Simulation test method for overlying strata deformation and gas migration in inclined coal seam mining process

Abstract

The invention belongs to the technical field of stress measurement and analysis, and relates to an overlying strata deformation and gas migration simulation test method in an inclined coal seam mining process, which comprises the following steps of: sequentially paving a coal seam and a rock stratum by using similar materials to obtain a simulated mine environment; performing gas filling and stress loading under dynamic and static loads on the simulated mine environment to obtain a simulated crustal stress environment; dynamic excavation is conducted on the simulated crustal stress environment, detection data of rock stratum stress, deformation, angle and gas pressure are obtained in real time in the excavation process, and the overlying strata deformation and coal seam gas migration rule under the dynamic and static load coupling stress environment is obtained according to the detection data. The coal seam gas seepage process simulation under dynamic and static load coupling is achieved through gas filling and dynamic and static combined loading, mining gas migration law research is achieved, and the defect that coal seam feature point gas pressure measured data is lacked in mining gas migration law research based on a numerical simulation method at present is overcome. And the accuracy of a test result is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of stress measurement and analysis, and in particular relates to a simulation test method for overburden deformation and gas migration during inclined coal seam mining. Background Art

[0002] In order to study the rock pressure distribution, surrounding rock deformation, overburden pressure distribution, rock movement and fracture law in underground space excavation activities such as underground mining, tunnel excavation, underground civil air defense projects, etc., similar simulation test methods are usually used for indoor test research. This test method is based on similarity theory and factor analysis theory, and can effectively solve the research work on pressure distribution, overburden deformation and fracture in underground space engineering. The similar simulation test method can effectively and intuitively carry out more in-depth and detailed research on engineering site problems in the laboratory, and has been widely used in engineering research fields such as water conservancy and hydropower, underground mining, and road and bridge slopes. However, among the many existing simulation test devices, most of the research on mine pressure, overburden displacement, rock fracture and its stress distribution law is mostly concentrated on the similar simulation test of establishing a plane model, which is quite different from the actual situation that the rock mass is in a triaxial stress state in the engineering site.

[0003] For underground mining projects, as the mining face continues to advance, the surrounding rock deforms and breaks, and the peak stress area moves forward until a new stress balance is reached. During the whole process, the breaking and stress distribution of the overburden rock layer are dynamically changing. With the rapid development of modern science and technology, human beings are developing and utilizing underground space more and more. Therefore, it is necessary to use a large-scale three-dimensional similarity simulation test system to carry out relevant experimental research on underground chamber excavation, tunnel excavation and excavation progress under three-dimensional stress.

[0004] 1. Three-dimensional similarity simulation test machine - Xi'an University of Science and Technology

[0005] The three-dimensional similarity simulation testing machine system developed by Xi'an University of Science and Technology has a design model size of 3600×2000×2000mm. It can only apply vertical stress to simulate the displacement and fracture laws of the overlying rock strata during coal mining at different depths. However, the equipment can only add vertical stress and cannot add horizontal stress.

[0006] 2.3D Fluid-Solid Interaction Simulation Test Bench——Taiyuan University of Technology GLOH-1200

[0007] The three-dimensional fluid-solid coupling similarity simulation test bench developed by the 211 Project of Taiyuan University of Technology has a simulation size of 3000×2000×2000mm and a maximum axial loading force of 900t. When conducting similarity simulation tests with a geometric ratio of 1:30, the maximum mining depth that can be simulated is 1200m. The lateral stress-free application device has a lateral constraint that is applied laterally by the horizontal constraint reaction force generated by the axial load. Among the four lateral surfaces, two sides are equipped with transparent plexiglass for rock surface displacement detection. In addition, the device can also conduct fluid-solid coupling simulation tests to reveal the deformation and permeability laws of rock masses in underground mining projects under the action of fluid-solid coupling.

[0008] 3True 3D Similarity Model Test System——Shandong University

[0009] The true three-dimensional similar model test system developed by Shandong University has a maximum simulation size of 1000×1000×1000mm, which is mainly composed of a high-pressure loading system, an intelligent hydraulic control system and a reaction device system. Its high-pressure loading system mainly includes jacks and loading plates, which are mainly used to apply model stress and simulate the ground stress field of engineering rock mass at a certain buried depth; the intelligent hydraulic control system is mainly composed of a test bench, a motor, a fuel tank, a control valve and an intelligent sensor, which is mainly used for independent reaction, loading and pressure stabilization in the front, back, left, right and up and down directions of the test model; the reaction device system mainly includes a reaction frame, a flange and a reaction transmission plate, which is mainly used as a reaction device for loading the force model.

[0010] Existing large-scale three-dimensional similarity simulation test systems usually use a test box to make simulation specimens before the experiment. After the simulation specimens are laid with similar materials according to predetermined requirements, a hydraulic device is used to give unidirectional independent static pressurization so that the similar materials can meet the requirements of simulating the ground stress field of engineering rock masses at a certain burial depth, and then excavation and loading are carried out on the simulation specimens.

[0011] However, due to the special environment of underground space projects, most of them are gas-solid coupling environments. Although the current simulation specimens can simulate the basic configuration of underground space projects to a certain extent, they do not take into account the existence of gas and the influence of gas on the deformation of the engineering rock mass during excavation. The influence of gas-solid coupling on the dynamic deformation process of the engineering rock mass structure is ignored, resulting in biased test results and failure to reveal the true law of gas migration. Summary of the invention

[0012] In view of this, the present invention provides a simulation test method for overburden deformation and gas migration during inclined coal seam mining, which adds measured data of coal seam characteristic points, and can realize the simulation of coal seam gas seepage process under dynamic and static load coupling. Through gas injection and dynamic and static coupling loading, and using a dot matrix measurement and control system pre-deployed in the coal seam and rock formation to test relevant parameters, the dynamic evolution analysis of the three-dimensional spatial distribution of gas pressure in the coal seam mining process under dynamic and static load coupling can be realized. Based on this, the deformation of overburden and the law of coal seam gas migration under the dynamic and static load coupling stress environment during the mining process are studied, which solves the technical problems in the above-mentioned prior art.

