A full-stage goaf flow field similar simulation device and method for delamination grouting

Abstract

The application discloses a kind of full-stage gob flow field similar simulation equipment and method of delaminating grouting, the equipment includes gob box, ventilation gas injection system, pressurizing system, heating temperature measuring system, gas extraction gas measuring system;Gob box is provided with simulation layer, simulation layer includes from top to bottom layer by layer arranged overburden similar material, fissure zone similar material and the caving zone similar material with air inlet and return airway and working face;The application selects rubber material instead of broken coal rock mass, sets the additional mine pressure of delaminating grouting to gob by the way of synchronous pressurization by similarity theory, realizes the flow environment of gob pressure-bearing porous medium by smaller pressure, and further realizes the action law of analyzing gob flow field.

Description

Technical Field

[0001] This invention relates to the field of coal mine safety, specifically to a similar simulation device and method for the flow field of goaf in the entire stage of delamination grouting; applicable to the analysis and study of the flow field in goaf under delamination grouting conditions. Background Technology

[0002] Coal mining under "three-under" conditions (buildings, railways, and water bodies) is widespread in my country. The resulting goaf collapses cause surface subsidence, severely damaging the ecological environment and infrastructure. Delamination grouting technology, which involves filling delaminations with grout through surface drilling, artificially interferes with the compression process of the fractured rock mass within the goaf, altering air leakage. Since spontaneous combustion of coal mainly occurs in the difficult-to-monitor goaf, delamination grouting makes it difficult to predict the spontaneous combustion hazard zone and ignition location, resulting in poor fire suppression effectiveness. Therefore, it is necessary to establish technical methods to study the gas flow patterns in the goaf under the additional stress of delamination grouting, guiding the delineation of spontaneous combustion hazard zones and the prevention and control of spontaneous combustion in the field.

[0003] In recent years, scholars have been using physical simulations in laboratories to study the flow field and spontaneous combustion of coal in the goaf of fully mechanized longwall mining faces. Currently, most existing physical models of goafs are formed by filling them with crushed stone, crushed coal, etc. These filling materials are not loaded with overlying rock strata to create pressure, or they have pressurization devices but are limited by equipment to realize the process of crushing and compacting the goaf under pressure, as well as the application of additional stress by delamination grouting. Summary of the Invention

[0004] To address the aforementioned technical shortcomings, the purpose of this invention is to provide a similar simulation device and method for the flow field in the goaf during the entire stage of delamination grouting. It selects rubber material to replace the broken coal and rock mass, and uses similarity theory to set the additional mine pressure on the goaf by delamination grouting through synchronous pressurization. It achieves the flow environment of the pressure-bearing porous medium in the goaf with a relatively small pressure, thereby realizing the analysis of the effect law of the flow field in the goaf.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention is divided into two parts: pressure bearing test of similar materials and grouting similarity test of delamination.

[0007] Compressive stress tests on similar materials and fractured raw coal and rock:

[0008] To ensure the accuracy of simulating the compression process of goaf rock using similar materials, it is necessary to conduct experimental tests to ensure that the stress-deformation curve of the rubber-similar material is the same functional curve as that of the stress-deformation curve of the coal and rock in the field. Furthermore, by controlling the particle size and shape of the rubber, it is necessary to maintain the same initial porosity and fractal dimension as the fractured coal and rock under the same volume. Macroscopically, the initial porosity of the pressure-bearing experimental material is:

[0009]

[0010] in ρ is the initial porosity; m is the sample mass (kg); ρ is the sample density (kg / m³). 3 Q is the cross-sectional area of ​​the sample, in meters. 2 H represents the initial loading height of the crushed sample, in meters (m).

[0011] Let m1 be the mass of the original material, ρ1 be the density of the original material, m2 be the mass of the similar material, and ρ2 be the density of the similar material. Then, when m1ρ2 = m2ρ1, the similar material and the original material have the same initial porosity.

