A monitoring device for laboratory simulation of stress deformation of filling body

Abstract

The patent of the present invention discloses a test device for simulating the stress and deformation of a filling body in a laboratory. Through similar simulation material tests, the geological conditions and stress environment of the filling working face are simulated. By closing the connecting hose, the liquid in the device is ensured to be in a closed state, so that the effect of the overlying rock strata on the piston is expressed in the form of liquid pressure in the liquid tank. Through the connecting hole on the inner wall of the liquid tank, the internal liquid pressure is expressed as the elastic deformation of the rubber sheath. Through the strain gauge attached to the rubber sheath, the elastic deformation of the rubber sheath is output in the form of an electrical signal, and the data of the stress change of the filling body is recorded and inverted. Through the calibration of the rubber sheath, the hydraulic stress-rubber strain relationship of the liquid tank is obtained. Through the calibration of the hydraulic force measuring device, the device can be used to reflect the stress change characteristics of the filling body.

Description

Technical Field

[0001] The invention relates to the technical field of engineering rock mass, in particular to a monitoring device for simulating stress deformation of a filling body in a laboratory. Background Art

[0002] When studying the deformation law of overburden, filling materials and filling effects of backfilling working faces, it is often necessary to select backfill bodies with nonlinear mechanical properties as physical similarity simulation materials, and monitor the stress changes of backfill bodies in combination with similar material simulation tests. In the process of laboratory research on backfill bodies in backfilling working faces, there is a lack of similar simulation materials that can accurately reflect the nonlinear mechanical properties of backfill bodies, which limits the in-depth study of the action mechanism of backfill bodies in backfilling working faces in the laboratory. The data on rock formation stress changes in similar simulation material tests mostly come from pressure boxes and strain bricks buried in advance at the observation location. The measurement locations are all located in the rock or filling material, and the measurement accuracy is not high. Summary of the invention

[0003] The purpose of the present invention is to provide a monitoring device for laboratory simulation of the stress deformation of filling bodies in order to solve the above-mentioned technical problems. In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

[0004] A monitoring device for simulating the stress and deformation of a filling body in a laboratory, the monitoring device comprising a plane strain test bench, the plane strain test bench comprising a containing cavity, the interior of the containing cavity is provided with a similar simulated material layer, a simulated coal seam working face advancement layer and a hydraulic force measuring device, the hydraulic force measuring device is arranged in the simulated coal seam working face advancement layer; the hydraulic force measuring device comprises a piston push head, a bottom liquid tank and an external rubber leather sleeve, the bottom liquid tank comprises a base and a tank body; the tank body is arranged on the base, the piston push head is slidably arranged on the tank body, the outer side of the tank body is sleeved with an external rubber leather sleeve, the upper end and the lower section of the external rubber leather sleeve are both sealed and connected to the outer side of the tank body, a plurality of rectangular slits are evenly opened at the middle and lower positions of the tank body, the external rubber leather sleeve is provided with strain gauges corresponding to the positions of the rectangular slits, wherein the sum of the piston push head height, the liquid height in the tank body and the base height is equal to the equivalent mining height of the filling body in the simulation test.

[0005] Furthermore, the piston push head includes a piston shaft and a rubber pressure head. The rubber pressure head is arranged at the lower end of the piston shaft, the rubber pressure head is in contact with the liquid in the bottom liquid tank, and a sliding sealing component is arranged between the outer circumferential surface of the piston shaft and the inner circumferential surface of the bottom liquid tank.

[0006] Furthermore, the piston push head also includes reinforcing ribs, a support column is arranged inside the piston push head, a hollow cavity is formed between the support column and the outer circumferential surface of the piston push head, and a plurality of reinforcing ribs are arranged in the hollow cavity.

[0007] Furthermore, the piston push head also includes a connecting hose, which is arranged in the hollow cavity and is used to inject or extract liquid into the bottom liquid tank.

[0008] Furthermore, a switch valve is provided on the communication hose.

