Research method on evolution law of coal wall mining dynamics behavior in large-angle and large-height mining areas

Abstract

The present invention discloses a method for studying the evolution law of coal wall mining dynamics behavior in a large-dipping-angle and large-mining-height mining area, including: using numerical calculation to construct numerical models of different mining conditions and perform excavation calculations, preliminarily clarifying the dynamic change law of the mechanical environment of coal walls in different areas and different positions of the working face inclination; using a physical similarity simulation experimental method to pave and numerically calculate the physical similarity model of the same mining condition partition direction and excavate, and comprehensively determining the evolution law of the coal wall bearing environment in different areas during the mining process under the coupling effect of the inclination angle and interlayer effect by combining the numerical calculation results; performing multi-path mechanical performance tests and step-by-step partition loading physical similarity material experiments, and systematically studying the evolution law of coal wall mining dynamics behavior in a large-mining-height mining area. It can reflect the dynamic change of the coal wall bearing environment, the evolution law of mechanical response behaviors such as the deformation displacement and internal structure state evolution of the coal wall under different pressure paths, and provide scientific guidance for the prevention and control of coal wall disasters in large-dipping-angle and large-mining-height mining areas.

Description

Technical Field

[0001] The present invention relates to the technical field of coal wall prevention and control in mining areas with large dip angles and large mining heights, and in particular to a method for studying the evolution law of coal wall mining dynamics behavior in mining areas with large dip angles and large mining heights. Background Art

[0002] Due to its technical advantages such as high single-face production efficiency and low resource loss, large mining height has been applied in the mining of some high-angle thick coal seams. Although it has achieved good economic benefits, the problem of coal wall spalling is relatively prominent, and the technical advantages of large mining height are seriously limited. The core of the surrounding rock control of high-angle working faces is the dynamic stability control of the "roof-support body-floor" system. As one of the components of the support structure, the coal wall has multi-directional bearing coupling, a large unconstrained height, and poor self-stability. Once it spalls, it can easily induce the working face bearing system to become unbalanced, aggravating surrounding rock disasters and causing derivative dynamic disasters such as roof falls and flying waste, which restrict the safe production of the working face. There is an urgent need for a theory to prevent and control coal wall disasters.

[0003] Coal wall disaster prevention and control is the key to ensuring large-scale, high-tech and efficient mining of complex and difficult-to-mine high-quality coal resources at large angles. Scholars have conducted research from multiple angles, but the current focus is mainly on coal wall disaster morphology, mechanical analysis models, support pressure distribution evolution, disaster mechanism and control measures. Although certain results have been achieved, there are still limitations. Coal wall disasters can be understood as the dynamic development of quantitative changes in the displacement and deformation of coal media to qualitative changes in structure during the force-behavior (deformation, displacement, etc.) response of the internal coal body. After the internal structure deteriorates, the medium state changes, and the integrity structure evolves into a loose and broken structure, and then the macro-destructive phenomenon manifested by large-scale migration occurs. It can be seen that the dynamic change law of force-behavior during coal wall mining is the core content of its disaster research. In order to effectively prevent and control coal wall instability in mining areas with large inclination angles and large mining heights, a method is urgently needed to effectively determine the temporal and spatial distribution evolution of coal wall bearing under inclination and interlayer effects, as well as the dynamic change laws of coal body deformation, internal structure destruction evolution, and crack development evolution, so as to provide a basis for the prediction and control of surrounding rock dynamic disasters in working faces with large inclination angles and large mining heights. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and to provide a method for studying the mining dynamics of coal walls in mining areas with large inclinations and large mining heights. The method can reflect the dynamic changes in the bearing environment of the coal wall, the evolution of the mechanical response behaviors such as the deformation and displacement of the coal wall under different pressure paths, and the evolution of the internal structure state, and provide scientific guidance for the prevention and control of coal wall disasters in mining areas with large inclinations and large mining heights.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the invention is: a method for studying the evolution law of coal wall mining dynamics behavior in a large-angle and large-height stope, characterized by comprising:

[0006] Numerical calculations were used to construct numerical models for different mining conditions and perform excavation calculations. The spatial distribution of coal wall bearing and its evolution curve were plotted, and the dynamic changes in the mechanical environment, such as the bearing strength, load increase coefficient, and disturbance range of the coal wall at different locations and in different working face inclinations, were preliminarily clarified.

