A goaf separation multi-layer position grouting surface subsidence control test device and method

Abstract

The present application relates to the technical field of coal mining, and more particularly to a goaf separation multi-layer grouting surface subsidence control test device and method. The test device comprises: a main simulation unit and a loading unit; the main simulation unit comprises a counterforce frame, the counterforce frame comprises six sides and has a hollow chamber, loading oil cylinders are arranged on the left, right, upper and rear sides of the counterforce frame, and the loading unit is connected with the loading oil cylinders; water injection pipes and water outlet pipes are arranged on the front and rear sides of the counterforce frame, respectively, coal seam simulation material is arranged at the bottom of the hollow chamber, and the coal seam simulation material is NaHCO3. The experimental device realizes the simulation test of goaf separation multi-layer grouting under true triaxial loading, and simplifies the simulation process of coal seam excavation.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, and in particular to a test device and method for controlling surface subsidence through multi-layer grouting in goaf areas. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Continuous and intensive mining of coal resources has led to the depletion of coal resources in some mining areas. This has resulted in surface subsidence, causing increasingly prominent ecological and environmental problems such as damage to surface buildings and roads, land abandonment, and deterioration of the groundwater environment. In recent years, overburden separation grouting technology has become one of the effective technical approaches to address these problems. Overburden separation grouting fully utilizes the space separated from the coal seam after mining, injecting filling material into the separated area through surface boreholes to slow down the bending and subsidence of the rock strata, thus mitigating surface subsidence. It effectively achieves parallel operations of underground mining and surface grouting without interference, and features low cost, high coal recovery rate and production efficiency, making it suitable for high-capacity operations. Currently, some scholars have studied the theory and numerical model of overburden separation grouting. However, due to numerous influencing conditions restricting field measurements and practical research, there is an urgent need to design a device that can simulate overburden separation grouting under actual production conditions. This device would then be used to verify and correct existing theoretical and numerical simulation studies, providing a reliable basis for filling mining in coal mines.

[0004] Patent CN114351685A discloses a method and device for controlling surface subsidence through grouting in overburden delamination. This invention improves upon existing delamination grouting technology by employing directional drilling and vacuum negative pressure techniques to grout the delamination space, meeting the requirements of ultra-long pumping and support for subsidence reduction. However, the device is only designed for small-scale models, is relatively simple, has limited functionality, and cannot simulate real geological formations. Patent CN113433132A discloses a device for simulating grouting and filling in overburden delamination. The device can be flexibly moved according to the test site, can simulate different coal seam dip angles, can change the box size according to the design, can flexibly adjust the position of the grouting pipe according to the location of the delamination zone during the excavation process, and can simulate multi-layer delamination grouting and multiple working faces simultaneously carrying out delamination grouting operations. However, although the device can realize different similarity ratio models, it does not realize true triaxial loading. It is only a small-sized box-type delamination grouting mechanism study, which can not truly simulate the stress environment of the actual site conditions. Moreover, the simulation of coal seam excavation methods is complicated. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a test device for controlling surface subsidence through multi-level grouting in goaf areas, thereby simulating multi-level grouting in goaf areas under true triaxial loading and simplifying the simulation process of coal seam excavation.

[0006] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0007] A test device for controlling surface subsidence through multi-layer grouting in goaf areas includes: a main simulation unit and a loading unit; the main simulation unit includes a reaction frame, which has six sides and a hollow cavity, and loading cylinders are provided on the left, right, upper, and rear sides of the reaction frame, and the loading unit is connected to the loading cylinders; water injection pipes and water outlet pipes are respectively provided on the front and rear sides of the reaction frame, and coal seam simulation material, namely NaHCO3, is provided at the bottom of the hollow cavity.

[0008] Preferably, the reaction frame is composed of frame-type unit frames, which are welded from steel plates and connected to each other by bolts.

