Experimental method for simulation of overburden deformation and gas migration during mining of inclined coal seams

Abstract

This invention belongs to the field of stress measurement and analysis technology, and relates to a simulation test method for overburden deformation and gas migration during inclined coal seam mining. The method includes the following steps: simulating a mine environment by sequentially laying coal seams and rock strata using similar materials; simulating a geostress environment by injecting gas and applying stress under dynamic and static loads; and dynamically excavating the simulated geostress environment, acquiring real-time data on rock strata stress, deformation, angle, and gas pressure during excavation, and obtaining the overburden deformation and coal seam gas migration patterns under dynamic and static load coupled stress conditions based on the data. This invention utilizes gas injection and dynamic-static composite loading to simulate the coal seam gas seepage process under dynamic and static load coupling, enabling the study of mining-induced gas migration patterns. This overcomes the current deficiency in numerical simulation-based studies of mining-induced gas migration patterns, which lacks measured gas pressure data at characteristic coal seam points, thus improving the accuracy of the experimental results.

Description

Technical Field

[0001] This invention belongs to the field of stress measurement and analysis technology, specifically relating to a simulation test method for overburden deformation and gas migration during inclined coal seam mining. Background Technology

[0002] To study the distribution of rock pressure, surrounding rock deformation, overlying rock pressure distribution, and the movement and fracture patterns of rock strata in underground space excavation activities such as underground mining, tunnel excavation, and underground civil defense projects, similarity simulation experiments are commonly used for indoor testing. This experimental method, based on similarity theory and factor analysis, can effectively address research on pressure distribution, overlying rock deformation, and fracture in underground space engineering. The similarity simulation method allows for more in-depth and detailed research on engineering site problems within the laboratory, and is now widely used in engineering research fields such as water conservancy and hydropower, underground mining, and road and bridge slope protection. However, many existing simulation devices, especially those focusing on mine pressure, overlying rock displacement, rock strata fracture, and stress distribution, primarily concentrate on similarity simulation experiments using planar models. This differs significantly from the actual situation of rock masses under triaxial stress in engineering sites.

[0003] In underground mining engineering, as the mining face advances, the surrounding rock deforms and fractures, and the peak stress zone shifts forward until a new stress equilibrium is reached. Throughout this process, the fracture and stress distribution of the overlying rock strata are dynamically changing. With the rapid development of modern technology, human beings are increasingly developing and utilizing underground space. Therefore, it is necessary to utilize large-scale three-dimensional similarity simulation test systems to conduct experimental research on underground chamber excavation, tunnel excavation, and tunneling under triaxial stress.

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

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

[0006] 2. Three-dimensional fluid-structure interaction similarity simulation test bench - Taiyuan University of Technology GLOH-1200

[0007] The three-dimensional fluid-structure interaction similarity simulation test bench developed by Taiyuan University of Technology under the 211 Project has simulation dimensions of 3000×2000×2000mm and a maximum axial loading force of 900t. When conducting similarity simulation tests at a geometric scale of 1:30, it can simulate a maximum mining depth of 1200m. The lateral stress-free application device applies lateral constraints by relying on the horizontal constraint reaction force generated by the axial load. Two of the four lateral surfaces are equipped with transparent plexiglass, which can be used to detect rock surface displacement. In addition, the device can also conduct fluid-structure interaction simulation tests to reveal the deformation and permeability laws of rock masses in underground mining engineering under fluid-structure interaction.

[0008] 3 True 3D Similarity Model Experimental System – Shandong University

[0009] The true three-dimensional similarity model test system developed by Shandong University has a maximum simulation size of 1000×1000×1000mm. It mainly consists of a high-pressure loading system, an intelligent hydraulic control system, and a reaction device system. The high-pressure loading system primarily includes jacks and loading plates, mainly used for applying stress to the model and simulating the geostress field of engineering rock masses at a certain burial depth. The intelligent hydraulic control system mainly consists of a test bench, motor, oil tank, control valves, and intelligent sensors, mainly used for independent reaction forces, loading, and pressure stabilization in the front-back, left-right, and up-down directions of the test model. The reaction device system mainly includes a reaction frame, flange, and reaction transmission plate, mainly used for applying reaction forces to the model.

[0010] Existing large-scale three-dimensional similarity simulation test systems typically employ the following steps: before the experiment, a simulated specimen is prepared using a test chamber. After the simulated specimen is laid with similar materials according to predetermined requirements, a hydraulic device is used to apply unidirectional independent static pressure so that the similar materials can meet the requirements of simulating the geostress field of an engineering rock mass at a certain burial depth. Then, excavation and loading are carried out on the simulated specimen.