[0012] Laterally confined axial bearing tests were conducted. During compaction, there was a certain correlation between axial stress and porosity. Based on the experimental relationship between the two, the formula for calculating axial stress was defined as follows:

[0013]

[0014] Where σ is the axial stress, MPa; a and b are regression coefficients, determined by the pressure test curve; This represents the decrease in porosity.

[0015] Therefore, the formula for calculating the stress application in similar experiments is established as follows:

[0016]

[0017] In the formula, σ1 is the axial stress of the original material; a1 and b1 are the regression coefficients of the original material; a2 and b2 are the regression coefficients of the similar material; and σ2 is the axial stress of the similar material.

[0018] After determining the axial stress to be applied to the original coal and rock material, the axial stress to be applied to similar materials can be obtained by substituting it into the formula.

[0019] Similar experiment of delamination grouting:

[0020] This invention provides a goaf flow field similarity simulation device for the entire stage of delamination grouting, including a goaf box simulating the goaf, a ventilation and gas injection system, a pressurization system, a heating and temperature measurement system, and a gas sampling and measurement system;

[0021] The goaf box is equipped with a simulation layer, which includes overlying rock strata similar materials, fracture zone similar materials, and caving zone similar materials with intake and return airways and working faces arranged layer by layer from top to bottom; a number of pressurization systems for applying pressure to the simulation layer are arranged between the overlying rock strata similar materials and the top plate of the goaf box.

[0022] The ventilation and gas injection system includes a gas injection system and a ventilation system. The gas injection system is used to control the mixed gas of CH4 and N2 to enter the bottom of the goaf box. The main pipeline in the ventilation and gas injection system is connected to the working face and is provided with small holes for releasing gas, so that the gas can slowly enter the interior of the goaf caving zone similar material and the fracture zone similar material.

[0023] The ventilation system also includes a fan connected to the working face; the working face is connected to the intake and return airway and is provided with multiple evenly arranged holes to simulate air leakage at the working face;

[0024] The gas sampling and measurement system includes a gas sampling device located within the simulation layer. This device is positioned at a pre-defined sampling point and connected to an external gas chromatograph. The gas chromatograph and pressurization system are electrically connected to an industrial computer. The gas chromatograph can analyze O2, CH4, CO2, N2, and C. X H Y The specific gravity of the gas components.

[0025] The heating and temperature measurement system includes a resistance temperature detector (RTD) located at the gas intake point and a heating plate located at the bottom of the goaf chamber. The RTD is electrically connected to an external temperature acquisition instrument, and the heating plate is electrically connected to a goaf temperature controller to control the temperature of the simulation layer.

[0026] Preferably, the pressurization system includes mutually compatible thin hydraulic jacks, hydraulic control valves, and hydraulic sensors. Each pressurization system is electrically connected to the others, employing electro-hydraulic servo technology and a synchronous pressure-dividing control circuit. It receives electrical signals from an industrial computer, amplified and transmitted via a PLC, driving the hydraulic control valves connected to the thin hydraulic jacks to manipulate their movements, thus achieving programmed pressurization. The hydraulic sensors transmit display information to the industrial computer, enabling pressure-dividing control of each pressurization system based on the displayed data.

[0027] Preferably, the thin hydraulic jack in the pressurization system is connected to an oil tank and a hydraulic pump outside the goaf box, and the outlet of the hydraulic pump is equipped with a check valve.

[0028] Preferably, the gas injection system includes two high-pressure gas cylinders for storing CH4 and N2 respectively. A pressure reducing valve, a pressure stabilizing valve, a flow stabilizing valve, a pressure gauge, a gas resistance valve, and a flow sensor are arranged sequentially on the pipes connected to the outlets of the high-pressure gas cylinders. The two pipes are connected to the main pipeline after the flow sensor is connected. The main pipeline extends into the bottom of the caving zone similar material in the goaf box.

