Visualizing device and method for slurry diffusion in water-filled goaf under varying hydraulic gradient

Abstract

This invention relates to the field of mine environmental management, and particularly to a visualization device and method for slurry diffusion in water-filled goaf areas under varying hydraulic gradients. By independently setting up inlet and outlet modules, the water levels at both ends of the simulation test chamber can be independently controlled, creating a stable lateral hydraulic gradient within the chamber. Furthermore, by simulating dynamic water level changes under different working conditions using stepped or continuous variation modes, it solves the problem that existing technologies cannot simulate the slurry diffusion process under varying hydraulic gradients. Through a nested design of inner and outer pipes, combined with the sealing and isolation effect of nitrogen bags, precise water level control is achieved while ensuring the stability of the seepage fluid's environmental indicators. The outer pipe returns the overflow fluid to the supply tank via a flexible hose, realizing the recycling of the seepage fluid at the supply end and saving experimental costs.

Description

Technical Field

[0001] This invention relates to the field of mine environmental management, and in particular to a visualization device and method for the diffusion of slurry in a water-filled goaf under varying hydraulic gradients. Background Technology

[0002] Due to the historical impact of large-scale open-pit mining methods, the existing volume of goaf areas in my country has reached approximately 1.2 billion cubic meters, many of which have evolved into water-filled goaf areas. With the increasingly prominent contradiction between land resource supply and demand, the demand for land use above goaf areas is rising year by year. Their existence poses serious safety hazards to major engineering construction, making the remediation and treatment of water-filled goaf areas an urgent priority. Grouting and backfilling is the most direct and effective means of treating water-filled goaf areas. However, because the treatment target area is deeply buried underground, actual construction usually adopts a blind injection method. The diffusion process of grout in the residual voids of the strata is difficult to directly observe, and the selection of key engineering parameters relies excessively on engineering experience, resulting in significant uncertainty in the remediation effect and high engineering costs.

[0003] To investigate the diffusion patterns of grout in formation pores, researchers have attempted to use indoor simulation experiments. For example, Chinese patent CN116448620A discloses a transparent porous formation dynamic water grouting test system, which uses a transparent medium material to fill a visual container to simulate porous formations and records the grout diffusion process through image acquisition equipment. However, this approach has significant shortcomings: First, its hydraulic conditions are dynamic water environments with constant flow or constant temperature, which cannot simulate the hydraulic gradient scenarios when the groundwater level dynamically changes due to factors such as seasons and rainfall; second, the sensors are pre-embedded during model construction, which physically interferes with the grout diffusion flow field, making non-destructive monitoring difficult; third, it does not consider the influence of the unique anoxic hydrochemical environment (such as redox conditions and ionic composition) of goaf areas on the grout hydration reaction. In addition, existing indoor experiments generally use sampling and detection methods to obtain data, and the sampling process itself interferes with the grout and groundwater flow field, leading to distorted experimental data.

[0004] Therefore, it is necessary to use indoor experiments and other methods to investigate the diffusion law of slurry in the residual voids of the formation under varying hydraulic gradients, so as to provide a theoretical basis for the scientific development of water-filled goaf remediation work. Summary of the Invention

[0005] Technical objective: In order to overcome the shortcomings of the existing technology, the present invention provides a visualization device and method for the diffusion of slurry in a water-filled goaf under varying hydraulic gradients, which enables non-destructive, quantitative and visual monitoring of the diffusion process of slurry in the residual voids of the formation under varying hydraulic gradients.

[0006] Technical Solution: To achieve the above objectives, this invention discloses a visualization device for slurry diffusion in a water-filled goaf under varying hydraulic gradients, comprising:

[0007] The water supply and drainage module includes a liquid supply unit and a drainage unit. The liquid supply unit includes a liquid supply tank for storing and supplying seepage liquid under simulated water environment conditions in a goaf area. The drainage unit includes a drainage tank for collecting seepage liquid discharged during the experiment.

[0008] The hydraulic gradient control module includes an inlet water level control module and an outlet water level control module. The liquid supply unit is connected to the inlet water level control module to supply seepage liquid to it, and the drainage unit is connected to the outlet water level control module to receive the seepage liquid discharged by it.

[0009] The slurry diffusion visualization simulation module includes a transparent test chamber filled with residual formation media. The test chamber is connected to the corresponding water level control module and water level control module via several horizontal connecting pipes arranged at vertical intervals.

[0010] The data acquisition module is used for the collection and analysis of monitoring data;

[0011] The non-destructive quantitative monitoring module is used to acquire images during the experiment.

[0012] Furthermore, water distribution plates are respectively installed near the left and right walls inside the test chamber, and the two water distribution plates are respectively sealed to the outer side of the adjacent side walls to form a water collection cavity; the top of the test chamber is provided with a simulated grouting pipe that can move horizontally and vertically, and the bottom of the test chamber is provided with independent inlet and outlet water ports, which are connected to the liquid supply tank pipeline.