[0011] However, due to the special environment of underground space engineering, which is mostly a gas-solid coupling environment, the current simulation samples can simulate the basic configuration of underground space engineering to a certain extent. However, because they do not take into account the presence of gas and the influence of gas on the deformation of the engineering rock mass during excavation, they ignore the influence of gas-solid coupling on the dynamic deformation process of the engineering rock mass structure, resulting in biased test results and failing to reveal the true gas migration law. 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. It increases the measured data of coal seam characteristic points, enabling the simulation of coal seam gas seepage under dynamic and static load coupling. Through gas injection and dynamic-static coupling loading, and by using a pre-deployed array-type measurement and control system in the coal and rock strata to test relevant parameters, it can realize the dynamic evolution analysis of the three-dimensional spatial distribution of gas pressure during coal seam mining under dynamic-static load coupling. Based on this, the study of overburden deformation and coal seam gas migration laws under dynamic-static load coupling stress environment during mining can be conducted, solving the technical problems in the prior art mentioned above.

[0013] The technical solution of this invention is:

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

[0015] By sequentially laying coal seams and rock strata using similar materials, a simulated mine environment can be obtained.

[0016] Gas injection and stress loading under dynamic and static loads were performed on a simulated mine environment to obtain a simulated geostress environment under the coupled action of dynamic and static loads.

[0017] Dynamic excavation was conducted under simulated geostress environment. During the excavation process, real-time data on rock stress, deformation, angle, and gas pressure were acquired from multiple measuring points at different strata. The acquired data were mapped one-to-one with the two-dimensional coordinates of the measuring points and then converted into three-dimensional space for marking. Different colors were used to represent rock stress, deformation, angle, and gas pressure, forming real-time cloud maps of rock stress, deformation, angle, and gas pressure based on three-dimensional space. Based on these real-time cloud maps, the deformation of overburden and the migration patterns of coal seam gas under dynamic and static load coupled stress environment were determined.

[0018] Preferably, during the coal seam laying process, gas injection pipes are pre-embedded and connected to an external gas source.

[0019] Preferably, the simulated in-situ stress environment under dynamic and static loads by gas injection and stress loading in a simulated mine environment includes the following steps:

[0020] Based on the actual three-dimensional geostress in the specified simulated mine area and the predetermined similarity ratio, determine the triaxial stress and gas pressure values ​​required for the experiment.

[0021] Based on the required triaxial stress and gas pressure values ​​for the experiment, triaxial stress loading is first performed until the triaxial loading pressure reaches the predetermined value.

[0022] A gas substitute at the target pressure value is injected through an injection tube;

[0023] After the internal gas pressure of the sample stabilizes, the rock stratum deformation detection component, rock stratum stress detection component, rock stratum dip angle detection component and gas pressure detection component are activated to collect data corresponding to each layer, which are used as the initial data of all measurement and control systems before mining disturbance.

[0024] Dynamic load stress is applied on a two-dimensional plane, and the dynamic load is a periodic load.

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

[0026] Preferably, a monitoring and control system is deployed simultaneously during the laying of the coal seam and rock strata. The monitoring and control system includes a rock strata deformation detection component, a rock strata stress detection component, a rock strata dip angle detection component, and a gas pressure detection component. The rock strata deformation detection component is used to detect deformation in three directions on the rock strata. The rock strata stress detection component is used to detect the stress field of the rock strata. The rock strata dip angle detection component is used to detect the dip angle of the rock strata. The gas pressure detection component is used to detect the gas pressure in the rock strata and within the coal seam during coal mining.

[0027] Preferably, the arrangement method of the rock deformation detection component includes the following steps:

[0028] In the coal seam and rock strata, a first sensing fiber group, a second sensing fiber group, and a third sensing fiber group are sequentially deployed layer by layer. The first sensing fiber group includes multiple axial sensing fibers, which are arranged at intervals along the axial direction. The second sensing fiber group includes multiple directional sensing fibers, which are arranged at intervals along the directional direction. The third sensing fiber group includes multiple normal sensing fibers, which are arranged at intervals along the normal direction. The axial sensing fibers, normal sensing fibers, and directional sensing fibers are phase-differentiated. The axial sensing fibers, normal sensing fibers, and directional sensing fibers are connected by connecting fibers to form a fiber optic network. The fiber input end of the fiber optic network is connected to a broadband light source, and the fiber output end is sequentially connected to a fiber optic grating demodulator and a fiber optic stress analyzer.

[0029] Preferably, the method for arranging the rock stress detection component includes the following steps:

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

[0031] Preferably, the arrangement method of the rock stratum dip angle detection component includes the following steps:

[0032] Based on the distribution of caving zones, fissure zones, and bending deformation zones in numerical simulations, dynamic tilt sensors are deployed in each of these zones. A survey line is designed to be arranged along both the axial and dip directions for each layer, with multiple dynamic tilt sensors deployed along each survey line. One dynamic tilt sensor is placed at the intersection of two survey lines, and the spacing between adjacent dynamic tilt sensors is 45cm to 55cm. The dynamic tilt sensors are connected to the signal acquisition instrument.

