A two-dimensional physical similarity simulation test device and method for fluid-solid coupling in coal mining

Abstract

The invention discloses a two-dimensional physical similarity simulation test device and method for fluid-solid coupling of coal seam mining. The device is composed of a fluid-solid coupling physical similarity model steel frame, a vertical loading device, a lateral loading device, an aquifer, and a water supply test device. The fluid-solid coupling physical similarity model steel frame is composed of a solid base, two side fixed vertical pillars, a hollow steel plate top beam welded and fixed to the vertical pillars, and front and rear side channel steels. The vertical loading device is composed of an air bag, an air pipe, a pressure gauge, an air inlet valve, a pressure relief valve, and a high-pressure N 2 The test device is composed of a gas cylinder, the side loading device is composed of an electric hydraulic jack combination and a push plate, the aquifer is set as follows: the rock strata for the physical similarity simulation of fluid-solid coupling in coal seam mining are all made of the designed proportions of similar materials of the aquiclude and the aquifer, and the water supply test device is set as follows: the aquifer is supplied with water through a water supply hose connected to the aquifer water source tank.

Description

Technical Field

[0001] The invention relates to a fluid-solid coupling two-dimensional physical similarity simulation test device and method for coal seam mining, belonging to the field of coal mining physical similarity simulation experiments. Background Art

[0002] The problem of mine water inrush faced by underground coal mining is becoming increasingly prominent. Physical similarity simulation test is one of the important means to study the deformation and damage of roof and floor rock strata caused by coal seam mining and the evolution process of groundwater hydrological cycle. The physical similarity simulation test method is used to reproduce the deformation, fracture and movement of surrounding rock caused by coal seam excavation, analyze the periodic deformation and damage process of surrounding rock and the characteristics of groundwater hydrological cycle changes, and provide a scientific basis for the production practice of coal mining engineering.

[0003] In the traditional fluid-solid coupling physical simulation test of coal mining, the impact of coal seam mining on aquifers is mainly judged by the height of water-conducting fissures. The physical simulation of aquifers is mostly considered to use closed water storage belts with non-cemented fine sand, gravel and other materials, and connect to the pressurized water supply source for setting. However, in the actual application of two-dimensional physical similarity simulation experiments, after the laying and drying of two-dimensional physical similarity simulation experimental materials, when the front channel steel is ready to be removed for coal seam excavation and optical observation of water-conducting fissures, water belts or film-like similar simulation aquifer materials are subjected to the overlying rock formations and lateral stresses. The "front unconstrained and internally uncemented" physical similarity simulation aquifer materials are very likely to cause accidental collapse due to improper setting, resulting in the early failure of the two-dimensional physical similarity simulation experiment of fluid-solid coupling in coal seam mining. Secondly, the use of closed water storage belts with non-cemented fine sand, gravel and other materials inside to set up simulated aquifers will cause an overall problem of the physical strength of the aquifer structure itself. The aquifer is also divided into a rock layer in the simulated stratum, and the upper and lower interfaces of the rock layer are constrained by the water belt, making it impossible for it to break and generate cracks. Similarly, the collapse of the simulated aquifer in the collapse zone is hindered, making it difficult to achieve the movement of the simulated aquifer by the water belt. Summary of the invention

[0004] The present invention aims to propose a method for setting up an aquifer in a fluid-solid coupling physical similarity simulation test of coal seam mining, so as to solve the technical problems of experimental accidents caused by unreasonable aquifer setting in the existing fluid-solid coupling physical similarity simulation technology, and to solve the technical problems of the aquifer rock migration being affected by constraints during coal seam excavation.

[0005] To achieve the above objectives, the present invention mainly carries out technical transformation on the similar simulation material layout system and pressurized water supply system of the aquifer in the fluid-solid coupling physical similarity simulation test of coal seam mining, and innovates the connection method of the two systems.

[0006] The invention provides a two-dimensional physical similarity simulation test device for fluid-solid coupling of coal seam mining, which is composed of a fluid-solid coupling physical similarity model steel frame, a vertical loading device, a lateral loading device, an aquifer, and a water supply test device.

[0007] The steel frame of the fluid-solid coupling physical similarity model consists of a solid base, fixed vertical struts on both sides, a hollow steel plate top beam welded and fixed to the vertical struts, and channel steels on both sides. Furthermore, the internal space size of the steel frame is 3000mm*2000mm*200mm, and the channel steels on both sides are 20#B type, and the channel steels are fixed to the vertical struts on both sides through alignment hole bolts.