[0013] Furthermore, both the inlet water level control module and the outlet water level control module include an inner pipe and an outer pipe. The inner pipe has multiple drain outlets spaced vertically along its side wall, and each drain outlet is equipped with an opening and closing device to control the opening and closing of the corresponding drain outlet. The bottom of the inner pipe is connected to the liquid supply tank via a flexible hose, and a micro pump is installed on the flexible hose. A water pressure sensor is also installed at the bottom of the inner pipe to monitor the water level pressure in real time. The inner pipe is connected to the water collection chamber via the horizontal connecting pipe. The outer pipe is sealed and fitted over the inner pipe, forming a water storage space between the inner pipe and the outer pipe. A nitrogen bag is connected to the top of the outer pipe. The lower end of the outer pipe is connected to the liquid supply tank via a flexible hose, allowing the overflow liquid to be discharged between the inner and outer pipes.

[0014] Furthermore, both the inlet water level control module and the outlet water level control module include a continuous water level control module, a transistor and a potentiometer. The micro pump, the continuous water level control module, the transistor and potentiometer, and the water pressure sensor are electrically connected to achieve liquid level regulation.

[0015] Furthermore, the simulated grouting pipe is a glass flower pipe with a rotating clamp connected to its upper end. The rotating clamp is mounted on an electric slide rail, which is located at the top of the test chamber. Both the electric slide rail and the rotating clamp are connected to a program control system to control the laying depth and injection angle of the simulated grouting pipe.

[0016] Furthermore, a long strip-shaped optical calibration plate is set below the observation surface of the test chamber for calibrating data errors caused by light source fluctuations at different time points.

[0017] Furthermore, the data acquisition module includes negative pressure sensors vertically distributed on the left side wall of the test chamber, moisture content sensors vertically distributed on the right side wall, and pressure sensors installed on the rear wall. It also includes a data acquisition unit, and each sensor is connected to the data acquisition unit through a data converter.

[0018] Furthermore, the non-destructive quantitative monitoring module includes a multi-band light source, a digital camera, a polarizer, and an analyzer. The polarizer is positioned on the observation surface of the test chamber, and the analyzer is positioned between the multi-band light source and the digital camera to calibrate the optical path angle.

[0019] Furthermore, the opening and closing element is a mechanical valve or a pluggable sealing plug, and a stepped water level setting is achieved by opening the drain outlets at different heights.

[0020] A non-destructive, quantitative, and visual experimental method for the diffusion of residual grout in grouting voids in a water-filled goaf under varying hydraulic gradients includes the following steps:

[0021] S1 Pressure Sensor Installation: Pressure sensors are installed on the back of the test chamber at preset monitoring intervals;

[0022] S2 Grouting Layer and Angle Determination: The position of the rotary clamp on the electric slide rail is controlled by the program to accurately set the pre-embedded depth and injection angle of the simulated grouting pipe;

[0023] S3 Material Filling: Fill the test chamber with the screened and graded residual formation medium;

[0024] S4 Moisture content sensor and negative pressure sensor placement: When the material is filled to the preset depth of the sensor, place the moisture content sensor and negative pressure sensor in the corresponding layer on the side wall of the test chamber, continue filling and vibrate to compact;

[0025] S5 Water Environment Condition Control: The seepage liquid is prepared according to the actual water chemistry conditions of the goaf and aerated until the oxidation-reduction conditions are consistent with those of the goaf. It is then stored in the liquid supply tank of the liquid supply unit.

[0026] S6 Formation Residual Medium Saturation: Close the valves connecting the test chamber to the inlet water level control module and the outlet water level control module on both sides, open the valves at the bottom inlet and outlet, and slowly inject the seepage liquid in the supply unit into the test chamber from bottom to top until the air in the medium pores is completely displaced and the medium reaches a uniform saturation state.

[0027] S7 Hydraulic Gradient Establishment and Control: Close the valves at the bottom inlet and outlet, open the valves connecting the test chamber to the inlet and outlet water level control modules, and independently control the inlet and outlet water levels through the inlet and outlet water level control modules respectively to form a preset hydraulic gradient within the test chamber and continue operating for a preset duration; the establishment and control of the hydraulic gradient includes a stepped water level change mode and a continuously changing water level mode.

[0028] The stepped water level change mode is as follows: by opening the drain outlet at a preset height on the inner wall of the water inlet or outlet and closing the other drain outlets, the water level is stabilized at the corresponding height, and the step change of water level is achieved by switching drain outlets at different heights.

[0029] The continuously changing water level mode is as follows: by inputting commands through the water level continuous control module, the speed of the micro pump is adjusted by transistors and potentiometers, and the pressure signal is fed back in real time by the water pressure sensor to achieve stepless continuous change of water level.

[0030] S8 Grouting: The grout is prepared according to the preset water-cement ratio and injected into the design layer through the simulated grouting pipe by the grouting pump at the set pressure. Grouting is stopped after the grout diffusion plume stabilizes.

[0031] S9 Data Acquisition and Image Acquisition: Starting from the beginning of grouting, various sensors and data acquisition devices are activated to record data in real time. At the same time, digital cameras are used to acquire images of slurry diffusion plumes at different time points in a darkroom. By coupling and analyzing the image data and sensor data, the slurry diffusion mechanism is obtained.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] 1. By independently setting the inlet and outlet water level control modules, independent control of the water levels at both ends of the simulation test chamber is achieved, forming a stable lateral hydraulic gradient within the chamber. Furthermore, by using a stepped or continuously changing mode to simulate dynamic water level changes under different working conditions, this solves the problem that existing technologies cannot simulate the slurry diffusion process under varying hydraulic gradients.

