Simulation Device and Method for Damage of Overlying Thick Aquifer with Multiple Water Sources Recharge in Coal Seam Mining

Abstract

The present application relates to a simulation device and method for multi-source recharge of damaged overlying thick aquifers in coal seam mining. Among them, the simulation device includes a box body, an aquifer recharge system and a vertical pressure relief component; the box body has an accommodation space, and a water-resistant layer, an aquifer and an overlying stratum pressurizing device located above the aquifer are laid from bottom to top in the accommodation space; the aquifer recharge system has a plurality of water injection devices, and the water injection devices are configured to inject water into different depth positions of the aquifer; the number of the vertical pressure relief components is multiple, and the multiple vertical pressure relief components are dispersedly arranged below the water-resistant layer and are configured to support the water-resistant layer and control the pressure relief at different positions of the water-resistant layer. The present application realizes the accurate simulation of the development process of mining-induced fractures and the change of the seepage field under mining in the thick aquifer.

Description

Technical Field

[0001] This application belongs to the technical field of coal mining, and more particularly relates to a simulation device and method for multi-source recharge of overlying thick aquifers damaged by coal seam mining. Background Art

[0002] In coal mining areas, especially in arid regions, the aquiferous strata are not only the water inrush sources of coal mine water inrush disasters, but also a natural storage space for precious natural resources - groundwater resources. For example, a certain basin is located in an arid and semi-arid area with a fragile ecological environment. The thick Cretaceous aquifer in the center of the basin (generally 300 - 800m) has a total water resource of about 7 billion cubic meters per year. As coal mining around the basin gradually extends towards the hinterland, the damage to the Cretaceous water body caused by mining and the induced eco-geological environment disasters have become increasingly prominent. Moreover, the groundwater seepage system of the thick Cretaceous aquifer in this basin has obvious particularities. The regional and local water flow systems overlap each other, each with different circulation depths, and have a special vertical multi-layered difference pattern and seepage patterns with various thick layered structures. In the northern part of the Cretaceous aquifer, the structure is relatively uniform. The seepage path is affected by the water head, and the seepage direction shows an obvious orthogonal tendency to the formation attitude direction. The water seepage path passes through different water-bearing rock layers, presenting a water flow pattern of multi-layer cross-strata seepage. In the southern part of the Cretaceous, the main seepage pattern is multi-layer bedding seepage. The hydraulic connection between the groundwater of each water-bearing rock group within the Cretaceous is significantly weakened compared to within the water-bearing rock group. Whether it is the regional or local water flow system, the overall seepage is along the internal stratification of the water-bearing rock group. The depth water head difference of each water-bearing rock group within the aquifer is obvious, with the characteristics of multi-layer bedding seepage pattern.

[0003] Currently, the following defects exist in the fluid-solid coupling similarity simulation tests for coal mining:

[0004] 1) Existing simulation test devices focus on coal mine water inrush disasters, only considering the aquiferous strata as the water inrush source, and using various water storage devices such as water storage belts and flexible water tanks, without considering the natural recharge seepage conditions of aquifer groundwater. Especially in the seepage pattern environment of the thick Cretaceous aquifer, it is impossible to simulate the disturbance of coal mining on the internal seepage field of the aquifer.

[0005] 2) The water injection ports of existing simulation test devices use hose openings or directly drill holes in the side wall of the box. Whether using hose openings or directly drilling holes in the side wall of the box as the water injection ports, the permeability is quite different from the actual formation permeability, resulting in local distortion due to disturbing the water injection layer position, and there is a possibility that the injected water flows back into the water supply pipeline, and the rock layer simulation material particles filled in the box enter the water supply pipeline and damage the sensors and water pump units.

[0006] 3) The existing simulation test device depends on monitoring whether the development range of the water-conducting fissure zone reaches the overlying aquifer to measure the impact of coal mining on the aquifer water body, and it is unable to simulate the disturbance process of the aquifer water body caused by the development of separation layers inside the aquifer. Summary of the Invention

[0007] In view of the above analysis, the embodiments of the present invention aim to provide a simulation device and method for multi-source recharge of damaged overlying thick aquifers in coal seam mining, so as to solve one or more of the above technical problems existing in the prior art.

[0008] The object of the present invention is achieved as follows:

[0009] On the one hand, a simulation device for multi-source recharge of damaged overlying thick aquifers in coal seam mining is provided, including:

[0010] A box body, the box body has an accommodation space, and a water-proof layer, an aquifer, and an overlying strata pressurizing device located above the aquifer are laid from bottom to top in the accommodation space;

[0011] An aquifer recharge system, the aquifer recharge system has a plurality of water injection devices, and the water injection devices are configured to inject water into different depth positions of the aquifer;

[0012] A vertical pressure relief assembly, the number of the vertical pressure relief assemblies is multiple, and the multiple vertical pressure relief assemblies are dispersedly arranged below the water-proof layer, and are configured to support the water-proof layer and control the pressure relief at different positions of the water-proof layer.

[0013] Further, a water level monitoring pipe is arranged in the aquifer, a piezometer is arranged on the water level monitoring pipe, and the piezometer can monitor the water pressure at different positions in the aquifer.

[0014] Further, the water injection device includes a water injection port assembly and a water supply hose, and the water outlet of the water injection device is connected to the water injection port assembly through the water supply hose; wherein, the water injection port assembly is buried in the aquifer, and the water injection port assembly is filled with a permeable material, and by filling the permeable material, the water injection port assembly can have the same permeability as the aquifer at the pre-buried location.

