Non-hydrophilic similar simulation test system and similar simulation test method

Abstract

The invention provides a non-hydrophilic similar simulation test system and a similar simulation test method. The test system comprises a two-dimensional model test bed, a loading device, a first water pressure supply device, a non-hydrophilic similar model and a detection system, the non-hydrophilic similar model is made of a non-hydrophilic similar material; the loading system comprises a paradigm frame and a loading oil cylinder mounted on the counter-force frame; the first water pressure supply device comprises a plurality of bags and an air supply device for supplying air to the bags; the detection system comprises a high-speed camera arranged right opposite to the non-hydrophilic similar model, a plurality of pressure sensors and a static stress-strain test analysis system used for analyzing data of the pressure sensors. The test system reduces test interference and guarantees the repeatability of the test. According to the method, the test system is adopted for simulation, and the complete process of working face advancing can be completely simulated.

Description

Technical Field

[0001] This application relates to the field of similarity simulation testing technology, and in particular to a non-hydrophilic similarity simulation testing system and a similarity simulation testing method. Background Technology

[0002] With the increasing depth and intensity of coal mining, the challenges to mine safety are becoming increasingly severe, especially the problem of coal mine water hazards. Statistics show that 80% of mine water inrush accidents in my country are closely related to fault structures. Small faults, due to their small displacement, short extension, limited fracture zone width, and poor water conductivity, cause delayed floor water inrushes induced by their activation. These inrushes are characterized by their high degree of concealment, significant destructiveness, and difficulty in prediction and control, making them a key challenge restricting the safe mining of deep coal resources.

[0003] As mining depth increases, mining activities gradually approach the confined aquifer at the bottom, intensifying the threat of water inrush. Existing geophysical exploration technologies (such as transient electromagnetic methods and direct current methods) can accurately detect medium to large faults and control water hazards by leaving waterproof coal pillars or grouting. However, the detection of small faults and... Water hazard prevention and control still faces significant challenges. Small faults are characterized by their strong concealment, small fracture zones, and certain water-blocking capabilities, leading to fault activation and water inrush only occurring after a certain period of mining disturbance. The damage to small faults caused by mining stress and floor water pressure exhibits a certain lag. The unique characteristics of small faults and the mechanism of delayed water inrush are complex: on the one hand, due to differences in particle size distribution, dip angle variations, and relatively good initial closure, small faults exhibit a multi-stage activation characteristic under the coupled action of mining stress and seepage—"stress redistribution—gradual fracture expansion—seepage erosion—water channel connection"—rather than the instantaneous water inrush mode of traditional large faults; on the other hand, existing technologies struggle to dynamically capture the interaction between mining paths (such as advance speed and stop location) and the structural heterogeneity of small faults (such as cementation degree and fracture zone width), resulting in theoretical models failing to accurately characterize the dynamic evolution of water inrush channels, and prevention and control measures lacking specificity and timeliness.

[0004] As the working face advances and gradually approaches the small fault, the coal seam roof gradually forms caving zones, fracture zones, and bending subsidence zones. The coal seam floor, subjected to concentrated lateral stress from the roof strata, suffers damage, forming a floor failure zone within a certain range of the floor and the small fault. After the working face pushes past the fault, the coal seam floor undergoes upward bending deformation under mining stress, leading to slippage between the hanging wall and footwall at the small fault, a necessary condition for water inrush.

[0005] To reveal the evolution of fractures in the working face floor and small faults under mining influence, this invention proposes a non-hydrophilic similarity simulation test system and method. The aim is to observe and monitor the damage characteristics of the coal seam floor strata and small faults at different approach distances. By analyzing the fracture propagation, stress, and displacement changes in the coal seam floor and small faults, the characteristics of working face floor failure and small fault activation can be understood. Summary of the Invention

[0006] The purpose of this application is to provide a non-hydrophilic similarity simulation test system and similarity simulation test method to solve or alleviate the problems existing in the prior art.

[0007] To achieve the above objectives, this application provides the following technical solution: A non-hydrophilic similarity simulation test system includes a two-dimensional model test bench, a loading device, a first water pressure supply device, a non-hydrophilic similarity model, a sealing structure, and a detection system; The two-dimensional model test bench includes a base, a reaction frame set on the base, an inner frame fixed on the base and located inside the reaction frame, and several transparent plates detachably set on the inner frame. The non-hydrophilic similarity model is housed within the base; the non-hydrophilic similarity model is made of a non-hydrophilic similarity material; The loading device includes a first transverse hydraulic cylinder installed on one side of the reaction frame, a second transverse hydraulic cylinder installed on the other side of the reaction frame, a vertical hydraulic cylinder installed on the top of the reaction frame, a first push plate for padding between the model and the first transverse hydraulic cylinder, a second push plate for padding between the non-hydrophilic similar model and the second transverse hydraulic cylinder, and a loading cover plate for padding between the model and the vertical hydraulic cylinder. The first water pressure supply device includes a plurality of bags and an air supply device for supplying air to the bags; The second water pressure supply device includes a nitrogen cylinder, a water storage tank, and a water pressure control system; The sealing structure includes a side pressure plate and a middle pressure plate that are detachably installed on the outside of the inner frame. The transparent plate can be pressed and fixed to the inner frame by the side pressure plate and the middle pressure plate. The detection system includes a high-speed camera positioned facing the non-hydrophilic similar model, several pressure sensors, and a static stress-strain test and analysis system for analyzing the pressure sensor data.

[0008] Furthermore, the non-hydrophilic similarity model material uses transparent water-based polyurethane, cement, and dimethicone as binders, fine dry sand and barite powder as aggregates, and is mixed with an appropriate amount of water; and the proportions are adjusted according to the basic physical and mechanical parameters of each rock layer.

[0009] Furthermore, the steps for creating the non-hydrophilic similarity model include: The raw materials of each rock layer are prepared layer by layer to obtain rock layer similar materials, and then molded. Each layer of rock layer similar material is placed in the space enclosed by the base, the first push plate, the second push plate and the transparent plates on both sides, and the top surface of the rock layer similar material is smoothed to the corresponding height. Then mica sheets are sprinkled on it. The above steps are repeated until the maximum height is reached. During the molding process, measuring points are arranged and faults are simulated; After the model is completed, let it sit naturally until it is completely dry, which takes 2 to 3 weeks.

[0010] Furthermore, each rock layer is 0.5 to 3.0 cm thick; after each layer of raw materials is mixed evenly, it is filled within 5 to 10 minutes.