[0034] 2. Through the nested design of the inner and outer pipes, combined with the sealing and isolation effect of the nitrogen bag, precise water level control is achieved while ensuring the stability of the seepage water environment indicators. The outer pipe returns the overflow liquid to the supply tank through a flexible hose, realizing the recycling of the seepage liquid at the supply end and saving experimental costs.

[0035] 3. Through the rectifying effect of the water distribution plate, the water flow entering and exiting the test chamber is evenly distributed on the cross-section, which truly restores the laminar flow and seepage state in the underground aquifer and avoids experimental errors caused by local turbulence. The measuring ends of the water content sensor and the negative pressure sensor are located in the residual medium of the formation inside the water distribution plate, which can truly reflect the changes in water content and capillary negative pressure inside the pores.

[0036] 4. By installing negative pressure sensors and moisture content sensors on the left and right side walls of the test chamber, as well as pressure sensors on the rear wall, and using non-destructive optical monitoring methods such as digital cameras and multi-band light sources, intuitive and visual monitoring of the slurry diffusion process can be achieved. Combined with image processing technology, images can be converted into optical signal data to achieve non-destructive quantitative analysis of slurry diffusion morphology and dilution degree. Attached Figure Description

[0037] Figure 1 This is a front view of the overall structure of the visualization device of the present invention;

[0038] Figure 2 This is a schematic diagram of the data acquisition module structure;

[0039] Figure 3 A three-dimensional view of the overall structure of the visualization device of the invention.

[0040] In the diagram, A is the water supply and drainage module; A1 is the liquid supply unit; A2 is the drainage unit; B is the hydraulic gradient control module; B1 is the inlet water level control module; B2 is the outlet water level control module; C is the slurry diffusion visualization simulation module; D is the data acquisition module; E is the non-destructive quantitative monitoring module; 1 is the liquid supply tank; 2 is the test bench; 3 is the nitrogen bag; 4 is the inner tube; 5 is the outer tube; 6 is the hose; 7 is the water pressure sensor; 8 is the continuous water level control module; 9 is the transistor and potentiometer; 10 is the negative pressure sensor. ; 11. Simulated grouting pipe; 12. Rotary clamp; 13. Electric slide rail; 14. Test chamber; 15. Polarizer; 16. Hoses II; 17. Base; 18. Inlet and outlet; 19. Optical calibration plate; 20. Water distribution plate; 21. Moisture content sensor; 22. Horizontal connecting pipe; 23. Opening and closing device; 24. Drainage tank; 25. Water collection chamber; 26. Pressure sensor; 27. Data converter; 28. Data acquisition unit; 29. ​​Polarizer; 30. Multi-band light source; 31. Digital camera. Detailed Implementation

[0041] The following is in conjunction with the appendix Figure 1 To be continued Figure 3 The principles and features of the present invention are described, and the examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0042] like Figures 1 to 3 As shown, the visualization device for slurry diffusion in a water-filled goaf under varying hydraulic gradients provided by the present invention mainly includes a water supply and drainage module A, a hydraulic gradient control module B, a slurry diffusion visualization simulation module C, a data acquisition module D, and a non-destructive quantitative monitoring module E.

[0043] The water supply and drainage module A includes a liquid supply unit A1 and a drainage unit A2. The hydraulic gradient control module B includes an inlet water level control module B1 and an outlet water level control module B2. The slurry diffusion visualization simulation module C is located in the middle of the device, with its left end connected to the inlet water level control module B1 and its right end connected to the outlet water level control module B2. The liquid supply unit A1 is connected to the inlet water level control module B1 to supply it with seepage liquid, and the drainage unit A2 is connected to the outlet water level control module B2 to receive the discharged seepage liquid. The data acquisition module D is used for the acquisition and analysis of monitoring data during the experiment; the non-destructive quantitative monitoring module E is used for the acquisition of images during the experiment. Each module will be described in detail below.

[0044] (a) Water supply and drainage module A

[0045] The liquid supply unit A1 includes a liquid supply tank 1, used to store and supply seepage liquid simulating the water environment conditions of a goaf. The seepage liquid is prepared using ultrapure water according to the actual water chemistry conditions of the goaf, and after being aerated with nitrogen to the actual redox conditions of the goaf, it is sealed and stored to avoid the influence of air on the water environment. The liquid supply tank 1 is connected to the bottom of the inlet water level control module B1 via a flexible hose, realizing the liquid supply regulation of the inlet water level control module B1. A micro pump for adjusting the liquid pumping flow rate is installed on the flexible hose.

[0046] The drainage unit A2 is set up in a similar manner to the liquid supply unit A1, including a drainage tank 24. The drainage tank 24 is also connected to the outlet water level control module B2 through a flexible pipe, and is used to collect the seepage liquid discharged from the outlet water level control module B2 during the experiment.

