofs of the two tunnels, the stress distribution beside the tunnel, the pressure relief angle, the collapse range and the pressure relief range.

[0024] The beneficial effects of the present invention are:

[0025] (1) The numerical simulation research method of the global pressure relief characteristics of the goaf with top-cut pressure relief can obtain the stress distribution of the roadway roof and roadside, as well as the internal stress distribution of the goaf that is difficult to monitor on site. By comparing the pressure relief range in the horizontal and vertical directions under different mining modes, the pressure relief characteristics of the goaf under the top-cut pressure relief mining mode are obtained, and the air flow and gas migration characteristics of the goaf can be clarified. According to the law of air flow migration, the main air leakage areas between the working face and the goaf can be grasped, so as to carry out targeted air leakage prevention and plugging.

[0026] (2) Based on the overall decompression characteristics of the goaf, the main storage space of gas in the goaf can be determined. Based on the decompression range of the goaf, a reasonable gas extraction layer can be determined in the decompression area to perform decompression gas extraction and improve gas extraction efficiency.

[0027] (3) It can provide basic support for preventing air leakage in goafs and accurately extracting gas from goafs under the top-cutting and pressure-relieving mining mode, and is also of great significance for ensuring the safe promotion of top-cutting and pressure-relieving mining technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the FLAC3D numerical calculation model adopted by the present invention;

[0029] Figure 2 is the curve of stress concentration variation beside the lane;

[0030] Figure 3 is the stress distribution curve of the road roof;

[0031] Figure 4 It is the distribution diagram of the pressure relief angle of the goaf in the traditional mining mode;

[0032] Figure 5 It is the distribution diagram of the pressure relief angle of the goaf in the single-side top cutting pressure relief mining mode;

[0033] Figure 6 It is the distribution diagram of the pressure relief angle of the goaf in the double-side top cutting pressure relief mining mode;

[0034] Figure 7 It is the vertical stress distribution diagram of the goaf in the traditional mining mode;

[0035] Figure 8 It is the vertical stress distribution diagram of the goaf in the single-side top cutting and pressure relief mining mode;

[0036] Fig. 9 It is the vertical stress distribution diagram of the goaf in the double-side top cutting and pressure relief mining mode;

[0037] Fig.10 It is the distribution map of the pressure relief range of the goaf. DETAILED DESCRIPTION

[0038] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0039] The present invention provides a numerical simulation research method for the global pressure relief characteristics of the goaf area with top cutting and pressure relief, such as Figures 1 to 10 As shown, the steps are as follows:

[0040] (1) Collect, organize, analyze and study mine data and geological conditions related to the working face.

[0041] The mine data and working face geological conditions mainly include: working face burial depth, working face length and advancement distance, coal seam inclination, working face top and bottom plate rock layer distribution, coal rock mass physical and mechanical properties, top cutting height and angle; among them, coal rock mass physical and mechanical properties include rock layer thickness, density, bulk modulus, shear modulus, cohesion, internal friction angle and tensile strength.

[0042] (2) The numerical model was established using FLAC3D simulation software based on the rock properties of the top and bottom plates of the working face.

[0043] The FLAC3D model is constructed according to the length of the working face and the advancement distance. A certain distance of coal pillars should be reserved around the working face to eliminate the boundary effect. The model is established layer by layer according to the distribution of rock strata on the top and bottom plates of the working face, and the model grid size is determined according to the actual situation.

[0044] (3) The Mohr-Coulomb constitutive model is used in the simulation, and the strength criterion formula is:

[0045]

[0046] Among them, σ 1 is the maximum principal stress, MPa; σ 3 is the minimum principal stress, MPa; is the internal friction angle of rock, °; c is the cohesion, MPa; when fs When <0, the material will be damaged.

[0047] (4) Based on measured experience and mine pressure theory, horizontal displacement constraint boundaries are set on the front, back, left and right surfaces of the model, and vertical displacement constraint boundaries are set on the lower surface. The upper surface of the model is set as a free boundary and self-weight stress is uniformly applied.

[0048] (5) Perform initial ground stress balance, and the balance condition is that the maximum balance ratio is less than 1e-5.

[0049] (6) Excavate the tunnel and perform calculations. The equilibrium condition is that the maximum equilibrium ratio is less than 1e-5.

[0050] (7) Use an empty model to excavate the working face, turn on the large deformation mode, calculate the equilibrium condition as the maximum equilibrium ratio is less than 1e-5, obtain the simulation results of the goaf under the traditional mining mode, save and extract the data.

[0051] (8) Call the data file calculated in step (6), use an empty model to cut the top of the tunnel according to the cutting top height and angle in the data, and perform calculations. The balance condition is that the maximum balance ratio is less than 1e-5.