[0013] The technical solution of the present invention is:

[0014] The simulation test method of overburden deformation and gas migration during inclined coal seam mining includes the following steps:

[0015] Using similar materials to lay coal and rock layers in sequence, a simulated mine environment is obtained;

[0016] Gas injection and stress loading under dynamic and static loads are performed on the simulated mine environment to obtain the simulated ground stress environment under the coupling of dynamic and static loads;

[0017] Dynamic excavation is carried out in a simulated ground stress environment. During the excavation process, the detection data of rock stress, deformation, angle and gas pressure of multiple measuring points in different layers are obtained in real time. The detection data of rock stress, deformation, angle and gas pressure of multiple measuring points in different layers are matched one by one with the two-dimensional position coordinates of the measuring points, and converted into three-dimensional space for marking. Different colors are used to represent rock stress, deformation, angle and gas pressure, respectively, to form real-time cloud maps of rock stress, deformation, angle and gas pressure based on three-dimensional space. According to the real-time cloud maps of rock stress, deformation, angle and gas pressure, the deformation of overburden and the migration law of coal seam gas under the dynamic and static load coupling stress environment are determined.

[0018] Preferably, during the coal seam laying process, a gas injection pipe is pre-buried, and the gas injection pipe pre-buried in the coal seam is connected to an external gas source.

[0019] Preferably, gas injection and stress loading under dynamic and static loads are performed on the simulated mine environment to obtain a simulated ground stress environment under the coupling of dynamic and static loads, including the following steps:

[0020] According to the real three-dimensional ground stress of the designated simulated mine area and the predetermined similarity ratio, the three-dimensional stress and gas pressure values ​​required for the experiment are determined;

[0021] According to the three-dimensional stress and gas pressure values ​​required for the experiment, three-dimensional stress loading is first performed until the three-dimensional loading pressure reaches a predetermined value;

[0022] Injecting a gas substitute of a target pressure value through the gas injection pipe;

[0023] After the gas pressure inside the sample is stable, the rock deformation detection component, rock stress detection component, rock inclination detection component and gas pressure detection component are turned on to collect data corresponding to each layer, which will be used as the initial data of all measurement and control systems before mining disturbance;

[0024] Dynamic load stress loading is performed on a two-dimensional plane, and the dynamic load is a cyclic load.

[0025] Preferably, the methane gas substitute is CO2 gas, nitrogen or helium.

[0026] Preferably, the measurement and control system is laid out synchronously during the laying of the coal seam and the rock stratum, and the measurement and control system includes a rock formation deformation detection component, a rock formation stress detection component, a rock formation inclination detection component and a gas pressure detection component, wherein the rock formation deformation detection component is used for deformation detection in three directions on the rock formation, the rock formation stress detection component is used for rock formation stress field detection, the rock formation inclination detection component is used for rock formation inclination detection, and the gas pressure detection component is used for detection of gas pressure in the rock formation and the coal seam during coal seam mining.

[0027] Preferably, the method for arranging the rock formation deformation detection assembly comprises the following steps:

[0028] A first sensing fiber group, a second sensing fiber group and a third sensing fiber group are arranged in layers in the coal seam and the rock stratum, wherein the first sensing fiber group includes a plurality of axial sensing fibers, and the plurality of axial sensing fibers are arranged at intervals along the axial direction, the second sensing fiber group includes a plurality of dip sensing fibers, and the plurality of dip sensing fibers are arranged at intervals along the dip direction, the third sensing fiber group includes a plurality of normal sensing fibers, and the plurality of normal sensing fibers are arranged at intervals along the normal direction, and the axial sensing fibers, the normal sensing fibers and the dip sensing fibers have phase differences, respectively; the axial sensing fibers, the normal sensing fibers and the dip sensing fibers are connected through connecting fibers to form a fiber network, the fiber input end of the fiber network is connected to a broadband light source, and the fiber output end is sequentially connected to a fiber grating demodulator and a fiber stress analyzer.

[0029] Preferably, the method for arranging the rock formation stress detection assembly comprises the following steps:

[0030] A multi-layer detection surface is set along the vertical depth of the coal seam, and a plurality of measuring points are arranged on the detection surface. The plurality of measuring points are distributed in a rectangular array, and a pressure sensor is arranged at each measuring point. A plurality of pressure sensors are buried in the surrounding coal pillars at the same depth as the detection surface, and the pressure sensors are connected to the signals of an external signal acquisition instrument, and the signal acquisition instrument is connected to a computer system.

[0031] Preferably, the method for arranging the rock formation dip detection assembly comprises the following steps:

[0032] Based on the distribution of collapse zones, fracture zones and bending deformation zones in numerical simulation, dynamic inclination sensors are arranged in the collapse zones, fracture zones and bending deformation zones respectively. It is designed that each layer is arranged with a survey line along the axial direction and the dip direction respectively. Multiple dynamic inclination sensors are arranged on each survey line, and a dynamic inclination sensor is arranged at the intersection of two survey lines. The spacing between adjacent dynamic inclination sensors is 45 cm to 55 cm. The dynamic inclination sensor is connected to the signal acquisition instrument.

[0033] Preferably, the arrangement method of the gas pressure detection assembly comprises the following steps:

[0034] A multi-layer detection surface is set along the vertical depth direction of the coal seam and the rock layer, and a plurality of measuring points are arranged on the detection surface. The plurality of measuring points are distributed in a rectangular array. A gas-specific pressure sensor is arranged at each measuring point, and the gas-specific pressure sensor is connected to the signal of the signal acquisition instrument.