[0015] Further, the water injection device further includes a seepage pressure sensor, a water pump speed display meter, a water pump frequency converter, a water pump frequency controller, a water pump unit and a water tank; wherein, the water tank supplies water into the water supply hose through the water pump unit, the seepage pressure sensor is arranged on the water supply hose for monitoring the water injection pressure; the seepage pressure sensor is electrically connected to the water pump frequency controller, and the water pump unit is electrically connected to the water pump frequency controller through the water pump frequency converter.

[0016] Further, the water injection port assembly includes a main cylinder, a front cylinder, and a rear cover. The front cylinder is detachably provided at the front end of the main cylinder, and the rear cover is detachably provided at the rear end of the main cylinder. Both axial ends of the front cylinder are open. One end of the rear cover is open, and the other end has a rear cover bottom plate. A first through hole is provided on the rear cover bottom plate, and the first through hole is connected to the water supply hose. A first permeable stone is provided between the front cylinder and the main cylinder, and a second permeable stone is provided between the rear cover and the main cylinder. The space between the first permeable stone and the second permeable stone is filled with the permeable material.

[0017] Further, the water injection port assembly further includes a water injection port adjusting screw. The water injection port adjusting screw is a hollow tube, and an external thread is provided on the outer wall of the hollow tube. An internal thread is provided in the first through hole of the rear cover bottom plate, and the water injection port adjusting screw is threadedly installed in the first through hole of the rear cover bottom plate. One end of the water injection port adjusting screw abuts against the second permeable stone, and the other end is located outside the box body and is connected to the water supply hose. After the rear cover is fixedly connected to the rear end of the main cylinder, there is a moving space between the rear cover bottom plate and the rear end of the main cylinder. The second permeable stone can move in the moving space under the action of the water injection port adjusting screw.

[0018] Further, the water injection port assembly further includes a pressurizing airbag, an air supply pipe, and a water injection port control gas cylinder. The pressurizing airbag is connected to the control gas cylinder through the air supply pipe. The pressurizing airbag is provided in the space between the first permeable stone and the second permeable stone, and the permeable material is filled in the space formed by the first permeable stone, the second permeable stone, and the pressurizing airbag. A second through hole is provided on the side wall of the main cylinder, and the air supply pipe passes through the second through hole.

[0019] Further, a flexible net is also laid below the water barrier layer. Side end support seats are respectively provided on both sides below the water barrier layer. The top surface of the side end support seat is a plane, which is configured to support the water barrier layer and fix both ends of the flexible net. A plurality of the vertical pressure relief assemblies are located between the two side end support seats and directly support the flexible net.

[0020] Further, the vertical pressure relief assembly includes a lifting screw, a metal backing plate, a crank, and a base. The metal backing plate is rotatably provided at the top end of the lifting screw through a rotating shaft. The lower part of the lifting screw is vertically movable on the base. The crank is connected to the lifting screw through a transmission mechanism, and the lifting of the lifting screw is realized by rotating the crank. The gap between adjacent two metal backing plates is less than 5 mm, and water permeable holes are provided on the metal backing plate.

[0021] Further, the box body has a metal outer frame. The metal outer frame is provided with a metal back plate and a glass plate that are arranged parallel and opposite to each other. The edges of the metal back plate and the glass plate are provided with two metal side plates that are arranged parallel to each other. The metal back plate, the glass plate, the two metal side plates, and the flexible net arranged at the bottom form the accommodation space of the box body.

[0022] Further, mounting holes are arranged on the metal side plates, and the water injection device is hermetically connected to the mounting holes.

[0023] Further, the overlying formation pressurizing device includes a gas cylinder and an airbag connected to the gas cylinder. The airbag is located in the space between the upper part of the aquifer and the top fixing plate of the box body, and the airbag is hermetically arranged with the inner wall surface of the box body.

[0024] Further, it further includes a display terminal. The display terminal is electrically connected to the osmometer, the osmotic pressure sensor, and the water injection device, and is used for real-time display of various parameters during the operation of the experimental device.

[0025] Further, a water collecting tank is arranged below the box body. The top of the water collecting tank is open. The water collecting tank is used for collecting the water inrush flowing out from the bottom water outlet hole of the experimental device during the test. The water collecting tank is provided with a water outlet, and the water outlet is communicated with the sedimentation tank. The water inrush flows out from the water outlet of the water collecting tank and enters the sedimentation tank for sedimentation.

[0026] On the other hand, a simulation method for multi-source recharge of the damaged overlying thick aquifer in coal seam mining is provided. Using the above-mentioned simulation device for multi-source recharge of the damaged overlying thick aquifer in coal seam mining, the method includes the following steps:

[0027] Step 1: Lay a water isolation layer and an aquifer in sequence at the bottom of the box body. Both ends of the water isolation layer are supported by side end support seats, and the middle part of the water isolation layer is supported by a plurality of vertical pressure relief components. Install the overlying formation pressurizing device above the aquifer, and connect a plurality of water injection devices according to the depth position of the actual formation aquifer recharge water source in accordance with the corresponding depth ratio.

[0028] Step 2: Set the pressure applied by the overlying formation pressurizing device to the aquifer according to the overlying formation pressure of the actual formation. Turn on the water injection device to inject water into the aquifer to make the aquifer reach the saturated moisture content.

[0029] Step 3: Use the vertical pressure relief components to control the pressure relief at different positions of the water isolation layer, and control the water injection pressure of the corresponding position water injection device according to the actual formation recharge water source situation, and observe the pressure relief and caving process of the water isolation layer through the glass plate.