[0047] (II) Visual Simulation Module C for Slurry Diffusion

[0048] The slurry diffusion visualization simulation module C includes a test chamber 14, used to fill the experimental residual stratum medium. This medium can be selected from quartz sand or actual residual stratum medium from the goaf, depending on experimental needs, and is screened and graded according to the different porosity conditions of the residual stratum in different goaf areas. The test chamber 14 is made of transparent material for easy observation and photography. In this embodiment, the test chamber 14 is made of plexiglass with a wall thickness of 20mm and an internal volume of 1000mm × 30mm × 900mm (length × width × height). Fastening screws are installed and sealed at 200mm from the left and right walls and 150mm from the top and bottom walls to prevent expansion or damage due to internal pressure during filling. Water distribution plates 20 are installed near the left and right walls inside the test chamber 14, a simulated grouting pipe 11 that can move horizontally and vertically is provided at the top, and independent inlet and outlet water ports 18 are provided at the bottom. The test chamber 14 is supported by a base 17 and placed on the ground or a test platform.

[0049] The water distribution plate 20 is densely covered with tiny through holes, which allows the water to flow evenly as it enters or exits the test chamber 14, avoiding the formation of preferential flow or eddies. The two water distribution plates 20 are separated from the left and right walls of the test chamber 14, respectively, to form water collection chambers 25, serving as buffer zones before the water enters and exits the test chamber 14. The water collection chambers 25 on both sides are connected to the corresponding inlet water level control module B1 and outlet water level control module B2 via several horizontally spaced horizontal connecting pipes 22 arranged vertically.

[0050] The inlet and outlet 18 are connected to the liquid supply tank 1 through pipelines and are equipped with independent valves. They are only used when the residual medium in the formation is saturated with water before the experiment. During the experiment, the valves are kept closed.

[0051] The simulated grouting pipe 11 is an acrylic perforated pipe with multiple grout outlet holes on its wall. The length of the simulated grouting pipe 11 can range from 100 to 800 mm, and its inner diameter is approximately 15 mm. A rotating clamp 12 is connected to the upper end of the simulated grouting pipe 11. The rotating clamp 12 is mounted on an electric slide rail 13, which is located at the top of the test chamber 14. The electric slide rail 13 can move the rotating clamp 12 horizontally and can rotate itself to change the inclination angle of the grouting pipe. Both the electric slide rail 13 and the rotating clamp 12 are connected to a program control system. By inputting commands, the pre-embedding depth and injection angle of the simulated grouting pipe 11 within the test chamber can be precisely controlled. The specific structures of the rotating clamp 12 and the electric slide rail 13 are existing technologies and will not be described in detail here.

[0052] (III) Hydraulic gradient control module B

[0053] The inlet water level control module B1 and the outlet water level control module B2 are located on the left and right sides of the test chamber 14, respectively. They have the same structure and independently control the water level at the inlet and outlet of the test chamber 14. Both the inlet water level control module B1 and the outlet water level control module B2 include an inner pipe 4 and an outer pipe 5 that are sleeved and connected, as well as a water pressure sensor 7, a continuous water level control module 8, and a transistor and potentiometer 9.

[0054] The inner tube 4 is a vertically arranged plexiglass tube with multiple drain outlets spaced at intervals along its sidewall. Each drain outlet is equipped with an opening / closing element 23 to control the opening and closing of the corresponding drain outlet. The opening / closing element 23 is a mechanical valve or a pluggable sealing plug (such as a rubber stopper). By using the opening / closing element 23 to open drain outlets at different heights, a stepped water level change mode is achieved. During the test, excess water enters the gap between the inner tube 4 and the outer tube 5 and flows back to the water supply tank 1 via a micro pump. Specifically, an operating port is provided on the outer tube 5 at a location corresponding to the drain outlet. The operating port is equipped with a pluggable sealing plug similar to the opening / closing element 23. Opening this operating port facilitates the operation of the opening / closing element 23. The bottom of the inner tube 4 is connected to the liquid supply tank 1 via a flexible hose 6. Liquid supply is achieved at the inlet water level control module B1, and liquid discharge is achieved at the outlet water level control module B2. A water pressure sensor 7 is also installed at the bottom of the inner tube 4 to monitor the water level and pressure inside the inner tube 4 in real time. The water pressure sensor 7, transistor and potentiometer 9, and micro pump are all connected to the water level continuous control module 8. The pressure data fed back by the water pressure sensor 7 in real time is converted into water head height by the water level control module. By setting the built-in program input command of the water level continuous control module 8, the direction and speed of water flow of the micro pump can be adjusted by the transistor and potentiometer 9 to achieve a specific mode of stepless continuous change of water level. One end of the horizontal connecting pipe 22 is connected to the inner tube 4, and the other end passes through the outer pipe 5 and is connected to the water collection chamber 25.

[0055] The outer pipe 5 is a larger diameter pipe that is sealed and fitted over the inner pipe 4, forming a water storage space between the inner pipe 4 and the outer pipe 5. A nitrogen bag 3, filled with nitrogen, is connected to the top of the outer pipe 5 to isolate it from external air and prevent oxygen from entering the system through the overflow liquid, thereby maintaining stable redox conditions for the permeate. The lower end of the side wall of the outer pipe 5 is connected to the supply water tank 1 via a flexible hose 16, allowing the liquid overflowing into the water storage space between the inner pipe 4 and the outer pipe 5 to be discharged.