[0035] Preferably, dynamic excavation is performed in a simulated geostress environment, comprising the following steps:

[0036] Step 1: Put the excavation tool into the cutting hole, place the cutter head at one end of the excavation tool, adjust the cutting surface of the excavation tool to be parallel to the cut surface, and connect the power supply and gas line of the excavation tool console;

[0037] Step 2: Tighten the jacking cylinder and push the push cylinder to make the excavation tool close to the cutting surface;

[0038] Step 3: The push cylinder and the tightening cylinder are reset, and the excavation motor and the feed motor rotate forward;

[0039] Step 4: The cutter head moves to the other end of the excavation tool, the excavation motor rotates forward, the feed motor rotates reversely, and the cutter head returns to its original position;

[0040] Step 5: Repeat steps 2 to 4. The excavation machine excavates back and forth multiple times according to the predetermined single advance to complete the excavation of the coal seam.

[0041] Compared with the prior art, the simulation test method for overburden deformation and gas migration during inclined coal seam mining provided by the present invention constructs a simulation environment by gas injection and dynamic and static composite loading, realizes the simulation of inclined coal seam excavation under the stress environment of coupling horizontal two-way dynamic load and three-way static load, can truly simulate the deformation and fracture behavior of overburden in the coal seam excavation process under the complex underground stress environment, realizes the simulation of coal seam gas seepage process under the coupling of dynamic and static loads, and uses the dot matrix measurement and control system pre-deployed in the coal seam and rock formation to test relevant parameters, realizes the dynamic evolution analysis of the three-dimensional spatial distribution of gas pressure in the coal seam mining process under the coupling of dynamic and static loads, and studies the deformation of overburden and coal seam gas migration law under the dynamic and static load coupling stress environment during the mining process on this basis. This method makes up for the deficiency of the lack of measured data of gas pressure of coal seam characteristic points in the current study of mining gas migration law based on numerical simulation method, and because the influence of gas-solid coupling on the dynamic deformation process of the structure is taken into account, the accuracy of the test results is improved, the practicability is strong, and it is worthy of promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a flow chart of the present invention.

[0043] Figure 2 The local structure of the present invention Figure 1 .

[0044] Figure 3 The local structure of the present invention Figure 2 .

[0045] Figure 4 The local structure of the present invention Figure 3 .

[0046] Figure 5 The local structure of the present invention Figure 4 .

[0047] Figure 6 The local structure of the present invention Figure 5 .

[0048] Figure 7 The local structure of the present invention Figure 6 .

[0049] Figure 8 The local structure of the present invention Figure 7 .

[0050] Fig. 9 The local structure of the present invention Figure 8 .

[0051] Fig.10 The local structure of the present invention Fig. 9 .

[0052] Fig.11 The local structure of the present invention Fig.10 .

[0053] Fig.12 The local structure of the present invention Fig.11 .

[0054] Fig.13 It is a dynamic-static coupling stress loading path diagram in the test method of the present invention. DETAILED DESCRIPTION

[0055] The present invention provides a simulation test method for overburden deformation and gas migration during inclined coal seam mining. Figure 1 Flowchart of Figures 2 to 12 The structural diagram and Fig.13 The present invention is described with reference to a dynamic-static coupled stress loading path diagram.

[0056] Example 1

[0057] The present invention provides a simulation test method for overburden deformation and gas migration during inclined coal seam mining based on an indoor large-scale three-dimensional similarity simulation system. The flow chart is as follows: Figure 1 As shown, the test method mainly includes the following steps:

[0058] (1) Using similar materials, coal seam 1 and rock layer 2 are laid in sequence to obtain a simulated mine environment.

[0059] (2) Gas injection and stress loading under dynamic and static loads are performed on the simulated mine environment to obtain a simulated ground stress environment under the coupling of dynamic and static loads.

[0060] (3) Dynamic excavation is performed in a simulated ground stress environment. During the excavation process, the detection data of rock formation stress, deformation, angle and gas pressure at multiple measuring points in different layers are obtained in real time. The detection data of rock formation stress, deformation, angle and gas pressure at multiple measuring points in different layers are matched one by one with the two-dimensional position coordinates of the measuring points, and converted into three-dimensional space for marking. Different colors are used to represent rock formation stress, deformation, angle and gas pressure, respectively, to form real-time cloud maps of rock formation stress, deformation, angle and gas pressure based on three-dimensional space. According to the real-time cloud maps of rock formation stress, deformation, angle and gas pressure, the deformation of overburden and the migration law of coal seam gas under the dynamic and static load coupling stress environment are obtained.

[0061] The above-mentioned test method uses similar materials to make simulated specimens, and the simulated specimens are realized using the above-mentioned method. In summary, the coal seam 1 and the rock layer 2 are laid in sequence to construct a simulated mine environment, and the simulated mine environment is again gas-filled and stress-loaded under dynamic and static loads to obtain a simulated geostress environment under the coupling of dynamic and static loads, and finally the simulated geostress environment is dynamically excavated.

[0062] It should be noted that during the laying of the coal seam 1, the measurement and control system is laid out and the gas injection pipe 11 is pre-buried, and the gas injection pipe 11 pre-buried in the coal seam 1 is connected to the external gas source 12, and the basic equipment for gas injection is pre-built. During the dynamic process of excavation, the measurement and control system is used to obtain real-time detection data on rock formation stress, deformation, angle and gas pressure, and based on the detection data, the deformation of the overburden and the migration law of coal seam gas under the dynamic and static load coupled stress environment are obtained.

[0063] Specifically, the above-mentioned measurement and control system includes a rock formation deformation detection component, a rock formation stress detection component, a rock formation inclination detection component and a gas pressure detection component.