[0030] Compared with the prior art, the simulation device and method for multi-source recharge of overlying thick aquifers damaged in coal seam mining provided by the present invention have an aquifer recharge system with multiple juxtaposed and independently controlled water injection devices, which can simulate multiple recharge water sources for extremely thick aquifers. According to the different permeabilities and water head heights of the strata at different horizons of the aquifer, a water injection port assembly with adjustable permeability is used to perform constant-pressure water injection at different pressures for different horizons inside the aquifer, which can restore the natural recharge conditions and natural seepage field environment of the overlying thick aquifer of the coal seam, realize the simulation of the development process of mining-induced fractures and the change of the seepage field under mining in the thick aquifer, and the simulation results are closer to the actual mining situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the embodiments of this specification. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0032] Figure 1 Structural schematic diagram of the simulation device for multi-source recharge of overlying thick aquifers damaged in coal seam mining provided by the present invention;

[0033] Figure 2 Top view of the simulation device for multi-source recharge of overlying thick aquifers damaged in coal seam mining provided by the present invention;

[0034] Figure 3 Structural schematic diagram of the water injection device provided by the present invention;

[0035] Figure 4 Structural schematic diagram of the aquifer recharge system with the first type of water injection port assembly provided by the present invention;

[0036] Figure 5 Structural schematic diagram of the first type of water injection port assembly provided by the present invention;

[0037] Figure 6 Radial sectional structural schematic diagram of the first type of water injection port assembly provided by the present invention;

[0038] Figure 7 Structural schematic diagram of the aquifer recharge system with the second type of water injection port assembly provided by the present invention;

[0039] Figure 8 Structural schematic diagram of the second type of water injection port assembly provided by the present invention;

[0040] Figure 9 Structural schematic diagram of the third type of water injection port assembly provided by the present invention;

[0041] Figure 10 The first - angle structural schematic diagram of the vertical pressure - relief component provided by the present invention;

[0042] Figure 11 The second - angle structural schematic diagram of the vertical pressure - relief component provided by the present invention;

[0043] Figure 12 The fitting curve graph of the load pressure and the permeability coefficient of the water - permeable material filled in the water - injection port component provided by the present invention;

[0044] Figure 13 The fitting curve graph of the compaction rate and the permeability coefficient of the water - permeable material filled in the water - injection port component provided by the present invention.

[0045] Reference numerals:

[0046] 1 - Metal outer frame; 2 - Metal side plate; 3 - Water - supply hose; 4 - Water - injection device; 5 - Aquifer recharge system; 6 - Aquifer; 7 - Aquiclude; 8 - Flexible net; 9 - Piezometer; 10 - Display terminal; 11 - Side - end support seat; 12 - Vertical pressure - relief component; 13 - Lifting screw; 14 - Permeable stone; 15 - Water - injection port component; 16 - Metal back plate; 17 - Rubber plug; 18 - Metal backing plate; 19 - Osmotic pressure sensor; 20 - Water - pump speed display meter; 21 - Water - pump frequency converter; 22 - Water - pump frequency - conversion controller; 23 - Water - pump unit; 24 - Water tank; 25 - Glass plate; 26 - Base; 27 - Gas cylinder; 28 - Overlying - formation pressurizing device; 29 - Water - injection - port control gas cylinder; 30 - Water - injection - port adjusting screw; 31 - Pressurized airbag; 32 - Crank; 33 - Water - level monitoring pipe; 34 - Water - permeable material; 35 - Main cylinder; 36 - Front cylinder; 37 - Rear cover body; 38 - Gas supply pipe; 39 - Moving space; 40 - Rotating shaft; 41 - Permeable hole. Detailed implementation manners

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. It should be noted that, without conflict, the implementation manners and the features in the implementation manners in the present disclosure can be combined, separated, interchanged, and / or rearranged. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0048] In the drawings, for clarity and / or descriptive purposes, the dimensions and relative dimensions of components may be exaggerated. When exemplary embodiments may be implemented differently, the specific process orders may be performed in an order different from that described. For example, two consecutively described processes may be performed substantially simultaneously or in an order opposite to the described order. In addition, the same reference numerals denote the same components.

[0049] When a component is referred to as being “on” or “above” another component, “connected to” or “coupled to” another component, the component may be directly on, directly connected to, or directly coupled to the other component, or there may be intervening components. However, when a component is referred to as being “directly on” another component, “directly connected to” or “directly coupled to” another component, there are no intervening components. For this reason, the term “connected” may refer to physical connection, electrical connection, etc., and may or may not have intervening components.

[0050] For descriptive purposes, the present disclosure may use spatial relative terms such as “top”, “bottom”, “beneath”, “below”, “under”, “lower”, “above”, “upper”, “on”, “over”, “higher”, etc. with respect to a component to describe the relationship of one component to another (other) component as shown in the drawings.

[0051] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, unless the context clearly dictates otherwise, the singular forms “a”, “an” and “the” are also intended to include the plural forms. In addition, when the terms “comprises” and / or “comprising” and variations thereof are used in this specification, it is specified that there are the stated features, integers, steps, operations, components, assemblies, and / or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, assemblies, and / or groups thereof. It should also be noted that, as used herein, the terms “substantially”, “about” and other similar terms are used as approximate terms and not as degree terms, so they are used to explain the inherent deviations of measured, calculated and / or provided values that would be recognized by a person of ordinary skill in the art.