[0033] Preferably, the method for arranging the gas pressure detection component includes the following steps:

[0034] Multiple detection surfaces are set along the vertical depth direction of the coal seam and rock strata. Multiple measuring points are arranged on the detection surfaces 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 acquisition instrument.

[0035] Preferably, dynamic excavation under simulated geostress environment includes the following steps:

[0036] Step 1: Insert the excavator into the cutting hole, place the cutter head at one end of the excavator, adjust the cutting surface of the excavator to be parallel to the surface being cut, and connect the power and air supply to the control console of the excavator.

[0037] Step 2: Tighten the jacking cylinder and advance the propulsion cylinder to make the excavator tool fit tightly against the surface to be cut;

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

[0039] Step 4: When the cutter head moves to the other end of the excavator, the excavation motor rotates forward, the feed motor rotates in reverse, and the cutter head returns to its original position;

[0040] Step 5: Repeat steps 2 to 4, with the excavating equipment digging repeatedly according to the predetermined single advance, to complete the excavation of the coal seam.

[0041] Compared with existing technologies, the simulation test method for overburden deformation and gas migration during inclined coal seam mining provided by this invention utilizes gas injection and dynamic-static composite loading to construct a simulation environment. This method simulates inclined coal seam excavation under a coupled geostress environment of horizontal biaxial dynamic load and triaxial static load. It can realistically simulate overburden deformation and fracture behavior during coal seam excavation under complex underground stress conditions, and simulate the coal seam gas seepage process under coupled dynamic and static loads. Furthermore, it uses a pre-deployed array-type monitoring and control system in the coal and rock strata to test relevant parameters, enabling dynamic evolution analysis of the three-dimensional spatial distribution of gas pressure during coal seam mining under coupled dynamic and static loads. Based on this, the study of overburden deformation and coal seam gas migration laws under coupled dynamic and static load stress during mining can be conducted. This method overcomes the lack of measured gas pressure data at characteristic points in the coal seam in current numerical simulation-based studies of mining gas migration laws. Moreover, by considering the influence of gas-solid coupling on the dynamic deformation process of the structure, the accuracy of the test results is improved. It is highly practical and worthy of promotion. Attached Figure Description

[0042] Figure 1 This is a flowchart of the present invention.

[0043] Figure 2 This is a partial structure of the present invention. Figure 1 .

[0044] Figure 3 This is a partial structure of the present invention. Figure 2 .

[0045] Figure 4 This is a partial structure of the present invention. Figure 3 .

[0046] Figure 5 This is a partial structure of the present invention. Figure 4 .

[0047] Figure 6 This is a partial structure of the present invention. Figure 5 .

[0048] Figure 7 This is a partial structure of the present invention. Figure 6 .

[0049] Figure 8 This is a partial structure of the present invention. Figure 7 .

[0050] Figure 9 This is a partial structure of the present invention. Figure 8 .

[0051] Figure 10 This is a partial structure of the present invention. Figure 9 .

[0052] Figure 11 This is a partial structure of the present invention. Figure 10 .

[0053] Figure 12 This is a partial structure of the present invention. Figure 11 .

[0054] Figure 13 This is a diagram of the dynamic-static coupling stress loading path in the test method of the present invention. Detailed Implementation

[0055] This invention provides a simulation test method for overburden deformation and gas migration during inclined coal seam mining. The following is a combination of... Figure 1 Flowchart, Figures 2 to 12 Structural diagram and Figure 13 The dynamic-static coupling stress loading path diagram is used to illustrate the present invention.

[0056] Example 1

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

[0058] (1) Coal seam 1 and rock layer 2 were laid in sequence using similar materials to obtain a simulated mine environment.

[0059] (2) Gas injection and stress loading under dynamic and static loads were performed on the simulated mine environment to obtain the simulated geostress environment under the coupled action of dynamic and static loads.

[0060] (3) Dynamic excavation is carried out in the simulated geostress environment. During the excavation process, the rock stress, deformation, angle and gas pressure of multiple measuring points at different layers are acquired in real time. The acquired rock stress, deformation, angle and gas pressure of multiple measuring points at 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, forming real-time cloud maps of rock stress, deformation, angle and gas pressure based on three-dimensional space. Based on 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 dynamic and static load coupled stress environment are obtained.

[0061] The above-mentioned test method uses similar materials to make simulated specimens. The simulated specimens are made using the above method. In summary, the coal seam 1 and rock stratum 2 are laid in sequence to construct a simulated mine environment. Then, gas is injected and stress is applied under dynamic and static loads to the simulated mine environment to obtain a simulated geostress environment under the coupled action of dynamic and static loads. Finally, dynamic excavation is carried out on the simulated geostress environment.