[0008] The vertical loading device consists of an airbag, an air pipe, a pressure gauge, an air intake valve, a pressure relief valve and a high-pressure N2 gas cylinder. The airbag is set inside the top beam by adjusting the air intake valve. The top beam is a hollow steel plate. The airbag is connected to the high-pressure N2 gas cylinder through the air pipe. A pressure gauge is set on the top of the high-pressure N2 gas cylinder. An air intake valve is set at one end of the airbag connected to the high-pressure N2 gas cylinder, and a pressure relief valve is set at the other end. The pressure gauge is observed to determine the vertical load value applied by the airbag to the top of the model. After the test, the air intake valve is closed and the pressure relief valve is slowly opened to relieve the pressure of the airbag.

[0009] The lateral loading device consists of an electric hydraulic jack combination and a push plate, wherein the electric hydraulic jack combination consists of an electric control console and four hydraulic jacks. The hydraulic jack is placed horizontally, one end of which is fixed on a vertical support and the other end is fixed on a push plate that can move laterally. The hydraulic jack simulates horizontal stress by applying lateral pressure. The upper and lower ends of the push plate are connected to the top beam and the base by means of sliding rails.

[0010] Aquifer setting: The rock formations for the fluid-solid coupling physical similarity simulation of coal seam mining are all made using the designed proportions of similar materials for aquifers and aquicludes. The designed proportions of the similar materials for aquifers and aquicludes are determined by similar material proportioning experiments based on the similarity ratios of various physical strengths and hydraulic parameters of the aquifers and aquicludes in the experimental requirements; the aquifer-similar materials are partially wrapped by rubber hoses, and both ends are embedded in the aquifer-similar simulation materials; the aquiclude-similar materials use river sand, paraffin, vaseline, calcium carbonate and gypsum with uniform particle size of 0-2mm; the aquifer-similar materials use 3mm thick rubber hoses with 20-50mm large-size smooth pebbles and 5-8mm gravel particles to form skeleton particles to simulate the aquifer, and the specific operations are as follows:

[0011] Aquifer similarity simulation setting water hose shape setting: a 3mm thick rubber water hose is laid flat in a 3000mm wide steel frame in the fluid-solid coupling physical similarity model. The length and diameter of the water hose need to be selected according to the test plan to meet the following conditions: ① The front and rear sides of the rubber water hose are laid close to the channel steel; ② The two ends of the rubber water hose are sealed with AB glue for 100mm; ③ The distance between the sealing end of the rubber water hose and the steel frames on the left and right sides is 200mm. Holes with a spacing of 2cm and an aperture of 2mm are arranged on the upper and lower contact surfaces of the water hose in contact with the aquifer material, so that the water in the aquifer can seep from the contact surface of the rock layer through the dense holes into the upper and lower rock layers. The aquifer similarity simulation water hose is paved with 20~50mm large-size smooth pebbles and 5~8mm gravel particles inside and outside to form skeleton particles. The center of the aquifer rubber water hose is a water supply hose. In addition, 4 aquifer water level monitoring pipes are evenly distributed.

[0012] The water supply test device is set up as follows:

[0013] The water supply hose is connected to the water source tank of the aquifer to supply water to the aquifer. The water supply valve controls the water flow rate. The water source penetration pressure is provided to the simulated water bag mainly by utilizing the height difference between the water level of the water source tank and the water level of the rubber water hose inlet. The water level setting of the water source tank is achieved by adjusting the height of the movable door crane.

[0014] The aquifer device is connected to the water supply test device, and the connection relationship between the two is as follows:

[0015] The hole in the middle and upper part of the back side of the simulated aquifer water hose is used as the aquifer water injection port. The hole in the rubber water hose and the connection method with the water supply source tank are as follows:

[0016] The connecting device mainly includes the following parts: water supply hose, fixed stainless steel box, hollow outer concave ring rubber plug, reducing external joint, full external threaded pipe, bellows, water hose connecting joint, silicone gasket, water filter net, stainless steel hoop.

[0017] ① Open a hole in the back channel steel as the water inlet for the simulated water hose supply in the aquifer, weld and fix a stainless steel iron box inside the water inlet, and install a water hose pipe joint at the water inlet in the middle and upper part of the back side of the water hose, and install a silicone gasket at the connection between the water hose pipe joint and the water hose water inlet;

[0018] ②Install a bellows in a fixed stainless steel box, and place a silicone gasket and a water filter at the connection between the bellows and the hose pipe joint. The bellows curl length meets the vertical displacement of the aquifer (the aquifer, as the basic rock layer, is displaced vertically with the mining of the underlying coal seam, which is mainly related to the excavation coal seam height set in the model scheme and the vertical distance between the aquifer and the excavated ore body. The key is that the vertical displacement range does not exceed the excavation coal seam height), ensuring that the aquifer is not affected during the rock movement of coal seam mining;

[0019] ③The connecting head at the other end of the corrugated pipe is connected to the reducing external joint through a full external threaded pipe. Silicone gaskets must be placed on both ends of the full external threaded pipe, and a water filter net must be installed at the silicone gasket to ensure that the water supply pipeline is unobstructed; one end of the reducing external joint is an internal threaded interface connected to the full external threaded pipe, and the other end is an external threaded interface connected to the water supply hose.