[0052] Embodiment 1

[0053] A specific embodiment of the present invention, as Figures 1 to 2As shown, a simulation device for multi-source recharge of overlying thick aquifer damage in coal seam mining is disclosed, which can be used for coal mining simulation under a super-thick aquifer, such as simulating an aquifer with a thickness of 300 - 800 m. The simulation device includes a box body, an aquifer recharge system 5 and a vertical pressure relief assembly 12; wherein, the box body has an accommodation space, and a water-resistant layer 7, an aquifer 6 and an overlying formation pressurizing device 28 located above the aquifer 6 are laid in the accommodation space from bottom to top; the aquifer recharge system 5 has a plurality of juxtaposed and independently controlled water injection devices 4, and the water injection devices 4 are configured to inject water into different depth positions of the aquifer 6; the number of the vertical pressure relief assemblies 12 is multiple, and the multiple vertical pressure relief assemblies 12 are dispersedly arranged below the water-resistant layer 7 and are configured to support the water-resistant layer 7 and control the pressure relief at different positions of the water-resistant layer 7, simulating the loosening and caving of the upper rock stratum caused by coal seam mining.

[0054] In this embodiment, a water level monitoring pipe 33 is arranged in the aquifer 6, and a piezometer 9 is arranged on the water level monitoring pipe 33, and the piezometer 9 can monitor the water pressure at different positions in the aquifer 9.

[0055] In this embodiment, the water-resistant layer 7 and the aquifer 6 are laid with similar materials, and the water-resistant layer 7 and the aquifer 6 are slowly laid by the method of tamping layer by layer.

[0056] In order to avoid disturbing the aquifer material during the water injection process, the permeability of the water injection port assembly 15 is consistent with the permeability of the simulated aquifer formation, so that the simulation result is closer to the actual situation. Based on this, the permeability of the water injection end of the water injection device 4 in this embodiment is adjustable. Specifically, the water injection device 4 includes a water injection port assembly 15 and a water supply hose 3, and the water outlet of the water injection device 4 is connected to the water injection port assembly 15 through the water supply hose 3; wherein, the water injection port assembly 15 is buried in the aquifer 6, and the water injection port assembly 15 is filled with a permeable material 34, and by filling the permeable material 34, the water injection port assembly 15 can have the same permeability as the aquifer 6 at the pre-buried location. The water injection device 4 can be used to control the water injection pressure at different layers of the aquifer 6, and can also restore the actual groundwater seepage environment of the aquifer water body.

[0057] In order to achieve precise control of the water injection pressure, the water injection device 4 further includes an osmotic pressure sensor 19, a water pump speed display 20, a water pump frequency converter 21, a water pump frequency conversion controller 22, a water pump unit 23, and a water tank 24. Among them, the water tank 24 supplies water into the water supply hose 3 through the water pump unit 23. The osmotic pressure sensor 19 is arranged on the water supply hose 3 for monitoring the water injection pressure. The osmotic pressure sensor 19 is electrically connected to the water pump frequency conversion controller 22, and the water pump unit 23 is electrically connected to the water pump frequency conversion controller 22 through the water pump frequency converter 21. The water injection device 4 with this structure can set different aquifer water pressures for different formation horizons. The water pump unit 23 pumps water from the water tank through the water supply hose 3 to inject water into the aquifer. The osmotic pressure sensor 19 can sense the water pressure condition of the corresponding water injection rock formation and transmit the signal to the water pump frequency conversion controller 22. The water pump frequency conversion controller 22 receives the signal, distinguishes whether the designed water pressure value is reached, and then transmits the signal to the water pump frequency converter 21. The water pump frequency converter 21 analyzes the received signal and finally displays the water pressure signal value through the water pump speed display 20. The required water pressure value can be adjusted by controlling the water pump unit.

[0058] In one implementation, the water injection port assembly 15 includes a main cylinder 35, a front cylinder 36, and a rear cover 37. The front cylinder 36 is detachably arranged at the front end of the main cylinder 35, and the rear cover 37 is detachably arranged at the rear end of the main cylinder 35. Both axial ends of the front cylinder 36 are open. One end of the rear cover 37 is open, and the other end has a rear cover bottom plate. A first through hole is provided on the rear cover bottom plate, and the first through hole is connected to the water supply hose 3. The filled permeable material is clamped by two parallel permeable stones 14. Specifically, a first permeable stone is provided between the front cylinder 36 and the main cylinder 35, and a second permeable stone is provided between the rear cover 37 and the main cylinder 35. The space between the first permeable stone and the second permeable stone is filled with the permeable material 34. The water injection port assembly 15 is set to be detachably assembled into three parts, and by selecting permeable stones and permeable materials with different water permeabilities, the water permeability of the water injection port assembly 15 is made to be the same as or approximate to the actual formation water permeability. Optionally, the permeable material 34 is made of quartz sand particles, and the particle size of the quartz sand particles is 0.2 - 0.8 mm, preferably 0.5 mm.

[0059] In this embodiment, the filled permeable material 34 in the water injection assembly is in a cylindrical structure. Both the axial pressure and the radial pressure of the permeable material 34 affect the permeability of the water injection port assembly 15. Therefore, in this embodiment, the water injection port assembly 15 includes the following three structures:

[0060] The water injection port assembly 15 of the first structure, such as Figures 4 to 6As shown, it further includes a pressurizing airbag 31, an air supply pipe 38, and a water injection port control gas cylinder 29. The pressurizing airbag 31 is connected to the control gas cylinder 29 through the air supply pipe 38; the pressurizing airbag 31 is arranged in the space between the first permeable stone and the second permeable stone, and the permeable material 34 is filled in the space formed by the first permeable stone, the second permeable stone, and the pressurizing airbag 31; a second through hole is provided on the side wall of the main cylinder body 35, and the air supply pipe 38 passes through the second through hole. By adjusting the gas pressure of the pressurizing airbag 31, a pressurized load is applied to the permeable material 34 filled in the water injection port assembly 15, thereby changing the permeability coefficient of the water injection port assembly 15.