[0029] The present invention also provides a method for using the goaf flow field similarity simulation equipment for the entire stage of delamination grouting, comprising the following steps:

[0030] S1. To test the actual rock mechanics parameters of the coal and rock mass in the goaf of the coal mine, select the corresponding rubber-like material to ensure that the rubber-like material has a similar fractal dimension to the original material, i.e., the real broken rock. Furthermore, by controlling the particle size and shape of the rubber, the mass and density relationship between the rubber-like material and the original material is made to satisfy m1ρ2=m2ρ1, and the same initial porosity is maintained with the broken coal and rock under the same volume.

[0031] S2. Conduct axial bearing tests on two materials under lateral confinement conditions, and define the axial stress-porosity change model as follows:

[0032]

[0033] Where σ is the axial stress in Pa; a and b are regression coefficients, determined by the pressure test curve. This represents the decrease in porosity.

[0034] The model coefficients for similar and original materials were determined through experiments.

[0035] S3. Calculate the equivalent stress applied in similar experiments. The calculation formula is as follows:

[0036]

[0037] In the formula, σ1 is the axial stress of the original material; a1 and b1 are the regression coefficients of the original material; a2 and b2 are the regression coefficients of the similar material; and σ2 is the axial stress of the similar material.

[0038] S4. Lay a similar material for the caving zone according to the particle size distribution law and pressure test results of the caving zone in the goaf. Lay a similar material for the fracture zone on top of the similar material for the caving zone. Arrange thin hydraulic jacks on top of the similar material for the overlying strata according to the grouting borehole positions. The bottom of the thin hydraulic jacks must be intact rocks and the upper surface must be kept horizontal. The top of the thin hydraulic jacks must be in contact with the top plate of the goaf box. The similar material for the overlying strata is formed by mixing gypsum powder and borax.

[0039] S5. Turn on the gas injection system at the bottom of the goaf box and slowly introduce N2 into the goaf platform. During the gas supply process, take gas multiple times at 10-minute intervals. When the volume fraction of O2 in the goaf gas is less than 2%, the initial gas environment setup is complete.

[0040] S6. Based on the required simulated on-site grouting conditions, the pressurization process is divided into the following stages in chronological order: no-pressure stage, pressurization stage, pressure stabilization stage, and overpressure stage.

[0041] Based on the additional pressure characteristics of filling at different stages, the hydraulic control valves are controlled by an industrial computer to drive each thin hydraulic jack to apply pressure; at the same time, the ventilation system connecting the goaf is turned on, and the wind speed and air volume are converted according to the similarity ratio of the goaf size. After the grouting stage of each simulation is stable, the air intake point is monitored.

[0042] The pressureless stage simulates the state before grouting or the stage at the beginning of grouting when a low-concentration slurry is injected, and no pressure is applied to each thin hydraulic jack;

[0043] During the pressurization stage, which simulates the initial stage of grouting where the grout filling volume is greater than the delamination development volume, the pressure applied by the thin hydraulic jack is less than the design value of the grouting pressure, and the pressure of the thin hydraulic jack gradually increases from the working face to the rear of the goaf.

[0044] The pressure stabilization stage simulates the grouting pressure reaching the design value and stabilizing. This stage lasts the longest. All thin hydraulic jacks apply the same pressure, and the value is the equivalent value of the grouting pressure.

[0045] The overpressure stage is the final stage of grouting. Grouting continues until the grouting pressure exceeds the design pressure. Each thin hydraulic jack applies the same pressure, and the value exceeds the equivalent value of the grouting pressure.

[0046] The beneficial effects of this invention are as follows:

[0047] 1. The device design meets the requirements of similar simulation, realizing the gas flow field simulation of the pressure-bearing process of broken coal and rock in the goaf of a real coal mine under relatively small pressure conditions, thus avoiding the equipment cost under high pressure.