[0007] Physical similarity simulation experimental methods are used to construct physical similarity material models under different mining conditions and perform excavation calculations. Mining experiments under numerical models are used to support the results and determine the evolution of the bearing environment during mining under the coupling of inclination angle and interlayer effects.

[0008] Based on the bearing law of coal wall, multi-path mechanical properties test and step-by-step partitioned loading of physically similar materials experiments were carried out. The results of physical and mechanical properties test, mechanical properties numerical calculation experiment and step-by-step partitioned loading of physically similar materials experiments were comprehensively analyzed to systematically study the evolution law of coal wall mining dynamics behavior in large mining height mining areas.

[0009] The above-mentioned method for studying the evolution law of coal wall mining dynamics in a high-angle and high-mining stope is characterized in that a dielectric layer is embedded between the numerical model direct roof and the numerical model coal seam, and the thickness of the dielectric layer is 1 / 5 to 1 / 2 of the thickness of the numerical model direct roof; multiple stress measurement lines are arranged in the numerical model direct roof and the dielectric layer from the opening of the cut to the boundary area;

[0010] Among them, the stress measuring lines in the direct top of the numerical model are arranged at a distance of 1 / 5 to 1 / 4 of the thickness of the direct top of the numerical model to the medium layer, the measuring line spacing is 1m to 2m, and the measuring point spacing is 0.2m to 0.5m; the measuring lines and measuring points are arranged along the vertical middle of the medium layer, and the spacing between the measuring lines and measuring points corresponds to the positions of the measuring lines and measuring points in the basic top of the numerical model; the measuring lines in the coal seam are arranged from the simulated coal wall to the boundary surface area, and the numerical model coal seam is divided into three layers of upper, middle and lower layers according to the thickness of the numerical model coal seam in the vertical direction, and the measuring lines and measuring points are arranged at 1 / 6 of the thickness of the layer in different layers, and the spacing between the measuring lines and measuring points is consistent with the spacing between the measuring lines and measuring points in the direct top.

[0011] The above-mentioned method for studying the evolution law of coal wall mining dynamics behavior in a large-angle and large-mining-height mining area is characterized in that when the physical similarity material model is laid, a pressure sensor is buried at the bottom of the coal seam of the physical similarity material model, and soil pressure boxes are pre-buried in the direct top, medium layer and coal seam of the physical similarity material model along the working face, and the buried spacing and the spacing between the measuring points of the numerical model satisfy a geometric ratio relationship. After the experiment, the numerical calculation and physical similarity material experimental monitoring data are comprehensively analyzed to determine the stress zoning and distribution status of the coal wall in different areas of the working face under the inclination and interlayer effects.

[0012] The above-mentioned method for studying the evolution law of coal wall mining dynamics behavior in large-angle and large-mining-height mining areas is characterized by the use of numerical calculation to construct numerical models of different mining conditions and perform excavation calculations. Specifically, it is based on the on-site comprehensive coal seam histogram and coal rock mechanics parameters under the background of the research project, and with the help of FLAC3D numerical calculation software, numerical calculation models of different inclinations and interlayer properties are established and excavation calculations are performed.

[0013] The above-mentioned method for studying the evolution law of coal wall mining dynamics behavior in large-angle and large-mining-height mining areas is characterized in that the mechanical properties test includes physical sample mechanical properties test and numerical model mechanical simulation test.

[0014] The above-mentioned method for studying the evolution law of coal wall mining dynamics in a large-angle and large-mining-height mining area is characterized in that the mechanical properties test of the physical samples is specifically as follows: samples are taken on-site from the middle position of the upper, middle and lower areas of the working face and processed into test samples, and acoustic wave testing is performed with the help of an ultrasonic detector. The ends of the samples are coated with coupling agent and placed vertically between probes. The wave velocity changes are statistically analyzed, and samples of the same type with obvious wave velocity differentiation are eliminated. SEM electron microscope scanning is used to differentially characterize the initialization state of the coal body in different areas of the working face. During the mechanical properties test, a high-bandwidth acoustic signal collector and a high-speed camera are used to dynamically monitor and record the damage and destruction of the internal structure of the coal body and the fracture formation evolution process. During the test, the sample is placed between the acoustic signal probes and placed together in the pressure head room of the pressure testing machine to monitor the wave velocity changes and energy changes in real time. The loading value is determined based on the stress evolution of the coal body during mining 3m to 5m in front of the coal wall. After the test, the coal body fracture type can be determined with the help of an SME electron microscope.