[0061] The water injection port assembly 15 of the second structure, as Figures 7 to 8 shown, further includes a water injection port adjusting screw 30. The water injection port adjusting screw 30 is a hollow pipe, and external threads are provided on the outer wall of the hollow pipe. Internal threads are provided in the first through hole of the rear cover bottom plate. The water injection port adjusting screw 30 is threadedly installed in the first through hole of the rear cover bottom plate; one end of the water injection port adjusting screw 30 abuts against the second permeable stone, and the other end is located outside the box body and is connected to the water supply hose 3; after the rear cover body 37 is fixedly connected to the rear end of the main cylinder body 35, there is a moving space 39 between the rear cover bottom plate and the rear end of the main cylinder body 35. The second permeable stone can move in the moving space 39 under the action of the water injection port adjusting screw 30. By rotating the water injection port adjusting screw 30 outside the water injection port assembly 15, the inner permeable stone 14 of the water injection port assembly 15 squeezes the permeable material 34 filled inside, thereby changing the compaction rate of the filling material to adjust the permeability coefficient of the water injection port assembly 15.

[0062] The water injection port assembly 15 of the third structure, as Figure 9 shown, belongs to the combination of the water injection port assembly 15 of the first structure and the water injection port assembly 15 of the second structure. That is to say, the water injection port assembly 15 of the third structure can not only adjust the radial extrusion pressure of the filled permeable material 34 through the pressurizing airbag 31, but also make the permeable stone 14 squeeze the permeable material 34 filled inside by screwing the water injection port adjusting screw 30, so as to realize the adjustment of the axial extrusion pressure of the permeable material 34.

[0063] In order to realize the smooth collapse of the water - resistant layer after pressure relief, a flexible net 8 is further laid below the water - resistant layer 7; a side - end support seat 11 is respectively provided on both sides below the water - resistant layer 7. The side - end support seat 11 is made of stainless - steel metal material. The top surface of the side - end support seat 11 is a plane, which is configured to support the water - resistant layer 7 and fix both ends of the flexible net 8; a plurality of the vertical pressure - relief components 12 are located between the two side - end support seats 11 and directly support the flexible net 8.

[0064] Further, as Figures 10 to 11As shown in the figure, the vertical pressure relief assembly 12 includes a lifting screw 13, a metal backing plate 18, a crank 32, and a base 26; the metal backing plate 18 is connected to the lifting screw 13 through a movable joint and can simulate the ground settlement at different positions. Specifically, the metal backing plate 18 is rotatably arranged at the top end of the lifting screw 13 through a rotating shaft 40, the lower part of the lifting screw 13 is arranged on the base 26 in a liftable manner, the crank 32 is connected to the lifting screw 13 through a transmission mechanism, and the lifting of the lifting screw 13 is realized by rotating the crank 32; the gap between two adjacent metal backing plates 18 is less than 5 mm, and the metal backing plate 18 is provided with water permeable holes 41. During the simulation process, when it is necessary to simulate the settlement of the water-resisting layer above the coal seam after mining, only need to rotate the crank 32 at the simulated position to lower the corresponding lifting screw 13.

[0065] In this embodiment, the box body has a metal outer frame 1, the metal outer frame 1 is provided with a metal back plate 16 and a glass plate 25 arranged parallel and opposite to each other, the edges of the metal back plate 16 and the glass plate 25 are provided with two parallel metal side plates 2, and the metal back plate 16, the glass plate 25, the two metal side plates 2, and the flexible net 8 arranged at the bottom form the accommodating space of the box body.

[0066] In this embodiment, mounting holes are arranged on the metal side plate 2, and the water injection device 4 is hermetically connected to the mounting holes.

[0067] Exemplarily, the water supply hose 3 passes through the mounting hole through a rubber plug 17. Further, in the technical solution where the water injection port adjusting screw 30 is arranged in the water injection port assembly 15, the water injection port adjusting screw 30 is hermetically installed in the mounting hole through a rubber plug; in the technical solution where the pressurized air bag 31 is arranged in the water injection port assembly 15, both the air supply pipe 38 and the water supply hose 3 pass through the mounting hole through rubber plugs.

[0068] In this embodiment, the overlying stratum pressurizing device 28 includes a gas cylinder 27 and an air bag connected to the gas cylinder 27. The air bag is located in the space between the upper part of the aquifer 6 and the top fixing plate of the box body, and the air bag is hermetically arranged with the inner wall surface of the box body. The fixing plate is detachably arranged on the top of the box body. By arranging the fixing plate, when the gas cylinder 27 is used to inflate the air bag, the air bag expands and applies a downward pressure to the lower aquifer 6. The specific inflation amount is set according to the formation pressure at the actual depth of the simulated aquifer.

[0069] In this embodiment, the simulation device for the damage of the overlying thick aquifer and multi-source recharge during coal seam mining is characterized in that it further includes a display terminal 10, and the display terminal 10 is electrically connected to the osmotic pressure gauge 9, the osmotic pressure sensor 19, and the water injection device 4, and is used for displaying various parameters during the working process of the experimental device in real time.

[0070] In this embodiment, a water collecting tank is provided below the box body. The top of the water collecting tank is open, and the water collecting tank is used to collect the water inrush flowing out of the water outlet holes at the bottom of the test device during the test. The water collecting tank is provided with a water outlet, and the water outlet is communicated with the sedimentation tank. The water inrush flows out of the water outlet of the water collecting tank and enters the sedimentation tank for sedimentation. Larger particles of sediment are sedimented first and then enter the flowmeter to reduce the impact of particulate matter in the water on the flowmeter.