[0064] In this experiment, the simulation specimen prepared according to the size of the specimen box of the simulation test system is a large cubic specimen. The length × width × height of the large cubic specimen is 3m × 3m × 3m. The rock deformation detection component, rock stress detection component, rock inclination detection component and gas pressure detection component are all buried in the large three-dimensional simulation specimen of this size.

[0065] Among them, the rock formation deformation detection component is used for deformation detection in three directions on the rock formation 2. The instruments used in the actual experiment are the NBX-6055 distributed optical fiber stress analyzer and the SM225 optical fiber Bragg grating demodulator. Specifically, the sensing optical fiber of the NBX-6055 distributed optical fiber stress analyzer is divided into three groups, which are respectively recorded as the first sensing optical fiber group, the second sensing optical fiber group and the third sensing optical fiber group. They are classified and marked before use, and then laid out layer by layer.

[0066] like Figure 3 As shown, the first sensing fiber group includes multiple axial sensing fibers 3, and the multiple axial sensing fibers 3 are arranged at intervals along the axial direction. Specifically, the length of the axial sensing fiber 3 is 2.2 m, there are 5 arrangement planes and they are all in the overlying rock layer 2 on the coal seam 1, the planes are parallel to each other and arranged along the axial plane of the coal seam 1, and the spacing between the sensing fibers is 50 cm.

[0067] like Figure 2As shown, the second sensing fiber group includes multiple inclination sensing fibers 4, and the multiple inclination sensing fibers 4 are arranged at intervals along the inclination. Specifically, the length of the inclination sensing fiber 4 is 2.2 m, there are 5 arrangement planes and they are all in the overlying rock layer 2 on the coal seam 1, the planes are parallel to each other and arranged along the inclination plane of the coal seam 1, and the arrangement spacing of each inclination sensing fiber 4 is 50 cm.

[0068] like Figure 4 As shown, the third sensing fiber group includes multiple normal sensing fibers 5, and the multiple normal sensing fibers 5 are arranged at intervals along the normal direction. Specifically, the length of the normal sensing fiber 5 is 2.4 m, there are 5 arrangement planes and they are all in the overlying rock layer 2 on the coal seam 1, the planes are parallel to each other and arranged along the normal plane of the coal seam 1, and the arrangement spacing of each sensing fiber is 50 cm.

[0069] It should be noted that the axial sensing optical fiber 3, the normal sensing optical fiber 5 and the inclination sensing optical fiber 4 are 90 degrees apart from each other. After all the axial sensing optical fibers 3, the normal sensing optical fibers 5 and the inclination sensing optical fibers 4 are arranged, they are connected by connecting optical fibers 6 to form an optical fiber network. The structure of the optical fiber network is as follows: Figures 2 to 4 shown.

[0070] During specific use, after the fiber optic network is laid, a broadband light source is connected to one end of the optical fiber to input high-power laser pulses. At the same time, the other end of the optical fiber is connected to the SM225 fiber grating demodulator and the NBX-6055 distributed optical fiber stress analyzer in sequence. The NBX-6055 distributed optical fiber stress analyzer uses a wavelength demodulation mode to analyze the changes in the wavelength of light waves at different times, and saves the data at equal intervals, and then inverts the strain conditions at different positions.

[0071] Among them, the rock formation stress detection component is used for rock formation stress field detection. In the actual test, the pressure sensor 7 is used to measure the stress during the mining process of the coal seam 1. The pressure sensor 7 is preferably a SCYG315 pressure sensor, and its test range is 0MPa to 3MPa, and the measurement accuracy is ±0.5%. Before the test, according to the distribution of the collapse zone, fracture zone, and bending deformation zone in the numerical simulation, the pressure sensor 7 is arranged in 4 layers along the vertical depth direction of the rock layer 2 and the coal seam 1. The arrangement positions are respectively the middle and lower part of the collapse zone, the boundary between the collapse zone and the fracture zone, the middle part of the fracture zone, and the middle part of the bending deformation zone. Five measuring lines are arranged along the inclination of each layer of pressure sensor 7, and the spacing between each measuring line is 50cm. Five pressure sensors 7 are arranged along the axial direction of each measuring line, and the spacing between each pressure sensor 7 is 50cm. The design requires a total of 100 separation gauges. In addition, numerical calculations show that during the mining process of coal seam 1, there are obvious pressurized areas on both sides of coal seam 1. Therefore, in order to detect the stress change law of the pressurized area during the mining process of coal seam 1, it is planned to bury 5 pressure sensors 7 in the surrounding coal pillars 8 at the same depth as the coal seam 1. As mentioned above, a total of 120 pressure sensors 7 are required, and the layout diagram is shown in the figure. Figure 5 As shown, the layout diagram on the bottom layer of coal seam 1 is as follows Figure 6 As shown, the pressure sensor 7 is not arranged on the coal seam bottom plate 16 , and the pressure sensor 7 is only buried in the surrounding coal pillars 8 .

[0072] Among them, the rock formation inclination detection component is used for rock formation 2 inclination detection. In the actual test, a dynamic inclination sensor 9 is used for detection. The dynamic inclination sensor 9 is preferably an MDTQJ60-485-A1 / C dynamic inclination sensor. The sensor has an accuracy of 0.1° and a measurement range of -90° to +90°. Before the test, according to the distribution of the collapse zone, fracture zone, and bending deformation zone in the numerical simulation, the dynamic inclination sensors 9 are arranged in the collapse zone, fracture zone, and bending deformation zone respectively. It is designed that each layer is arranged with a measuring line along the axial direction and the dip direction respectively, and 5 dynamic inclination sensors 9 are arranged on each measuring line, wherein one dynamic inclination sensor 9 is arranged at the intersection of two measuring lines, and the spacing between adjacent dynamic inclination sensors 9 is 45cm to 55cm. Preferably, the spacing between adjacent dynamic inclination sensors 9 is 50cm. A total of 9 dynamic inclination sensors 9 are used in each layer, and a total of 27 dynamic inclination sensors 9 are used in the test. The layout diagram is shown as follows Figure 7 and Figure 8 .