[0056] The continuous water level control module 8 and the transistor and potentiometer 9 are electrically connected to the micro pump and the water pressure sensor 7, forming a closed-loop control system. The continuous water level control module 8 is used to input preset water level change commands. The transistor and potentiometer 9 adjusts the power supply parameters of the micro pump according to the commands, thereby precisely controlling the speed and flow rate of the micro pump. The water pressure sensor 7 monitors the water level and pressure in the inner pipe 4 in real time and feeds the signal back to the continuous water level control module 8, realizing dynamic closed-loop regulation of the water level.

[0057] The working process of the inlet water level control module B1 and the outlet water level control module B2 can be divided into a stepped water level control mode and a continuously changing water level control mode. The specific working principle is as follows.

[0058] Driven by a micro pump, the seepage fluid in the supply tank 1 enters the inner tube 4 of the inlet water level control module B1 from the bottom through hose 6. As the seepage fluid is continuously pumped in, the water level in the inner tube 4 gradually rises.

[0059] (1) The control principle of the stepped water level control mode is as follows:

[0060] When the water level needs to be set at a specific height, the operator opens the drain outlet 23 at that height. If a rubber stopper is used, it is removed at that height, while ensuring that the opening / closing parts 23 of all other drain outlets are closed. As the micro pump continuously pumps the seepage fluid into the inner pipe 4, the water level in the inner pipe 4 rises continuously. The seepage fluid flows through the horizontal connecting pipe 22 into the water collection chamber 25 on the left side of the test chamber 14, and then enters the test chamber through the water distribution plate 20. When the water level exceeds the set height, the seepage fluid flows out from the opened drain outlet into the water storage space between the inner pipe 4 and the outer pipe 5. The lower end of the outer pipe 5 uses a hose 16 to return the overflow fluid in the water storage space to the supply tank 1 using the micro pump, realizing the recycling of the seepage fluid. The micro pump pumps the returned seepage fluid, along with the fresh seepage fluid in the supply tank 1, back into the inner pipe 4, forming a closed loop. Once the water level falls below the set height, the drain outlet stops overflowing, and the micro pump continues to supply water to restore the water level. In this way, the water level in the inner tube 4 is precisely locked at the set height, which is the water head height applied to the left end of the test chamber 14.

[0061] Similarly, the outlet water level control module B2 independently controls the water level in its inner pipe 4 to lock the outlet water head at a preset height at the right end of the test chamber 14. The head difference between the left and right ends forms a hydraulic gradient, driving the water flow from left to right through the test chamber. The structure of the outlet water level control module B2 is the same as that of the inlet water level control module B1, but its function is to control the water level on the outlet side. The hoses 6 and 16 before the outlet water level control module B2 and the drain tank 24 are both used for drainage. The water level in the inner pipe 4 of the outlet water level control module B2 is also set by the opening and closing element 23 or the water level continuous control module 8. The water flow on the right side of the test chamber 14, after passing through the water distribution plate 20, collects in the right water collection chamber 25, and then flows into the inner pipe 4 of the outlet water level control module B2 through the horizontal connecting pipe 22. Water in the inner pipe 4 of the outlet water level control module B2 that is higher than the opening of the drain outlet overflows into the water storage space between the inner pipe 4 and the outer pipe 5 of the outlet water level control module B2, and is finally discharged into the drain tank 24 for collection through the pipeline.

[0062] (2) The control principle of the continuously changing water level control mode is as follows:

[0063] In this mode, the opening / closing element 23 does not need to be operated. The operator inputs a preset water level change curve into the continuous water level control module 8. The preset water level change curve can be a periodic or irregular hydraulic change scenario, such as a stepped, sinusoidal, or other type. The continuous water level control module 8 transmits the command to the transistor and potentiometer 9, which adjusts the speed of the micro pump, so that the flow rate pumped into the inner pipe 4 changes sequentially according to the preset pattern. As a result, the water level in the inner pipe 4 rises and falls smoothly. At the same time, the water pressure sensor 7 monitors the water level in real time and feeds the signal back to the control module, forming a closed-loop regulation to ensure that the water level changes strictly according to the preset curve.

[0064] (iv) Data Acquisition Module D

[0065] The data acquisition module D includes a negative pressure sensor 10 vertically distributed on the left side wall of the test chamber 14, a moisture content sensor 21 vertically distributed on the right side wall, and a pressure sensor 26 installed on the rear wall. Each sensor is connected to the data acquisition unit 28 through a data converter 27.

[0066] Negative pressure sensor 10 is used to monitor the dynamic changes of capillary negative pressure at the inlet under different hydraulic gradient conditions. Moisture content sensor 21 is used to monitor the changes in moisture content in the pores of the residual formation medium during grouting under different hydraulic gradient conditions. The measuring ends of both negative pressure sensor 10 and moisture content sensor 21 penetrate from the side wall of the test chamber 14, extending into the residual formation medium and located inside the corresponding side water distribution plate 20, to ensure that the measured data represent the true capillary negative pressure and moisture content within the pore medium. Pressure sensors 26 are arranged on the back of the test chamber 14 in a set spacing matrix to monitor the dynamic changes in pressure during grout diffusion under different hydraulic gradient conditions. Data converter 27 converts the electrical signals from the sensors into digital signals, which are automatically recorded in real-time by data acquisition unit 28 and transmitted to the data storage system, achieving real-time online monitoring of pressure, moisture content, and capillary negative pressure.