[0011] This invention also proposes a similarity simulation test method using the aforementioned non-hydrophilic similarity simulation test system. In the first stage, a first model is constructed using a first water pressure supply device and excavated to study the rock strata damage and fault activation instability characteristics before and after the working face on the confined aquifer pushes past a small fault. In the second stage, a second model is constructed using a second water pressure device and excavated to study the small fault activation and water inrush mechanism before and after the working face on the confined aquifer pushes past a small fault. The similarity simulation test method includes the following steps: Phase 1: Step S11: Lay out a non-hydrophilic similar model and arrange measuring points, simulated faults, and burr bags during the laying process; lay the burr bags flat in the rock strata of the simulated aquifer in the non-hydrophilic similar model; arrange the measuring points in the rock strata of the bottom plate of the coal seam to be measured and in the rock strata of the hanging wall and footwall of the simulated small fault; apply white light calcium carbonate as a base color to the front of the model and use a brush to dot uneven black spots on the front of the model so that the high-speed camera can monitor the deformation of the coal seam bottom plate; Step S12: After the model is air-dried, the air supply device is used to inject air into the bag and maintain constant pressure. The static stress-strain test and analysis system is debugged and balanced. Then, simulated excavation is carried out. The excavation is carried out in multiple stages. Image analysis software is used to analyze the deformation values ​​of the bottom rock layer after each excavation. During the model excavation process, stress changes are monitored in real time, the damage of the top and bottom plates is continuously observed, and photos are collected in real time using a high-speed camera. Step S13: After excavation, analyze the crack propagation, stress, and displacement changes in the coal seam floor and small faults; Phase Two: Step S21: Lay out a non-hydrophilic similar model. During the laying process, arrange measuring points and simulated faults, and seal the joints between transparent plates except for the excavation location with sealant. The measuring points are arranged in the bottom rock strata of the coal seam to be measured and in the hanging wall and footwall rock strata of the simulated small fault. Step S22: After the model is air-dried, water is introduced into the bottom of the model using the second water pressure supply device and the pressure is kept constant. The water in the bottom aquifer flows only through the mining-induced fractures. The static stress-strain test and analysis system is debugged and balanced, and then simulated excavation is carried out. The excavation is carried out in multiple stages. During the model excavation, stress changes are monitored in real time, and the damage to the top and bottom plates is continuously observed. Step S23: After excavation, analyze the characteristics of delayed water inrush at the bottom plate during the activation of small faults and the water conduction process at the bottom plate.

[0012] Furthermore, in step S11, the steps for creating the simulated fault are as follows: During the model laying process, steel plates are embedded to simulate faults, and the shape of the steel plates is customized according to the specific shape of the small faults. When the fault simulation reaches the pinch-out stage, the steel plates simulating the small faults are extracted one by one, and a mixed dry similar material is injected into the small faults to ensure the accuracy and continuity of the small fault simulation.

[0013] Furthermore, the process for fabricating similar materials used to simulate faults is as follows: Based on the thickness of the simulated fault, rock particles of different sizes are mixed together, and cement and gypsum are added; cement and gypsum each account for 3% to 5% of the total mass of the rock particles; the mixture is then injected into the fault; the rock particles of the simulated fault are selected from three particle size grades from 0~0.5mm, 0.5~1.0mm, 1.0~2.0mm, 2.0~4.0mm, 4.0~6.0mm, and 6.0~8.0mm according to the fault characteristics, and the mass of rock particles of each particle size grade is calculated using a continuous gradation formula.

[0014] Furthermore, the rock particles were selected with a particle size distribution of 0.4, and the corresponding mass proportions of 0~0.5mm, 0.5~1.0mm, and 1.0~2.0mm rock particles were 57.4%, 18.4%, and 24.2%, respectively.

[0015] Furthermore, the dimensions of the non-hydrophilic similar model are 1000×1000×200mm; during model excavation, excavation is carried out from one side of the model, with each excavation being 5cm, for a total of 16 excavations, resulting in a total excavation of 80cm, simulating a working face advancement of 160m.

[0016] Furthermore, a measuring line with a total of 9 pressure sensors is arranged in the bottom strata of the coal seam to be tested, with a distance of 10cm between two adjacent pressure sensors; one pressure measuring line is arranged in the hanging wall and footwall of the small fault, with a vertical spacing of 15cm between the pressure sensors.

[0017] The technical solution of this application has the following beneficial effects: The similarity simulation test system of this application uses non-hydrophilic similarity simulation materials, which can realistically simulate the characteristics of the roof and floor strata (limestone) of the coal seam. The air pressure provided by the bag of the first water pressure supply device simulates the water pressure of the aquifer. Compared with the direct water injection method, it reduces the loss of model materials due to water flow erosion, avoids the distortion of materials due to water absorption, and can maintain the state of the strata under pressure for a long time. This makes the fracture development only affected by mining stress, reduces test interference, and ensures the repeatability of the test. The water pressure provided by the second water pressure supply device can simulate the fault activation and channel erosion effect of water pressure during the mining of each layer. It can make up for the lack of water seepage in the water guiding channel in the previous model, and provide a test equipment basis for a comprehensive understanding of the evolution law of the delayed water inrush channel in the floor of the small fault in the working face. At the same time, the design of the two-dimensional model test platform can more intuitively observe and image the changes in the floor of the working face and the small fault fractures during the excavation process, which is convenient for subsequent analysis.

[0018] The similar simulation test method proposed in this application can completely simulate the entire process of working face advancement, and synchronously monitor the two core data of stress and displacement. At the same time, it can take real-time photos to record the damage of the roof and floor, making the processes of crack propagation and rock strata failure visible, and providing accurate and reliable test basis for the prevention and control of water inrush in actual coal mines. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. Wherein: Figure 1 This is a schematic diagram of the structure of a two-dimensional model test bench according to an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of the arrangement of non-hydrophilic similarity models according to an embodiment of the present invention.

[0021] Figure 3 This is a comprehensive histogram of the working surface in the model of this embodiment of the invention.

[0022] Figure 4 This refers to the model laying steps in the first stage of this embodiment of the invention.

[0023] Figure 5 This is a diagram showing the arrangement of measuring points in the model in an embodiment of the present invention.

[0024] Figure 6 This describes the evolution process of the model working surface base plate and small fault fractures in the first stage of this embodiment of the invention.

[0025] Figure 7 This is the curve showing the change in vertical stress of the coal seam floor as the working face advances in the first stage model of this invention.

[0026] Figure 8 This is a curve showing the change of vertical stress on the hanging wall of the fault with the advance distance in the model of the first stage in this embodiment of the invention.

[0027] Figure 9 This is a curve showing the change in vertical stress in the footwall of the fault with the advance distance in the model of the first stage in this embodiment of the invention.

[0028] Figure 10 This is a cloud map of rock strata displacement at different advance distances of the working face in the first stage model of this embodiment of the invention.

[0029] Figure 11 This is a curve showing the layout of the survey lines and the vertical displacement of the base plate in the model of the first stage in this embodiment of the invention.

[0030] Figure 12 The figures show the vertical and horizontal displacement curves of the surrounding rock of the fault in the first stage of the model in this embodiment of the invention.

[0031] Figure 13 This describes the assembly status of the similar simulation test system in the second stage of this embodiment of the invention.

[0032] Figure 14 This refers to the second stage of the model small fault activation and bottom water conduction process in this embodiment of the invention.