[0009] Preferably, a multi-stratum simulation material is provided on the upper side of the coal seam simulation material in the hollow cavity, and a roadbed is provided on the upper side of the multi-stratum simulation material; the piston rod of the loading cylinder is connected to a pressure plate, and the pressure plate presses against the roadbed.

[0010] Preferably, it also includes a grouting unit, wherein a delamination grouting pipe is provided in the middle of the upper side of the reaction frame, and curtain grouting pipes are provided on both sides of the upper side. The grouting unit is connected to the delamination grouting pipe and the curtain grouting pipe.

[0011] Preferably, pressure gauges and flow meters are installed at the top of both the delamination grouting pipe and the curtain grouting pipe to detect grouting pressure and flow rate.

[0012] Preferably, the grouting unit includes a delamination grouting pump, a curtain grouting pump, and a two-position two-way solenoid valve. The delamination grouting pump and the curtain grouting pump are connected to one end of the two-position two-way solenoid valve, and the other end of the two-position two-way solenoid valve is connected to the delamination grouting pipe and the curtain grouting pipe.

[0013] Preferably, a support is provided on the left side of the bottom surface of the reaction frame, the bottom of the support is fixed to the bottom surface, and the top of the support is rotatably connected to the reaction frame; the right side of the bottom surface of the reaction frame is connected to a rotating support fixed to the ground through a diagonal brace loading cylinder, and the diagonal brace loading cylinder is rotatably connected to both the reaction frame and the rotating support.

[0014] Preferably, it also includes a water injection unit, which includes a water tank, a water pump, and a water control solenoid valve. The water tank is connected to the water pump, and one end of the water control solenoid valve is connected to the water pump, while the other end is connected to the water injection pipe.

[0015] Preferably, it also includes a monitoring unit, which includes a stress sensor, a seepage pressure sensor and a displacement sensor disposed in the hollow cavity.

[0016] This invention also provides a test method for the above-mentioned multi-layer grouting surface subsidence control test device for goaf, comprising: laying simulated material in the hollow cavity of the reaction frame; pre-burying several curtain grouting pipes on both sides in the width direction and pre-burying a delamination grouting pipe in the middle during the laying process; controlling the loading cylinder to apply static load to the overlying rock layer of the goaf by the loading unit to simulate the real ground stress state; controlling the upper loading cylinder to apply dynamic load to simulate the load of highway vehicles; performing curtain grouting while monitoring the grouting pressure and flow rate data during the curtain grouting process; controlling the water outlet of the water injection pipe to dissolve NaHCO3 to simulate coal seam excavation; performing delamination grouting by the grouting unit while monitoring the grouting pressure and flow rate during the delamination grouting process; collecting multi-data at corresponding locations through stress sensors, seepage sensors, and displacement sensors deployed in the simulated material during the curtain grouting and delamination grouting processes, and performing imaging, analysis, and reproduction by the monitoring unit.

[0017] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0018] 1. This invention utilizes loading cylinders arranged in three directions on a reaction frame to create a simulation test device for multi-level grouting in goaf areas under true triaxial loading. This places the model under a stress combination state with unequal principal stresses, applying triaxial stress to the model to more realistically simulate the actual stress environment on-site, enabling the monitoring of the entire process of surface subsidence control during grouting in the upper part of the goaf. Simultaneously, by setting main and outlet water pipes on the reaction frame, and using NaHCO3 as a coal seam simulation material, the rapid dissolution of NaHCO3 in water is used to simulate coal seam excavation, simplifying the simulation process.

[0019] 2. This invention, through the cooperation of the loading unit and the loading cylinder, can apply dynamic load to the model to simulate the load of highway vehicles, thereby obtaining an evaluation of the grouting effect.

[0020] 3. This invention can simulate delamination curtain grouting by using a grouting unit in conjunction with a curtain grouting pipe, thereby studying the influence of the grouting curtain on delamination development and delamination grouting.