[0067] (v) Non-destructive quantitative monitoring module E

[0068] The non-destructive quantitative monitoring module E includes a multi-band light source 30, a digital camera 31, a polarizer 15, and an analyzer 29. The front of the test chamber 14 is the observation surface, which is free of sampling holes and sensor elements to ensure a complete and clear imaging field of view. The polarizer 15 is positioned on the front observation surface of the test chamber 14, and the analyzer 29 is positioned between the multi-band light source 30 and the digital camera 31. The polarizer 15 and analyzer 29 work together to calibrate the angular positions between the digital camera 31, the multi-band light source 30, and the test chamber, ensuring image quality and data repeatability. A long, narrow optical calibration plate 19 is positioned below the observation surface of the test chamber 14. This optical calibration plate 19 is located in the same vertical plane as the observation surface and is used to calibrate light intensity data errors caused by slight changes in current during the experiment due to fluctuations in the light source. The multi-band light source 30 can illuminate the test chamber 14 at different wavelengths, and the digital camera 31 acquires images of the slurry diffusion plume at different time points. The acquired images are converted into optical signal data by image processing software. By analyzing the changes in the optical signal, information on the diffusion morphology and dilution degree of the slurry can be quantitatively obtained.

[0069] (vi) Visual experimental method for slurry diffusion in water-filled goaf under varying hydraulic gradient

[0070] The following section provides a detailed explanation of the method for conducting simulation experiments using this device, based on specific experimental procedures.

[0071] The first stage is the experimental preparation stage, and the specific procedures are as follows:

[0072] S1: Pressure sensor installation.

[0073] On the rear wall of the test chamber 14, mark the monitoring points according to the preset monitoring interval, and install and fix the pressure sensors 26 one by one. The pressure sensors 26 can be reused, and different layout schemes can be set according to the test purpose.

[0074] S2: Determination of grouting layer location and angle.

[0075] By inputting instructions through the program control system, the rotary clamp 12 is controlled to move on the electric slide rail 13 to the target horizontal position, and then the rotary clamp 12 is controlled to rotate to the target angle, so as to accurately set the pre-embedded depth and injection angle of the simulated grouting pipe 11.

[0076] S3: Material filling.

[0077] Based on experimental requirements, different gradations of residual formation media (quartz sand or actual goaf media) were selected and layered for filling test chamber 14. During the filling process, vibration compaction was performed according to the experimental design to avoid the formation of cavities or local unevenness.

[0078] S4: Installation of moisture content sensor and negative pressure sensor.

[0079] When the material is filled to the preset depth of each sensor, the measuring ends of the moisture content sensor 21 and the negative pressure sensor 10 are placed in the test chamber 14, with their measuring ends located in the residual medium of the formation inside the corresponding side water distribution plate 20. Then, filling and vibration compaction are continued. All sensors are connected to the data acquisition unit 28 through the data converter 27 and calibrated.

[0080] Step 5: Water environment condition regulation.

[0081] Prepare the seepage solution according to the actual hydrochemical conditions of the goaf (using ultrapure water with added appropriate ionic components), then treat the seepage solution with nitrogen aeration until the oxidation-reduction potential value is the same as that of the goaf. Store the treated seepage solution in supply water tank 1 and seal it for preservation.

[0082] Step 6: Saturation of residual medium in the formation.

[0083] Connect the supply water tank 1 to the inlet / outlet 18 via pipeline. Close the connecting valves between the left and right sides of the test chamber 14 and the inlet water level control module B1 and the outlet water level control module B2. Open the valve at the bottom inlet / outlet 18. Start the micro pump to slowly inject the seepage liquid into the test chamber 14 from bottom to top. The bottom-up injection method completely displaces and expels the air in the pores of the filling medium until the medium reaches a uniform saturation state, then stop the injection. Close the valve at the bottom inlet / outlet 18.

[0084] The second stage is the formal experimental stage, and the specific procedures are as follows:

[0085] Step 7: Establishment and control of hydraulic gradient.

[0086] Open the valves on both sides of the test chamber 14 between the inlet water level control module B1 and the outlet water level control module B2. Start the micro pump on the pipeline between the liquid supply unit A1 and the inlet water level control module B1 to supply liquid to the inner tube 4 of the inlet water level control module B1, establishing the inlet head according to the preset water level height. The water level in the inner tube 4 of the outlet water level control module B2 is set according to the preset outlet head. After the lateral water flow in the test chamber is basically stable, continue running for 24 hours until the water and air reach relative equilibrium. The establishment and control of the hydraulic gradient includes two modes, which should be selected according to the experimental requirements:

[0087] Stepped water level change mode: According to the experimental design, the operator opens and closes the opening and closing parts 23 of the drain outlets at preset heights on the inner pipes 4 of the inlet water level control module B1 and the outlet water level control module B2, and closes the opening and closing parts 23 of the remaining drain outlets. When it is necessary to switch water levels, the drain outlet at the target height is opened and the drain outlet at the original height is closed, realizing a step-like change in water level. The nitrogen bag 3 connected to the top of the outer pipe 5 maintains the anaerobic environment of the water storage space throughout the process, preventing air intrusion from affecting the physicochemical conditions of the seepage liquid.