[0009] Furthermore, the monitoring device is implemented by the following steps:

[0010] (1) Combined with the geological and mining-related data of the research object, the rock properties and mechanical parameters of the top and bottom plates of the filling working face are mastered, including the elastic modulus E d , tensile strength σ t , compressive strengthσ c , shear strength τ, cohesion C, internal friction angle Φ, Poisson's ratio v, etc., and fully understand the mining conditions of the working face near the mining area and the layout of the tunnels;

[0011] (2) According to the similarity law, determine the geometric similarity ratio, bulk density similarity ratio, elastic modulus similarity ratio, stress similarity ratio and boundary conditions of this similarity simulation test;

[0012] (3) Determine the ratio of similar simulation materials for simulating various rock formations through a ratio test of river sand, gypsum and putty powder in the laboratory, and take the mechanical parameters of the specimens formed by the combination of the three materials as close to the lithology and mechanical parameters in step (1) as being in accordance with the law of similarity;

[0013] (4) Based on geological data and according to different mix ratios, similar simulation materials of various rock formations are sequentially built on the plane strain test bench. After the construction is completed, the materials are left to stand for 20-30 days to allow the water in the materials to fully evaporate;

[0014] (5) Calibration of the hydraulic force measuring device: Three groups of prototype filling specimens were selected and subjected to uniaxial compression tests. The measured elastic modulus, peak compressive strength and other important deformation parameters were averaged, and the stress-strain curve of the filling material was obtained;

[0015] (6) Select three sets of hydraulic force measuring devices, inject liquid into the hydraulic force measuring devices through the connecting hose, place the entire device on a uniaxial testing machine, close the connecting hose, and perform a uniaxial compression test to obtain the average value of important deformation parameters such as the elastic modulus of the device, and obtain the stress-strain curve of the test device;

[0016] (7) By adjusting the type of liquid in the tank, the rubber material and thickness of the external rubber sheath, the elastic modulus and other important deformation parameters obtained by the uniaxial compression test of the force measuring device meet the stress similarity ratio relationship, the calibration of the hydraulic force measuring device is completed, and the type of liquid, rubber material and thickness used in this simulation are determined;

[0017] (8) Calibrate the external rubber cover on the surface of the calibrated hydraulic force measuring device: paste strain gauges perpendicular to the long axis of the rectangular slits at the center positions of the multiple rectangular slits left in the liquid tank, and connect the strain gauges to the DH3816N static strain test system;

[0018] (9) Select 10 weights of equal weight, wait for the strain-time curve to be stable, add the weights to the top of the piston one by one, wait for the curve to be stable after adding, and remove the weights from the top of the piston one by one; note that you need to wait for the curve to be stable after adding or removing each weight before adding or removing it;

[0019] (10) Repeat step (9) with three force measuring devices and take the average value of the experimental data. Calculate the hydraulic stress-rubber strain curve of the liquid tank through the elastic thick-walled cylinder theory to complete the calibration of the rubber holster.

[0020] (11) Excavate the working face according to the test research object, place the hydraulic device in the observation position, inject the liquid determined by the calibration process of the hydraulic force measuring device into the liquid tank through the connecting hose, use the liquid to push the piston upward until it contacts the top plate, and close the connecting hose;

[0021] (12) As the experiment progresses, the working face continues to advance, and the monitoring device is continuously deployed in the goaf. The roof sinks and acts on the piston and compression occurs. The time-strain data is recorded. The stress-strain relationship obtained by calibrating the rubber material is combined with the outer surface scale of the tank body to calculate the stress evolution and deformation characteristics of the filling body in the filling working face.

[0022] (13) By repeating steps (5) to (10) and changing the liquid, rubber type and thickness in the tank of the hydraulic force measuring device, the stress conditions of different types of filling bodies in the filling working surface can be simulated.