[0073] Among them, the gas pressure detection component is implemented using a gas-specific pressure sensor 10, and the gas-specific pressure sensor 10 is preferably an OSP1.5 gas pressure sensor, which is used to detect the gas pressure in the overburden and coal seam 1 during the mining process of the coal seam 1. A multi-layer detection surface is set along the vertical depth direction of the coal seam 1 and the rock layer 2, and a plurality of measuring points are arranged on the detection surface. The plurality of measuring points are distributed in a rectangular array, and a gas-specific pressure sensor 10 is arranged at each measuring point.

[0074] Specifically, the gas-specific pressure sensor 10 is arranged in the plane of the coal seam 1, and is designed to be arranged according to 4 measuring lines, with a spacing of 60 cm between each measuring line, and a spacing of 60 cm between adjacent sensors on the same measuring line. In the overlying rock layer 2, 3 planes parallel to the coal seam 1 are selected at equal spacing to arrange the gas-specific pressure sensors 10. The spacing between the gas-specific pressure sensors 10 on each plane is the same as the spacing between the gas-specific pressure sensors 10 in the coal seam 1. The arrangement of the gas-specific pressure sensors 10 on each plane is as follows: Fig. 9 and Fig.10 .

[0075] The above-mentioned pressure sensor 7, gas-specific pressure sensor 10, signal acquisition instrument and computer system constitute the dot matrix measurement and control system used in this experiment. The pressure sensor 7 and the gas-specific pressure sensor 10 are electrically connected to the signal acquisition instrument, and the signal acquisition instrument is electrically connected to the computer system. The computer system contains acquisition test software. During the test, first turn on the computer system and start the acquisition test software, and then check whether the pressure sensor 7 and the gas-specific pressure sensor 10 are successfully connected to the computer system. Ensure that there is beating data on the software channel interface, which indicates that the pressure sensor 7, the gas-specific pressure sensor 10 are well connected to the signal acquisition instrument. During the data acquisition process, the acquisition test software automatically saves the detection data of all channels, obtains the detection data of rock formation stress, deformation, angle and gas pressure of multiple measuring points in different layers in real time, and corresponds the detection data of rock formation stress, deformation, angle and gas pressure of multiple measuring points in different layers to the two-dimensional position coordinates of the measuring points one by one, and converts them into three-dimensional space for marking. Different colors are used to represent rock formation stress, deformation, angle and gas pressure, respectively, to form real-time cloud maps of rock formation stress, deformation, angle and gas pressure based on three-dimensional space. According to the real-time cloud maps of rock formation stress, deformation, angle and gas pressure, the deformation of overburden and the migration law of coal seam gas under dynamic and static load coupled stress environment are obtained.

[0076] Working process:

[0077] (1) Preparation of similar materials

[0078] Taking the coal seam 1 mining face of a designated mine as the simulation object, firstly, the coal rock samples of the top and bottom rock layers 2 and coal seam 1 of the working face were collected for indoor mechanical parameter testing to obtain the basic mechanical parameters of the coal rock in the simulation area. Then, the strength of the similar simulation materials required for each rock layer 2 and coal seam 1 was calculated according to the appropriate geometric similarity ratio and strength similarity ratio. Finally, according to the strength, the appropriate ratio of river sand, gypsum and cement was selected, and similar materials for each rock layer 2 were prepared with the selected ratio.

[0079] (2) Calculation of material consumption

[0080] First, the volume of each rock layer 2 model is calculated, and then the total weight of the corresponding model rock layer 2 is calculated according to the bulk density of the model rock layer 2. According to the geometric similarity ratio of 1:40, bulk density similarity ratio of 1:1.6, stress similarity ratio of 1:64 and time similarity ratio of 1:6.3, the bulk density, compressive strength and other mechanical properties of the model rock are calculated. Then, according to the above similarity ratios, the mass of river sand, gypsum and cement required in all rock layer 2 and coal seam 1 simulation materials is calculated in turn, and a material list of each rock layer 2 and coal seam 1 is prepared. Finally, the total amount of materials required for the model test is summarized. The detailed calculation process of this part can be referred to "Similarity Simulation Experiment of Mine Pressure" for reference.

[0081] (3) Laying of rock layer 2

[0082] First, the specimen box is tilted with an angle consistent with the inclination of the simulated actual coal seam 1. Then, similar materials of each rock layer 2 are prepared in order from bottom to top. According to the ingredient list of the river sand, gypsum and cement mass required for each rock layer 2 calculated in step 2, the river sand, gypsum and cement of the required mass for the corresponding rock layer 2 are put into the mixer, and an appropriate amount of water is added. After mixing evenly, they are laid layer by layer in the order of the rock layer 2. Finally, the sensors are arranged according to the sensor arrangement schematic diagram in each test method specified in the "Experimental Test Method" until all simulated strata are laid.

[0083] (4) Laying of coal seam 1

[0084] Specific requirements: Since the coal seam 1 should not only be equipped with sensors, but also should have the conditions for the excavation equipment to excavate smoothly, the laying of the coal seam 1 is an important part of this method. The thickness of the coal seam 1 is designed to be 10cm, so that it meets the minimum height required for the excavation equipment to move. Considering that sufficient space for excavation equipment needs to be reserved before excavation of the coal seam 1, a cut eye 13 is made at the front end of the axial direction of the coal seam 1. The cut eye 13 is arranged along the inclination of the coal seam 1. According to the size of the excavation equipment, the cut eye 13 is designed to be 45cm wide and 285cm long. At the same time, two return air lanes 15 are arranged along the axial direction of the coal seam 1. The reserved return air lanes 15 can provide a good space for the excavation equipment to move, so as to avoid the excavation equipment being stuck by the coal wall at both ends during the excavation process, which affects the excavation progress. The length of the return air lanes 15 is 190cm and the width is 40cm.