[0088] Continuous water level variation mode: The operator inputs a preset water level variation curve (such as the rate of change, target water level, duration, etc.) into the continuous water level control module 8. The continuous water level control module 8 transmits the command to the transistor and potentiometer 9 to adjust the speed of the micro pump and change the flow rate of the liquid entering the inner pipe 4. The water pressure sensor 7 monitors the water level in the inner pipe 4 in real time and feeds the signal back to the control module. After comparing it with the preset value, a closed-loop regulation is formed, so that the water level changes continuously and strictly according to the preset curve. No manual intervention of the opening and closing component 23 is required during this process.

[0089] Step 8: Grout injection.

[0090] Prepare the grout according to the preset water-cement ratio and mix it evenly using a mixing tank. Inject the grout into the designed layer through the simulated grouting pipe 11 using a mud pump at a set pressure. During the grouting process, the depth and angle of the grouting pipe can be adjusted in real time through a program control system. Grouting is stopped once the grout diffusion plume has completely stabilized.

[0091] Step 9: Data Acquisition and Image Acquisition

[0092] The data acquisition unit 28 is activated as soon as grouting begins. Data from the negative pressure sensor 10, moisture content sensor 21, and pressure sensor 26 are continuously recorded by the data acquisition unit 28. The acquisition frequency can be set to 1 minute to ensure that the data is accurate enough.

[0093] Simultaneously, by adjusting the wavelength of the multi-band light source 30, photographs of the slurry diffusion plume are captured by a digital camera 31 in a darkroom environment before grouting and at different grouting time points. Image processing software is used to convert the captured images into optical signal data to analyze the slurry diffusion morphology and dilution degree.

[0094] By coupling and analyzing image data of slurry diffusion morphology and dilution process with data on pressure, water content and negative pressure, the diffusion mechanism of slurry under varying hydraulic gradient conditions is revealed.

[0095] For the same simulation conditions, the experiment can be repeated multiple times to ensure the reliability of the data.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A visualization device for slurry diffusion in a water-filled goaf under varying hydraulic gradients, characterized in that, include: The water supply and drainage module (A) includes a liquid supply unit (A1) and a drainage unit (A2). The liquid supply unit (A1) includes a liquid supply tank (1) for storing and supplying seepage liquid under simulated goaf water environment conditions. The drainage unit (A2) includes a drainage tank (24) for collecting seepage liquid discharged during the experiment. The hydraulic gradient control module (B) includes an inlet water level control module (B1) and an outlet water level control module (B2). The liquid supply unit (A1) is connected to the inlet water level control module (B1) to supply seepage liquid to it, and the drainage unit (A2) is connected to the outlet water level control module (B2) to receive the seepage liquid discharged by it. The slurry diffusion visualization simulation module (C) includes a transparent test chamber (14) filled with residual formation media. The test chamber (14) is connected to the corresponding water level control module (B1) and water level control module (B2) via several horizontal connecting pipes (22) arranged vertically at intervals. The data acquisition module (D) is used for the collection and analysis of monitoring data; The non-destructive quantitative monitoring module (E) is used to acquire images during the experiment.

2. The visualization device for slurry diffusion in a water-filled goaf under varying hydraulic gradients as described in claim 1, characterized in that, The test chamber (14) is provided with water distribution plates (20) near the left and right side walls respectively, and the two water distribution plates (20) form water collection cavities (25) with the adjacent side walls respectively; the top of the test chamber (14) is provided with a simulated grouting pipe (11) that can move horizontally and vertically, and the bottom of the test chamber (14) is provided with independent inlet and outlet water ports (18), which are connected to the supply water tank (1) pipeline.

3. The visualization device for slurry diffusion in a water-filled goaf under varying hydraulic gradients as described in claim 2, characterized in that, Both the inlet water level control module (B1) and the outlet water level control module (B2) include an inner pipe (4) and an outer pipe (5). The inner tube (4) has multiple drain outlets spaced vertically along its sidewall. Each drain outlet is equipped with an opening and closing device (23) to control the opening and closing of the corresponding drain outlet. The bottom of the inner tube (4) is connected to the liquid supply tank (1) via a hose (6). A micro pump is installed on the hose (6). A water pressure sensor (7) is also installed at the bottom of the inner tube (4) to monitor the water level and pressure in real time. The inner tube (4) is connected to the water collection chamber (25) via the horizontal connecting pipe (22). The outer tube (5) is sealed outside the inner tube (4), and a water storage space is formed between the inner tube (4) and the outer tube (5). A nitrogen bag (3) is connected to the top of the outer tube (5). The lower end of the outer tube (5) is connected to the liquid supply tank (1) through a second hose (16) to realize the discharge of liquid overflowing between the inner tube (4) and the outer tube (5).