[0021] 4. This invention adjusts the angle of the reaction frame by coordinating the inclined bracing loading cylinder, rotating support, and support, which facilitates the laying of inclined strata and the simulation of strata at multiple angles.

[0022] Advantages of additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 This is a schematic diagram of the experimental apparatus according to Embodiment 1 of the present invention;

[0026] Figure 2 This is a diagram showing the internal strata and pipeline layout of the test apparatus according to Embodiment 1 of the present invention;

[0027] Figure 3 This is a schematic top view of the grouting curtain according to Embodiment 1 of the present invention;

[0028] Figure 4 This is a diagram illustrating the state changes of a coal seam excavation leading to a goaf, as simulated by the experimental apparatus of Embodiment 1 of the present invention.

[0029] Figure 5 This is a schematic diagram of the grouting unit of the test device according to Embodiment 1 of the present invention;

[0030] Figure 6 This is a schematic diagram of the water injection unit of the test device according to Embodiment 1 of the present invention;

[0031] Figure 7 This is a flowchart of the test method of Embodiment 2 of the present invention;

[0032] In the diagram: 1. Main simulation unit, 2. Loading unit, 3. Grouting unit, 4. Water injection unit, 5. Monitoring unit, 1-1. Roadbed, 1-2. Bearing plate, 1-3. Separation grouting pipe, 1-4. Curtain grouting pipe, 1-5. Coal seam, 1-6. Loading cylinder, 1-7. Water outlet pipe, 1-8. Water injection pipe, 1-9. Inclined brace loading cylinder, 1-10. Rotary support, 1-11. Separation, 1-12. Pressure gauge, 1-13. Flow meter, 1-14. Grouting curtain, 1-15. Reaction frame, 3-1. Two-position two-way solenoid valve, 3-2. Curtain grouting pump, 3-3. Separation grouting pump, 3-4. Pressure sensor, 3-5. Flow sensor, 3-6. Data sensing and control system, 4-1. Water tank, 4-2. Water pump.

[0033] The distances or dimensions between parts have been exaggerated to show their positions; the diagram is for illustrative purposes only. Detailed Implementation

[0034] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] For ease of description, the words "up," "down," "left," "right," "front," and "back" appearing in this invention only indicate that they are consistent with the up, down, left, and right directions of the accompanying drawings themselves. They do not limit the structure and are merely for the purpose of facilitating the description of this invention and simplifying the description. They do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0036] Existing experimental devices have failed to achieve true triaxial loading and simulate real strata. Furthermore, the methods for simulating coal seam excavation are complex. Therefore, this invention proposes a multi-layer grouting surface subsidence control experimental device for goaf areas. This device can simulate goaf overburden collapse conditions and perform goaf grouting reinforcement and detection model tests, revealing the goaf grouting reinforcement control mechanism. The device includes: a main simulation unit and a loading unit; the main simulation unit includes a reaction frame with six faces and a hollow chamber. Loading cylinders are installed on the left, right, top, and rear sides of the reaction frame, and the loading unit is connected to the loading cylinders; water injection pipes and water outlet pipes are respectively installed on the front and rear sides of the reaction frame; coal seam simulation material, NaHCO3, is placed at the bottom of the hollow chamber.

[0037] This invention utilizes loading cylinders positioned in three directions of the reaction frame to create a simulation test device for multi-level grouting in goaf areas under true triaxial loading. This device can apply triaxial stress to the model and monitor the entire process of surface subsidence control during grouting in the upper part of the goaf. Simultaneously, by installing a main water pipe and an outlet water pipe on the reaction frame, and using NaHCO3 as a coal seam simulation material, the rapid dissolution of NaHCO3 in water is leveraged to simulate coal seam excavation, simplifying the simulation process.

[0038] Existing experimental devices often feature small-sized models, which can lead to size effects and fail to realistically simulate the entire process of delamination grouting reinforcement. The reaction frame of this invention measures 2.00m x 1.54m x 1.46m, with an internal model size of 1.3m x 0.73m x 0.73m. This large-sized reaction frame is composed of modular unit frames, each welded from 50mm steel plates and assembled with bolts to form the model's internal space. This large-sized reaction frame mitigates the impact of size effects, making it closer to a realistic on-site simulation.