[0015] The above-mentioned research method for the evolution law of coal wall mining dynamics behavior in a large-angle and large-mining-height mining area is characterized in that the numerical model mechanical simulation test is specifically: carried out with the help of 3DEC numerical calculation software, and the pressurization method is set to two paths of pressurization: axial pressure-unloading confining pressure and cyclic axial pressure-unloading confining pressure to ensure that the research conditions are consistent and the numerical model is equivalent to the physical specimen; both path pressurization experiments require the axial and lateral pressures to be pressurized according to the stress level of the original rock of the coal seam to simulate the initial stress state, and perform a pressure stabilization operation of 100 to 200 calculation steps, and then add axial pressure and unload lateral pressure until the model is destroyed. For the cyclic experiment, the number of cycles and the intensity are determined according to the bearing environment 3m to 5m in front of the coal wall.

[0016] The above-mentioned research method for the evolution law of coal wall mining dynamics behavior in a large-angle and large-mining-height mining area is characterized in that the step-by-step zoning loading physical similarity experiment is specifically as follows: with the help of an adjustable loading simulation experimental device, a zoning similarity material model of the working face is paved, and horizontal and vertical cross-shaped oblique joints are preset when paving the coal seam in the key area to be mined. The joint cutting angle can be set with reference to the fracture angle of the coal sample mechanical experiment; optical fibers and earth pressure boxes are pre-buried layer by layer in the coal seam, and a hydraulic loading device is used to apply load to simulate the original rock stress state before the experiment. During the experiment, the position of the maximum support pressure is determined according to the load-bearing law during the coal wall mining process, and step-by-step zoning loading is carried out. Dynamic monitoring is carried out using optical fibers, earth pressure boxes, and microseismic systems.

[0017] The above-mentioned research method for the evolution law of coal wall mining dynamics behavior in large-angle and large-mining-height mining areas is characterized by comprehensively analyzing the physical and mechanical properties test, mechanical properties numerical calculation experiment and step-by-step partitioning loading physical similar material experimental results to reveal the evolution law of coal wall mining dynamics behavior in large-mining-height mining areas.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The present invention can reflect the dynamic changes in the coal wall bearing environment, the evolution of the mechanical response behavior such as the deformation and displacement of the coal wall under different pressure paths and the evolution of the internal structure state, and provide scientific guidance for the prevention and control of coal wall disasters in large-angle and large-height mining areas.

[0020] 2. The present invention can study the effectiveness of the inclination angle and interlayer effect on the destructive effect of the coal wall, and can more intuitively reflect the temporal and spatial variation laws of the coal wall bearing and mechanical response behavior.

[0021] The invention is further described in detail below through the accompanying drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It shows a schematic diagram of the three-dimensional structure of the spatial layer distribution of coal and rock and the arrangement of survey lines in an embodiment of the present invention.

[0023] Figure 2 It shows the main structural diagram of the spatial layer distribution of coal and rock and the arrangement of survey lines in an embodiment of the present invention.

[0024] Figure 3 A schematic diagram of the arrangement of inclined joints in a coal seam according to an embodiment of the present invention is shown.

[0025] Figure 4 A schematic diagram of the experimental logic in an embodiment of the present invention is shown.

[0026] Description of the accompanying drawings:

[0027] 1—coal seam; 2—medium layer; 3—stress measurement line;

[0028] 4—direct roof; 5—measuring point; 6—longitudinal oblique joints of coal seam;

[0029] 7—Transverse oblique joints in coal seams. DETAILED DESCRIPTION

[0030] The present invention discloses a method for studying the evolution law of coal wall mining dynamics in a high-inclination-angle and high-mining-height stope. The method uses numerical calculation to construct numerical models of different mining conditions and perform excavation calculations. The method then plots the spatial distribution of coal wall bearing and its evolution curve, preliminarily clarifying the dynamic change law of the mechanical environment, such as the bearing strength, load increase coefficient, and disturbance range of the coal wall at different working face inclination areas and different strike positions.

[0031] Physical similarity simulation experimental methods are used to construct physical similarity material models under different mining conditions and perform excavation calculations. Mining experiments under numerical models are used to support the results and determine the evolution of the bearing environment during mining under the coupling of inclination angle and interlayer effects.