[0020] ④ Use a hollow concave ring rubber plug to fix it at the opening of the back channel steel to seal the aquifer space. The diameter of the middle opening of the hollow concave ring rubber plug should be suitable for the passage of the reducing external joint and the bellows connector, and vaseline is used at the contact point for lubrication and water blocking.

[0021] ⑤ The connection between the water supply hose and the reducing external joint is achieved by wrapping the waterproof tape around the reducing external joint connection head and then nesting it with the water supply hose. At the same time, a stainless steel iron hoop is used to tighten and fix the connection at the water supply hose connection.

[0022] The connection arrangement between the water level monitoring pipe and the rubber water hose is completely consistent with the connection arrangement between the water supply hose and the rubber water hose mentioned above.

[0023] The present invention provides a fluid-solid coupling two-dimensional physical similarity simulation test method, comprising the following steps:

[0024] (1) Monitor the geological and hydrogeological conditions under the field conditions of fluid-solid coupling physical similarity simulation as needed, generalize and design the selection and proportioning parameters of similar materials for each rock layer within the model scale, and determine the vertical ground stress and lateral surrounding rock stress levels that need to be loaded on the model;

[0025] (2) According to the above-mentioned fluid-solid coupling physical similarity simulation experiment design plan, various rock materials containing water-blocking layers are configured, and channel steels are installed layer by layer from bottom to top on the rear side of the similar model steel frame. The base line for laying each water-blocking layer material is laid out on the inner channel steel using ink lines. The front channel steel is installed layer by layer according to the laying of similar materials in a layer-by-layer compaction method until the laying of similar materials is completed. At the same time, waterproof glass glue is injected at the joints between channel steels and between channel steels and vertical pillars to block water;

[0026] ① When laying similar materials of each aquifer-containing rock layer, when laying similar materials of the aquifer, use a rubber hose with 20~50mm large-size smooth pebbles and 5~8mm gravel particles built in it to form skeleton particles as aquifer-like materials, and set drainage holes on the upper and lower sides of the rubber hose to ensure the water pressure effect of the aquifer on the upper and lower aquifers;

[0027] ②The rubber hose is connected to the corresponding opening of the channel steel as the water inlet hose, and the rubber hose is connected to the water supply hose of the water supply source tank;

[0028] ③ Generally, soil pressure sensors and pore water pressure sensors are used to dynamically monitor the changes in formation pressure and pore water pressure of key layers of concern determined according to experimental requirements. Therefore, when laying similar materials of rock layers containing aquicludes in similar simulation experimental schemes, soil pressure sensors and pore water pressure sensors need to be pre-buried at the corresponding positions of key monitoring layers according to the experimental scheme design;

[0029] (3) After the similar simulation materials of the model are laid, a vertical loading device is installed on the uppermost surface of the model material. The uppermost end of the model steel frame is a welded and fixed hollow top beam. A vertical loading airbag is designed inside the top beam, and the lower end surface of the loading airbag is in direct contact with the model material.

[0030] (4) After the similar simulation materials are laid, they are dried to meet the strength requirements of the experimental design. The front channel steel of the model steel frame is removed, and the exposed surface of the similar material is polished and leveled with sandpaper. A 5 mm thick 0# transparent lubricating silicone grease is evenly applied on the surface to make a transparent tempered glass that is sealed and waterproof. The tempered glass is fixed to the vertical pillars on both sides of the model steel frame with bolts;

[0031] (5) Determine the vertical loading and lateral loading parameter values ​​of the similar model according to the experimental design plan to load the similar model. At the same time, open the water supply valve to saturate the aquifer in the model and check the leakage points of the model steel frame. Inject waterproof glass glue to block the leakage points in time to ensure the water tightness of the model.

[0032] (6) Coal seam excavation was carried out according to the experimental design plan. The rock stress and pore water pressure changes were monitored in real time using pressure sensors. The digital image correlation method was used to dynamically monitor the movement of the rock formations. The mechanism of water filling of the aquifer in the overburden during coal seam mining to the mining working face was analyzed.

[0033] Beneficial effects of the present invention:

[0034] (1) The method for setting up a water belt simulated aquifer proposed in the present invention solves the problem that the physically similar simulated aquifer materials such as water belts or thin films, which have no front constraints and no internal bonding, are very likely to collapse due to improper setting when subjected to the overlying rock strata and lateral stress.