[0033] Figure 15 This is a water pressure change curve during the activation of a small fault in the model during the second stage of this invention embodiment.

[0034] Figure 16 The diagram below illustrates the three-stage delayed water inrush induced by a small fault according to an embodiment of the present invention.

[0035] Explanation of reference numerals in the attached figures: 1-First transverse hydraulic cylinder, 2-Second transverse hydraulic cylinder, 3-Vertical hydraulic cylinder, 4-First push plate, 5-Second push plate, 6-Loading cover plate, 7-First column, 8-Second column, 9-Top frame, 10-Base, 11-Bag, 12-Steel plate simulating small faults, 13-Pressure sensor, 14-First inner frame, 15-Second inner frame, 16-Top inner frame, 17-Bottom pressure plate, 18-Side pressure plate, 19-Middle pressure plate, 20-Transparent plate, 21-Water tank. Detailed Implementation

[0036] This application will now be described in detail with reference to the accompanying drawings and embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing embodiments of this disclosure only and is not intended to limit this disclosure.

[0037] In the description of this application, the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and do not require this application to be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0038] Example This embodiment takes the hydrogeological conditions of the working face of a confined aquifer in Liulin, Shanxi as the background. Based on the coal and rock mechanics parameters of the roof and floor, a non-hydrophilic hydraulic coupling similarity simulation test model is constructed to analyze the development height of the aquifer's conduction zone, the evolution characteristics of floor fractures, and the water inrush process activated by small faults under confined water conditions. It also aims to understand the evolution law of the delayed water inrush channel induced by the activation of small faults in the working face of the confined aquifer.

[0039] Workface Overview: The mining and hydrogeological conditions of the 8101 working face were selected as the engineering background. The thickness and lithology of the roof and floor strata of the No. 8 coal seam are detailed below. Figure 3 A comprehensive columnar chart of the working face.

[0040] The 8101 working face is 787m long and 146m wide. The coal seam generally exhibits a monocline structure dipping northwest, with a thickness of 2.00-3.10m, averaging 2.65m, and a dip angle of 2-8°, averaging 5°. The working face depth is 346-397m. The coal seam structure is simple to relatively simple, with stable occurrence. The mining method is subduction mining of the entire height in one pass. The northern part of the working face is the mine boundary safety pillar; the southern part is the No. 8 coal seam's main transport roadway and return airway; the western part is the mine boundary safety pillar; the eastern part is solid coal; and the lower part is the No. 9 coal seam solid coal. The corresponding surface is mostly farmland with no water bodies. The ground elevation is 836.8-990m, averaging 913.8m, and the working face coal seam floor elevation is 530-593m, averaging 561.5m.

[0041] The No. 8 coal seam is 70.2 m away from the Ordovician Middle Series Fengfeng Formation (O2f) limestone aquifer, with a water pressure of 3.0 MPa. The water pressure at the bottom of the No. 8 coal seam is 2.3 MPa. All mining faces of the No. 8 coal seam are operated under pressure. The water level of the Ordovician Middle Series Fengfeng Formation (O2f) limestone aquifer is at an elevation of +798 m, with a unit inflow (injection) of 0.0010~0.5178 L / s·m and a permeability coefficient of 0.013~0.7139 m / d. The aquifer has weak (moderate) water-bearing capacity and is uneven.

[0042] The bottom of the Taiyuan Formation (C3t) of the Upper Carboniferous is K1 medium-grained sandstone, with an average thickness of 8m. It is 35m away from the No. 8 coal seam, with a water level of +760~+766m, a unit yield of 0.0151~0.1L / s·m, and a permeability coefficient of 0.0690~0.2644m / d. It is a weakly water-rich aquifer and does not pose a threat to the mining of the No. 8 and No. 9 coal seams.

[0043] Similar simulation parameters: The dimensions of the non-hydrophilic similarity model are 1000×1000×200mm. Based on the purpose of this similarity simulation, and considering the operability and reliability of the experiment, the similarity simulation parameters are selected according to the three similarity theorems as follows: The geometric similarity ratio is 1:200, the Poisson's ratio similarity ratio is 1:1.5, the unit weight similarity ratio is 1:1.5, the stiffness similarity ratio is 1 / 300, the time similarity ratio is 1 / 12, and the permeability coefficient similarity ratio is 0.106.

[0044] The actual hydrostatic pressure in the aquifer region at the bottom of the coal seam is between 2.8 and 3.0 MPa, with the maximum value of 3.0 MPa used in the experiment. Based on the specific mining and hydrogeological conditions, the aquifer pressure in the model can be calculated to be 0.01 MPa.

[0045] Test system: The test system adopts a non-hydrophilic similarity simulation test system independently developed by the inventor's team, including a two-dimensional model test bench, a loading device, a first water pressure supply device, a second water pressure supply device, a non-hydrophilic similarity model, and a detection system; The two-dimensional model test bench includes a base 10, a reaction frame mounted on the base 10, side pressure plates 18, middle pressure plates 19, bottom pressure plates 17, an inner frame fixed to the base 10 and located within the reaction frame, and several transparent plates 20 (transparent acrylic plates) detachably mounted on the inner frame. The reaction frame includes a first column 7 fixed to one end of the base 10, a second column 8 fixed to the other end of the base 10, and a top frame 9 detachably mounted on the top of the first column 7 and the second column 8. A first transverse hydraulic cylinder 1, a second transverse hydraulic cylinder 2, and a vertical hydraulic cylinder 3 are respectively fixed to the first column 7, the second column 8, and the top frame 9. The inner frame includes a first inner frame 14, a second inner frame 15, and a top inner frame 16 with a square frame structure. The width of the first inner frame 14 is greater than that of the second inner frame 15. The inner frame 15 has several threaded mounting holes; the bottom pressure plate 17 is fixed on the base 10, and the outer side of the bottom pressure plate 17 is aligned with the first inner frame 14. The inner side of the bottom pressure plate 17 and the outer side of the second inner frame 15 have a gap for the transparent plate 20 to be inserted; when laying the model, after the transparent plate 20 is inserted into the gap, the side pressure plate 18, which is bolted to the second inner frame 15, is used to press and fix the edge of the transparent plate 20. The middle pressure plate 19 is fixed to the bottom pressure plate 17 and the top inner frame 16 using bolts; the middle pressure plate 19 has several threaded holes, and bolts are installed in the threaded holes. The inner end of the bolts supports the transparent plate 20 to maintain its shape and prevent the middle part from bulging outward; a water tank 21 is provided on the base 10. The side of the water tank 21 has a water inlet, and the top surface of the water tank 21 has several water permeable holes; The non-hydrophilic similarity model is disposed within the base 10; the non-hydrophilic similarity model is made of a non-hydrophilic similarity material; The loading device includes a first transverse hydraulic cylinder 1 installed on one side of the reaction frame, a second transverse hydraulic cylinder 2 installed on the other side of the reaction frame, a vertical hydraulic cylinder 3 installed on the top of the reaction frame, a first push plate 4 for placing between the model and the first transverse hydraulic cylinder 1, a second push plate 5 for placing between the non-hydrophilic similar model and the second transverse hydraulic cylinder 2, and a loading cover plate 6 for placing between the model and the vertical hydraulic cylinder 3; the first transverse hydraulic cylinder 1, the second transverse hydraulic cylinder 2, and the vertical hydraulic cylinder 3 all use a 100MPa light manual hydraulic pump (model CGSB100-1); the first transverse hydraulic cylinder 1 / second transverse hydraulic cylinder 2 can supplement the horizontal stress on the model, and the vertical hydraulic cylinder 3 can compensate for the load on the unsimulated rock strata; The first water pressure supply device includes a plurality of bags 11 and an air supply device for supplying air to the bags 11; the air supply device is used to supply pressure to the bags 11 to simulate the water pressure of the aquifer. The second water pressure supply device includes a nitrogen cylinder, a water storage tank, and a water pressure control system. The nitrogen cylinder is used to provide a pressure source, and the water pressure control system includes a water pressure sensor and a flow control valve. By setting the pressure of the water pressure control system, the output water pressure can be controlled. The second water pressure supply device is connected to the inlet of the water tank 21 through a hose to provide water pressure to the aquifer. It should be noted that the first and second water pressure supply devices are not used simultaneously. In the first stage, the first model was constructed and excavated using the first water pressure supply device to study the characteristics of rock strata damage and fault damage activation instability before and after the working face on the confined aquifer pushes over the small fault. In the second stage, the second model was constructed and excavated using the second water pressure device to study the mechanism of water inrush activation of the small fault before and after the working face on the confined aquifer pushes over the small fault. The detection system includes a high-speed camera positioned facing the non-hydrophilic similar model, several pressure sensors 13 (model EVT-14D), and a static stress-strain test and analysis system (model DH3816N) for analyzing the data from the pressure sensors 13. Figure 1 , Figure 2 The structure of the experimental system is schematically drawn in the diagram. Figure 2 In order to show the model layout and display the first push plate 4, the second push plate 5, and the third push plate, the transparent plate 20, the inner frame, the side pressure plate 18, the middle pressure plate 19, and the bottom pressure plate 17 are not shown.