[0062] It should be noted that during the laying of coal seam 1, the monitoring and control system is deployed and the gas injection pipe 11 is pre-embedded. The gas injection pipe 11 pre-embedded in coal seam 1 is connected to the external gas source 12. The basic equipment for gas injection is built in advance. During the dynamic process of excavation, the monitoring and control system is used to obtain the detection data of rock stress, deformation, angle and gas pressure in real time. Based on the detection data, the deformation of overburden and the movement of coal seam gas under dynamic and static load coupled stress are obtained.

[0063] Specifically, the aforementioned measurement and control system includes a rock stratum deformation detection component, a rock stratum stress detection component, a rock stratum dip angle detection component, and a gas pressure detection component.

[0064] In this experiment, the simulated specimen prepared according to the size of the specimen box of the simulation test system was a large cubic specimen. The length × width × height of the large cubic specimen was 3m × 3m × 3m. The rock stratum deformation detection component, rock stratum stress detection component, rock stratum dip angle detection component and gas pressure detection component were all embedded in the large three-dimensional simulated specimen with this size.

[0065] Among them, the rock stratum deformation detection component is used to detect deformation in three directions on rock stratum 2. The instruments used in the actual test are NBX-6055 distributed fiber optic stress analyzer and SM225 fiber optic demodulator. Specifically, the sensing fiber of the NBX-6055 distributed fiber optic stress analyzer is divided into three groups, which are respectively called the first sensing fiber group, the second sensing fiber group and the third sensing fiber group. Before use, they are classified and marked, and then deployed layer by layer.

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

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

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

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

[0070] In practical use, after the fiber optic network is laid, a broadband light source is connected to one end of the fiber and a high-power laser pulse is input. At the same time, the other end of the fiber is connected to an SM225 fiber optic grating demodulator and an NBX-6055 distributed fiber optic stress analyzer. The NBX-6055 distributed fiber optic stress analyzer uses wavelength demodulation mode to analyze the changes in light wavelength at different times and saves the data at equal intervals, thereby inverting the strain at different locations.

[0071] The rock strata stress detection component is used for detecting the rock strata stress field. In the actual test, pressure sensor 7 was used to measure the stress during the mining process of coal seam 1. The pressure sensor 7 is preferably an SCYG315 pressure sensor, with a testing range of 0MPa to 3MPa and a measurement accuracy of ±0.5%. Before the test, based on the distribution of the caving zone, fracture zone, and bending deformation zone in the numerical simulation, pressure sensors 7 were arranged in four layers along the vertical depth direction of rock strata 2 and coal seam 1. The arrangement positions were the lower middle part of the caving zone, the boundary between the caving zone and the fracture zone, the middle of the fracture zone, and the middle of the bending deformation zone. Five measuring lines were arranged along the dip direction of each layer of pressure sensors 7, with a spacing of 50cm between each measuring line. Five pressure sensors 7 were arranged along the axial direction of each measuring line, with a spacing of 50cm between each pressure sensor 7. A total of 100 pressure sensors are required. Furthermore, numerical calculations show that significant pressure-increasing zones exist on both sides of coal seam 1 during mining. Therefore, to detect the stress variation patterns in these pressure-increasing zones during mining, it is proposed to embed 5 pressure sensors 7 in the surrounding coal pillars 8 at the same depth as coal seam 1. As mentioned above, a total of 120 pressure sensors 7 are needed, as shown in the layout diagram. Figure 5 As shown, the layout diagram of the bottom layer of coal seam 1 is as follows: Figure 6 As shown, pressure sensors 7 are not installed on the coal seam floor 16, but are only embedded in the surrounding coal pillars 8.

[0072] The rock strata dip angle detection component is used for dip angle detection of rock stratum 2. In the actual experiment, dynamic dip angle sensors 9 are used for detection. The preferred dynamic dip angle sensor 9 is the MDTQJ60-485-A1 / C type dynamic dip angle sensor, which has an accuracy of 0.1° and a measurement range of -90° to +90°. Before the experiment, based on the distribution of caving zones, fracture zones, and bending deformation zones in the numerical simulation, dynamic dip angle sensors 9 are arranged in the caving zones, fracture zones, and bending deformation zones respectively. A measuring line is designed to be arranged along both the axial and dip directions for each stratum, with 5 dynamic dip angle sensors 9 arranged on each measuring line. One dynamic dip angle sensor 9 is arranged at the intersection of two measuring lines. The spacing between adjacent dynamic dip angle sensors 9 is 45cm to 55cm, preferably 50cm. A total of 9 dynamic dip angle sensors 9 are used for each stratum, and a total of 27 dynamic dip angle sensors 9 are used in the experiment. The arrangement diagram is shown below. Figure 7 and Figure 8 .

[0073] The gas pressure detection component is implemented using a dedicated gas pressure sensor 10, preferably an OSP1.5 gas pressure sensor, which is used to detect the gas pressure in the overlying rock and within the coal seam 1 during the mining process. Multiple detection surfaces are set along the vertical depth direction of the coal seam 1 and the rock strata 2, and multiple measuring points are arranged on the detection surfaces. The multiple measuring points are distributed in a rectangular array, and a dedicated gas pressure sensor 10 is arranged on each measuring point.