[0048] 2. By applying stress through a pressurization system, and by applying pressure synchronously or individually through thin hydraulic jacks, the compaction effect of the delamination filler on the goaf can be simulated under different grouting stages when a small pressure is applied. This allows for the simulation of the goaf flow field throughout the entire life cycle of delamination grouting mining, and can also be used for related similar simulation experiments of the goaf flow field under stress.

[0049] 3. The pressurization system can precisely control the output power through an industrial computer, reducing construction deviations. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0051] Figure 1 This is a schematic diagram of a goaf flow field similarity simulation device for the entire stage of delamination grouting provided in an embodiment of the present invention;

[0052] Figure 2 A flowchart illustrating the method of using a goaf flow field similarity simulation device for the entire stage of delamination grouting, as provided in this embodiment of the invention;

[0053] Figure 3 This is a top view of the experimental device platform for flow field similarity test in goaf area provided in the embodiment of the present invention;

[0054] Figure 4 Stress curves of the original material and similar materials provided for embodiments of the present invention.

[0055] Explanation of reference numerals in the attached figures:

[0056] 1. High-pressure gas cylinder; 2. Pressure reducing valve; 3. Pressure regulating valve; 4. Flow regulating valve; 5. Pressure gauge; 6. Gas resistance; 7. Flow sensor; 8. Oil tank; 9. Hydraulic pump; 10. Motor; 11. Check valve; 12. Thin hydraulic jack; 13. Goaf box; 14. Overlying strata similar material; 15. Fracture zone similar material; 16. Collapse zone similar material; 17. Working face; 18. Intake and return airway; 19. Industrial computer; 20. Gas chromatograph; 21. Goaf temperature controller; 22. Flow meter; 23. Fan. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] like Figure 1 , Figure 3 As shown, a flow field similarity simulation device for the entire stage of goaf grouting is presented.

[0059] It includes a goaf box 13 simulating a goaf, a ventilation and gas injection system, a pressurization system, a heating and temperature measurement system, and a gas sampling and measurement system;

[0060] The goaf box 13 is equipped with a simulation layer inside. The simulation layer includes overlying rock strata similar material 14, fracture zone similar material 15, and caving zone similar material 16 arranged from top to bottom, which are equipped with intake and return airway 18 and working face 17. Several pressurization systems for applying pressure to the simulation layer are arranged between the overlying rock strata similar material 14 and the top plate of the goaf box 13.

[0061] The ventilation and gas injection system includes a gas injection system and a ventilation system. The gas injection system is used to control the mixed gas of CH4 and N2 to enter the bottom of the goaf box 13. The main pipeline in the ventilation and gas injection system is connected to the working face and is provided with small holes for releasing gas, so that the gas can slowly enter the interior of the goaf caving zone similar material 16 and the fracture zone similar material 15.

[0062] The ventilation system also includes a fan 23 connected to the working face 17; the working face 17 is connected to the air inlet and outlet tunnel 18 and is provided with a plurality of evenly arranged holes to simulate air leakage in the working face 17; the fan 23 is equipped with a flow meter 22.

[0063] The gas sampling and measurement system includes a gas sampling device located in the simulation layer. The gas sampling device is located at a preset gas sampling point and connected to an external gas chromatograph. The gas chromatograph and the pressurization system are electrically connected to an industrial computer 19.

[0064] The heating and temperature measurement system includes a resistance temperature detector (RTD) located at the gas intake point and a heating plate located at the bottom of the goaf chamber 13. The RTD is electrically connected to an external temperature acquisition instrument, and the heating plate is electrically connected to a goaf temperature controller 21 to control the temperature of the simulated layer. The heating plate is used to simulate the heating of residual coal in the goaf, and the RTD is used to monitor heat transfer caused by convective heat transfer of leaking air in the goaf.

[0065] Gas sampling points are located inside the goaf chamber 13 at distances of 2cm, 6cm, and 15cm from the bottom plate, with four sampling points on each floor. The sampled gas is fed to a gas chromatograph 20, which can analyze O2, CH4, CO2, N2, and C. X H Y The specific gravity of the gas components.