[0032] Based on the bearing law of coal wall, multi-path mechanical properties test and step-by-step partitioned loading of physically similar materials experiments were carried out. The results of physical and mechanical properties test, mechanical properties numerical calculation experiment and step-by-step partitioned loading of physically similar materials experiments were comprehensively analyzed to systematically study the evolution law of coal wall mining dynamics behavior in large mining height mining areas.

[0033] The experimental logic of the present invention is as follows Figure 4 As shown in the figure, to understand the dynamic change law of coal wall mining dynamic behavior, the key is to determine the force and its corresponding behavior during the dynamic change of coal wall position. Therefore, the first thing to solve is to clarify the spatiotemporal change law of coal wall bearing environment under mining conditions. To this end, numerical calculation and physical similarity material experiment methods can be used to construct research models for different mining conditions (inclination, mining height, and mechanical properties of the layer). The interlayer effect will appear due to the interface barrier between the coal and rock masses. In order to better simulate the actual mining field and ensure the experimental effect, both numerical and physical similarity material models need to take this effect into account. A medium layer can be embedded between the direct roof and the coal seam in the model for simulation. The thickness of the medium layer should be 1 / 5 to 1 / 2 of the thickness of the direct roof of the model, and simulated excavation operations are performed. In order to obtain the stress environment and bearing state of the coal wall during working face mining, multiple stress measurement lines are arranged in the direct roof and medium layer from the opening eye to the boundary area in the numerical model, such as Figure 1 and Figure 2As shown in the figure, stress measurement lines within the direct roof are arranged along a distance of 1 / 5 to 1 / 4 of the direct roof thickness from the dielectric layer, with a line spacing of 1m to 2m and a measurement point spacing of 0.2m to 0.5m. Stress measurement lines with measurement points and line spacing corresponding to the basic roof position are arranged along the vertical middle of the dielectric layer. Measurement lines in the coal seam are laid from the simulated coal wall to the boundary surface area, with the line and point spacing consistent with the direct roof measurement lines. To reflect the evolution of internal ballast in the coal body, measurement lines are arranged at 1 / 6 of the thickness of the coal seam in different layers (vertically divided into upper, middle, and lower layers according to the coal seam thickness). When laying the physical similarity material model, pressure sensors are buried at the bottom of the coal seam. Earth pressure cells are pre-buried in the direct roof, dielectric layer, and coal seam along the working face. The buried spacing and the spacing of the measurement points in the numerical model meet the geometric ratio relationship. After the experiment, the numerical calculation and physical similarity material experimental monitoring data are comprehensively analyzed to determine the stress zoning and distribution of the coal wall in different areas of the working face under the influence of inclination and interlayer effects.

[0034] Further, based on the bearing law of the coal wall, its destruction evolution process can be studied, and multi-path mechanical performance tests and step-by-step partitioned loading experiments on physically similar materials can be carried out. Among them, the key to mechanical experiments is the visualization of coal body destruction phenomena. It is considered to use two methods: rock mechanics experiments and numerical calculation experiments. Both experimental objects are based on the same geological conditions. For rock mechanics experiments, the test objects are standard specimens processed after sampling from different areas above, middle and below the working face. In order to ensure the test effect, the specimens must be screened after production. With the help of an ultrasonic detector, the specimens with large wave velocity fluctuations are removed. Then, SEM electron microscope scanning can be performed to differentially characterize the initial destruction status of the coal body in different areas, and then mechanical testing experiments are carried out. During the loading process, high-speed cameras, acoustic wave signal acquisition and analysis instruments and other monitoring systems are used to dynamically monitor the evolution of mechanical behaviors such as coal body deformation and energy. SEM electron microscope scanning is used to study the fracture mode of the internal structure of the coal body in different areas of the working face. The numerical model has obvious advantages in three-dimensional visualization and is mainly used for axial-lateral pressure loading. The experiment of step-by-step zoned loading of physical similar materials uses an adjustable loading device to pave the zoned similar material model of the working face. When paving the coal seam within the intended excavation range, horizontal and vertical cross-shaped oblique joints are preset. The joint cutting angle can be set by referring to the fracture angle of the coal sample mechanical experiment, and optical fiber and earth pressure box are pre-buried layer by layer in the coal seam. Before the experiment, a hydraulic loading device is used to simulate the stress state of the original rock. In the experiment, the position of the maximum support pressure is determined according to the load-bearing law during coal wall mining, and step-by-step zoned loading is carried out (the secondary pressurization range is limited to the plastic zone, and the pressurization form is the step-by-step adjustment of the pressurization intensity). During the simulated mining process, optical fiber, earth pressure box and microseismic system are used for dynamic monitoring. Finally, the results of physical and mechanical properties test, mechanical properties numerical calculation experiment and step-by-step zoned loading of physical similar material experiment are comprehensively analyzed to systematically study the evolution law of coal wall mining dynamic behavior in large mining height mining area.