[0071] This embodiment also discloses a simulation method for multi-source recharge of damaged overlying thick aquifers in coal seam mining. Using the above-mentioned simulation device for multi-source recharge of damaged overlying thick aquifers in coal seam mining, it includes the following steps:

[0072] Step 1: Lay a water isolation layer 7 and an aquifer 6 in sequence at the bottom of the box body. Both ends of the water isolation layer 7 are supported by side end supports 11, and the middle of the water isolation layer 7 is supported by a plurality of vertical pressure relief components 12. An overlying strata pressurizing device 28 is installed above the aquifer 6, and a plurality of water injection devices 4 are connected according to the depth position of the actual strata aquifer recharge water source in the corresponding depth ratio.

[0073] Step 2: Set the pressure applied by the overlying strata pressurizing device 28 to the aquifer 6 according to the overlying strata pressure of the actual strata. Turn on the water injection device 4 to inject water into the aquifer 6 to make the aquifer 6 reach the saturated water content rate.

[0074] Step 3: After the state is stable, use the vertical pressure relief components 12 to control the pressure relief at different positions of the water isolation layer 7, and control the water injection pressure of the corresponding position water injection device 4 according to the actual strata recharge water source situation, and observe the pressure relief and caving process of the water isolation layer through the glass plate 25.

[0075] In Step 1, the water isolation layer 7 and the aquifer 6 are laid with similar materials. The water isolation layer 7 and the aquifer 6 laid with similar materials have the same or approximate petrological properties as the water isolation layer and the aquifer of the actual strata. The similar materials and their mixing ratio parameters can be realized by using the existing technology. Exemplarily, the similar material of the water isolation layer uses bentonite, paraffin, vaseline, calcium carbonate and gypsum with a particle size of 0 - 1 mm and uniform grading; the similar material of the aquifer uses 0 - 3 mm river sand, diatomite particles, PC425 white cement, calcium carbonate and gypsum to form a skeleton particle to simulate the aquifer.

[0076] In Step 1, before actually laying the water - proof layer 7 and the aquifer 6, first build a box body, check the sealing performance of the box body, fix the side - end support seat 11 and the vertical pressure - relief component 12. The top surfaces of the fixed side - end support seat 11 and the vertical pressure - relief component 12 are located on the same plane. First, lay a flexible net 8 on the top surfaces of the fixed side - end support seat 11 and the vertical pressure - relief component 12, and then slowly lay the water - proof layer 7 and the aquifer 6 by the method of tamping layer by layer. For example, when the thickness of the water - proof layer of the simulated actual formation is 60 m, the thickness of the aquifer of the simulated actual formation is 540 m, and the size of the accommodation space in the box body is 5000 mm * 500 mm * 2000 mm. Taking the thickness ratio of the similar rock layer to the actual formation of 300:1 as an example, the thickness of the water - proof layer material is 200 mm, the thickness of the aquifer material is 1800 mm, the two ends of the laid material are sealed and water - blocked for 100 mm in length, and mica - sheet particles with a particle size of 2 - 5 mm and a thickness of 5 mm are laid between the aquifer and the water - proof layer to simulate the weak surface between the formations;

[0077] While laying the similar materials of each rock layer, according to the experimental design scheme determined according to the actual formation conditions, bury the pressure sensors at the positions to be monitored; at the same time, according to the water - level observation data of the actual aquifer at different depths, determine the burial depth and injection pressure of the water - injection port assembly 15, and bury the water - injection port assembly 15 and the water - supply hose. Optionally, the water - injection port assembly 15 is buried 500 mm from the edges of both ends of the material inside. Apply waterproof gel at the joints of the box body and between the water - proof layer and the aquifer and the inner wall of the box body for sealing.

[0078] According to the actual formation conditions to be simulated, determine the overburden stress to be loaded. Specifically, after laying the water - proof layer 7 and the aquifer 6 and burying the required water - level monitoring pipes 33, piezometers 9, water - injection port assemblies 15 and other components, install the overburden - formation pressurizing device 28 on the top of the aquifer. The overburden - formation pressurizing device 28 can vertically apply pressure downward to simulate the pressure of the overlying formation of the aquifer. The overburden - formation pressurizing device 28 is pressurized by means of an airbag, and the overburden - formation pressurizing device 28 is fixed by the top - plate of the box body. The overburden - formation pressurizing device 28 is closely attached to the top surface of the underlying aquifer 6.

[0079] In Step 2, according to the numerical values of the lateral and vertical loading forces of the aquifer 6 determined by the experimental design scheme, conduct the initial - stress loading. Specifically, set the overburden - formation pressurizing device 28 to apply corresponding pressure to the aquifer 6 according to the overburden pressure of the actual formation; at the same time, according to the set recharge pressures at different positions, turn on the aquifer recharge systems 5 on both sides to saturate the aquifer 6.

[0080] In Step 3, for the determined coal seam excavation location, the vertical pressure relief component 12 is used to control the pressure relief of the aquifuge 7 at the coal seam excavation location, so as to simulate the stress release and the influence of rock layer bending and subsidence generated by coal seam excavation on the roof, and further simulate the stress change and deformation of the roof rock layer. During the simulation process, the water injection device of the two-side aquifer recharge system 5 is used to replenish water to the aquifer 6. Multiple water injection devices 4 can realize differential water replenishment for water replenishment sources at different depth positions, so as to realize the simulation of multi-source recharge of the actual aquifer, and can also realize the monitoring of the dynamic movement of the rock layer. The osmotic pressure meter arranged in the aquifer is used to monitor the osmotic pressure, and the influence of coal mining on the roof aquifer is analyzed.