[0035] (2) The water belt simulated aquifer connection water supply device and the method of setting it up in the model steel frame proposed in the present invention creatively solve the problem that the simulated aquifer is a rock layer in the simulated stratum, and among the rock layers that undergo rock movement during coal seam excavation, the simulated water-bearing rock layer developed in the collapse zone can achieve a large vertical displacement that is more consistent with the actual situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1This is a diagram of the two-dimensional physical similarity simulation test device for fluid-solid coupling in coal mining.

[0037] Figure 2 This is the layout diagram of the aquifer rubber hose.

[0038] Figure 3 This is the arrangement diagram of the holes on the upper and lower ends of the aquifer rubber hose.

[0039] Figure 4 The connection diagram of the aquifer rubber hose and the water supply test device (corresponding to Figure 2 (section view along line AA' in the figure).

[0040] In the figure, 1 is a solid base, 2 is a vertical support, 3 is a top beam, 4 is a channel steel, 5 is an air bag, 6 is an air pipe, 7 is a pressure gauge, 8 is an air intake valve, 9 is a pressure relief valve, 10 is a high-pressure N2 gas cylinder, 11 is a push plate, 12 is an electric control console, 13 is a hydraulic jack, 14 is a rubber water hose, 15 is an aquifer water level monitoring pipe, 16 is a water supply hose, 17 is a water supply source tank, 18 is a fixed stainless steel box, 19 is a hollow outer concave ring rubber plug, 20 is a reducing external joint, 21 is a full external threaded pipe, 22 is a bellows, 23 is a water hose pipe joint, 24 is a silicone gasket, 25 is a water filter net, 26 is a stainless steel iron hoop, 27 is a door hanger, 28 is a water supply valve, and 29 is an aquifer. DETAILED DESCRIPTION

[0041] The present invention is further illustrated by the following examples, but is not limited to the following examples.

[0042] Example 1: Simulation test of flow-solid coupling of overburden aquifer on working face during coal mining

[0043] (1) Based on the geological and hydrogeological conditions of the field conditions for the fluid-solid coupling physical similarity simulation, the selection and proportioning parameters of similar materials for each rock layer within the model scale are generalized and designed, and the vertical ground stress and lateral surrounding rock stress levels that need to be loaded on the model are determined.

[0044] (2) According to the above-mentioned fluid-solid coupling physical similarity simulation experiment design, various rock materials containing impermeable layers are configured, and a similar model steel frame ( Figure 1 ) The channel steels required for the design are installed layer by layer on the rear side from bottom to top. The ink line is used to design the baseline for laying each waterproof layer material on the inner channel steel layout experimental plan. The front channel steel is installed layer by layer according to the laying of similar materials in a layer-by-layer compaction method until the laying of similar materials is completed. At the same time, waterproof glass glue is injected at the connection between the channel steel and the channel steel and the vertical support 2 to block water.

[0045] ① When laying similar materials of each aquifer-containing rock layer, when laying similar materials of the aquifer, a rubber hose 14 with 20~50mm large-size smooth pebbles and 5~8mm gravel particles built in is used as aquifer similar materials. The laying plan of the rubber hose 14 is shown in Figure 2 In order to ensure the water pressure of the aquifer on the upper and lower aquicludes, drainage holes are set on the upper and lower sides of the rubber water hose 14. Figure 3 .

[0046] ② The rubber hose 14 is connected to the corresponding channel steel opening as a water inlet hose 16, and the rubber hose 14 is connected to the water supply hose 16 of the water supply source tank 17;

[0047] ③ Generally, soil pressure sensors and pore water pressure sensors are used to dynamically monitor the changes in formation pressure and pore water pressure of the key layers in the design of experimental schemes. Therefore, when laying similar materials containing aquicludes in similar simulation experimental schemes, soil pressure sensors and pore water pressure sensors need to be pre-buried in the corresponding positions of the key monitoring layers according to the experimental scheme design.

[0048] (3) After the similar simulation materials of the model are laid, a vertical loading device is installed on the uppermost surface of the model material. The uppermost end of the model steel frame is a welded and fixed hollow top beam 3, and a vertical loading airbag 5 is designed inside the top beam. The lower end surface of the loading airbag is in direct contact with the model material.

[0049] (4) After the similar simulation material is laid, it is dried to meet the strength requirements of the experimental design scheme. The front channel steel of the model steel frame is removed, and the surface of the exposed similar material is polished and leveled with sandpaper. A transparent tempered glass with a thickness of 5 mm and a 0# transparent lubricating silicone grease is evenly applied on the surface to make it sealed and waterproof. The tempered glass is fixed to the vertical pillars 2 on both sides of the model steel frame by bolts.