[0039] The large-size loading reaction frame is equipped with loading cylinders on its left, right, top, and rear sides to apply ground stress. The loading cylinders are mounted on the loading reaction frame via front flanges, and the piston rods of the loading cylinders are connected to the pressure plate, which acts on the model surface.

[0040] Existing testing equipment cannot simulate highway vehicle loads after delamination grouting, resulting in a lack of evaluation of the grouting effect. In this invention, a multi-stratum simulation material is placed on top of the coal seam simulation material in the hollow cavity, and a roadbed is placed on top of the multi-stratum simulation material. The piston rod of the loading cylinder is connected to a pressure plate, which presses against the roadbed. Through the cooperation of the loading unit and the loading cylinder, dynamic loads can be applied to the model to simulate highway vehicle loads, thereby obtaining an evaluation of the grouting effect.

[0041] Existing experimental setups cannot simulate curtain grouting. This invention employs a grouting unit, with a delamination grouting pipe positioned in the middle of the upper side of the reaction frame and curtain grouting pipes positioned on both sides of the upper side. The grouting unit is connected to both the delamination grouting pipes and the curtain grouting pipes. By combining the grouting unit with the curtain grouting pipes, delamination curtain grouting can be simulated, thereby studying the influence of the grouting curtain on delamination development and delamination grouting.

[0042] A support is installed on the left side of the bottom surface of the reaction frame. The bottom of the support is fixed to the bottom surface, and the top of the support is rotatably connected to the reaction frame. The right side of the bottom surface of the reaction frame is connected to a rotating support fixed to the ground via a diagonal brace loading cylinder. The diagonal brace loading cylinder is rotatably connected to both the reaction frame and the rotating support. The angle of the reaction frame can be adjusted by coordinating the diagonal brace loading cylinder, the rotating support, and the support, which facilitates the laying of inclined strata and the simulation of strata at multiple angles.

[0043] The monitoring unit includes a computer and flow sensors, pressure sensors, temperature sensors, oil pressure sensors, displacement sensors, and a phased array ultrasonic detector. The output signal lines of all sensors are connected to the computer to monitor changes in data within the model.

[0044] The experimental device of this invention effectively solves a series of problems such as the significant impact and damage of overlying strata collapse in mining areas on existing buildings and projects, threatening safe operation. It can be widely applied in the field of grouting technology for delamination of mining subsidence strata, providing important reference for grouting design and construction.

[0045] Example 1

[0046] The following description, in conjunction with the embodiments and accompanying drawings, will illustrate the experimental device for controlling surface subsidence through multi-layer grouting in goaf areas of highways provided by the present invention.

[0047] like Figure 1This invention relates to a large-scale, multi-layered grouting surface subsidence control test device for goaf areas in simulated highways. The device comprises a main simulation unit 1, a loading unit 2, a grouting unit 3, a water injection unit 4, and a monitoring unit 5. It can conduct model tests on grouting reinforcement under goaf overburden collapse conditions, enabling the detection of the entire process of grouting reinforcement within large-scale goaf overburden rock strata and the monitoring of its effects. The device also reveals the control mechanism of grouting reinforcement and the formation mechanism of the directional grouting vein network.

[0048] The main simulation unit 1 is the main body of the experiment. The loading unit 2 provides loading power to the main simulation unit 1. The grouting unit 3 can control the delivery of grout in the main simulation unit 1. The water injection unit 4 can control the water injection in the main simulation unit 1. The monitoring unit 5 is a multi-dimensional physical information detection system used to monitor changes in data inside the model of the main simulation unit 1.