[0023] The present invention has significant technical effects due to the adoption of the above technical solutions: (1) The device realizes the unified integration of the simulation of the nonlinear mechanical characteristics of the filling body and the real-time monitoring of the force and deformation; (2) The present invention provides a method for monitoring the force and deformation characteristics of the filling body in the filling working surface, which can be used for in-depth research on the action mechanism of the filling body in the filling working surface in the laboratory. At the same time, by changing the type of liquid in the hydraulic force measuring device and the material and thickness of the rubber sheath, similar materials of different types of filling bodies can be tested; (3) Since a hydraulic force measuring device is equipped with multiple strain gauges, multiple groups of data can be observed at the same position, which greatly reduces the error of the obtained data and can provide more accurate data for research. At the same time, through the calibrated force measuring device, the direct and continuous measurement of the stress state of the filling material is realized by changing the pressure of the liquid. (4) Simulate the geological conditions and stress environment of the filling working face through similar simulation material tests, inject liquid into the device through the connecting hose, push the piston upward to contact the working face roof, and install the device at the filling body stress monitoring position in the goaf; (5) Ensure that the liquid in the device is in a closed state by closing the connecting hose, so that the effect of the overlying rock strata on the piston is expressed in the form of liquid pressure in the liquid tank, and through the connecting holes on the inner wall of the liquid tank, the internal liquid pressure is expressed as elastic deformation of the rubber sheath, and through the strain gauge attached to the rubber sheath, the elastic deformation of the rubber sheath is output in the form of electrical signals, and the data of the force change of the filling body is recorded and inverted. Through the calibration of the rubber sheath, the hydraulic stress-rubber strain relationship of the liquid tank is obtained. Through the calibration of the hydraulic force measuring device, the device can be used to reflect the force change characteristics of the filling body. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of the monitoring device used for simulating the stress deformation of the filling body in the laboratory of the present invention;

[0025] Figure 2 It is a filling body stress observation flow chart of the monitoring method for laboratory simulation of filling body stress deformation in the present invention;

[0026] Figure 3 The figure is a schematic diagram of the structure of the hydraulic force measuring device in the monitoring device for simulating the stress deformation of the filling body in the laboratory according to the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the description of the present invention, it should be noted that the terms "vertical", "upper", "lower", "horizontal", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, "first", "second", "third", and "fourth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0029] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection, it can be a mechanical connection, it can be an electrical connection, it can be a direct connection, it can be connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] like Figure 1-3 As shown, a monitoring method for laboratory simulation of filling body stress deformation in the present invention is implemented by a monitoring device, the monitoring device includes a plane strain test bench, the plane strain test bench includes a containing cavity, the inside of the containing cavity is provided with a similar simulation material layer 1, a simulated coal seam working face advancing layer 2 and a hydraulic force measuring device 3, the hydraulic force measuring device 3 is arranged in the simulated coal seam working face 2 advancing layer; the hydraulic force measuring device 3 includes a piston push head 10, a bottom liquid tank 11 and an external rubber leather cover 7, the bottom liquid tank 11 includes a bottom Seat 9 and tank body 11; the tank body 11 is arranged on the base 9, the piston push head 10 is slidably arranged on the tank body 11, the outer side of the tank body 11 is sleeved with an external rubber leather cover 7, the upper end and the lower section of the external rubber leather cover 7 are both sealed and connected to the outer side of the tank body 11, a plurality of rectangular slits are evenly opened at the lower position of the tank body 11, the external rubber leather cover 7 is provided with strain gauges 8 corresponding to the positions of the rectangular slits, wherein the sum of the height of the piston push head 10, the height of the liquid in the tank body 11 and the height of the base 9 is equal to the equivalent mining height of the filling body in the simulation test.

[0031] The piston push head 10 includes a piston shaft 4 and a rubber pressure head 12. The lower end of the piston shaft is provided with a rubber pressure head 12, and the rubber pressure head 12 is in contact with the liquid in the bottom liquid tank 11. A sliding sealing component is provided between the outer circumference of the piston shaft 4 and the inner circumference of the bottom liquid tank 11.

[0032] The piston push head 10 further includes a reinforcing rib 5. A support column is disposed inside the piston push head 10. A hollow cavity is formed between the support column and the outer circumferential surface of the piston push head 10. A plurality of reinforcing ribs are disposed in the hollow cavity.

[0033] The piston push head 10 further includes a connecting hose 6 , which is disposed in the hollow cavity and is used to inject or extract liquid into the bottom liquid tank 11 .

[0034] The communication hose 6 is provided with a switch valve.