[0035] The specific invention is based on the on-site comprehensive coal seam histogram and coal rock mechanical parameters under the background of research engineering. With the help of FLAC3D numerical calculation software, numerical calculation models of different inclination angles and interlayer properties (strength properties) are established and excavation calculations are performed. By laying out multiple stress measurement lines with a spacing of 0.2m to 0.5m between measuring points, the cross-layer transmission of mining stress and its influence on the evolution of coal wall bearing distribution are monitored. With the help of origin software, the data is post-processed to draw the spatial distribution of coal wall bearing and its evolution curve. The dynamic change law of the mechanical environment such as the coal wall bearing strength, load increase coefficient, disturbance range, etc. in different areas and directions of the working face is preliminarily clarified. The mining experiment under the same geological conditions is carried out in the form of physical similar material experiments to supplement the verification. Taking into account the intuitiveness of the experimental cycle and its experimental phenomena, the similar model is paved with the trend model with the help of a loadable experimental frame. The model is based on the upper, middle and lower areas of the working face. The model should be paved according to the mining conditions in the middle. When paving the model, the direct roof, medium layer and coal seam should be paved in multiple layers, and the thickness of each layer should be 0.5cm~1cm. The model height should be controlled from the basic top of the working face to the thickness of 2~3 rock layers above it. For unpaved rock layers, the hydraulic cylinder of the experimental frame can be used to simulate the pressure. The loading value needs to be estimated according to γH (γ is the rock layer bulk density, H is the thickness of the unpaved rock layer) and determined based on the stress similarity ratio. When paving, the position of the cut eye should be determined in advance. In the medium layer and the direct roof, the soil pressure box should be embedded from the left boundary of the cut eye to the simulated mining boundary area. In the coal seam, the soil pressure box should be embedded from the coal wall of the cut eye to the mining boundary area. The embedding spacing should be in geometric ratio with the spacing between the measuring points of the numerical model, and should be 1cm~5cm. The numerical calculation and similar material experimental stress monitoring data are comprehensively analyzed to determine the evolution law of the bearing environment during the mining process under the coupling of the inclination angle and interlayer effect.