[0074] Specifically, the gas-specific pressure sensors 10 are arranged within the plane of coal seam 1, designed with four measuring lines, each line spaced 60cm apart. The spacing between adjacent sensors along the same measuring line is also 60cm. Three planes parallel to coal seam 1 are selected at equal intervals in the overlying strata 2, and the gas-specific pressure sensors 10 are arranged on each plane. 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 within coal seam 1. The arrangement of the gas-specific pressure sensors 10 on each plane is as follows: Figure 9 and Figure 10 .

[0075] The pressure sensor 7, the gas-specific pressure sensor 10, the signal acquisition instrument, and the computer system described above constitute the dot matrix measurement and control system used in this experiment. Both the pressure sensor 7 and the gas-specific pressure sensor 10 are electrically connected to the signal acquisition instrument, which is also electrically connected to the computer system. The computer system contains acquisition and testing software. During the test, the computer system is first turned on and the acquisition and testing software is started. Then, it is checked whether the pressure sensor 7 and the gas-specific pressure sensor 10 are successfully connected to the computer system. Ensuring that there is jumping data on each channel interface of the software indicates that the pressure sensor 7 and the gas-specific pressure sensor 10 are well connected to the signal acquisition instrument. During the data acquisition process, the software automatically saves the detection data of all channels, and acquires the detection data of rock stress, deformation, angle and gas pressure of multiple measuring points at different layers in real time. The obtained detection data of rock stress, deformation, angle and gas pressure of multiple measuring points at different layers are matched one-to-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, forming real-time cloud maps of rock stress, deformation, angle and gas pressure based on three-dimensional space. Based on 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 dynamic and static load coupled stress environment are obtained.

[0076] Work process:

[0077] (1) Preparation of similar materials

[0078] Taking the coal seam 1 mining face of a designated mine as the simulation object, firstly, coal and rock samples from the roof and floor rock strata 2 and coal seam 1 of the working face are collected for indoor mechanical parameter testing to obtain the basic mechanical parameters of coal and rock in the simulation area. Then, according to the appropriate geometric similarity ratio and strength similarity ratio, the strength of the similar simulation material required for each rock strata 2 and coal seam 1 is calculated. Finally, based on the strength, the appropriate ratio of river sand, gypsum and cement is selected, and the similar material is prepared for each rock strata 2 using the selected ratio.

[0079] (2) Calculation of material usage

[0080] First, the volume of each rock layer 2 model is calculated. Then, the total weight of the corresponding rock layer 2 is calculated based on its unit weight. According to the geometric similarity ratio of 1:40, the unit weight similarity ratio of 1:1.6, the stress similarity ratio of 1:64, and the time similarity ratio of 1:6.3, the mechanical property parameters such as the unit weight and compressive strength of the model rocks are calculated. Then, according to the above similarity ratios, the mass of river sand, gypsum, and cement required in the simulation materials of all rock layers 2 and coal seams 1 are calculated in turn, and the batching tables of each rock layer 2 and coal seam 1 are made. Finally, the total amount of materials required for the model test is calculated. The detailed calculation process of this part can be found in "Similarity Simulation Experiment of Mine Pressure".

[0081] (3) Laying of rock layer 2

[0082] First, tilt the specimen box at an angle consistent with the dip angle of the simulated actual coal seam 1. Then, prepare similar materials for each rock layer 2 in order from bottom to top. According to the batching table of the required mass of river sand, gypsum, and cement for each rock layer 2 calculated in step 2, put the required mass of river sand, gypsum, and cement for the corresponding rock layer 2 into the mixer, add an appropriate amount of water, mix evenly, and then lay them layer by layer in the order of rock layers 2. Finally, arrange the sensors according to the sensor arrangement diagram in each test method in the "Test Method" until all simulated strata are laid.

[0083] (4) Laying of coal seam 1

[0084] Specific requirements: Since not only sensors need to be installed in coal seam 1, but also conditions must be met for the excavation equipment to move smoothly, the laying of coal seam 1 is a crucial step in this method. The thickness of coal seam 1 is designed to be 10cm to meet the minimum height required for the excavation equipment to move. Considering that sufficient space needs to be reserved for the excavation equipment before excavation of coal seam 1, a cut-in 13 is made at the foremost point along the axial direction of coal seam 1. The cut-in 13 is arranged along the dip of coal seam 1. Based on the size of the excavation equipment, the width of the cut-in 13 is designed to be 45cm and the length to be 285cm. At the same time, two return air roadways 15 are arranged along the axial direction of coal seam 1. The reserved return air roadways 15 can provide good space for the movement of the excavation equipment and avoid the excavation progress being affected by the excavation equipment being stuck at both ends by the coal wall. The length of each return air roadway 15 is 190cm and the width is 40cm.