[0035] As a preferred embodiment, the upper piston push head 10 has a height of H=50mm and a diameter of D=36mm, and is composed of a middle piston shaft 4 (diameter D=20mm), a cross reinforcing rib (4mm×4mm×40mm), a rubber pressure head 12 (diameter D=36mm, height H=2mm) and a connecting hose 6 (D=3mm); the bottom liquid tank 11 (inner diameter D=36mm, outer diameter D=40mm, height H=30mm) is divided into a tank body 11 and a base 9, wherein the tank body 11 has four 2mm×10mm rectangular slits crosswise at a position 15mm from the bottom surface, the tank body 11 is transparent as a whole, and a scale is engraved on the outer surface for observing the liquid level. ; The external rubber sheath 7 (inner diameter D=18mm, outer diameter D=20, height H=20mm) is stretched and put on the outside of the tank body 11, and a strain gauge 8 is glued to the center of the four rectangular connecting holes reserved in the tank body 11; the above dimensions are all design dimensions for this time, and the actual device dimensions used for the test are related to the engineering scenario, among which the sum of the height of the piston push head 10, the height of the liquid in the tank body 11 and the height of the base 9 is equal to the equivalent mining height of the filling body in the simulation test; the material and thickness of the liquid in the bottom liquid tank 11 and the rubber sheath are determined by the mechanical properties of the simulated filling material; when the mining height of the simulated working surface involved is large, the diameter of the device should be appropriately adjusted to ensure the stability of the device.

[0036] The above-mentioned device in the present invention is implemented by the following method: A monitoring method for laboratory simulation of filling body stress deformation involves the following steps:

[0037] (1) Combined with the geological and mining data of the research object, the rock properties and mechanical parameters of the top and bottom plates of the filling working face (including the elastic modulus E d , tensile strength σ t , compressive strengthσ c , shear strength τ, cohesion C, internal friction angle Φ, Poisson's ratio v, etc.), and fully understand the mining conditions of the working face near the mining area and the layout of the tunnels;

[0038] (2) According to the similarity law, determine the geometric similarity ratio, bulk density similarity ratio, elastic modulus similarity ratio, stress similarity ratio and boundary conditions of this similarity simulation test;

[0039] (3) Determine the ratio of similar simulation materials for each rock layer through the ratio test of river sand, gypsum and putty powder in the laboratory. (The mechanical parameters of the test piece formed by the combination of the three materials and the mechanical parameters of the top and bottom plates in step (1) are approximately in accordance with the similarity law).

[0040] (4) Based on geological data, similar simulation materials of various rock formations are sequentially built on the plane strain test bench according to different ratios. After the construction is completed, they are left to stand for 20-30 days to allow the water in the materials to fully evaporate and better achieve the simulation effect of the formation;

[0041] (5) Calibration of the hydraulic force measuring device: Three groups of prototype filling specimens were selected and subjected to uniaxial compression tests. The measured elastic modulus, peak compressive strength and other important deformation parameters were averaged, and the stress-strain curve of the filling material was obtained;

[0042] (6) Select three sets of hydraulic force measuring devices, inject liquid into the hydraulic force measuring devices through the connecting hose, place the entire device on a uniaxial testing machine, close the connecting hose, and perform a uniaxial compression test to obtain the average value of important deformation parameters such as the elastic modulus of the device, and obtain the stress-strain curve of the test device;

[0043] (7) By adjusting the type of liquid in the tank, the rubber material and thickness of the external rubber sheath, the important deformation parameters such as the elastic modulus obtained from the uniaxial compression test of the force measuring device satisfy the stress similarity ratio relationship, the calibration of the hydraulic force measuring device is completed, and the type of liquid, rubber material and thickness used in this simulation are determined.

[0044] (8) Calibrate the external rubber sheath on the surface of the calibrated hydraulic force measuring device: paste strain gauges perpendicular to the long axis of the rectangular slits at the center positions of the multiple (preferably four) rectangular slits left in the liquid tank, and connect the strain gauges to the DH3816N static strain test system.

[0045] (9) Select 10 weights of equal weight, for example 50g, wait for the strain-time curve to be stable, add the weights to the top of the piston one by one, wait for the curve to be stable after adding, and remove the weights from the top of the piston one by one. Note that each time you add (remove) a weight, you need to wait for the curve to be stable before adding (removing) it.

[0046] (10) Take three force measuring devices and repeat step (9) and take the average value of the experimental data. The hydraulic stress-rubber strain curve of the liquid tank is calculated through the elastic thick-walled cylinder theory to complete the calibration of the rubber holster.