[0036] The study of the evolution of mechanical response behavior during the transformation of coal wall position needs to be carried out from both macro and micro aspects. The study of the microscopic deformation and failure of coal mainly adopts two methods: physical specimen mechanical property testing and numerical model mechanical simulation testing. When sampling on site, it is necessary to take samples from the middle position of the upper, middle and lower areas of the working face and process them into test samples. Acoustic testing is carried out with the help of an ultrasonic detector. In order to ensure full contact between the sample and the acoustic probe, a coupling agent is applied to the end of the sample and it is placed vertically between the probes. The wave velocity changes are statistically analyzed, and samples of the same type with obvious wave velocity differences are eliminated. SEM electron microscope scanning is used to differentially characterize the initialization state of the coal body in different areas of the working face. During the mechanical properties test, a high-bandwidth acoustic signal collector and a high-speed camera are used to dynamically monitor and record the damage and destruction of the internal structure of the coal body and the evolution of its fracture formation. During the test, the sample is placed between the acoustic signal probes and placed together in the pressure head room of the pressure testing machine to monitor the wave velocity changes and energy changes in real time to characterize the damage to the internal structure of the coal body. The loading value is determined based on the stress evolution during coal mining 3m to 5m in front of the coal wall. After the test, the coal body fracture type can be determined with the help of SME electron microscope. The numerical mechanical simulation test is carried out with the help of 3DEC numerical calculation software, which can realize the visualization of the evolution process of coal body failure. To ensure the consistency of research conditions, the numerical model is equivalent to the physical specimen, and the pressurization method is set to axial pressure-unloading confining pressure and cyclic axial pressure-unloading confining pressure. To simulate the initial stress state, both path pressurization experiments need to pressurize the axial and lateral pressures according to the original rock stress level of the coal seam, and perform a pressure stabilization operation of 100 to 200 calculation steps, and then add axial pressure and unload lateral pressure until the model is destroyed. For the cyclic experiment, the number of cycles and intensity are determined according to the load-bearing environment 3m to 5m in front of the coal wall. Comprehensive analysis of the physical specimen test and numerical model test data can clarify the dynamic changes of the internal structure damage and energy of the coal wall under different loading conditions, and determine the damage limit when the coal body breaks. The macroscopic destruction research of coal mainly adopts the similar material experimental method. With the help of an adjustable loading device, similar material models are laid according to the geological conditions in the middle of different areas of the working face. The thickness of the coal seam in the model should be 10cm to 20cm. Figure 3 As shown, the joints within the coal seam are arranged in a horizontal and vertical oblique pattern. Optical fibers and earth pressure cells are installed at different vertical levels of the coal seam to monitor coal deformation and stress changes. Before the experiment, a microseismic probe was placed a certain distance in front of the coal wall (the initial roof pressure step) to monitor dynamic energy changes. During the experiment, the simulated in-situ rock stress value applied by the loading cylinder was maintained at a steady state. A spare loading cylinder was used to simulate dynamic loads. The loading position and intensity were determined based on the equivalent change in the coal wall load with the advance distance. The pressure was adjusted step by step. After the experiment, the experimental results were comprehensively analyzed to establish the response mechanism between force, displacement, and energy. This can more systematically characterize the evolution of coal mining dynamics in high-dipping coal seams with large mining heights.

[0037] The above is only a preferred embodiment of the invention and does not limit the invention in any way. Any simple modification, change and equivalent structural transformation made to the above embodiment based on the technical essence of the invention shall still fall within the scope of protection of the technical solution of the invention.

Claims

1. A method for studying the evolution law of coal wall mining dynamics behavior in a large-angle and large-height mining area, characterized in that: include: Numerical models of different mining conditions were constructed by numerical calculation and excavation calculation was performed to draw the spatial distribution of coal wall bearing and its evolution curve, and to preliminarily clarify the dynamic change law of the mechanical environment of coal wall bearing strength, load increase coefficient and disturbance range in different areas and positions of the working face; A physical similarity simulation experiment method is used to construct a physical similarity material model of the same mining conditions as the numerical calculation and to perform excavation calculations. The mining experiment under the numerical model is used as a supplement to determine the evolution law of the bearing environment during the mining process under the coupling of inclination and interlayer effects. Based on the bearing law of coal wall, multi-path mechanical properties test and step-by-step partition loading of physically similar materials experiments were carried out, and the results of physical and mechanical properties test, mechanical properties numerical calculation experiment and step-by-step partition loading of physically similar materials experiments were comprehensively analyzed to systematically study the evolution law of coal wall mining dynamics behavior in large mining height mining areas; A dielectric layer is embedded between the numerical model direct roof and the numerical model coal seam, and the thickness of the dielectric layer is 1 / 5 to 1 / 2 of the thickness of the numerical model direct roof; multiple stress measurement lines are arranged in the numerical model direct roof and the dielectric layer from the opening of the cut to the boundary area; Among them, the stress measuring lines in the direct roof of the numerical model are arranged at a distance of 1 / 5~1 / 4 of the direct roof thickness of the numerical model to the dielectric layer, the measuring line spacing is 1m~2m, and the measuring point spacing is 0.2m~0.5m; the measuring lines and measuring points are arranged along the vertical middle of the dielectric layer, and the spacing between the measuring lines and measuring points corresponds to the positions of the measuring lines and measuring points in the basic roof of the numerical model; the measuring lines in the coal seam are arranged from the simulated coal wall to the boundary surface area, and the numerical model coal seam is divided into three layers of upper, middle and lower vertically according to the thickness of the numerical model coal seam, and the measuring lines and measuring points are arranged at 1 / 6 of the thickness of the layer in different layers, and the spacing between the measuring lines and measuring points is consistent with the spacing between the measuring lines and measuring points in the direct roof; The numerical calculation is used to construct numerical models of different mining conditions and perform excavation calculations. Specifically, based on the on-site coal seam comprehensive columnar diagram and coal rock mechanics parameters under the research engineering background, with the help of FLAC3D numerical calculation software, numerical calculation models of different inclination angles, mining heights, and interlayer properties are established and excavation calculations are performed; The mechanical property test includes a physical specimen mechanical property test and a numerical model mechanical simulation test.