[0052] (9) Use an empty model to excavate the working face, turn on the large deformation mode, calculate the equilibrium condition as the maximum equilibrium ratio is less than 1e-5, obtain the simulation results of the goaf under the top cutting and pressure relief mining mode, and save and extract the data.

[0053] (10) The simulation data under different mining modes were extracted for analysis and comparison, including the stress distribution of the roof of the two tunnels, the stress distribution of the side of the tunnel, the pressure relief angle, the collapse range and the pressure relief range, so as to obtain the pressure relief characteristics of the whole goaf area;

[0054] Among them, the stress distribution curve of the tunnel roof and the stress distribution curve beside the tunnel obtained by data extraction can be used to compare the stress reduction in the goaf area of ​​the working face along the strike and dip directions, and obtain the pressure relief characteristics of the goaf in the horizontal direction; by slicing along the middle of the goaf in the dip direction, the size of the goaf pressure relief angle can be obtained. The larger the pressure relief angle, the more sufficient the goaf is in the vertical direction, thus obtaining the pressure relief characteristics of the goaf in the vertical direction; slicing along the roof height in the vertical direction of the goaf can be obtained to obtain the degree of collapse of the goaf. The greater the degree of collapse, the more sufficient the pressure relief of the goaf is; the vertical stress is extracted, and the area below the original rock stress is the pressure relief area of ​​the goaf. The data is processed and drawn into a pressure relief range map of the goaf.

[0055] The overall pressure relief characteristics of the goaf area in the 12201 working face of a certain mine are analyzed and explained as follows.

[0056] (1) Based on the collected mine data and the geological conditions of the 12201 working face, the basic parameters of the overlying and underlying rock formations of the 12201 working face coal seam are shown in Table 1:

[0057] Table 1 Physical and mechanical parameters of coal strata

[0058]

[0059] (2) The mining model of the 12201 working face is established based on the three-dimensional rectangular coordinate system, in which the X, Y, and Z directions are specified as the inclination, strike, and gravity direction, respectively. The 12201 working face is a nearly horizontal coal seam with a inclination length of 320m, a working face advancement of 400m, and a coal seam mining height of 2m. Therefore, the model is established horizontally, and the mining range is 320m×400m×2m. 100m coal pillars are reserved around the model to eliminate the boundary effect. Therefore, the size of the numerical model is established as length×width×height=530m×600m×80m, and the upper 58m of the coal seam is selected as the roof, and 20m of the bottom of the coal seam is reserved as the floor. The model is as follows Figure 1 shown.

[0060] (3) The Mohr-Coulomb constitutive model is used in the simulation, and the strength criterion formula is:

[0061]

[0062] Among them, σ 1 is the maximum principal stress, MPa; σ 3 is the minimum principal stress, MPa; is the internal friction angle of rock, °; c is the cohesion, MPa; when f s When <0, the material will be damaged.

[0063] (4) Based on measured experience and mine pressure theory, horizontal displacement constraint boundaries are set on the front, back, left and right surfaces of the model, and vertical displacement constraint boundaries are set on the lower surface. The upper surface of the model is set as a free boundary and self-weight stress is uniformly applied.

[0064] (5) Perform initial ground stress balance, and the balance condition is that the maximum balance ratio is less than 1e-5.

[0065] (6) Excavate the tunnel and perform calculations. The equilibrium condition is that the maximum equilibrium ratio is less than 1e-5.

[0066] (7) Use an empty model to excavate the working face, turn on the large deformation mode, set the excavation length to 400 m, and calculate the equilibrium condition as a maximum equilibrium ratio less than 1e-5. Obtain the simulation results of the goaf under the traditional mining mode, save and extract the data.

[0067] (8) Call the data file calculated in step (6), use the empty model to cut the top of the tunnel, the cutting height is 6m, and calculate, the equilibrium condition is that the maximum equilibrium ratio is less than 1e-5.

[0068] (9) Use an empty model to excavate the working face, start the large deformation mode, and set the excavation length to 400 m. The calculation equilibrium condition is that the maximum equilibrium ratio is less than 1e-5. The simulation results of the goaf under the top cutting and pressure relief mining mode are obtained, and the data are saved and extracted.

[0069] (10) Comparison of the stress concentration curves of the roadway between the traditional mining mode and the top-cutting and pressure-relieving mining mode. Figure 2 As shown; the stress distribution curve of the tunnel roof is shown in Figure 3 As shown; the distribution of the relief angle of the goaf is shown in 4; the vertical stress distribution of the goaf is shown in Figure 5 As shown; the distribution of pressure relief range in goaf is as follows Figure 6 shown.