[0081] In addition, in Step 3, the permeability of the water injection port assembly 15 can also be accurately adjusted to be the same as or approximate to the permeability of the actual formation aquifer by filling permeable materials 34 with different particle size parameters, controlling the axial pressure or / and radial pressure of the filled permeable materials, so that the simulation results are more accurate.

[0082] If the water injection port assembly 15 with the first structure is adopted, the permeability coefficient of the water injection port assembly 15 can be obtained in the laboratory for quartz sand particles with different particle sizes under different radial pressure loads. Exemplarily, as Figure 12 shown, the permeable material 34 uses quartz sand with a particle size of 0.5 mm, and the fitting formula of different pressure loads and permeability coefficients is obtained by testing in the laboratory:

[0083] K=-7×10 -5 p 2 -0.0122p+13.836

[0084] where K is the permeability coefficient (10 -3 cm / s), and P is the load gas pressure (kPa); if the gas pressure load injected by the water injection port control gas cylinder 29 is in the range of 0-400 kPa, the permeability coefficient of the water injection port assembly 15 can be adjusted to be 0.79×10 -3 ~13.39×10 -3 cm / s.

[0085] If the water injection port assembly 15 with the second structure is adopted, the permeability coefficient of the water injection port assembly 15 can be obtained in the laboratory for quartz sand particles with different particle sizes under different axial pressure loads. Exemplarily, as Figure 13 shown, the permeable material 34 uses quartz sand with a particle size of 0.5 mm, and the fitting formula of the compaction rate and the permeability coefficient is obtained by conducting the permeability change test of quartz sand particles under different compaction rates in the laboratory:

[0086] K=3×10 13 ·e -32.61·T

[0087] The calculation formula of compaction rate T is:

[0088]

[0089] The above formulas are combined to obtain the permeability coefficient:

[0090]

[0091] Where K is the permeability coefficient, 10 -3 cm / s); T is compaction rate, %); ρ max The maximum dry density measured in the laboratory is 1.73g / cm 3 ; ρ is the actual density, g / cm 3 ; m is the mass of the permeable material, g; v min , v and Δv are the minimum volume, actual volume and reduced volume of the material, respectively, all in cm 3 ; d and Δd are the original radial length and the screw length of the water injection port adjustment screw, cm; r is the filling inner radius of the water injection port assembly, cm; the adjustable permeability range of the water injection port assembly of the second structure is 1.61×10 -3 ~40.68×10 -3 cm / s.

[0092] Similarly, the fitting formula can be obtained by conducting permeability tests on the axial pressure and radial pressure of the permeable material in the laboratory, and the adjustable permeability coefficient range of the water injection port assembly of the third structure can be obtained.

[0093] Compared with the prior art, the simulation device and method for multi-source water supply for damage to thick aquifers overlying coal seam mining provided in this embodiment have at least one of the following beneficial effects:

[0094] 1. The coal mining conditions are simulated by using the settlement of the strata above the coal mining. It is not necessary to lay the coal seam, but only the impermeable layer and aquifer above the coal seam. This can achieve similar simulation of water body damage under the coupling of overburden movement and groundwater seepage field in coal seam mining under thick aquifers, simplifying the test process and improving test efficiency.

[0095] 2. The aquifer recharge system has multiple parallel and independently controlled water injection devices, which can simulate multiple recharge water sources for extremely thick aquifers. According to the different permeabilities and head heights of different strata in the aquifer, an injection port assembly with adjustable permeability is used to perform constant pressure water injection at different pressures in different strata inside the aquifer. This can restore the natural recharge conditions and natural seepage field environment of the thick aquifer overlying the coal seam, and realize the simulation of the development process of mining-induced fractures in the thick aquifer and the changes in the seepage field under mining.

[0096] 3. It can be widely applied to the fluid-solid coupling test in coal seam mining, realizing the function of simulating the disturbance mechanism of the water body in the aquifer under the coupling action of the overlying rock movement and the groundwater seepage field in the aquifer during coal seam mining under a thick aquifer, which is of great significance for the prevention and control of water body damage environmental disasters during coal seam mining under a thick aquifer.

[0097] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of this application. It should be understood that the above are only specific embodiments of this application and are not used to limit the protection scope of this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims

1. A simulation device for multi-source recharge of overlying thick aquifer damage in coal seam mining, characterized in that include: A box body, wherein the box body has a containing space, and a water-proof layer, an aquifer, and an overlying stratum pressurizing device located above the aquifer are laid in the containing space from bottom to top; An aquifer recharge system, wherein the aquifer recharge system has a plurality of water injection devices, wherein the water injection devices are configured to inject water into different depths of the aquifer, and according to different permeabilities and water head heights of different layers of the aquifer, a water injection port assembly with adjustable permeability is used to perform constant pressure water injection at different pressures at different layers inside the aquifer; A vertical pressure relief assembly, wherein the number of the vertical pressure relief assemblies is plural, and the plurality of the vertical pressure relief assemblies are dispersedly arranged below the waterproof layer, and are configured to support the waterproof layer and control the pressure relief at different positions of the waterproof layer; Among them, the water injection device includes a water injection port assembly and a water supply hose, and the water outlet of the water injection device is connected to the water injection port assembly through the water supply hose; the water injection port assembly is filled with permeable material, and by filling the permeable material, the water injection port assembly can have the same permeability as the aquifer at the pre-buried location; the filled permeable material is clamped by two parallel arranged permeable stones; permeable stones and permeable materials with different permeabilities are selected to ensure that the permeability of the water injection port assembly is consistent with the actual stratum permeability.