[0085] Specific process:

[0086] To achieve the arrangement of the aforementioned cut-in 13 and return airway 15 in coal seam 1, after the laying of the coal seam floor 16 and rock strata 2, firstly, before laying coal seam 1, according to the dimensions of the cut-in 13 and return airway 15, prefabricate the outer contour molds of the cut-in 13 and return airway 15 using wooden boards 14, and place them in designated positions to prevent blockage of the cut-in 13 and return airway during the laying of coal seam 1. Then, prepare similar materials for coal seam 1 by pre-calculating the proportions of river sand, gypsum, and cement. These similar materials are then sequentially loaded into all areas of the box except for the template contour molds. Sensors and air injection pipes 11 are then installed according to design requirements. After all the similar materials are loaded into the box and reach a design height of 10cm, the laying is stopped. After air drying for one week, the prefabricated outer contour molds of the cut-in 13 and return airway 15 using wooden boards 14 are removed. The space revealed after removal is the cut-in 13 and return airway 15, thus completing the laying of coal seam 1. A detailed plan view of the completed coal seam 1 is shown below. Figure 11 .

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

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

[0089] In this experiment, three gas injection pipes 11 were arranged at equal intervals on the side of coal seam 1. The length of each gas injection pipe 11 extending into coal seam 1 was 50cm. The spacing between each gas injection pipe 11 was 50cm. The outer side of each gas injection pipe 11 was 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 coal seam 1 can be actively regulated and controlled by the gas pressure valve at the gas injection port. The arrangement of the gas injection pipe 11 inside the sample is as follows: Figure 12 .

[0091] (6) Stress loading and gas injection of the specimen

[0092] After all rock strata 2 and coal seam 1 were laid and the similar materials dried, the specimen box was returned to a horizontal position. This simulation experiment used a mining face in a mine in Pingdingshan as the simulation object. Based on the actual three-dimensional geostress in the specified simulated mine area and a predetermined similarity ratio, the triaxial stress σ required for this simulation experiment was calculated. x σ y σ z The pressures were 0.5 MPa, 0.78 MPa, and 0.61 MPa, respectively. Based on the predetermined stress and gas pressure values, the three-dimensional orientation of the sample was first set: the vertical direction was defined as the Z-axis, the horizontal direction as the X-axis, and the axial direction as the Y-axis. Then, all oil pumps were turned on, and the X-axis horizontal loading pressure, Y-axis horizontal loading pressure, and Z-axis vertical loading pressure were applied sequentially using force control until the three-dimensional loading pressure reached the predetermined value and the three-dimensional stress loading rate remained constant. Finally, the gas injection port valve outside the chamber was opened to start injecting a gas substitute into the sample. The target pressure value of the gas injection port valve was set between 0.2 MPa and 0.5 MPa. After the gas pressure inside the sample stabilized, all sensor acquisition systems were turned on to record the data from all pressure sensors 7 and the gas-specific pressure sensor 10 at each layer. This data was used as the initial data of all sensors before the mining disturbance.

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

[0094] (7) Coal seam excavation under dynamic and static load coupled stress environment

[0095] By coupling the static load heads in three different directions (Z-axis, X-axis, and Y-axis) of the specimen box with the dynamic load heads in the X and Y directions, a simulated geostress environment under dynamic-static load coupling is constructed.

[0096] The steps for applying coupled stress under dynamic and static loads are as follows:

[0097] First, activate the hydraulic control system of the Z-direction static load head, apply the Z-direction load (vertical load) pressure between 0.5 MPa and 0.8 MPa, and maintain stability. Then, simultaneously activate the hydraulic control systems of the X and Y directions, except for the bottom row of dynamic load heads. Set the target values ​​for the X-direction load to 0.5 MPa to 0.8 MPa and the Y-direction load to 0.5 MPa to 0.8 MPa, and maintain stability. This completes the initial static load stress loading.

[0098] After the stresses in the X, Y, and Z directions have stabilized, dynamic load stress is applied in the two-dimensional plane, i.e., in the X and Y directions:

[0099] The hydraulic control system of the bottom row of dynamic load heads in both the X and Y directions is activated simultaneously. Horizontal dynamic loads are applied via hydraulic servo valves. The lower limit stress value of the dynamic load is set to 0.5 MPa, and the upper limit is set to 1.0 MPa. The load is periodic, with a vibration frequency of 5 Hz. The dynamic-static coupled stress loading path is as follows: Figure 13 .

[0100] In this experiment, the pressure of the Z-direction load (vertical load) was 0.61 MPa, the target value of the X-direction load was set to 0.5 MPa, and the target value of the Y-direction load was set to 0.78 MPa.