[0049] like Figure 2 , 3 As shown in Figure 4, the main simulation unit 1 includes a large-size reaction frame 1-15, a pressure plate 1-2, a delamination grouting pipe 1-3, a curtain grouting pipe 1-4, a loading cylinder 1-6, a water outlet pipe 1-7, a water injection pipe 1-8, a diagonal bracing loading cylinder 1-9, a rotating support 1-10, a pressure gauge 1-12, and a flow meter 1-13. The interior is paved with a roadbed 1-1 and a coal seam 1-5, which can simulate the generation, development, and grouting treatment of delamination 1-11, ultimately forming a grouting curtain 1-14. The large-size loading reaction frame 1-15 is composed of unit frame frames, which are assembled by bolts. Hydraulic cylinders 1-6 are installed on the left, right, top, and rear sides of the large-size loading reaction frame, all mounted on the front flange of the hydraulic cylinders. The left and right cylinders are responsible for applying stress in the left and right directions, the top cylinder is responsible for providing stress in the up and down directions, and the rear cylinder is responsible for providing stress in the front and back directions. The piston rod of the loading cylinder is connected to the pressure plate 1-2, which acts on the surface of the model to apply triaxial stress to the coal and rock composite.

[0050] Loading cylinders 1-6 are controlled by loading unit 2 (servo hydraulic loading control system, i.e., hydraulic station), which can realize synchronous loading, linkage loading, or separate loading of the loading cylinders. The loading cylinders are equipped with displacement sensors. The pressure in the oil circuit and the loading displacement of the cylinder piston are detected in real time by the computer fully digital servo control system to realize servo control of the hydraulic cylinders.

[0051] The delamination grouting pipe 1-3 is installed in the middle of the large-size reaction frame 1-15, extending into the stratum. Grouting is injected into the delamination of the model through grouting unit 3. Pressure gauge 1-12 and flow meter 1-13 are installed on the outside of the grouting pipe to detect the grouting pressure and flow rate. Several curtain grouting pipes 1-4 are installed on both sides of the large-size reaction frame 1-15, and curtain grouting is performed on both sides of the delamination of the model through grouting unit 3. Water injection pipe 1-8 and water outlet pipe 1-9 are located at the front and rear of the model, respectively, and water is injected into the coal seam through water injection unit 4 to simulate coal seam excavation.

[0052] The large-size loading reaction frame 1-15 is connected to the support 1-16. The rotating support 1-10 and the inclined brace loading cylinder 1-9 are located at the bottom of the large-size loading reaction frame 1-15, which can achieve overall rotation, making it convenient to lay inclined strata and simulate strata at multiple angles.

[0053] like Figure 5 As shown, grouting unit 3, also known as automated grouting unit, includes a delamination grouting pump 3-3, a curtain grouting pump 3-2, a two-position two-way solenoid valve 3-1, a flow sensor 3-5, a pressure sensor 3-4, and a data sensing and control system 3-6. The motors on the delamination grouting pump 3-3 and the curtain grouting pump 3-2 are connected to the data sensing and control system 3-6, which controls their grouting parameters. The grouting port is connected to one end of several two-position two-way solenoid valves 3-1, and the other end of the two-position two-way solenoid valves 3-1 is connected to the delamination grouting pipe 1-3 and the curtain grouting pipe 1-4, which control the grouting on / off. A pressure sensor 3-4 and a flow sensor 3-5 are connected to each grouting pump to transmit the grouting pressure and flow information to the data sensing and control system 3-6.

[0054] like Figure 6 As shown, the water injection unit 4, also known as the water injection simulation control system, includes a water tank 4-1, a water pump 4-2, a water control solenoid valve, a pressure sensor, a flow sensor, and a data sensing and control system. The water tank 4-1 is connected to the water pump 4-2, and the motor on the water pump 4-2 is connected to the data sensing and control system 3-6. The water injection parameters are controlled by the data sensing and control system 3-6. The water control solenoid valve is also a two-position two-way solenoid valve. The water injection port is connected to one end of several water control solenoid valves, and the other end of the water control solenoid valve is connected to the water injection pipe 1-8. The water injection is controlled by the water control solenoid valve. A pressure sensor and a flow sensor are connected to the outside of the water pump to transmit the water injection pressure and flow information to the data sensing and control system.