[0046] Similar simulation materials and model laying: The non-hydrophilic similarity model material uses transparent water-based polyurethane, cement, and dimethicone as binders, fine dry sand and barite powder as aggregates, and is mixed with an appropriate amount of water. Based on the basic physical and mechanical parameters of the lithology of the top and bottom plates of the No. 8 coal seam in a coal mine in Liulin, Shanxi, and combined with the results of the non-hydrophilic fluid-structure coupling similarity simulation material proportioning test, the proportion of each rock layer was calculated and selected. The specific proportion number and quality parameters are shown in Table 1.

[0047] Table 1. Material Proportioning Table for Non-Hydrophilic Similarity Simulation Tests

[0048] The compressive strength of the rock strata is arranged in the order of coarse sandstone > sandy mudstone = mudstone > limestone > coal, which are 0.111 MPa, 0.067 MPa, 0.067 MPa, 0.065 MPa and 0.053 MPa, respectively. The material ratio has been offset to eliminate the influence of thickness on strength, and the simulation focuses only on the mechanical properties of the rock itself.

[0049] The steps for creating the non-hydrophilic similarity model are as follows: First, prepare the ingredients layer by layer according to the proportions and rock strata distribution. Then, install the mold by filling it with the prepared ingredients and smoothing the surface to the appropriate height. Next, sprinkle mica sheets on top to simulate joint surfaces and bedding planes, making the rock strata in the model relatively distinct. Repeat these steps until the simulated height is reached. Figure 4 As shown. During the molding process, the thickness of each rock layer is generally 0.5~3.0cm. If it is too thick, it will be difficult to compact, resulting in a dense top and loose bottom layer, and uneven material distribution. If it is less than 0.5cm, it will make it difficult to form the rock layer. Before filling the mold, the mass of each material must be measured according to the strength ratio table, and after being mixed evenly, the filling should be completed within 5~10 minutes to prevent the material from solidifying before filling, which would affect the properties of similar materials. Figure 4 The model laying steps are as follows: (a) shows the model being compacted, (b) shows the aquifer bag 11 and the steel plate (12) simulating the small fault being buried, (c) shows the model being laid, and (d) shows the model being demolded and air-dried.

[0050] After the model is completed, it is left to air dry naturally for 2-3 weeks. Once the model is completely dry, the next step of excavation can begin. During the fault simulation laying process, we pre-prepared steel plates with a width of 20cm and a thickness of 3mm, equivalent to a pre-fabricated small fault fracture zone width of 0.6m. These steel plates are customized according to the specific shape of the fault and are securely embedded in the model. When the fault simulation reaches the pinch-out stage, the steel plates 12 simulating the small faults are extracted one by one, and a mixed dry similar material is injected into the small faults to ensure the accuracy and continuity of the small fault simulation. In this embodiment, the similar material raw materials used to simulate the fault are rock particles, cement, and gypsum, with cement and gypsum each accounting for 5% of the total mass of the rock particles. Among them, the rock particles are selected with a particle size distribution of 0.4, and the rock particles are selected from three particle size grades: 0~0.5mm, 0.5~1.0mm, and 1.0~2.0mm. The corresponding mass proportions of 0~0.5mm, 0.5~1.0mm, and 1.0~2.0mm rock particles are 57.4%, 18.4%, and 24.2%, respectively.

[0051] According to the experimental monitoring requirements, 15 pressure sensors (13) were deployed to monitor aquifer water pressure, coal seam floor stress, and coal seam floor deformation. One stress measurement line with 9 pressure sensors (13) was deployed directly on the bottom of the No. 8 coal seam. The model distance between the pressure sensors (13) was 10 cm, while the actual distance was 20 m. One pressure measurement line was deployed on both the hanging wall and footwall of the small fault. The vertical spacing of the pressure sensors (13) was 15 cm, while the actual distance was 30 m. The measurement points were arranged as follows: Figure 2 , Figure 5 As shown.

[0052] In this embodiment, the similarity simulation test method includes the following steps: Phase 1: (1) Aquifer water pressure simulation and monitoring: Six aquifer bags 11 are installed inside the aquifer to simulate water pressure with air pressure, and a stable pressure source is provided by an air pump. The bags 11 are connected in parallel through a three-way valve and connected to a high-precision pressure gauge to monitor pressure changes. At the same time, a pressure stabilizing valve is equipped to ensure that the pressure does not exceed the set value. The entire system is continuously pressurized by the air pump to maintain the aquifer pressure stability during the model excavation process.

[0053] (2) Coal seam floor deformation monitoring: The front of the model was coated with white light calcium carbonate as a base color, and then black speckles were unevenly dotted on the model with a brush. The deformation of the coal seam floor was monitored using a DIC high-speed camera, and the deformation results of the model were quickly photographed after each excavation. The deformation values ​​of the floor rock strata after each excavation were analyzed using DIC-2D Analysis software.