[0101] After the stress environment field of the above-mentioned dynamic and static load coupling is completed, the excavation equipment is put into the cut hole 13 to simulate the mining of 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 excavator with a gantry crane, and send it into the cut hole 13 through the reversing device. Place the cutter head at one end of the excavator, adjust the cutting surface of the excavator to be parallel to the surface to be cut, and connect the power supply and air circuit of the excavator control console.

[0103] Step 2: Tighten the jacking cylinder and advance the propulsion cylinder to make the excavator fit tightly against the surface to be cut.

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

[0105] Step 4: When the cutter head moves to the other end of the excavator, the limit indicator light will illuminate, the excavation motor will rotate forward, the feed motor will rotate in reverse, and the cutter head will return to its original position.

[0106] Step 5: Repeat steps 2 to 4, with the excavator advancing 10mm per step. Through repeated excavation, the entire excavation of simulated coal seam 1 is finally completed.

[0107] During the excavation process, the cutting speed was simulated based on the advance speed of the on-site tunneling face, and the stress of different rock strata 2 surfaces during the excavation process was collected through the data acquisition system.

[0108] (8) Data acquisition and analysis during the excavation process

[0109] During excavation, the monitoring and control system continuously monitors parameters such as rock strata stress, deformation, angle, and gas pressure. Data from pressure sensors 7 at each stratum is transmitted in real-time to the acquisition computer. Data visualization software displays the evolution of the stress field in the upper rock strata of coal seam 1 during the mining process. Pre-embedded axial sensing fiber 3, dip sensing fiber 4, and normal sensing fiber 5 are sequentially connected to the computer system to collect distributed sensing fiber test data during the coal seam 1 mining process. This acquires the three-dimensional spatial deformation evolution of rock strata 2 within each area traversed by the sensing fiber optic cables. Dynamic tilt sensors 9 at each stratum collect the dip angle data of rock strata 2 and transmit it in real-time. The data is collected and recorded by a designated computer system. Based on this, the evolution of the dip angle of the overlying stratum 2 during the mining process of coal seam 1 is analyzed. The mining-induced fractures in coal seam 1 form gas seepage channels, affecting the migration of gas in coal seam 1 and the overlying stratum. By acquiring gas pressure data at various measuring points in different layers through gas sensors inside the simulated sample and transmitting them to the computer system, the real-time data of all measuring points are visualized in real time on the computer system. This allows for the real-time observation of the evolution of gas pressure inside the overlying stratum during the mining process, thereby simulating the gas migration law of coal seam under the influence of mining.

[0110] Specifically, the real-time visualization of all measuring points in the computer system involves mapping the measured data of rock stress, deformation, angle, and gas pressure from multiple measuring points at different strata to the two-dimensional coordinates of the measuring points, and then converting them into three-dimensional space for marking. Different colors are used to represent rock stress, deformation, angle, and gas pressure, forming real-time cloud maps of rock stress, deformation, angle, and gas pressure based on three-dimensional space. In actual operation, the above visualization steps can be completed using Origin software to obtain the dynamic evolution characteristics of overburden bearing under pressure (increased pressure), overburden delamination and fracture (decreased pressure), and minor overburden disturbances (slight pressure fluctuations), the evolution law of overburden deformation during coal seam mining, and the gas enrichment situation in different areas of coal seams and overburden at different strata after each mining operation. Finally, by combining the above-mentioned overburden deformation and fracture laws, the dynamic evolution process of the goaf can be identified, thereby revealing the gas enrichment and migration laws during coal seam mining.

[0111] The above-disclosed embodiments are merely preferred embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for simulating overburden deformation and gas migration during inclined coal seam mining, characterized in that, Includes the following steps: By using similar materials to lay coal seam (1) and rock strata (2) in sequence, a simulated mine environment is obtained; Gas injection and stress loading under dynamic and static loads were performed on a simulated mine environment to obtain a simulated geostress environment under the coupled action of dynamic and static loads. Dynamic excavation was carried out under simulated geostress environment. During the excavation process, real-time detection data of rock stress, deformation, angle, and gas pressure at multiple measuring points at different strata were acquired. The obtained detection data of rock stress, deformation, angle, and gas pressure at multiple measuring points at different strata were mapped one-to-one with the two-dimensional position coordinates of the measuring points and converted into three-dimensional space for marking. Different colors were used to represent rock stress, deformation, angle, and gas pressure, forming real-time cloud maps of rock stress, deformation, angle, and gas pressure based on three-dimensional space. Based on 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 dynamic and static load coupled stress environment were determined. The simulated in-situ stress environment under dynamic and static load coupling by gas injection and stress loading in a simulated mine environment includes the following steps: Based on the actual three-dimensional geostress in the specified simulated mine area and the predetermined similarity ratio, determine the triaxial stress and gas pressure values ​​required for the experiment. Based on the required triaxial stress and gas pressure values ​​for the experiment, triaxial stress loading is first performed until the triaxial loading pressure reaches the predetermined value. Inject a gas substitute at the target pressure value through the injection pipe (11); After the internal gas pressure of the sample stabilizes, the rock stratum deformation detection component, rock stratum stress detection component, rock stratum dip angle detection component and gas pressure detection component are activated to collect data corresponding to each layer, which are used as the initial data of all measurement and control systems before mining disturbance. Dynamic load stress is applied on a two-dimensional plane, and the dynamic load is a periodic load.