[0070] Compared with the traditional mining mode, the pressure relief of the goaf in the top-cutting pressure relief mining has the global characteristics. In the horizontal direction, the peak value of the stress concentration area on the top-cutting side of the single-side top-cutting pressure relief mining is reduced by 0.66MPa, and the peak value of the stress concentration on both sides of the double-side top-cutting pressure relief mining mode is reduced by 0.96MPa, and the stress of the top plate of the roadway in the top-cutting pressure relief mining is less than that of the traditional mining mode throughout the whole process; in the vertical direction, the pressure relief angle on the top-cutting side of the single-side top-cutting pressure relief mining is increased by 15.3°, and the pressure relief angles on both sides of the double-side top-cutting pressure relief mining mode are increased by 14.2° and 16.2° respectively; the goaf collapses more fully in the top-cutting pressure relief mining mode, and the single-side top-cutting increases the pressure relief range of the goaf by 13m, and the double-side top-cutting increases the pressure relief range of the goaf by 26m. Compared with the traditional mining mode, the goaf in the top-cutting pressure relief mining mode has pressure relief in the horizontal and vertical directions, and has global characteristics, which can easily clarify the wind flow migration and gas migration characteristics of the goaf. According to the wind flow migration law, the main leakage areas of the working face and the goaf can be grasped, so as to carry out targeted anti-leakage sealing. According to the global pressure relief characteristics of the goaf, the main storage space of gas in the goaf can be grasped. According to the pressure relief range of the goaf, a reasonable gas extraction layer can be determined in the pressure relief area, and pressure relief gas extraction can be carried out to improve the gas extraction efficiency. It can provide basic support for preventing goaf leakage and accurately extracting goaf gas under the top-cutting pressure relief mining mode, and it is also of great significance to ensure the safe promotion of top-cutting pressure relief mining technology.

[0071] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the invention claimed for protection. The scope of protection claimed for the present invention is defined by the attached claims and their equivalents.

[0072] In the description of the present invention, it is necessary to understand that the terms "front", "rear", "left", "right", "center", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the protection content of the present invention.

Claims

1. A numerical simulation research method for the global pressure relief characteristics of the goaf with top cutting, characterized by: The following steps are involved: (1) Collect, organize and analyze mine data and relevant geological conditions of the working face; (2) According to the rock property parameters of the top and bottom plates of the working face, the numerical model was established using FLAC3D simulation software; (3) The simulation adopts the Mohr-Coulomb constitutive model, and the strength criterion formula is: Among them, σ1 is the maximum principal stress, MPa; σ3 is the minimum principal stress, MPa; is the rock internal friction angle, °; c is the cohesion, MPa; when f s When <0, the material will be destroyed; (4) Horizontal displacement constraint boundaries are set on the front, back, left, and right surfaces of the model. At the same time, a vertical displacement constraint boundary is set on the lower surface, while the upper surface is set as a free boundary and self-weight stress is uniformly applied; (5) Performing initial ground stress balance, the balance condition is that the maximum balance ratio is less than 1e-5; (6) Excavate the tunnel and perform calculations, and the equilibrium condition is that the maximum equilibrium ratio is less than 1e-5; (7) Using an empty model to excavate the working face, opening the large deformation mode, calculating the equilibrium condition with the maximum equilibrium ratio less than 1e-5, obtaining the simulation results of the goaf under the traditional mining mode, saving and extracting the data; (8) calling the data file calculated in step (6), using an empty model to cut the top of the tunnel according to the cutting height and angle, and performing calculations, and the balance condition is that the maximum balance ratio is less than 1e-5; The traditional mining model does not require this operation; (9) Using an empty model to excavate the working face, opening the large deformation mode, and allowing the goaf roof to collapse, the calculation equilibrium condition is that the maximum equilibrium ratio is less than 1e-5, and the goaf simulation results under the top cutting and pressure relief mining mode are obtained, and the data are saved and extracted; (10) The simulation data of the traditional mining mode, the single-side cutting-top pressure relief mining mode, and the double-side cutting-top pressure relief mining mode were extracted and analyzed and compared, and the overall pressure relief characteristics of the cutting-top pressure relief goaf were obtained.

2. The method for numerical simulation of the global pressure relief characteristics of the goaf with top cutting and pressure relief according to claim 1 is characterized by: In step (1), the mine data and geological conditions related to the working face include: working face burial depth, working face length and advancement distance, coal seam inclination, distribution of rock layers on the top and bottom plates of the working face, physical and mechanical properties of coal and rock mass, and top cutting height and angle.

3. The method for numerical simulation of the global pressure relief characteristics of the goaf with top cutting and pressure relief according to claim 2 is characterized by: The physical and mechanical properties of the coal rock mass include rock layer thickness, density, bulk modulus, shear modulus, cohesion, internal friction angle and tensile strength.

4. The method for numerical simulation of the global pressure relief characteristics of the goaf with top cutting and pressure relief according to claim 1 is characterized by: In step (9), the simulation data includes the stress distribution of the roofs of the two tunnels, the stress distribution beside the tunnel, the pressure relief angle, the collapse range and the pressure relief range.

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