[0066] The pressurization system includes mutually compatible thin hydraulic jacks 12, hydraulic control valves, and hydraulic sensors. Each pressurization system is electrically connected to the others, employing electro-hydraulic servo technology and a synchronous pressure-dividing control circuit. It receives electrical signals from the industrial computer 19, amplified and transmitted via a PLC, driving the hydraulic control valves connected to the thin hydraulic jacks 12 to manipulate their movements, thus achieving programmed pressurization. The hydraulic sensors transmit display information to the industrial computer 19, and the pressure-dividing control of each pressurization system is implemented based on the displayed data.

[0067] The thin hydraulic jack 12 in the pressurization system is connected to the oil tank 8 and hydraulic pump 9 outside the goaf box 13. The outlet of the hydraulic pump 9 is equipped with a one-way valve 11, and the hydraulic pump 9 is connected to the motor 10.

[0068] The gas injection system includes two high-pressure gas cylinders 1 for storing CH4 and N2 respectively. A pressure reducing valve 2, a pressure regulating valve 3, a flow regulating valve 4, a pressure gauge 5, a gas resistance valve 6, and a flow sensor 7 are arranged sequentially on the pipes connected to the outlets of the high-pressure gas cylinders 1. The two pipes are connected to the main pipeline after the flow sensor 7 is connected. The main pipeline extends into the bottom of the caving zone similar material 16 inside the goaf box 13.

[0069] like Figure 2 As shown, this embodiment provides a method for using the goaf flow field similarity simulation equipment for the entire stage of delamination grouting, including the following steps:

[0070] 1. By controlling the particle size and shape of the rubber blocks, the relationship between the original material (i.e., broken coal and rock) and the original material (m1ρ2=m2ρ1) is maintained under the same volume, so that they have the same initial porosity and fractal dimension.

[0071] 2. Conduct axial bearing tests on two materials under lateral confinement conditions, and define their axial stress-porosity change model as follows:

[0072]

[0073] Where σ is the axial stress in Pa; a and b are regression coefficients, determined by the pressure test curve. This represents the decrease in porosity.

[0074] The experiment yielded the following values ​​for the coal and rock materials: a1 = 0.331, b1 = 6.52, a2 ​​= 0.211, b2 = 3.503; the fitted curves of the applied stress and the change in porosity are shown in the attached figure. Figure 4 As shown.

[0075] 3. Calculate the equivalent stress applied in similar experiments. The formula is as follows:

[0076]

[0077] In the formula, σ1 is the axial stress of the prototype material; a1 and b1 are the regression coefficients of the prototype material; a2 and b2 are the regression coefficients of the similar material; and σ2 is the axial stress of the similar material.

[0078] 4. Lay a caving zone similar material 16 according to the particle size distribution law of the caving zone and the pressure test results. Lay a fracture zone similar material 15 on top of the caving zone similar material 16. Arrange thin hydraulic jacks 12 on top of the overlying rock stratum similar material 14 according to the grouting borehole positions. The bottom of the thin hydraulic jacks 12 should be a complete rock block and the upper surface should be kept horizontal. The top of the thin hydraulic jacks 12 should be in contact with the top plate of the caving zone box 13. The overlying rock stratum similar material 14 is formed by mixing gypsum powder and borax.

[0079] 5. Turn on the gas injection system at the bottom of the goaf box 13 and slowly introduce N2 into the goaf platform. During the gas supply process, take gas multiple times at 10-minute intervals. When the volume fraction of O2 in the goaf gas is less than 2%, the initial gas environment setup is complete.

[0080] 6. Based on the required simulated on-site grouting conditions, the pressurization process is divided into four stages in chronological order: no-pressure stage, pressurization stage, pressure stabilization stage, and overpressure stage.