[0054] (3) Model excavation: After the model is air-dried, air is injected into the aquifer using an air supply device and the pressure is kept constant. The DH3818 static strain tester is debugged and balanced to simulate the speed of the 8101 working face for coal seam excavation. Excavation begins 10cm from the left side of the model, with each excavation being 5cm, for a total of 16 excavations, resulting in a total excavation of 80cm and simulating a working face advance of 160m. During the excavation process, the stress is monitored and measured in real time, and the damage to the roof and floor is continuously observed, with real-time photography taken. After the experiment, the experimental data is compiled and analyzed to understand the changes in stress, fracture development, and water inrush flow of the floor strata as the coal seam is excavated; the damage characteristics of the coal seam floor strata and small faults are observed and monitored at different advance distances. By analyzing the fracture expansion, stress, and displacement changes of the coal seam floor and small faults, the characteristics of working face floor damage and small fault activation are understood.

[0055] Phase Two: To obtain the damage and failure of the working face floor and the activation and water inrush process of small faults, the same model mix and test conditions were used to reassemble the test system. The similar simulation test system for the second stage is shown below. Figure 13 In the second stage, compared to the first stage, a second water pressure supply device was used instead of the first. Simultaneously, during the installation of the transparent plate 20, the joint between the upper and lower transparent plates 20, except at the excavation location (corresponding to the No. 8 coal seam), was sealed with sealant to ensure that water in the bottom aquifer flowed only through mining-induced fractures. Furthermore, the similar material for the bottom aquifer was selected from coal cores with high porosity to ensure strong water flow and diffusion within the aquifer. Data acquisition primarily focused on the water pressure and images of the bottom aquifer. The laying and excavation of other rock strata and faults were carried out in the same manner as in the first stage of the simulation experiment.

[0056] Based on similarity theory and aquifer water pressure, the bottom plate water pressure used in the similarity simulation is converted proportionally to 0.01 MPa. In the early stage of mining, the water pressure is adjusted to 0.01 MPa. By monitoring the water pressure change, the activation process of the small fault can be understood. If the pressure at the injection end does not drop, it means that water has not entered the fault. The water pressure will drop only when water enters the fault.

[0057] Results of the first phase of the experiment: 1. Analysis results of the evolution characteristics of water-conducting fractures in the bottom plate of the working face (excluding the erosion effect of high-pressure water in the aquifer on the water-conducting channels).

[0058] Figure 6 The evolution process of the working face bottom plate and small fault fractures is shown. Figure 6 (a) The working face was excavated to 40m. The roof of the coal seam was initially pressed, but the floor did not suffer macroscopic damage. Figure 6 (b) When the working face is excavated to 60m, the roof of the coal seam is subjected to periodic pressure. At this time, the small fault is 10m away from being exposed. The floor of the coal seam begins to deform, and small macroscopic cracks appear in the floor failure zone. However, the cracks in the floor failure zone are not connected to the small fault. At this time, the small fault has not undergone obvious slippage activation. Figure 6 (c) After excavating 70m, the working face reaches the fault fracture zone. At this point, influenced by the fault fracture zone, the roof strata fracture and collapse along the fault plane, while the coal seam floor is damaged by mining stress. Tensile failure occurs at the small fault location at the bottom of the coal seam, but the fracture depth is shallow and does not penetrate the immediate bottom sandy mudstone. As the working face continues to advance, the influence of direct mining on the small fault gradually decreases, while the influence from the lithological combination of the floor strata, the filling material of the fault fracture zone, and water pressure increases. Figure 6 (e) After excavating 100m of the working face, the fractures in the small fault fracture zone further developed due to the influence of the later stage of mining, and it was in the initial stage of small fault slippage instability. Figure 6 (f) After excavating 120m in the working face, the small fault, affected by mining stress and water pressure, experienced slippage and displacement of the hanging wall and footwall. The fractures within the fault's fracture zone were completely connected, and the coal seam floor near the fault fracture zone showed significant bulging. At this point, the mine pressure and aquifer water pressure overcame the gravity of the upper O2 limestone strata, generating dynamic friction that exceeded the static friction of the hanging wall and footwall, causing slippage and failure, resulting in inconsistent deformation of the hanging wall and footwall. Figure 6 As shown in (g) and (h), as the working face continues to be excavated forward, the roof of the coal seam collapses periodically, the broken roof at the small fault is gradually compacted, and the stress on the coal seam floor around the small fault gradually increases, thereby inhibiting the slip deformation of the fault.

[0059] Observations of the activation of small faults and the development of floor fractures during mining reveal that the evolution of small fault fractures in the working face floor can be divided into three stages: the initial fracture closure stage, the intermediate fracture propagation stage, and the later fracture recovery and closure stage. In the initial fracture closure stage, as the working face approaches the small fault, the fracture zone is affected by pre-support pressure, but this pressure does not reach the ultimate failure value of the surrounding rock. The original fractures in the fracture zone close, and the porosity decreases. In the intermediate fracture propagation stage, as the working face pushes towards the small fault, it is affected by pre-support pressure, causing damage to the upper part of the floor fracture, but the fractures do not propagate deeper. As the working face continues to advance, the fractures within the fracture zone are further developed and propagated due to the slippage of the hanging wall and footwall, until the fractures connect with the aquifer. During the later stage of fracture recovery and closure in the small fault fracture zone, the fractured rock mass above the small fault is gradually compacted, and the force of the upper rock strata begins to be transmitted downward to the coal seam floor. The coal seam floor is subjected to downward stress, and the fractures in the small fault fracture zone begin to close to a certain extent.

[0060] 2. Test results of stress variation in the working face bottom plate: (1) Changes in vertical stress in the base plate: Figure 7 The graph shows the vertical stress variation curve of the floor slab as the working face advances. Affected by mining activities, the vertical stress variation of the floor slab exhibits a clear regularity, with variations at different locations. The vertical stress variation of the floor slab before and after the working face passes the small fault can be divided into three stages: increase, decrease, and gradual increase, with the most significant change observed at measuring point #3. The increase in floor slab stress is due to the working face gradually approaching the stress measuring point, causing stress concentration in the floor slab under the influence of the working face's advance support pressure, leading to increased stress. After the working face passes the stress measuring point, the stress in the upper part of the floor slab is released, and the vertical stress at that point decreases. As the working face moves further away from the stress measuring point, the collapsed overburden rock gradually compacts, and the gravity of the roof acts on the floor slab of the goaf through the fracture zone, causing the floor slab stress to gradually increase according to the load of the overburden strata. The stress inside the opening and stopping lines of the working face shows a gradual increasing trend, as shown by the data from measuring points #1 and #9. The increase in the data from pressure cell #1 is because the pressure cell is embedded under the boundary coal pillar. As the working face advances, the damage area of ​​the coal seam floor increases, and the roof stress borne by the coal pillar also increases. When the working face is far from measuring point #9, it does not affect the floor stress at the location of measuring point #9. However, as it gets closer, the stress gradually increases due to the influence of the support pressure.