[0050] (5) Load the similar model according to the vertical loading and lateral loading parameter values ​​of the similar model determined by the experimental design plan. At the same time, open the water supply valve 28 to saturate the aquifer in the model with water and check the leakage points of the model steel frame. Inject waterproof glass glue to block the leakage points in time to ensure the water tightness of the model.

[0051] (6) Coal seam excavation was carried out according to the experimental design plan. The rock stress and pore water pressure changes were monitored in real time using pressure sensors. The digital image correlation method was used to dynamically monitor the movement of the rock formations. The mechanism of water filling of the aquifer in the overburden during coal seam mining to the mining working face was analyzed.

[0052] The coal seam mining fluid-solid coupling two-dimensional physical similarity simulation test device set by the present invention is as follows Figure 1As shown: It consists of a fluid-solid coupling physical similarity model steel frame, a vertical loading device, a lateral loading device, an aquifer device, and a water supply test device.

[0053] The steel frame of the fluid-solid coupling physical similarity model consists of a solid base 1, fixed vertical struts 2 on both sides, a hollow steel plate top beam 3 welded and fixed to the vertical struts 2, and front and rear channel steels 4. The internal space size of the steel frame is 3000mm*2000mm*200mm, the front and rear channel steels 4 are both 20#B type, and the channel steels 4 are fixed to the vertical struts 2 on both sides by alignment hole bolts.

[0054] The vertical loading device is composed of an airbag 5, an air pipe 6, a pressure gauge 7, an air inlet valve 8, a pressure relief valve 9 and a high-pressure N2 gas cylinder 10. By adjusting the air inlet valve 8, the airbag 5 is arranged inside the hollow of the top beam 3. The airbag 5 is connected to the high-pressure N2 gas cylinder 10 through the air pipe 6. A pressure gauge 7 is arranged on the top of the high-pressure N2 gas cylinder 10. An air inlet valve 8 is arranged at one end where the airbag 5 is connected to the high-pressure N2 gas cylinder 10, and a pressure relief valve 9 is arranged at the other end. The pressure gauge 7 is observed to determine the vertical load value applied by the airbag 5 to the top of the model. After the test, the air inlet valve is closed, and the pressure relief valve is slowly opened to relieve the pressure of the airbag.

[0055] The lateral loading device consists of an electric hydraulic jack combination and a push plate, wherein the electric hydraulic jack combination consists of an electric control console 12 and four hydraulic jacks 13. The hydraulic jack is placed horizontally, one end of which is fixed to the vertical support 2, and the other end is fixed to the push plate 11 which can be moved laterally. The hydraulic jack 13 simulates horizontal stress by applying lateral pressure. The upper and lower ends of the push plate 11 are connected to the top beam 3 and the base 1 by means of slide rails.

[0056] Aquifer setting: The rock formations used in the fluid-solid coupling physical simulation of coal seam mining are all made using the design ratio of aquiclude and aquiclude similar materials. Among them, the aquiclude similar materials use river sand, paraffin, vaseline, calcium carbonate and gypsum with a particle size of 0-2mm and uniform gradation; the aquifer similar materials use 3mm thick rubber water hose 14 with 20-50mm large-size smooth pebbles and 5-8mm gravel particles to form a skeleton particle simulation aquifer, and the specific operations are as follows:

[0057] Aquifer similarity simulation setting water hose shape setting: a 3mm thick rubber water hose is laid flat in a 3000mm wide steel frame in the fluid-solid coupling physical similarity model. The length and diameter of the water hose need to be selected according to the test plan to meet the following conditions: ① The front and rear sides of the rubber water hose are laid close to the channel steel; ② The two ends of the rubber water hose are sealed with AB glue for 100mm; ③ The distance between the sealing end of the rubber water hose and the steel frames on the left and right sides is 200mm. Holes with a spacing of 2cm and an aperture of 2mm are arranged on the upper and lower contact surfaces of the water hose in contact with the aquifer material, so that the water in the aquifer can seep from the contact surface of the rock layer through the dense holes into the upper and lower rock layers. The inside and outside of the aquifer similarity simulation water hose are paved with 20~50mm large-size smooth pebbles and 5~8mm gravel particles to form the skeleton particles. The center of the aquifer rubber water hose 14 is a water supply hose 16. In addition, 4 aquifer water level monitoring pipes 15 are evenly distributed. The detailed setting of the aquifer rubber water hose 14 is shown in Figure 2 and Figure 3 .