4. The visualization device for slurry diffusion in a water-filled goaf under varying hydraulic gradients as described in claim 3, characterized in that, The inlet water level control module (B1) and the outlet water level control module (B2) both include a continuous water level control module (8) and a transistor and potentiometer (9). The micro pump, the continuous water level control module (8), the transistor and potentiometer (9) and the water pressure sensor (7) are electrically connected to realize liquid level regulation.

5. The visualization device for slurry diffusion in a water-filled goaf under varying hydraulic gradients according to claim 2, characterized in that, The simulated grouting pipe (11) is a glass flower pipe with a rotating clamp (12) connected to its upper end. The rotating clamp (12) is installed on an electric slide rail (13), which is located at the upper end of the test chamber (14). Both the electric slide rail (13) and the rotating clamp (12) are connected to a program control system to control the layout depth and injection angle of the simulated grouting pipe (11).

6. The visualization device for slurry diffusion in a water-filled goaf under varying hydraulic gradients according to claim 2, characterized in that, A long strip optical calibration plate (19) is set below the observation surface of the test chamber (14) for calibrating data errors caused by light source fluctuations at different time points.

7. The visualization device for slurry diffusion in a water-filled goaf under varying hydraulic gradients according to claim 2, characterized in that, The data acquisition module (D) includes a negative pressure sensor (10) vertically distributed on the left side wall of the test chamber (14), a moisture content sensor (21) vertically distributed on the right side wall, and a pressure sensor (26) installed on the rear wall. It also includes a data acquisition unit (28), and each sensor is connected to the data acquisition unit (28) through a data converter (27).

8. The visualization device for slurry diffusion in a water-filled goaf under varying hydraulic gradients according to claim 1, characterized in that, The non-destructive quantitative monitoring module (E) includes a multi-band light source (30), a digital camera (31), a polarizer (15), and an analyzer (29). The polarizer (15) is located on the observation surface of the test chamber (14), and the analyzer (29) is located between the multi-band light source (30) and the digital camera (31) for calibrating the optical path angle.

9. The visualization device for slurry diffusion in a water-filled goaf under varying hydraulic gradients according to claim 3, characterized in that, The opening and closing component (23) is a mechanical valve or a pluggable sealing plug, which achieves stepped water level setting by opening the drain outlets at different heights.

10. A method for conducting a simulation experiment using the visualization device according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1 Pressure sensor layout: Pressure sensors (26) are arranged on the back of the test chamber (14) at a preset monitoring interval. S2 Grouting Layer and Angle Determination: By controlling the position of the rotating clamp (12) on the electric slide rail (13) through the program, the pre-embedded depth and injection angle of the simulated grouting pipe (11) are precisely set; S3 Material Filling: Fill the test chamber (14) with the screened and graded residual formation medium; S4 Moisture content sensor and negative pressure sensor placement: When the material is filled to the preset depth of the sensor, place the moisture content sensor (21) and negative pressure sensor (10) on the corresponding layer of the side wall of the test chamber (14), continue filling and vibrating to compact; S5 Water Environment Condition Control: The seepage liquid is prepared according to the actual water chemistry conditions of the goaf and aerated until the oxidation-reduction conditions are consistent with those of the goaf. It is then stored in the liquid supply tank (1) of the liquid supply unit (A1). S6 Formation Residual Medium Saturation: Close the connecting valves on both sides of the test chamber (14) to the inlet water level control module (B1) and the outlet water level control module (B2), open the valves at the bottom inlet and outlet (18), and slowly inject the seepage liquid in the liquid supply unit (A1) into the test chamber (14) from bottom to top until the air in the medium pores is completely displaced and the medium reaches a uniform saturation state; S7 Hydraulic gradient establishment and control: Close the valves of the bottom inlet and outlet (18), open the valves connecting the test chamber (14) to the inlet water level control module (B1) and the outlet water level control module (B2), and independently control the inlet water level and outlet water level through the inlet water level control module (B1) and the outlet water level control module (B2) respectively, so as to form a preset hydraulic gradient in the test chamber (14) and continue to run for a preset time; the establishment and control of the hydraulic gradient includes a stepped water level change mode and a continuous water level change mode: The stepped water level change mode is as follows: by opening the drain outlet at a preset height on the side wall of the inner pipe (4) at the inlet or outlet and closing the other drain outlets, the water level is stabilized at the corresponding height, and the step change of water level is achieved by switching drain outlets at different heights. The continuous water level change mode is as follows: by inputting instructions through the water level continuous control module (8), the speed of the micro pump is adjusted by the transistor and potentiometer (9), and the pressure signal is fed back in real time by the water pressure sensor (7) to realize the stepless continuous change of water level; S8 Grouting: The grout is prepared according to the preset water-cement ratio and injected into the design layer through the simulated grouting pipe (11) by the grouting pump at the set pressure. Grouting is stopped after the grout diffusion plume stabilizes. S9 Data Acquisition and Image Acquisition: Starting from the start of grouting, each sensor and data acquisition device (28) is activated to record data in real time. At the same time, digital camera (31) is used to acquire images of slurry diffusion plume at different time points in the dark room. By coupling and analyzing the image data and sensor data, the slurry diffusion mechanism is obtained.

Images