[0061] (2) Vertical stress changes around the fault: Figure 8The curve shows the variation of vertical stress in the hanging wall of the fault with the advancing distance. In the early stage, as the working face advances, the stress in the floor plate gradually increases due to the pressure from the advance support, and then decreases rapidly. In the later stage, the stress increases to some extent due to the self-weight of the collapsed rocks from the roof, but it cannot return to the original stress state. Before and after the working face crossed the fault, the initial stress at measuring point #10 was 0.25 MPa, the maximum stress was 0.40 MPa, and the maximum stress concentration factor was 1.6. After the working face was mined out, the stress recovered to 0.11 MPa, which is 0.44 times the original rock stress. The initial stress at measuring point #12 was 0.28 MPa, the maximum stress was 0.35 MPa, and the maximum stress concentration factor was 1.28. After the working face was mined out, the stress recovered to 0.26 MPa, which is 0.93 times the original rock stress. The initial stress at measuring point #14 was 0.25 MPa, the maximum stress was 0.27 MPa, and the maximum stress concentration factor was 1.08. After the working face was mined out, the stress recovered to 0.23 MPa, which is 0.92 times the original rock stress. Vertical analysis of the stress changes at measuring points 10#, 12#, and 14# reveals that the closer to the coal seam floor, the greater the impact of coal seam mining; the closer to the aquifer, the less affected by mining. After coal seam mining, there will be a slight decrease in stress.

[0062] Figure 9 The curves show the variation of vertical stress in the footwall of the fault with the advancing distance. Compared with the variation of vertical stress in the hanging wall of the small fault, the stress variation trend in the footwall is the same, but it is less affected by the advance support pressure. Before and after the working face passes the fault, the initial stress at measuring point #11 is 0.23 MPa, the maximum stress is 0.28 MPa, and the maximum stress concentration factor is 1.22. After the working face is mined out, the stress recovers to 0.13 MPa, which is 0.57 times the original rock stress. The initial stress at measuring point #13 is 0.24 MPa, the maximum stress is 0.29 MPa, and the maximum stress concentration factor is 1.21. After the working face is mined out, the stress recovers to 0.23 MPa, which is 0.96 times the original rock stress. The initial stress at measuring point #15 is 0.26 MPa, the maximum stress is 0.30 MPa, and the maximum stress concentration factor is 1.15. After the working face is mined out, the stress recovers to the original rock stress of 0.26 MPa. Vertical analysis of the stress changes at measuring points 11#, 13#, and 15# reveals that the closer to the coal seam floor, the greater the impact of coal seam mining. Points closer to the aquifer are less affected by mining. After mining, the stress at points 13# and 15# can basically recover to the original rock stress.

[0063] By comparing and analyzing the vertical stress changes in the hanging wall and footwall of the small fault, it was found that the hanging wall of the small fault was more affected by the advance support pressure of mining. The main reason for this is that before the fault was pushed through, the small fault blocked the transmission of stress, resulting in the footwall of the small fault being less affected by mining.

[0064] (3) Test results of displacement variation characteristics of the base plate: Figure 10 (a)-(d) are rock strata displacement contour maps at different advance distances of the working face. For example... Figure 10 As shown in (a), when the working face advanced to 40m, the sandy mudstone and limestone of the immediate base underwent slight deformation, and the fault was subjected to some compression deformation. Figure 10 As shown in (b), with the advancement of the working face, the deformation of the bottom heave further increases, exceeding the compression deformation of the fault. The deformation cloud map outline at the fault basically disappears, with only the top of the fault, affected by the advance of mining, showing significant deformation and still displaying some outline. Figure 10 As shown in (c), when the working face advanced 70m, a small fault was exposed. The deformation of the hanging wall above the small fault intensified further, reaching its maximum near the fault plane. Due to the influence of the fracture zone of the small fault, stress transmission was blocked, resulting in relatively small deformation of the hanging wall below the small fault. Figure 10 As shown in (d), when the working face advances to 100m, the deformation of the floor increases due to the movement of the working face. The deformation is greatest near the contact surface between the hanging wall and footwall of the fault, indicating that the hanging wall and footwall of the small fault have begun to slide and deform. As the working face continues to be mined, the small fault in the floor shows signs of slippage and activation.

[0065] Based on the displacement contour map data, three measuring lines were evenly distributed on the coal seam floor, named measuring line 1, measuring line 2, and measuring line 3 from top to bottom. One measuring line was also distributed on the hanging wall and footwall of the small fault, named measuring line 4 and measuring line 5 respectively. Figure 11 As shown, 20 displacement measuring points are evenly set up on each measuring line.

[0066] Depend on Figure 11 The vertical displacement curve of the floor shows that the deformation increases as the working face advances and the floor gets closer to the coal seam. Before the working face exposes the small fault, the floor deformation in the goaf exhibits an arched shape, higher in the middle and lower at both ends. After the working face pushes past the small fault for a certain distance, the upper and lower walls of the fault slip and shift, and the deformation in both walls exhibits a cliff-like change. Figure 11 As shown in (a), when the working face advanced to 60m, 10m from the small fault, slight bulging deformation of the bottom plate began to occur, with the maximum deformation of the bottom plate at survey line 1 being 49.36mm; Figure 11As shown in (a), when the working face advances to 70m, it is 0m away from the small fault, and the deformation of the base plate increases further. When the working face advances to 80m, it passes the small fault by 10m, and the deformation of the base plate increases further. The small fault begins to activate, and the maximum deformation of the base plate at the survey line 1 position is 218.08mm. When the working face advances to 100m, it passes the small fault by 30m, and the deformation of the base plate increases sharply. The maximum displacement changes from near the middle position to the ends of the upper and lower plates of the small fault. The maximum deformation of the upper plate of the fault at the survey line 1 position is 552.24mm, and the maximum deformation of the lower plate is 92.98mm. When the working face advanced to 120m, the maximum deformation of the floor reached a maximum of 599.18mm. When the working face advanced to 140m, the maximum deformation on the measuring line decreased to 561.17mm. The main reason is that the rock in the caving zone was compacted, possessing a certain capacity for support and force transmission, transferring the load of the roof to the coal seam floor, resulting in a decrease in deformation displacement. Under the influence of continuous compaction of the roof caving rock, the floor deformation showed a decreasing trend as the working face continued to advance.

[0067] Figure 12 The curves show the vertical and horizontal displacement changes of the surrounding rock of the fault in the base plate. Figure 12 (a) shows the vertical displacement curve of survey line 4 as the working face advances. The vertical displacement is related to the deformation of the base plate. When the working face advances to 100m, the small fault changes, and the vertical displacement increases rapidly. However, the relative deformation decreases with increasing depth. The change in horizontal displacement reflects the horizontal stress on the base plate. Figure 12 (b) shows the horizontal displacement curve of survey line 4 as the working face advances. Before the working face exposes the small fault, the hanging wall of the small fault is subjected to compression deformation by the advance support pressure. Therefore, the displacement change is negative when the working face advances to 40m and 60m.