[0081] Based on the additional pressure characteristics of filling at different stages, the industrial computer 19 controls the hydraulic control valve to drive each thin hydraulic jack 12 to apply pressure; at the same time, the heating plate is turned on to simulate the heating of residual coal in the goaf. The wind speed and air volume are converted according to the similarity ratio of the goaf size. After the grouting stage of each simulation is stable, the gas intake point is monitored, and the temperature data of the gas intake point location is monitored.

[0082] The pressureless stage simulates the state before grouting or the stage at the beginning of grouting when a low-concentration slurry is injected, and each of the thin hydraulic jacks 12 does not apply pressure;

[0083] During the pressurization stage, which simulates the initial stage of grouting where the grout filling volume is greater than the delamination development volume, the pressure applied by the thin hydraulic jack 12 is less than the design value of the grouting pressure, and the pressure of the thin hydraulic jack 12 gradually increases from the working face to the rear of the goaf.

[0084] The pressure stabilization stage simulates the grouting pressure reaching the design value and stabilizing, which is the longest stage. Each thin hydraulic jack 12 applies the same pressure, and the value is the equivalent value of the grouting pressure.

[0085] The overpressure stage is the final stage of grouting. Grouting continues until the grouting pressure exceeds the design pressure. Each thin hydraulic jack 12 applies the same pressure, and the value exceeds the equivalent value of the grouting pressure.