2. The method for studying the evolution law of coal wall mining dynamics behavior in a large-angle and large-height mining area according to claim 1 is characterized in that: When the physical similarity material model is laid, a pressure sensor is buried at the bottom of the coal seam of the physical similarity material model, and soil pressure boxes are pre-buried in the direct top, medium layer and coal seam along the working face of the physical similarity material model. The buried spacing and the spacing between the measuring points of the numerical model satisfy a geometric ratio relationship. After the experiment, the numerical calculation and physical similarity material experimental monitoring data are comprehensively analyzed to determine the stress zoning and distribution of the coal wall in different areas of the working face under the inclination and interlayer effect.

3. The method for studying the evolution law of coal wall mining dynamics behavior in a large-angle and large-height mining area according to claim 1 is characterized in that: The mechanical property test of the physical sample is specifically as follows: sampling is carried out on site from the middle position of the upper, middle and lower areas of the working face, and processed into test samples, and an ultrasonic test is carried out with the help of an ultrasonic detector. A coupling agent is applied to the end of the sample and it is placed vertically between probes, and the wave velocity change is statistically analyzed. Samples of the same type with obviously different wave velocities are eliminated, and SEM electron microscope scanning is used to differentially characterize the initialization state of the coal body in different areas of the working face. During the mechanical property test, a high-bandwidth acoustic wave signal collector and a high-speed camera are used to dynamically monitor and record the damage and destruction of the internal structure of the coal body and its fracture formation evolution process. During the test, the sample is placed between the acoustic wave signal probes and placed together in the pressure head room of the pressure testing machine to monitor the wave velocity change and its energy change in real time. The loading value is determined according to the stress evolution during the coal mining process at 3m~5m in front of the coal wall. After the test, the coal body fracture type can be determined with the help of an SME electron microscope.

4. The method for studying the evolution law of coal wall mining dynamics behavior in a large-angle and large-height mining area according to claim 1 is characterized in that: The mechanical simulation test of the numerical model is specifically as follows: the test is carried out with the aid of 3DEC numerical calculation software, and the pressurization method is set to two paths of pressurization: axial pressure-unloading confining pressure and cyclic axial pressure-unloading confining pressure, so as to ensure that the research conditions are consistent and the numerical model is equivalent to the physical specimen; both path pressurization experiments require the axial and lateral pressures to be pressurized according to the original rock stress level of the coal seam to simulate the initial stress state, and perform a pressure stabilization operation for 100 to 200 calculation steps, and then add axial pressure and unload lateral pressure until the model is destroyed. For the cyclic experiment, the number of cycles and the intensity are determined according to the bearing environment 3 to 5 meters in front of the coal wall.

5. The method for studying the evolution law of coal wall mining dynamics behavior in a large-angle and large-height mining area according to claim 1 is characterized in that: The physical similarity experiment of step-by-step zoning loading is specifically as follows: with the help of an adjustable loading simulation experimental device, a zoning similarity material model of the working face is paved, and when paving the coal seam in the key area to be mined, horizontal and vertical cross-shaped oblique joints are preset, and the joint cutting angle can be set with reference to the fracture angle of the coal sample mechanical experiment; optical fiber and earth pressure boxes are pre-buried layer by layer in the coal seam, and a hydraulic loading device is used to load and simulate the stress state of the original rock before the experiment. During the experiment, the position of the maximum support pressure is determined according to the load-bearing law during the coal wall mining process, and step-by-step zoning loading is carried out, and dynamic monitoring is carried out using optical fiber, earth pressure boxes, and a microseismic system.

6. The method for studying the evolution law of coal wall mining dynamics behavior in a large-angle and large-height mining area according to claim 1 is characterized in that: A comprehensive analysis of the results of physical and mechanical properties tests, numerical calculation experiments on mechanical properties, and step-by-step partitioned loading of physically similar materials is conducted to reveal the evolution of the dynamic behavior of coal wall mining in large mining height mining areas.

Images