[0058] The water supply test device is set up as follows:

[0059] The water supply hose 16 is connected to the water source tank 17 of the aquifer to supply water to the aquifer. The water supply valve 28 controls the water supply flow rate. The water source penetration pressure is provided to the simulated water bag mainly by utilizing the height difference between the water level of the water source tank 17 and the water level of the water inlet of the rubber water hose 14. The water level setting of the water source tank 17 is achieved by adjusting the height of the movable door hanger 27. For detailed water supply test system settings for similar simulations of aquifers, see Figure 1 .

[0060] The aquifer device is connected to the water supply test device, and the connection relationship between the two is as follows:

[0061] The opening in the middle and upper part of the back side of the simulated aquifer water belt is used as the aquifer water injection port, and the opening of the rubber water belt 14 and the connection method with the water supply water tank 17 are as follows: Figure 4 As shown:

[0062] The water hose injection hole and water hose connection method mainly include:

[0063] ① Open a hole in the back channel steel 4 as the water inlet for the simulated water hose supply of the aquifer, weld and fix the stainless steel box 18 inside the water inlet, and install a water hose pipe joint 23 at the water inlet in the middle and upper part of the back side of the water hose. A silicone gasket 24 must be installed at the connection between the water hose pipe joint 23 and the water hose water inlet;

[0064] ②According to Figure 3As shown, a bellows 22 is installed in the fixed stainless steel box 18, and a silicone gasket 24 and a water filter 25 are placed at the connection between the bellows 22 and the water hose joint 23, wherein the curled length of the bellows 22 must meet the vertical displacement of the aquifer rock formation to ensure that the aquifer is not affected during the rock movement process of coal seam mining;

[0065] ③ The connecting head at the other end of the corrugated pipe 22 is connected to the reducing external joint 20 through the full external threaded pipe 21 and installed. Silicone gaskets 24 must be placed on both ends of the full external threaded pipe 21, and a water filter net 25 is installed at the silicone gasket 24 of the reducing external joint 20 to ensure that the water supply pipeline is unobstructed; one end of the reducing external joint 20 is an internal threaded interface connected to the full external threaded pipe 21, and the other end is an external threaded interface connected to the water supply hose 16.

[0066] ④ Use the hollow outer concave ring rubber plug 19 to fix it at the opening of the back channel steel 4 to block the aquifer space. The hollow outer concave ring rubber plug 19 has a hole in the middle, and its hole diameter is suitable for the passage of the reducing external joint 20 and the bellows 22 connector, and vaseline is used to lubricate and block water at the contact part. The hollow outer concave ring rubber plug 19 is placed at the opening of the back channel steel 4 of the rubber hose 14, and the reducing external joint 20 is set in the hollow part inside. The outer side is a ring structure with a U-shaped groove, and its groove is connected to the channel steel.

[0067] ⑤ The water supply hose 16 is connected to the reducing external joint 20 by wrapping the waterproof tape around the reducing external joint 20 and then nesting it with the water supply hose 16. At the same time, a stainless steel iron hoop 26 is used to tighten and fix the connection at the joint of the water supply hose 16.

[0068] ⑥ The connection setting of the aquifer water level monitoring pipe 15 and the rubber water hose 14 similar to the aquifer simulation is completely consistent with the setting of the above-mentioned water supply hose 16.

[0069] Here, the overall waterproofness setting of the aquifer similarity simulation device is as follows: In order to facilitate the real-time observation and research of the overburden rock movement after coal seam excavation, it is necessary to strengthen the sufficient sealing and waterproofing measures of the water-proof layer material in the fluid-solid coupling similarity model. First, after the similar simulation material is laid, the front channel steel is removed to prepare for the laying of the transparent organic glass plate. Secondly, the transparent organic glass plate needs to be evenly coated with transparent lubricating silicone grease on the entire surface, and the coating thickness is adjusted according to the size of the surface to ensure the sealing and waterproofing between the layers of materials when the water-proof layer material moves. Finally, one side of the transparent organic glass plate coated with transparent lubricating silicone grease is in contact with the similar simulation material, and the contact between the steel frame frame and the transparent organic glass plate is sealed with a sealing strip, and the two are fixed with a U-shaped steel clamp. The above measures ensure the sealing and waterproofness of the two-dimensional physical similarity simulation device of fluid-solid coupling of coal seam mining.