[0055] Example 2

[0056] like Figure 7As shown, a test method for controlling surface subsidence in multi-layer grouting in highway goaf areas is provided. This method utilizes the aforementioned test device for controlling surface subsidence in multi-layer grouting in highway goaf areas. The steps include:

[0057] S1. Prepare similar materials for multiple strata models according to the physical and mechanical properties of the original rock and coal seam and the similarity ratio.

[0058] S2. Similar materials are filled into the device layer by layer, and sensors and pipelines are arranged in the corresponding simulated strata, with compaction performed at regular intervals. The top stratum is a similar stratum simulating the roadbed and pavement of a highway. The bottom layer consists of a 900mm × 400mm × 400mm area, with NaHCO3 as the similar material to simulate a coal seam. A water injection pipe is installed at the bottom; by injecting water into the coal seam, the water-soluble properties of NaHCO3 are used to simulate coal seam excavation. During the laying process, several curtain grouting pipes are pre-embedded on both sides of the model's width, and a separation grouting pipe is pre-embedded in the middle of the model.

[0059] S3. Assemble the top surface of the model assembly to seal the entire model within the assembly.

[0060] S4. The hydraulic station servo controls the loading cylinder to apply static load to the overlying rock strata of the goaf to simulate the real ground stress state.

[0061] S5. The grouting unit performs curtain grouting to form a curtain wall and make the curtain wall reach a certain strength. At the same time, the grouting pressure, flow rate and other data are monitored during the curtain grouting process. When the grouting pressure of the pipeline reaches the target value, the grouting is stopped.

[0062] S6. Control the water output from the injection pipe to dissolve NaHCO3, simulating coal seam excavation, and ultimately forming a cavity inside the model to simulate the goaf. As the working face of the goaf advances and the top delamination gradually expands, the grouting unit performs delamination grouting. Simultaneously, it monitors data such as grouting pressure and flow rate, and water injection pressure and flow rate during the delamination grouting process. By controlling the water flow rate and pressure, the dissolution rate of NaHCO3 is controlled, simulating the rate control during coal seam excavation. Excess water is discharged from the outlet. When the grouting pressure in the pipeline reaches the target value, it indicates that the delamination has stopped expanding, the grout has filled the delamination area, and grouting is stopped.

[0063] S7. During the curtain grouting and delamination grouting process, stress sensors, seepage pressure sensors, displacement sensors and other data at the corresponding locations are collected by the model and then imaged, analyzed and reproduced by the monitoring unit.

[0064] S8. Dynamic loads are applied to the upper cylinder by controlling the dynamic hydraulic station. By applying low strain rate vibration loads to the model, slope waves, harmonic waves, noise waves, pulse waves and their combinations can be simulated to simulate highway vehicle loads.

[0065] S9. After the delamination grout has stabilized, apply a certain load using the loading cylinder, while simultaneously monitoring the top settlement using a displacement sensor. Grouting is considered successful once the settlement reaches the required value; otherwise, grout needs to be replenished. The quantitative relationship between the main controlling factors such as delamination grouting pressure and flow rate and the stress distribution and physical and mechanical properties of the injected medium can be studied to obtain the subsequent grouting reinforcement law under conditions of changes in grouting pressure and the physical and mechanical properties of the medium.

[0066] S10. After the delamination grouting reinforcement is completed, disassemble the sensors and pipelines, remove the model materials, and end the simulation test.

[0067] A realistic simulation method for controlling surface subsidence through multi-level grouting in goaf areas along highways was developed, enabling full-process monitoring of surface subsidence control through multi-level grouting in large-scale goaf areas.