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

3. The simulation test method for overburden deformation and gas migration during inclined coal seam mining according to claim 2, characterized in that, The gas substitute is CO2, nitrogen, or helium.

4. The simulation test method for overburden deformation and gas migration during inclined coal seam mining according to claim 1, characterized in that, The measurement and control system is deployed simultaneously during the laying of the coal seam (1) and the rock stratum (2). The measurement and control system includes a rock stratum deformation detection component, a rock stratum stress detection component, a rock stratum dip angle detection component, and a gas pressure detection component. The rock stratum deformation detection component is used for deformation detection in three directions on the rock stratum (2). The rock stratum stress detection component is used for rock stratum stress field detection. The rock stratum dip angle detection component is used for rock stratum (2) dip angle detection. The gas pressure detection component is used for gas pressure detection in the rock stratum (2) and coal seam (1) during the mining of the coal seam (1).

5. The simulation test method for overburden deformation and gas migration during inclined coal seam mining according to claim 4, characterized in that, The method for arranging the rock strata deformation detection component includes the following steps: In the coal seam (1) and rock strata (2), a first sensing fiber group, a second sensing fiber group and a third sensing fiber group are arranged in layers one by one. 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. The second sensing fiber group includes multiple directional sensing fibers (4) and the multiple directional sensing fibers (4) are arranged at intervals along the directional direction. 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. The axial sensing fibers (3), normal sensing fibers (5) and directional sensing fibers (4) are 90 degrees apart. The axial sensing fibers (3), normal sensing fibers (5) and directional sensing fibers (4) are connected by connecting fibers (6) 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 connected to a fiber optic demodulator and a fiber stress analyzer in sequence.

6. The simulation test method for overburden deformation and gas migration during inclined coal seam mining according to claim 4, characterized in that, The method for arranging the rock stratum stress detection component includes the following steps: Multiple detection surfaces are set up vertically along the coal seam (1). Multiple measuring points are arranged on the detection surfaces. The multiple measuring points are distributed in a rectangular array. Pressure sensors (7) are arranged on each measuring point. Multiple pressure sensors (7) are buried in the surrounding coal pillars (8) at the same depth as the detection surface. The pressure sensors (7) are connected to the signal acquisition device of the external device and the signal acquisition device is connected to the computer system.

7. The simulation test method for overburden deformation and gas migration during inclined coal seam mining according to claim 4, characterized in that, The method for arranging the rock stratum dip angle detection component includes the following steps: Based on the distribution of the collapse zone, fissure zone, and bending deformation zone in the numerical simulation, dynamic tilt sensors (9) are arranged in the collapse zone, fissure zone, and bending deformation zone respectively. Each layer is designed to have a measuring line arranged along the axial direction and dip direction, and multiple dynamic tilt sensors (9) are arranged in each measuring line. One dynamic tilt sensor (9) is arranged at the intersection of two measuring lines. The spacing between each adjacent dynamic tilt sensor (9) is 45cm to 55cm. The dynamic tilt sensor (9) is connected to the signal acquisition instrument.

8. The simulation test method for overburden deformation and gas migration during inclined coal seam mining according to claim 4, characterized in that, The method for arranging the gas pressure detection component includes the following steps: Multiple detection surfaces are set along the vertical depth direction of the coal seam (1) and rock strata (2). Multiple measuring points are arranged on the detection surfaces, and the multiple measuring points are distributed in a rectangular array. A gas-specific pressure sensor (10) is arranged on each measuring point, and the gas-specific pressure sensor (10) is connected to the signal acquisition instrument.

9. The simulation test method for overburden deformation and gas migration during inclined coal seam mining according to claim 4, characterized in that, Dynamic excavation under simulated geostress environment includes the following steps: Step 1: Send the excavator into the cut (13), place the cutter head at one end of the excavator, adjust the cutting surface of the excavator to be parallel to the surface being cut, and connect the power supply and air circuit of the excavator control console; Step 2: Tighten the jacking cylinder and advance the propulsion cylinder to make the excavator tool fit tightly against the surface to be cut; Step 3: The push cylinder and the clamping cylinder are reset, and the excavation motor and the feed motor rotate forward; Step 4: When the cutter head moves to the other end of the excavator, the excavation motor rotates forward, the feed motor rotates in reverse, and the cutter head returns to its original position; Step 5: Repeat steps 2 to 4, and the excavation equipment will excavate repeatedly according to the predetermined single advance to complete the excavation of coal seam (1).

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