[0086] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A device for simulating the flow field of a goaf during the entire stage of delamination grouting, characterized in that, It includes a goaf box (13) simulating a goaf, a ventilation and gas injection system, a pressurization system, a heating and temperature measurement system for controlling the temperature of the simulated layer, and a gas sampling and measurement system; The goaf box (13) is equipped with a simulation layer inside. The simulation layer includes overlying strata similar material (14), fracture zone similar material (15), and caving zone similar material (16) with intake and return airways (18) and working face (17) arranged layer by layer from top to bottom. Several pressurization systems for applying pressure to the simulation layer are arranged between the overlying strata similar material (14) and the top plate of the goaf box (13). The ventilation and gas injection system includes a gas injection system and a ventilation system. The gas injection system is used to control the mixed gas of CH4 and N2 to enter the bottom of the goaf box (13). The main pipeline in the ventilation and gas injection system is connected to the working face and is provided with small holes for releasing gas, so that the gas can slowly enter the interior of the goaf collapse zone similar material (16) and the fracture zone similar material (15). The ventilation system also includes a fan (23) that connects to the working face (17); the working face (17) is connected to the air inlet and outlet airway (18) and is provided with a plurality of evenly arranged holes to simulate air leakage in the working face (17); The gas sampling and measurement system includes a gas sampling device located in the simulation layer. The gas sampling device is located at a preset gas sampling point and connected to an external gas chromatograph. The gas chromatograph and the pressurization system are electrically connected to an industrial computer (19). The pressurization system includes a thin hydraulic jack (12) that is compatible with each other, a hydraulic control valve, and a hydraulic sensor. Each pressurization system is electrically connected to the others. It adopts electro-hydraulic servo technology and synchronous pressure-dividing control circuit. It receives electrical signals sent by the industrial computer (19) and amplified and transmitted by the PLC, drives the hydraulic control valve connected to the thin hydraulic jack (12) to operate the thin hydraulic jack (12) and realize the pressurization work of the thin hydraulic jack (12); the hydraulic sensor transmits display information to the industrial computer (19) and realizes the pressure-dividing control of each pressurization system according to the display data; The thin hydraulic jack (12) in the pressurization system is connected to the oil tank (8) and hydraulic pump (9) outside the goaf box (13). The outlet of the hydraulic pump (9) is equipped with a check valve (11). The method of using the goaf flow field similarity simulation equipment for the entire stage of delamination grouting includes the following steps: S1. To simulate the actual rock mechanics parameters of coal and rock masses in a coal mine goaf for the test experiment, select a corresponding rubber-like material to ensure that the rubber-like material and the original material (i.e., the real fractured rock) have similar fractal dimensions; and by controlling the particle size and shape of the rubber, ensure that the mass and density relationship between the rubber-like material and the original material meets the requirements. It maintains the same initial porosity as fractured coal and rock within the same volume. S2. Conduct axial bearing tests on two materials under lateral confinement conditions, and define the axial stress-porosity change model as follows: in For axial stress, Pa; , The regression coefficients are determined using the pressure test curves. This represents the decrease in porosity. The model coefficients for similar and original materials were determined through experiments. S3. Calculate the equivalent stress applied in similar experiments. The calculation formula is as follows: In the formula, The axial stress of the original material; , The regression coefficients of the original materials; , The regression coefficients are for similar materials; For axial stress in similar materials; S4. Lay a similar material (16) of the caving zone according to the particle size distribution law and pressure test results of the caving zone. Lay a similar material (15) of the fracture zone above the similar material (16). Arrange a thin hydraulic jack (12) above the similar material (14) of the overlying rock layer according to the grouting borehole position. The bottom of the thin hydraulic jack (12) should be a complete stone block and the upper surface should be kept horizontal. The top of the thin hydraulic jack (12) should be in contact with the top plate of the caving box (13). The similar material (14) of the overlying rock layer is formed by mixing gypsum powder and borax. S5. Turn on the gas injection system at the bottom of the goaf box (13) and control N2 to slowly enter the goaf platform. Take gas multiple times during the gas supply process, with a time interval of 10 min. When the volume fraction of O2 taken from the goaf is less than 2%, the initial gas environment setup is completed. S6. Based on the required simulated on-site grouting conditions, the pressurization process is divided into the following stages in chronological order: no-pressure stage, pressurization stage, pressure stabilization stage, and overpressure stage. According to the characteristics of the additional pressure of filling at different stages, the hydraulic control valve is controlled by the industrial computer (19) to drive each thin hydraulic jack (12) to apply pressure; at the same time, the ventilation system connecting the goaf is turned on, the wind speed and air volume are converted according to the similar ratio of the goaf size, and the air intake monitoring of the air intake point is carried out after the grouting stage of each simulation is stable. The pressureless stage simulates the state without grouting or the stage of injecting low-concentration slurry at the beginning of grouting, and each thin hydraulic jack (12) does not apply pressure; During the pressurization stage, which simulates the initial stage of grouting, the grout filling volume is greater than the delamination development volume. The pressure applied by the thin hydraulic jack (12) is less than the grouting pressure design value, and the pressure of the thin hydraulic jack (12) gradually increases from the working face to the back of the goaf. The pressure stabilization stage simulates the stage where the grouting pressure reaches the design value and stabilizes. This stage lasts the longest. Each thin hydraulic jack (12) applies the same pressure, and the value is the equivalent value of the grouting pressure. The overpressure stage is the end of the grouting process. Grouting continues until the grouting pressure exceeds the design pressure. Each thin hydraulic jack (12) applies the same pressure, and the value exceeds the equivalent value of the grouting pressure.

2. The goaf flow field similarity simulation device for the entire stage of delamination grouting as described in claim 1, characterized in that, The gas injection system includes two high-pressure gas cylinders (1) for storing CH4 and N2 respectively. A pressure reducing valve (2), a pressure regulating valve (3), a flow regulating valve (4), a pressure gauge (5), a gas resistance (6), and a flow sensor (7) are arranged sequentially on the pipes connected to the outlet of the high-pressure gas cylinders (1). The two pipes are connected to the main pipeline after the flow sensor (7). The main pipeline extends into the bottom of the caving zone similar material (16) inside the goaf box (13).

3. The goaf flow field similarity simulation device for the entire stage of delamination grouting as described in claim 1, characterized in that, The heating and temperature measurement system includes a resistance thermometer located at the gas intake point and a heating plate located at the bottom of the goaf box (13). The resistance thermometer is electrically connected to an external temperature acquisition instrument, and the heating plate is electrically connected to a goaf temperature controller (21) to control the temperature of the simulation layer.

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