2. The simulation device for multi-source recharge of overlying thick aquifer damage in coal seam mining according to claim 1, characterized in that, A water level monitoring pipe is arranged in the aquifer, and a piezometer is arranged on the water level monitoring pipe. The piezometer can monitor the water pressure at different positions in the aquifer.

3. The simulation device for multi-source recharge of overlying thick aquifer damage in coal seam mining according to claim 1, characterized in that, The water injection port assembly includes a main cylinder, a front cylinder and a rear cover, wherein the front cylinder is detachably arranged at the front end of the main cylinder, and the rear cover is detachably arranged at the rear end of the main cylinder; both axial ends of the front cylinder are openings; one end of the rear cover is open, and the other end has a rear cover bottom plate, wherein a first through hole is arranged on the rear cover bottom plate, and the first through hole is connected to the water supply hose; a first permeable stone is arranged between the front cylinder and the main cylinder, and a second permeable stone is arranged between the rear cover and the main cylinder, and the space between the first permeable stone and the second permeable stone is filled with the permeable material.

4. The simulation device for multi-source recharge of overlying thick aquifer damage in coal seam mining according to claim 3, characterized in that, The water injection port assembly also includes a water injection port adjusting screw, which is a hollow tube, and an outer thread is arranged on the outer wall of the hollow tube, and an inner thread is arranged on the first through hole of the rear cover bottom plate, and the water injection port adjusting screw is threadedly installed in the first through hole of the rear cover bottom plate; one end of the water injection port adjusting screw abuts against the second permeable stone, and the other end is located on the outside of the box body and connected to the water supply hose; after the rear cover body is fixedly connected to the rear end of the main cylinder body, a moving space is provided between the rear cover bottom plate and the rear end of the main cylinder body, and the second permeable stone can move in the moving space under the action of the water injection port adjusting screw.

5. The simulation device for multi-source recharge of overlying thick aquifer damage in coal seam mining according to claim 3, characterized in that, The water injection device also includes an osmotic pressure sensor, a water pump speed display meter, a water pump frequency converter, a water pump frequency conversion controller, a water pump unit and a water pool; Wherein, the water pool supplies water into the water supply hose through the water pump unit, and the permeation pressure sensor is arranged on the water supply hose to monitor the water injection pressure; The osmotic pressure sensor is electrically connected to the water pump frequency conversion controller, and the water pump unit is electrically connected to the water pump frequency conversion controller through the water pump inverter.

6. The simulation device for multi-source recharge of overlying thick aquifer damage in coal seam mining according to claim 4, characterized in that, The water injection port assembly further includes a pressurizing airbag, an air supply pipe, and a water injection port control gas cylinder. The pressurizing airbag is connected to the control gas cylinder through the air supply pipe. The pressurizing airbag is arranged in the space between the first water-permeable stone and the second water-permeable stone, and the permeable material is filled in the space formed by the first water-permeable stone, the second water-permeable stone, and the pressurizing airbag. A second through hole is provided on the side wall of the main cylinder body, and the air supply pipe passes through the second through hole.

7. The simulation device for multi-source recharge of overlying thick aquifer damage in coal seam mining according to claim 1, characterized in that A flexible net is also laid below the water barrier layer. One side-end support seat is provided on each of the two sides below the water barrier layer. The top surface of the side-end support seat is a plane, which is configured to support the water barrier layer and fix the two ends of the flexible net. A plurality of the vertical pressure relief components are located between the two side-end support seats and directly support the flexible net.

8. The simulation device for multi-source recharge of overlying thick aquifer damage in coal seam mining according to claim 7, characterized in that The vertical pressure relief component includes a lifting screw, a metal backing plate, a crank, and a base. The metal backing plate is rotatably arranged at the top end of the lifting screw through a rotating shaft. The lower part of the lifting screw is arranged on the base in a liftable manner. The crank is connected to the lifting screw through a transmission mechanism, and the lifting of the lifting screw is realized by rotating the crank. The gap between two adjacent metal backing plates is less than 5 mm, and the metal backing plate is provided with water-permeable holes.

9. A simulation method for multi-source recharge of overlying thick aquifers damaged by coal seam mining, characterized in that, Using the simulation device for multi-source recharge of the damaged overlying thick aquifer in coal seam mining according to any one of claims 1 to 8, the simulation method includes the following steps: Step 1: Lay a water barrier layer and an aquifer in sequence at the bottom of the box body. The two ends of the water barrier layer are supported by side-end support seats, and the middle part of the water barrier layer is supported by a plurality of vertical pressure relief components. Install an overlying strata pressurizing device above the aquifer, and connect a plurality of water injection devices according to the depth position of the actual strata aquifer recharge water source in accordance with the corresponding depth ratio. Step 2: Set the pressure applied by the overlying strata pressurizing device to the aquifer according to the overlying strata pressure of the actual strata. Fill the water injection port assembly of the water injection device with a permeable material, and the filled permeable material can make the water injection port assembly have the same permeability as the aquifer at the pre-buried location. Open the water injection device to inject water into the aquifer to make the aquifer reach the saturated moisture content. Among them, water is injected into different depth positions of the aquifer according to the different permeabilities and water head heights of different strata of the aquifer, and a water injection port assembly with adjustable permeability is used to perform constant-pressure water injection at different pressures for different strata inside the aquifer. Step 3: Use the vertical pressure relief components to control the pressure relief at different positions of the water barrier layer, and control the water injection pressure of the corresponding position water injection device according to the actual strata recharge water source situation, and observe the pressure relief and caving process of the water barrier layer through the glass plate.

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