[0085] Specific process:

[0086] In order to realize the arrangement of the above-mentioned cutting eye 13 and return air roadway 15 in the coal seam 1, after the coal seam bottom plate 16 and rock layer 2 are paved, first, before the coal seam 1 is paved, according to the size of the cutting eye 13 and the return air roadway 15, the outer contour molds of the cutting eye 13 and the return air roadway 15 are pre-made with wooden boards 14, and placed in designated positions to prevent the cutting eye 13 and the roadway return air from being blocked during the paving process of the coal seam 1. Then, the proportions of river sand, gypsum and cement are pre-calculated to prepare similar materials for the coal seam 1. The similar materials are sequentially loaded into all areas of the box except the template contour mold, and sensors and gas injection pipes 11 are arranged according to design requirements. After all the similar materials are loaded into the box and reach the designed height of 10 cm, the paving is stopped. After naturally drying for a week, the outer contour molds of the cutting eye 13 and the return air roadway 15 pre-made by the wooden boards 14 are removed. The space presented after the removal is the cutting eye 13 and the return air roadway 15, and the paving of the coal seam 1 is finally completed. The detailed plan view after the paving of the coal seam 1 is shown in Fig.11 .

[0087] (5) Burying of the gas injection pipe 11

[0088] For safety reasons, the gas substitute used in this simulation can be one of CO2 gas, nitrogen or helium. To achieve gas injection, the gas injection pipe 11 needs to be pre-buried during the laying process of the coal seam 1. The gas injection pipe 11 pre-buried in the coal seam 1 is connected to the gas source 12 outside the box. This can realize gas injection in the enclosed space of a large three-dimensional similar simulation material, thereby simulating a high-gas coal seam 1.

[0089] In this experiment, three gas injection pipes 11 are arranged at equal intervals on the side of the coal seam 1. The length of the gas injection pipe 11 penetrating into the coal seam 1 is 50 cm. The distance between each gas injection pipe 11 is 50 cm. The outer side of the gas injection pipe 11 is connected to the external air inlet control valve and then connected to the external gas source 12 to provide sufficient gas substitute.

[0090] The gas pressure inside the coal seam 1 can be actively adjusted and controlled by the gas injection port pressure valve. The arrangement of the gas injection pipe 11 inside the sample is as follows: Fig.12 .

[0091] (6) Sample stress loading and gas filling

[0092] After all the rock layers 2 and coal layers 1 are paved and the similar materials are dried, the specimen box is restored to the horizontal position. This simulation experiment is carried out with the mining face of a mine in Pingdingshan as the simulation object. According to the real three-dimensional ground stress of the designated simulated mine area and the predetermined similarity ratio, the three-dimensional stress σ required for this simulation experiment is calculated. x , σ y , σ z They are 0.5MPa, 0.78MPa and 0.61MPa respectively. According to the above-mentioned established stress and gas pressure values, the three-dimensional direction of the sample is first set, with the up-down direction as the Z direction, the left-right inclination as the X direction, and the front-back axial direction as the Y direction. Then all oil pumps are turned on, and the force control method is used to load the X-direction horizontal loading, the Y-direction horizontal loading pressure, and the Z-direction vertical loading pressure in sequence until the three-dimensional loading pressure reaches the predetermined value and the three-dimensional stress loading rate is constant. Finally, the gas injection port valve outside the box is opened to start injecting gas substitutes into the sample. The target pressure value of the gas injection port valve is set to between 0.2MPa and 0.5MPa. After the gas pressure inside the sample is stable, all sensor acquisition systems are turned on to record the data of all pressure sensors 7 and gas-specific pressure sensors 10 in each layer, which are used as the initial data of all sensors before mining disturbance.

[0093] It should be noted that the target pressure value of the gas injection valve should be less than the minimum loading stress in the three directions. Therefore, the target pressure value of the gas injection valve was set to 0.4 MPa in the experiment.

[0094] (7) Excavation of coal seam 1 under dynamic and static load coupled stress environment

[0095] The construction of a simulated ground stress environment under static and dynamic load coupling is achieved by coupling static and dynamic load pressure heads in three different directions of the specimen box, namely the up and down direction, i.e., the Z direction, the left and right inclination direction, i.e., the X direction, and the front and rear axial direction, i.e., the Y direction, with the dynamic load pressure heads in the X and Y directions.

[0096] The loading steps of dynamic and static load coupling stress are:

[0097] First, the hydraulic control system of the Z-direction static load pressure head is turned on, and the pressure of the Z-direction load, i.e., the vertical load, is applied between 0.5MPa and 0.8MPa, and kept stable. Then, the hydraulic control systems corresponding to the remaining pressure heads in the X-direction and Y-direction except the bottom row of dynamic load pressure heads are turned on at the same time, and the target value of the X-direction load is set to 0.5MPa to 0.8MPa, and the target value of the Y-direction load is set to 0.5MPa to 0.8MPa, and kept stable. At this point, the initial static load stress loading is completed.

[0098] After the stress in the three directions of X, Y and Z is stable, dynamic load stress is applied in the two-dimensional plane, namely in the X and Y directions:

[0099] The hydraulic control system of the bottom row of dynamic load pressure heads in the X and Y directions is opened synchronously, and the dynamic loads in the horizontal directions are applied through the hydraulic servo valve. The lower limit stress value of the dynamic load is set to 0.5MPa, the upper limit value is set to 1.0MPa, the periodic load, the vibration frequency is 5Hz, and the dynamic-static coupling stress loading path is as follows: Fig.13 .

[0100] In this experiment, the pressure of the Z-direction load, i.e., the vertical load, was applied at 0.61 MPa, the target value of the X-direction load was set at 0.5 MPa, and the target value of the Y-direction load was set at 0.78 MPa.