[0047] (11) Excavate the working face according to the test research object, place the hydraulic device in the observation position, inject the liquid determined by the calibration process of the hydraulic force measuring device into the liquid tank through the connecting hose, use the liquid to push the piston upward until it contacts the top plate, and close the connecting hose.

[0048] (12) As the experiment progresses, the working face continues to advance, and the monitoring device is continuously deployed in the goaf. The roof sinks and acts on the piston, causing compression. The time-strain data is recorded, and the stress-strain relationship obtained by calibrating the rubber material is combined with the outer surface scale of the tank body to calculate the stress evolution and deformation characteristics of the filling body in the filling working face.

[0049] (13) By repeating steps (5) to (10) and changing the liquid, rubber type and thickness in the tank of the hydraulic force measuring device, the stress conditions of different types of filling bodies in the filling working surface can be simulated.

[0050] The patent of the present invention discloses a test method for simulating the stress of a filling body in a laboratory. The method simulates the geological conditions and stress environment of the filling working face through similar simulation material tests, injects liquid into the device through a connecting hose, pushes the piston to move upward until it contacts the top plate of the working face, and installs the device at the filling body stress monitoring position in the goaf. By closing the connecting hose, the liquid in the device is ensured to be in a closed state, so that the effect of the overlying rock strata on the piston is expressed in the form of liquid pressure in the liquid tank. Through the connecting hole on the inner wall of the liquid tank, the internal liquid pressure is expressed as the elastic deformation of the rubber sheath. Through the strain gauge attached to the rubber sheath, the elastic deformation of the rubber sheath is output in the form of an electrical signal, and the data of the force change of the filling body is recorded and inverted. Through the calibration of the rubber sheath, the hydraulic stress-rubber strain relationship of the liquid tank is obtained. Through the calibration of the hydraulic force measuring device, the device can be used to reflect the force change characteristics of the filling body.

[0051] The method of the present invention achieves the following effects: 1) The device realizes the unified integration of simulation of nonlinear mechanical characteristics of filling body and real-time monitoring of stress and deformation; 2) The present invention provides a method for monitoring stress and deformation characteristics of filling body in filling working surface, which can be used for in-depth research on the action mechanism of filling body in filling working surface in the laboratory, and at the same time, by changing the type of liquid in the hydraulic force measuring device, the material and thickness of the rubber leather cover, it can be used as a similar material for different types of filling bodies for testing; 3) Since a hydraulic force measuring device is equipped with four strain gauges, multiple groups of data can be observed for the same position, which greatly reduces the error of the obtained data and can provide more accurate data for research. At the same time, the calibrated force measuring device can realize direct and continuous measurement of the stress state of the filling material through the change of liquid pressure.

[0052] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0053] The above-mentioned embodiments only express the implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A monitoring device for laboratory simulation of filling body stress deformation, characterized by: The monitoring device includes a plane strain test bench, which includes a accommodating cavity, wherein a similar simulated material layer, a simulated coal seam working face advancement layer and a hydraulic force measuring device are arranged inside the accommodating cavity, and the hydraulic force measuring device is arranged in the simulated coal seam working face advancement layer; the hydraulic force measuring device includes a piston push head, a bottom liquid tank and an external rubber leather sleeve, and the bottom liquid tank includes a base and a tank body; the tank body is arranged on the base, and the piston push head is slidably arranged on the tank body, and an external rubber leather sleeve is arranged on the outer side of the tank body, and the upper end and the lower section of the external rubber leather sleeve are both sealed and connected to the outer side of the tank body, and a plurality of rectangular slits are evenly opened in the middle and lower part of the tank body, and the external rubber leather sleeve is provided with strain gauges corresponding to the positions of the rectangular slits, wherein the sum of the piston push head height, the liquid height in the tank body and the base height is equal to the equivalent mining height of the filling body in the simulation test; the piston push head includes a piston shaft and a rubber pressure head.

2. A monitoring device for laboratory simulation of stress deformation of filling bodies according to claim 1, characterized in that: The piston push head further comprises reinforcing ribs, a support column is arranged inside the piston push head, a hollow cavity is formed between the support column and the outer circumferential surface of the piston push head, and a plurality of reinforcing ribs are arranged in the hollow cavity.