Claims

1. A two-dimensional physical similarity simulation test device for fluid-solid coupling in coal seam mining, characterized by: It consists of a steel frame of a fluid-solid coupling physical similarity model, a vertical loading device, a lateral loading device, an aquifer, and a water supply test device. The steel frame of the fluid-solid coupling physical similarity model consists of a solid base, fixed vertical supports on both sides, a top beam welded and fixed to the vertical supports, and channel steels on both sides of the front and rear. The vertical loading device consists of an airbag, an air pipe, a pressure gauge, an air intake valve, a pressure relief valve and a high-pressure N2 gas cylinder. The airbag is arranged inside the top beam by adjusting the air intake valve. The top beam is a hollow steel plate. The airbag is connected to the high-pressure N2 gas cylinder through the air pipe. A pressure gauge is arranged on the top of the high-pressure N2 gas cylinder. An air intake valve is arranged at one end of the airbag connected to the high-pressure N2 gas cylinder, and a pressure relief valve is arranged at the other end. The lateral loading device is composed of an electric hydraulic jack combination and a push plate, wherein the electric hydraulic jack combination is composed of an electric control console and four hydraulic jacks. The hydraulic jack simulates horizontal stress by applying lateral pressure. The aquifer is: the rock formations for the fluid-solid coupling physical similarity simulation of coal seam mining are all made using the design ratio of similar materials of aquifers and aquicludes. The design ratio of similar materials of aquicludes and aquifers is determined by the similarity ratio of various physical strengths and hydraulic parameters of aquicludes and aquifers in the experimental requirements through similar material ratio experiments; the aquifer similar material is partially wrapped by a rubber water hose, and its two ends are built into the aquifer similar simulation material; The water supply test device is set up as follows: the water supply hose is connected to the water source tank of the aquifer to supply water to the aquifer, the water supply valve controls the water supply flow rate, and the water source penetration pressure is provided to the simulated water bag by utilizing the height difference between the water level of the water source tank and the water level of the rubber water hose inlet; the water level setting of the water source tank is achieved by adjusting the height of the movable door crane; The waterproof layer similar material adopts river sand, paraffin, vaseline, calcium carbonate and gypsum with uniform gradation of particle size 0-2mm; the aquifer similar material adopts 3mm thick rubber hose with built-in 20-50mm large-size smooth pebbles and 5-8mm gravel particles to form skeleton particles to simulate the aquifer, wherein the specific operation is: a 3mm thick rubber hose is laid flat in a 3000mm wide steel frame in the fluid-solid coupling physical similarity model, and the length and diameter of the hose need to be selected according to the test plan to meet the following conditions: ① The front and rear sides of the rubber hose are laid close to the channel steel; ② The rubber hose is placed on the front and rear sides of the hose; The two ends of the rubber water belt are sealed with AB glue to block water for 100mm; ③ The distance between the sealing end of the rubber water belt and the steel frames on the left and right sides is 200mm; holes with a spacing of 2cm and an aperture of 2mm are arranged on the upper and lower contact surfaces of the water belt in contact with the aquifer material, so that the water in the aquifer can seep into the upper and lower rock layers from the contact surface of the rock layer through the dense holes; the inside and outside of the water belt for similar simulation of the aquifer are paved with 20~50mm large-size smooth pebbles and 5~8mm gravel particles to form skeleton particles. The center of the aquifer rubber water belt is a water supply hose. In addition, 4 aquifer water level monitoring pipes are evenly distributed; The aquifer device is connected to the water supply test device. The connection device includes: water supply hose, fixed stainless steel box, hollow outer concave ring rubber plug, reducing outer joint, full outer threaded pipe, bellows, water hose pipe joint, silicone gasket, water filter net, stainless steel iron hoop; the upper middle opening on the back side of the simulated aquifer water hose is used as the aquifer water injection port, and the rubber water hose and the water supply hose connected to the water supply source tank are connected as follows: ① Open a hole in the back channel steel as the water inlet for the simulated water hose supply in the aquifer, weld and fix a stainless steel iron box inside the water inlet, and install a water hose pipe joint at the water inlet in the middle and upper part of the back side of the water hose, and install a silicone gasket at the connection between the water hose pipe joint and the water hose water inlet; ②Install a bellows in a fixed stainless steel box, and place a silicone gasket and a water filter at the connection between the bellows and the hose connection joint; ③The connector at the other end of the corrugated pipe is connected to the reducing external joint through a full external threaded pipe. Silicone gaskets are placed at both ends of the full external threaded pipe, and a water filter is installed at the silicone gasket at the end connected to the reducing external joint to avoid clogging of water channel particles and impurities, ensuring smooth water supply pipeline; ④ Use a hollow outer concave ring rubber plug to fix it at the opening of the back channel steel to seal the aquifer space. The middle part of the hollow outer concave ring rubber plug has a hole to allow the passage of the reducing external joint and the bellows connector, and vaseline is used at the contact part to lubricate and block water.

2. The coal seam mining fluid-solid coupling two-dimensional physical similarity simulation test device according to claim 1 is characterized by: The internal space size of the steel frame is 3000mm*2000mm*200mm. The channel steels on both the front and rear sides are 20#B type. The channel steels are fixed to the fixed vertical supports on both sides by means of alignment hole bolts.