[0101] After the above-mentioned dynamic and static load coupled stress environment field loading is completed, the excavation equipment is put into the opening 13 to simulate the mining of the coal seam 1. The specific process is as follows:

[0102] Step 1: Open the blocking plate of the reserved tunnel on one side of the box body X, lift the excavation tool with a gantry truck, and send it into the cutting eye 13 through the reversing device. Place the cutter head at one end of the excavation tool, adjust the cutting surface of the excavation tool to be parallel to the cut surface, and connect the power supply and gas circuit of the excavation tool console.

[0103] Step 2: Tighten the jacking cylinder and push the cylinder forward to make the excavation tool close to the cutting surface.

[0104] Step 3: The thrust cylinder and the tightening cylinder are reset, the excavation motor and the feed motor rotate forward, the excavation speed is 200r / min, and the feed motor is 6r / min.

[0105] Step 4: The cutter head moves to the other end of the excavation tool, the limit indicator light comes on, the excavation motor rotates forward, the feed motor rotates reversely, and the cutter head returns to its original position.

[0106] Step 5: Repeat steps 2 to 4, with the excavation equipment advancing 10 mm at a time, and complete all excavation work of the simulated coal seam 1 through multiple reciprocating excavations.

[0107] During the excavation process, the excavation is simulated according to the cutting speed converted from the advancing speed of the on-site excavation working face, and the stress of different surfaces of the rock layer 2 during the excavation process is collected through the data acquisition system.

[0108] (8) Data collection and analysis during excavation

[0109] During the excavation process, the measurement and control system detects rock stress, deformation, angle, gas pressure and other parameters in real time. The detection data of the pressure sensor 7 at each layer is transmitted to the acquisition computer in real time, and the evolution law of the stress field of the upper rock layer of the coal seam 1 during the mining process in the coal seam 1 is displayed in real time through the data visualization software. The pre-buried axial sensing optical fiber 3, the inclined sensing optical fiber 4 and the normal sensing optical fiber 5 are connected in sequence and connected to the computer system to collect the distributed sensing optical fiber test data during the mining process of the coal seam 1, and obtain the three-dimensional spatial deformation evolution law of the rock layer 2 in each area of ​​the rock layer 2 through the sensing optical fiber inside the rock layer 2. The dynamic inclination sensor 9 at each layer collects the inclination data of the rock layer 2 and transmits it in real time. , and the designated computer system collects and records it, and analyzes the evolution law of the inclination of the overlying rock stratum 2 during the mining process of coal seam 1 based on it. The mining cracks in coal seam 1 form gas seepage channels, which affect the migration of gas in coal seam 1 and overlying rock. By simulating the gas sensors inside the sample, the gas pressure data of each measuring point in different layers are obtained and transmitted to the computer system. After the real-time data of all measuring points are visualized in real time on the computer system, the evolution process of the gas pressure inside the overlying rock during the mining process can be observed in real time, thereby simulating the gas migration law of the coal seam under the influence of mining.

[0110] Specifically, the method used to visualize the real-time data of all measuring points in the computer system in real time is to correspond the detection data of rock formation stress, deformation, angle and gas pressure of multiple measuring points in different layers to the two-dimensional position coordinates of the measuring points one by one, and transform them into three-dimensional space for marking, and use different colors to represent rock formation stress, deformation, angle and gas pressure, respectively, to form real-time cloud map of rock formation stress, real-time cloud map of deformation, real-time cloud map of angle and real-time cloud map of gas pressure based on three-dimensional space. In actual operation, the above visualization steps can be completed with the help of origin software, so as to obtain the dynamic evolution characteristics of overburden bearing pressure (pressure increase), overburden separation and fracture (pressure reduction) and overburden micro-disturbance (slight pressure fluctuation), the evolution law of overburden deformation during coal seam mining process and the gas enrichment in different areas of coal seams and overburden after each mining. Finally, combined with the above-mentioned overburden deformation and fracture law, the dynamic evolution process of goaf area is found out, and then the gas enrichment and migration law in coal seam mining process is revealed.

[0111] The above disclosure is only a preferred specific embodiment of the present invention, but the embodiments of the present invention are not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A simulation test method for overburden deformation and gas migration during inclined coal seam mining, characterized in that: The following steps are involved: Using similar materials, the coal layer (1) and the rock layer (2) are laid in sequence to obtain a simulated mine environment; Gas injection and stress loading under dynamic and static loads are performed on the simulated mine environment to obtain the simulated ground stress environment under the coupling of dynamic and static loads; Dynamic excavation is carried out in a simulated ground stress environment. During the excavation process, the detection data of rock stress, deformation, angle and gas pressure of multiple measuring points in different layers are obtained in real time. The detection data of rock stress, deformation, angle and gas pressure of multiple measuring points in different layers are matched one by one with the two-dimensional position coordinates of the measuring points, and converted into three-dimensional space for marking. Different colors are used to represent rock stress, deformation, angle and gas pressure, respectively, to form real-time cloud maps of rock stress, deformation, angle and gas pressure based on three-dimensional space. According to the real-time cloud maps of rock stress, deformation, angle and gas pressure, the deformation of overburden and the migration law of coal seam gas under the dynamic and static load coupling stress environment are determined.

2. The method for simulating overburden deformation and gas migration during inclined coal seam mining according to claim 1, characterized in that: During the laying process of the coal seam (1), a gas injection pipe (11) is pre-buried, and the gas injection pipe (11) pre-buried in the coal seam (1) is connected to an external gas source (12).