[0068] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A goaf separation multi-layer position grouting ground subsidence control test device, characterized in that, The utility model relates to a coal seam simulation device, including: A main body simulation unit and a loading unit; The main body simulation unit includes a counterforce frame, the counterforce frame includes six surfaces and has a hollow chamber, loading oil cylinders are arranged on the left, right, upper and rear surfaces of the counterforce frame, and the loading unit is connected with the loading oil cylinders; Water injection pipes and water outlet pipes are arranged on the front and rear surfaces of the counterforce frame respectively, coal seam simulation material is arranged at the bottom of the hollow chamber, and the coal seam simulation material is NaHCO3; The utility model further includes a grouting unit, a separation grouting pipe is arranged in the middle of the upper surface of the counterforce frame, and curtain grouting pipes are arranged on both sides of the upper surface, and the grouting unit is connected with the separation grouting pipe and the curtain grouting pipes; Pressure gauges and flow meters are arranged at the top of the separation grouting pipe and the curtain grouting pipe to detect grouting pressure and flow; The utility model further includes a water injection unit, the water injection unit includes a water tank, a water pump and a water control electromagnetic valve, the water tank is connected with the water pump, one end of the water control electromagnetic valve is connected with the water pump, and the other end is connected with the water injection pipe; The utility model further includes a monitoring unit, the monitoring unit includes stress sensors, osmotic pressure sensors and displacement sensors arranged in the hollow chamber.

2. The gob separation multi-layer position grouting surface subsidence control test device of claim 1, wherein, The counterforce frame is composed of columnar unit frames, the columnar unit frames are welded from steel plates, and the columnar unit frames are connected through bolts.

3. The gob separation multi-layer position grouting surface subsidence control test device of claim 1, wherein, Multi-layer simulation material is arranged on the upper side of the coal seam simulation material in the hollow chamber, a roadbed is arranged on the upper side of the multi-layer simulation material, the piston rod of the loading oil cylinder is connected with a pressure bearing plate, and the pressure bearing plate bears on the roadbed.

4. The gob separation multi-layer position grouting surface subsidence control test device of claim 1, wherein, The grouting unit includes a separation grouting pump, curtain grouting pumps and a two-position two-way electromagnetic valve, the separation grouting pump and the curtain grouting pumps are connected with one end of the two-position two-way electromagnetic valve, and the other end of the two-position two-way electromagnetic valve is connected with the separation grouting pipe and the curtain grouting pipes.

5. The gob separation multi-layer position grouting surface subsidence control test device of claim 1, wherein, A support is arranged on the left side of the bottom surface of the counterforce frame, the bottom of the support is fixed to the bottom surface, and the top of the support is rotationally connected with the counterforce frame; the right side of the bottom surface of the counterforce frame is connected with a rotating support fixed to the ground through a diagonal bracing loading oil cylinder, and the diagonal bracing loading oil cylinder is rotationally connected with the counterforce frame and the rotating support.

6. The test method for the gob separation multi-layer position grouting surface subsidence control test device according to any one of claims 1-5, characterized in that, Including: Laying simulation material in the hollow chamber of the counterforce frame, embedding a plurality of curtain grouting pipes on both sides in the width direction and embedding a separation grouting pipe in the middle during the laying process; Controlling the loading oil cylinder to apply static load to the overburden strata of the goaf by the loading unit to simulate the real stress state; Performing curtain grouting while monitoring grouting pressure and flow data in the curtain grouting process; Controlling the water outlet of the water injection pipe to dissolve NaHCO3 to simulate coal seam excavation, performing separation grouting by the grouting unit while monitoring grouting pressure and flow in the separation grouting process; Controlling the upper loading oil cylinder to apply dynamic load to simulate highway vehicle load; Collecting multi-element data of corresponding positions through the stress sensors, osmotic pressure sensors and displacement sensors arranged in the simulation material during the curtain grouting and separation grouting processes, and imaging, analyzing and reproducing through the monitoring unit.

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