[0068] Figure 12 (c) is the vertical displacement curve of survey line 5 as the working face advances. Compared with the displacement change of survey line 4, the deformation characteristics of the footwall of the small fault are basically the same as those of the footwall, but the deformation amount is quite different. This is mainly due to the asynchronous bending deformation and relative slippage of the footwall and the footwall. The transverse rock strata length of the footwall of the small fault is 70m, and the rock strata length of the footwall of the fault is 30m, which results in the larger slippage of the footwall than that of the footwall. Figure 12 (d) is the horizontal displacement curve of measuring line 5 as the working face advances. The displacement deformation direction of measuring line 5 is to the left, which is opposite to the displacement change of measuring line 4. After the coal seam is mined, the stress concentration phenomenon in the bottom plate area of ​​the model is enhanced due to the redistribution of lateral stress.

[0069] Results of the second phase of the experiment: Figure 14 This is a process of small fault activation and bottom water conduction. For example... Figure 14As shown in (a), when the working face advanced 60m, the bottom plate exhibited an inverted saddle-shaped failure. At this point, the horizontal distance to the small fault was 20m, and there was no sign of the bottom plate aquifer rising. Figure 14 As shown in (b), when the working face advances to 80m, a small fault is exposed, and the area of ​​failure in the floor slab moves forward as the working face advances. Figure 14 As shown in (d), when the working face advances to 120m, having passed the small fault by 40m, the confined water in the bottom plate begins to rise continuously. Figure 14 As shown in (e), when the working face continued to advance to 140m, the water in the confined aquifer at the bottom completely broke through the barrier of the fractured interstitial material of the small fault and seeped into the working face floor, causing water inrush behind the goaf. After the working face continued to advance, the water inrush volume in the working face goaf floor remained basically stable, indicating that the water diversion channel was fully formed.

[0070] Figure 15 The graph shows the water pressure change during the activation of the small fault. Before the working face advances 10m past the small fault, the water pressure in the bottom aquifer remains relatively constant at around 0.01MPa, indicating that the water in the aquifer has not yet broken through the barrier of the small fault. When the working face advances 100m, the water pressure drops to 0.009MPa, indicating that the top interface of the aquifer has deformed and water has begun to enter the bottom of the small fault. As the working face advances to 120m, the aquifer water pressure begins to drop rapidly to 0.006MPa. Based on the water flow observed in the fault during excavation, it can be seen that the small fault has begun to activate. When the working face advances to 140m, the water in the bottom aquifer completely breaks through the small fault and has formed a stable water-conducting channel, with the water pressure value becoming 0.001MPa. The water pressure value remains basically unchanged as the working face continues to advance.

[0071] In-depth analysis reveals that the delayed water inrush induced by small faults can be divided into three stages, such as... Figure 16 As shown, they are respectively: I. Initial coal seam floor failure stage ( Figure 16 (See above), II. Mid-term small fault damage and slippage failure stage ( Figure 16 (Middle image), III Late stage of water-diverting channel erosion formation ( Figure 16(See diagram below). I. The initial stage of coal seam floor failure occurs before the working face exposes the small fault and 30-40m after it has passed the fault. During this stage, influenced by mining activity, the floor maintains a certain depth of failure and moves forward, forming the coal seam floor failure zone. Near the small fault, the depth of floor failure increases to some extent. II. The intermediate stage of small fault damage and slippage failure occurs when the upper and lower walls of the small fault are subjected to the combined effects of mine pressure and water pressure, resulting in structural instability. This stage is relatively short, occurring 30-40m after the small fault has passed the fault. At a certain stage; the later stage of the water-conducting channel erosion formation is formed on the basis of the failure and instability of the upper and lower walls of the small fault. The upper and lower walls of the fault slip and move, and the high-pressure water in the bottom plate breaks upward along the fracture zone of the small fault and the fracture channel of the damaged surrounding rock. During the high-pressure water seepage process, it will inevitably erode the fine particles in the original fractures. The water-conducting channel will become larger as erosion occurs. However, after the high-pressure water seepage carries out the fine particles, the water-conducting channel is basically formed, and the water inrush volume in the goaf will remain basically unchanged.

[0072] This embodiment analyzes the failure characteristics of the base plate, displacement changes of the base plate and the small fault, stress changes of the base plate and the small fault, and water pressure changes of the base plate aquifer before and after the working face of a confined aquifer pushes over a small fault through a non-hydrophilic similarity simulation test. The main conclusions are as follows: (1) As the working face advances and gradually approaches the small fault, the roof of the coal seam gradually forms a caving zone, a fracture zone, and a bending subsidence zone. The floor of the coal seam is subjected to concentrated lateral stress from the roof strata, resulting in certain damage and failure. A floor failure zone is formed within a certain range of the floor and the small fault. After the working face pushes past the fault, the floor of the coal seam undergoes upward bending deformation under the horizontal stress of mining. Slippage of the hanging wall and footwall occurs at the small fault, which is a necessary condition for water inrush.

[0073] (2) The vertical stress of the working face floor plate is affected by mining activities, and the changes in the floor plate exhibit obvious regularity. However, the stress changes vary depending on the location within the working face. In the middle of the working face, the floor plate stress increases, decreases, and then gradually increases again. Near the opening cut and the stop line of the working face, it only experiences two stages: increase and decrease. The stress in the hanging wall and footwall of the fault is initially affected by the pressure of the advance support, and the floor plate stress shows an initial gradual increase followed by a rapid decrease. Later, affected by the self-weight of the collapsed roof rock, the stress increases to some extent, but it cannot return to the original rock stress state.

[0074] (3) The delayed water inrush induced by small faults can be divided into three stages: the initial stage of coal seam floor failure, the intermediate stage of small fault slippage failure, and the later stage of water-conducting channel erosion formation. The initial stage of coal seam floor failure occurs before the working face exposes the small fault and 30-40 m after pushing past the small fault. The intermediate stage of small fault damage and slippage failure occurs when the upper and lower plates of the small fault are subjected to structural failure and instability under the combined action of mine pressure and water pressure. This stage is relatively short. The later stage of water-conducting channel erosion formation occurs after the upper and lower plates of the small fault fail and become unstable, during which the seepage gradually increases.