3. The coal seam mining fluid-solid coupling two-dimensional physical similarity simulation test device according to claim 1 is characterized by: The hydraulic jack is placed horizontally, with one end fixed on a vertical support and the other end fixed on a push plate that can move laterally; the upper and lower ends of the push plate are connected to the top beam and the base by means of slide rails.

4. The coal seam mining fluid-solid coupling two-dimensional physical similarity simulation test device according to claim 1 is characterized by: The curled length of the bellows meets the vertical displacement of the aquifer rock layer, ensuring that the aquifer is not affected during the rock movement process of coal seam mining.

5. The coal seam mining fluid-solid coupling two-dimensional physical similarity simulation test device according to claim 1 is characterized by: One end of the reducing external joint is an internal thread interface for connecting a full external threaded pipe, and the other end is an external thread interface for connecting a water supply hose; the water supply hose is connected to the reducing external joint by wrapping a waterproof tape around the reducing external joint connector and then nesting and connecting the water supply hose, and at the same time, the connection is tightened and fixed at the water supply hose connector by a stainless steel iron hoop.

6. The coal seam mining fluid-solid coupling two-dimensional physical similarity simulation test device according to claim 1 is characterized by: The connection arrangement between the water level monitoring pipe and the rubber water hose is the same as the connection arrangement between the water supply hose and the rubber water hose.

7. A two-dimensional physical similarity simulation test method for fluid-solid coupling of coal seam mining, using the two-dimensional physical similarity simulation test device for fluid-solid coupling of coal seam mining according to any one of claims 1 to 6, characterized in that The following steps are involved: (1) Monitor the geological and hydrogeological conditions under the field conditions of fluid-solid coupling physical similarity simulation as needed, generalize and design the selection and proportioning parameters of similar materials for each rock layer within the model scale, and determine the vertical ground stress and lateral surrounding rock stress levels that need to be loaded on the model; (2) According to the above-mentioned fluid-solid coupling physical similarity simulation experiment design plan, various rock materials containing water-blocking layers are configured, and channel steels are installed layer by layer from bottom to top on the rear side of the similar model steel frame. The base line for laying each water-blocking layer material is laid out on the inner channel steel using ink lines. The front channel steel is installed layer by layer according to the laying of similar materials in a layer-by-layer compaction method until the laying of similar materials is completed. At the same time, waterproof glass glue is injected at the joints between channel steels and between channel steels and vertical pillars to block water; ① When laying similar materials of each aquifer-containing rock layer, when laying similar materials of the aquifer, use a rubber hose with 20~50mm large-size smooth pebbles and 5~8mm gravel particles built in it to form skeleton particles as aquifer-like materials, and set drainage holes on the upper and lower sides of the rubber hose to ensure the water pressure effect of the aquifer on the upper and lower aquifers; ②The rubber hose is connected to the corresponding opening of the channel steel as the water inlet hose, and the rubber hose is connected to the water supply hose of the water supply source tank; ③Use soil pressure sensors and pore water pressure sensors to dynamically monitor the changes in formation pressure and pore water pressure of the key layers in the experimental scheme design. Therefore, when laying similar materials of rock layers containing aquicludes in similar simulation experimental schemes, it is necessary to pre-bury soil pressure sensors and pore water pressure sensors at the corresponding positions of the key monitoring layers according to the experimental scheme design; (3) After the similar simulation materials of the model are laid, a vertical loading device is installed on the uppermost surface of the model material. The uppermost end of the model steel frame is a welded and fixed hollow top beam. A vertical loading airbag is designed inside the top beam, and the lower end surface of the loading airbag is in direct contact with the model material. (4) After the similar simulation materials are laid, they are dried to meet the strength requirements of the experimental design scheme. The front channel steel of the model steel frame is removed, and the exposed surface of the similar material is polished and leveled with sandpaper. A transparent tempered glass with a thickness of 5 mm and 0# transparent lubricating silicone grease is evenly applied on the surface to make it sealed and waterproof. The tempered glass is fixed to the vertical pillars on both sides of the model steel frame with bolts; (5) Determine the vertical loading and lateral loading parameter values ​​of the similar model according to the experimental design plan to load the similar model. At the same time, open the water supply valve to saturate the aquifer in the model and check the leakage points of the model steel frame. Inject waterproof glass glue to block the leakage points in time to ensure the water tightness of the model. (6) Coal seam excavation was carried out according to the experimental design plan. The rock stress and pore water pressure changes were monitored in real time using pressure sensors. The digital image correlation method was used to dynamically monitor the movement of the rock formations. The mechanism of water filling of the aquifer in the overburden during coal seam mining to the mining working face was analyzed.

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