3. A monitoring device for laboratory simulation of stress deformation of filling bodies according to claim 2, characterized in that: The piston push head also includes a connecting hose, which is arranged in the hollow cavity and is used to inject or extract liquid into the bottom liquid tank.

4. A monitoring device for laboratory simulation of stress deformation of filling bodies according to claim 3, characterized in that: The communicating hose is provided with a switch valve.

5. The monitoring device for laboratory simulation of stress deformation of filling bodies according to claim 1, characterized in that: The monitoring device is implemented by the following steps: (1) Combined with the geological and mining-related data of the research object, the rock properties and mechanical parameters of the top and bottom plates of the filling working face are mastered, including the elastic modulus E d , tensile strength σ t , compressive strengthσ c , shear strength τ, cohesion C, internal friction angle Φ, Poisson's ratio v, and fully understand the mining conditions of the working face near the mining area and the layout of the tunnels; (2) According to the similarity law, determine the geometric similarity ratio, bulk density similarity ratio, elastic modulus similarity ratio, stress similarity ratio and boundary conditions of this similarity simulation test; (3) Determine the ratio of similar simulation materials for simulating various rock formations through a ratio test of river sand, gypsum and putty powder in the laboratory, and take the mechanical parameters of the specimens formed by the combination of the three materials as close to the lithology and mechanical parameters in step (1) as being in accordance with the law of similarity; (4) Based on geological data and according to different mix ratios, similar simulation materials of various rock formations are sequentially built on the plane strain test bench. After the construction is completed, the materials are left to stand for 20-30 days to allow the water in the materials to fully evaporate; (5) Calibration of the hydraulic force measuring device: Three groups of prototype filling specimens were selected and subjected to uniaxial compression tests. The elastic modulus and peak compressive strength were averaged and the stress-strain curve of the filling material was obtained. (6) Select three sets of hydraulic force measuring devices, inject liquid into the hydraulic force measuring devices through the connecting hose, place the entire device on a uniaxial testing machine, close the connecting hose, perform a uniaxial compression test, obtain the elastic modulus parameters of the device, take the average value, and obtain the stress-strain curve of the test device; (7) By adjusting the type of liquid in the tank, the rubber material and thickness of the external rubber sheath, the elastic modulus parameters obtained from the uniaxial compression test of the force measuring device meet the stress similarity ratio relationship, the calibration of the hydraulic force measuring device is completed, and the type of liquid, rubber material and thickness used in this simulation are determined; (8) Calibrate the external rubber cover on the surface of the calibrated hydraulic force measuring device: paste strain gauges perpendicular to the long axis of the rectangular slits at the center positions of the multiple rectangular slits left in the liquid tank, and connect the strain gauges to the DH3816N static strain test system; (9) Select 10 weights of equal weight, wait for the strain-time curve to be stable, add the weights to the top of the piston one by one, wait for the curve to be stable after adding, and remove the weights from the top of the piston one by one; note that you need to wait for the curve to be stable after adding or removing each weight before adding or removing it; (10) Repeat step (9) with three force measuring devices and take the average value of the experimental data. Calculate the hydraulic stress-rubber strain curve of the liquid tank through the elastic thick-walled cylinder theory to complete the calibration of the rubber holster. (11) Excavate the working face according to the test research object, place the hydraulic device in the observation position, inject the liquid determined by the calibration process of the hydraulic force measuring device into the liquid tank through the connecting hose, use the liquid to push the piston upward until it contacts the top plate, and close the connecting hose; (12) As the experiment progresses, the working face continues to advance, and the monitoring device is continuously deployed in the goaf. The roof sinks and acts on the piston and compression occurs. The time-strain data is recorded. The hydraulic stress-rubber strain relationship of the liquid tank obtained by rubber material calibration is combined with the change in liquid level obtained by the scale on the outer surface of the tank body to calculate the stress evolution and deformation characteristics of the filling body in the filling working face. (13) By repeating steps (5) to (10) and changing the liquid, rubber type and thickness in the tank of the hydraulic force measuring device, the stress conditions of different types of filling bodies in the filling working surface can be simulated.

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