[0075] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A non-hydrophilic similarity simulation test system, characterized in that: It includes a two-dimensional model test bench, a loading device, a first water pressure supply device, a non-hydrophilic similar model, a sealing structure, and a detection system; The two-dimensional model test bench includes a base (10), a reaction frame set on the base (10), an inner frame fixed on the base (10) and located inside the reaction frame, and several transparent plates (20) detachably set on the inner frame. The non-hydrophilic similar model is disposed within the base (10); the non-hydrophilic similar model is made of a non-hydrophilic similar material; The loading device includes a first transverse cylinder (1) installed on one side of the reaction frame, a second transverse cylinder (2) installed on the other side of the reaction frame, a vertical cylinder (3) installed on the top of the reaction frame, a first push plate (4) for padding between the model and the first transverse cylinder (1), a second push plate (5) for padding between the non-hydrophilic similar model and the second transverse cylinder (2), and a loading cover plate (6) for padding between the model and the vertical cylinder (3). The first water pressure supply device includes a plurality of bags (11) and an air supply device for supplying air to the bags (11); The second water pressure supply device includes a nitrogen cylinder, a water storage tank, and a water pressure control system; The sealing structure includes a side pressure plate (18) and a middle pressure plate (19) that are detachably installed on the outside of the inner frame. The transparent plate (20) can be pressed and fixed on the inner frame by the side pressure plate (18) and the middle pressure plate (19). The detection system includes a high-speed camera positioned facing the non-hydrophilic similar model, several pressure sensors (13), and a static stress-strain test and analysis system for analyzing the data from the pressure sensors (13).

2. The non-hydrophilic similarity simulation test system according to claim 1, characterized in that: The non-hydrophilic similarity model material uses transparent water-based polyurethane, cement, and dimethicone as binders, fine dry sand and barite powder as aggregates, and is mixed with an appropriate amount of water; the proportions are adjusted according to the basic physical and mechanical parameters of each rock layer.

3. The non-hydrophilic similarity simulation test system according to claim 1, characterized in that: The steps for creating the non-hydrophilic similarity model include: The raw materials of each rock layer are prepared layer by layer to obtain rock layer similar materials, and then molded; each layer of rock layer similar materials is placed in the space enclosed by the base (10), the first push plate (4), the second push plate (5) and the transparent plates (20) on both sides, and the top surface of the rock layer similar materials is smoothed to the corresponding height, and then mica sheets are sprinkled on it; the above steps are repeated until the maximum height is reached; During the molding process, measuring points are arranged and faults are simulated; After the model is completed, let it sit naturally until it is completely dry, which takes 2 to 3 weeks.

4. The non-hydrophilic similarity simulation test system according to claim 3, characterized in that: Each rock layer is 0.5-3.0 cm thick; after each layer of raw materials is mixed evenly, it is filled within 5-10 minutes.

5. A similarity simulation test method using the non-hydrophilic similarity simulation test system as described in any one of claims 1 to 4, characterized in that, In the first stage, the first model was constructed using the first water pressure supply device and excavated to study the characteristics of rock strata damage and fault damage activation instability before and after the working face on the confined aquifer pushed over the small fault. In the second stage, a second model was constructed using a second hydraulic pressure device and excavated to study the activation and water inrush mechanism of the small fault before and after the working face on the confined aquifer pushed past the small fault; the similarity simulation test method includes the following steps: Phase 1: Step S11: Lay out a non-hydrophilic similar model and arrange measuring points, simulated faults and bags (11) during the laying process; the bags (11) are laid flat in the rock strata of the simulated aquifer in the non-hydrophilic similar model; the measuring points are arranged in the rock strata of the bottom plate of the coal seam to be measured and in the rock strata of the upper and lower plates of the simulated small fault; white light calcium carbonate is applied to the front of the model as a base color, and uneven black spots are dotted on the front of the model with a brush so that the high-speed camera can monitor the deformation of the coal seam bottom plate; Step S12: After the model is air-dried, use the air supply device to inject air into the bag (11) and keep the pressure constant. Debug and balance the static stress-strain test and analysis system, and then carry out simulated excavation. The excavation is carried out in multiple stages. Use image analysis software to analyze the deformation value of the bottom rock layer after each excavation. Monitor stress changes in real time during the model excavation process, continuously observe the damage of the top and bottom plates, and collect photos in real time through a high-speed camera. Step S13: After excavation, analyze the crack propagation, stress, and displacement changes in the coal seam floor and small faults; Phase Two: Step S21: Lay out a non-hydrophilic similar model. During the laying process, arrange measuring points and simulated faults, and seal the joints between transparent plates (20) except for the excavation location with sealant. The measuring points are arranged in the bottom rock strata of the coal seam to be tested and in the upper and lower rock strata of the simulated small fault. Step S22: After the model is air-dried, water is introduced into the bottom of the model using the second water pressure supply device and the pressure is kept constant. The water in the bottom aquifer flows only through the mining-induced fractures. The static stress-strain test and analysis system is debugged and balanced, and then simulated excavation is carried out. The excavation is carried out in multiple stages. During the model excavation, stress changes are monitored in real time, and the damage to the top and bottom plates is continuously observed. Step S23: After excavation, analyze the characteristics of delayed water inrush at the bottom plate during the activation of small faults and the water conduction process at the bottom plate.

6. The non-hydrophilic similarity simulation test method according to claim 5, characterized in that: In step S11, the steps for creating the simulated fault are as follows: During the model laying process, steel plates are embedded to simulate faults. The shape of the steel plates is customized according to the specific shape of the small faults. When the fault simulation reaches the pinch-out stage, the steel plates (12) simulating the small faults are extracted one by one, and mixed dry similar materials are injected into the small faults to ensure the accuracy and continuity of the small fault simulation.

7. The non-hydrophilic similarity simulation test method according to claim 6, characterized in that: The process for fabricating similar materials used to simulate faults is as follows: Based on the thickness of the simulated fault, rock particles of different sizes are mixed together, and cement and gypsum are added; cement and gypsum each account for 3% to 5% of the total mass of the rock particles; the mixture is then injected into the fault; the rock particles of the simulated fault are selected from three particle size grades from 0~0.5mm, 0.5~1.0mm, 1.0~2.0mm, 2.0~4.0mm, 4.0~6.0mm, and 6.0~8.0mm according to the fault characteristics, and the mass of rock particles of each particle size grade is calculated using a continuous gradation formula.

8. The non-hydrophilic similarity simulation test method according to claim 6, characterized in that: The rock particles selected had a particle size distribution of 0.

4. The corresponding mass percentages of 0~0.5mm, 0.5~1.0mm, and 1.0~2.0mm rock particles were 57.4%, 18.4%, and 24.2%, respectively.

9. The non-hydrophilic similarity simulation test method according to claim 6, characterized in that: The dimensions of the non-hydrophilic similar model are 1000×1000×200mm. When excavating the model, it is excavated from one side of the model, 5cm at a time, for 16 times, for a total of 80cm, simulating the working face advancing 160m.

10. The non-hydrophilic similarity simulation test method according to claim 9, characterized in that: A measuring line is arranged in the bottom strata of the coal seam to be tested, with a total of 9 pressure sensors (13). The distance between two adjacent pressure sensors (13) is 10cm. One pressure measuring line is arranged in the upper and lower walls of the small fault, and the vertical spacing of the pressure sensors (13) is 15cm.

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