3. The method for simulating overburden deformation and gas migration during inclined coal seam mining according to claim 2 is characterized in that: The simulated mine environment is subjected to gas injection and stress loading under dynamic and static loads to obtain a simulated ground stress environment under the coupling of dynamic and static loads, including the following steps: According to the real three-dimensional ground stress of the designated simulated mine area and the predetermined similarity ratio, the three-dimensional stress and gas pressure values ​​required for the experiment are determined; According to the three-dimensional stress and gas pressure values ​​required for the experiment, three-dimensional stress loading is first performed until the three-dimensional loading pressure reaches a predetermined value; Injecting a gas substitute of a target pressure value through the gas injection pipe (11); After the gas pressure inside the sample is stable, the rock deformation detection component, rock stress detection component, rock inclination detection component and gas pressure detection component are turned on to collect data corresponding to each layer, which will be used as the initial data of all measurement and control systems before mining disturbance; Dynamic load stress loading is performed on a two-dimensional plane, and the dynamic load is a cyclic load.

4. The method for simulating overburden deformation and gas migration during inclined coal seam mining according to claim 3 is characterized in that: The methane gas substitute is CO2 gas, nitrogen gas or helium gas.

5. The method for simulating overburden deformation and gas migration during inclined coal seam mining according to claim 1, characterized in that: During the laying process of the coal seam (1) and the rock seam (2), the measurement and control system is laid out simultaneously. The measurement and control system comprises a rock seam deformation detection component, a rock seam stress detection component, a rock seam inclination detection component and a gas pressure detection component. The rock seam deformation detection component is used for deformation detection in three directions on the rock seam (2), the rock seam stress detection component is used for rock seam stress field detection, the rock seam inclination detection component is used for rock seam (2) inclination detection, and the gas pressure detection component is used for detection of gas pressure in the rock seam (2) and the coal seam (1) during the mining process of the coal seam (1).

6. The method for simulating overburden deformation and gas migration during inclined coal seam mining according to claim 5, characterized in that: The arrangement method of the rock formation deformation detection assembly comprises the following steps: A first sensing optical fiber group, a second sensing optical fiber group and a third sensing optical fiber group are arranged in layers in the coal seam (1) and the rock layer (2), wherein the first sensing optical fiber group includes a plurality of axial sensing optical fibers (3), and the plurality of axial sensing optical fibers (3) are arranged at intervals along the axial direction; the second sensing optical fiber group includes a plurality of dip sensing optical fibers (4), and the plurality of dip sensing optical fibers (4) are arranged at intervals along the dip direction; the third sensing optical fiber group includes a plurality of normal sensing optical fibers (5), and the plurality of normal sensing optical fibers (5) are arranged at intervals along the normal direction; the axial sensing optical fibers (3), the normal sensing optical fibers (5) and the dip sensing optical fibers (4) are 90 degrees apart from each other; the axial sensing optical fibers (3), the normal sensing optical fibers (5) and the dip sensing optical fibers (4) are connected via a connecting optical fiber (6) to form an optical fiber network; the optical fiber input end of the optical fiber network is connected to a broadband light source; and the optical fiber output end is connected to an optical fiber Bragg grating demodulator and an optical fiber stress analyzer in sequence.

7. The method for simulating overburden deformation and gas migration during inclined coal seam mining according to claim 5, characterized in that: The arrangement method of the rock formation stress detection assembly comprises the following steps: A multi-layer detection surface is provided along the vertical depth of the coal seam (1), a plurality of measurement points are arranged on the detection surface, the plurality of measurement points are distributed in a rectangular array, a pressure sensor (7) is arranged at each measurement point, and a plurality of pressure sensors (7) are respectively buried in the surrounding coal pillars (8) at the same depth as the detection surface, the pressure sensors (7) are connected to the signals of an external signal acquisition instrument, and the signal acquisition instrument is connected to a computer system.

8. The method for simulating overburden deformation and gas migration during inclined coal seam mining according to claim 5, characterized in that: The arrangement method of the rock formation dip detection assembly comprises the following steps: Based on the distribution of collapse zones, fracture zones and bending deformation zones in numerical simulation, dynamic inclination sensors (9) are arranged in the collapse zones, fracture zones and bending deformation zones respectively. A survey line is arranged in each layer along the axial direction and the dip direction respectively. Multiple dynamic inclination sensors (9) are arranged in each survey line. One dynamic inclination sensor (9) is arranged at the intersection of two survey lines. The spacing between adjacent dynamic inclination sensors (9) is 45 cm to 55 cm. The dynamic inclination sensors (9) are connected to the signal acquisition instrument.

9. The method for simulating overburden deformation and gas migration during inclined coal seam mining according to claim 5, characterized in that: The arrangement method of the gas pressure detection assembly comprises the following steps: A multi-layer detection surface is provided along the vertical depth direction of the coal seam (1) and the rock layer (2), a plurality of measurement points are arranged on the detection surface, the plurality of measurement points are distributed in a rectangular array, a gas-specific pressure sensor (10) is arranged at each measurement point, and the gas-specific pressure sensor (10) is connected to the signal acquisition instrument.

10. The method for simulating overburden deformation and gas migration during inclined coal seam mining according to any one of claims 4 or 5, characterized in that: Dynamic excavation for a simulated geostress environment includes the following steps: Step 1: Place the excavation tool into the cutting hole (13), place the cutter head at one end of the excavation tool, adjust the cutting surface of the excavation tool to be parallel to the cut surface, and connect the power supply and gas circuit of the excavation tool console; Step 2: Tighten the jacking cylinder and push the push cylinder to make the excavation tool close to the cutting surface; Step 3: The push cylinder and the tightening cylinder are reset, and the excavation motor and the feed motor rotate forward; Step 4: The cutter head moves to the other end of the excavation tool, the excavation motor rotates forward, the feed motor rotates reversely, and the cutter head returns to its original position; Step 5: Repeat steps 2 to 4, and the excavation machine excavates back and forth multiple times according to the predetermined single advance to complete the excavation of the coal seam (1).

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