Deep soft coal seam ground stress monitoring device and monitoring method thereof

Abstract

The deep soft coal seam ground stress monitoring device comprises oil bags, a plastic sleeve, oil pipes and a long guide pipe, the multiple oil bags are arranged in the plastic sleeve, one end of the plastic sleeve is provided with an open hole, the open hole is communicated to the outside of a drill hole through the long guide pipe, the multiple oil pipes are arranged in the long guide pipe, and the multiple oil pipes are communicated to the outside of the drill hole through the long guide pipe. One end of each oil pipe is connected with one oil bag, the other end of each oil pipe is connected to the four-way valve, the oil pipes are connected to the hydraulic machine after passing through the four-way valve, and valves are further arranged on the oil pipes and mounted on the oil pipes between the outer ports of the plastic sleeves and the four-way valves; the oil bag is connected with a pressure gauge through an oil pipe, a grouting pipe is inserted into a hole opening of the plastic sleeve, and a quick-setting expansion hole sealing agent is injected into the drill hole through the grouting pipe. According to the invention, rapid fitting is realized by using large deformation and self-adaptability of the nested oil bag, and the defects of limited deformation, low efficiency and poor stability of a traditional conservator type borehole stressometer are overcome.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, and in particular to a deep soft coal seam ground stress monitoring device and a monitoring method thereof. Background Art

[0002] At present, some mines in my country have entered the deep mining stage. With the gradual increase in the depth of coal mining, the ground stress on the coal seams is also increasing. The geological conditions faced by deep coal mines have become more complex, especially in the development of areas with high ground stress, high protrusion, and high burial depth. The ground stress levels in these areas often exceed the normal bearing range of the coal seams, forming a huge stress concentration area, which can easily lead to brittle failure of the coal seams, local fractures, interlayer slippage and other phenomena, posing huge risks to the safe production of mines.

[0003] Coal seam geostress parameters are an important indicator for formulating regional gas control plans and testing the effectiveness of regional outburst prevention measures. Especially for deep soft coal seams, due to their complex mechanical properties, the monitoring of geostress is more difficult. Therefore, the monitoring of coal seam geostress parameters is an important link in the prevention and control of coal and gas outbursts.

[0004] Existing geostress monitoring devices, such as oil pillow borehole stress gauges, have high requirements on borehole integrity and downhole environment, and have problems such as poor adaptability and stability. Single oil bladder borehole stress gauges have limited loading pressure, and have problems such as difficult and time-consuming installation, and cannot meet the needs of geostress monitoring in deep soft coal seams. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a deep soft coal seam ground stress monitoring device and a monitoring method thereof, which utilizes a nested oil bag group to measure the ground stress of deep soft coal seams and monitor stress changes, thereby solving the problems of poor applicability, unsatisfactory accuracy, long time consumption, high cost and difficult installation and movement of traditional ground stress measuring devices; utilizing an integrated full-section sealing and grouting process to reduce construction difficulty and construction costs, thereby realizing ground stress monitoring of deep soft coal seams, providing guidance for the adoption of coal and gas outburst prevention and control measures, and safely eliminating the danger of outbursts in outburst coal seams.

[0006] The object of the present invention is achieved in that: A deep soft coal seam ground stress monitoring device is applied to a deep soft coal seam ground stress test area, in which a through-layer drill hole is constructed to penetrate the coal to the center of the coal seam; The deep soft coal seam in-situ stress monitoring device includes an oil bladder, a plastic sleeve, oil pipes, and a long conduit. The plastic sleeve is arranged in a borehole in the deep soft coal seam in-situ stress measurement area. Multiple oil bladders are arranged inside the plastic sleeve. One end of the plastic sleeve is provided with an opening, and this opening is connected to the outside of the borehole through a long conduit. Multiple oil pipes are arranged in the long conduit. One end of each oil pipe is connected to an oil bladder, and the other end is connected to a four-way valve. After passing through the four-way valve, they are respectively connected to a hydraulic press. A valve is arranged on the oil pipe, and the valve is installed on the oil pipe between the outer port of the plastic sleeve and the four-way valve; The oil bladder is connected to a pressure gauge through an oil pipe, and the pressure it receives can be directly measured and read in real time; A grouting pipe is inserted into the orifice of the plastic sleeve, and a quick-setting expanding hole-sealing agent is injected into the borehole through the grouting pipe; A sieve pipe is arranged at the port where the long conduit passes through the borehole, and the whole-section hole sealing is realized through the sieve pipe for pressure relief; The oil bladder includes three composite layers from the inside to the outside. The inner layer is a carbon fiber reinforced rubber layer, the middle layer is an aramid fiber woven mesh layer, and the outer layer is a polyurethane graphene composite layer; The plastic sleeve includes three layers from the inside to the outside. The outer layer is a brittle epoxy resin layer, the middle layer is a glass fiber reinforced plastic layer, and the inner layer is a ultra-high molecular weight polyethylene layer; A micro MEMS pressure sensor is embedded in the oil bladder, and the micro MEMS pressure sensor uploads data to the ground monitoring platform in real time through a wireless transmission module.

[0007] Further, the bottom of the plastic sleeve is hemispherical.

[0008] Further, the pressure gauge transmits data to the ground monitoring platform in real time through a wireless transmission module to achieve remote monitoring.

[0009] Further, the long conduit is made of an alloy material, and its surface is coated with a lubricating coating to reduce friction and improve the feeding efficiency.

[0010] Further, the thickness of the carbon fiber reinforced rubber layer is 2 mm, and the elastic modulus is 50 MPa, providing core compressive support; The mesh density of the aramid fiber woven mesh layer is 200 meshes, which is used to disperse stress and inhibit local tearing; The thickness of the polyurethane graphene composite layer is 1 mm, and the friction coefficient is less than 0.1, which is used to reduce the friction resistance with the outside.

[0011] Further, the fracture strain of the brittle epoxy resin layer is 0.5%, and it preferentially breaks under pressure to release the initial stress; The fracture strain of the glass fiber reinforced plastic layer is 2%, which is used to control the pressure loading rate; The fracture strain of the ultra-high molecular weight polyethylene layer is 10%, and the full contact of the oil bladder is triggered when it finally breaks.

[0012] Furthermore, the pressure thresholds of the brittle epoxy resin layer, the glass fiber reinforced plastic layer, and the ultra-high molecular weight polyethylene layer are 5 MPa, 15 MPa, and 30 MPa respectively. Through the gradual rupture of the three-layer materials, the in-situ stress grading loading and measurement are realized.

[0013] Furthermore, between the ultra-high molecular weight polyethylene layer and the glass fiber reinforced plastic layer, and between the glass fiber reinforced plastic layer and the brittle epoxy resin layer, a composite adhesive is used for bonding. The composite adhesive is a mixed adhesive of epoxy resin and polyurethane.

[0014] Furthermore, the inside of the oil bag is filled with high-concentration silicone oil by a hydraulic press.

[0015] A monitoring method for the in-situ stress monitoring device of deep soft coal seams, based on the above-mentioned in-situ stress monitoring device for deep soft coal seams, includes the following contents: Step 1: Construct a cross-cut borehole in the area where the in-situ stress of the coal seam is to be measured, passing through the coal to the center position of the coal seam; Step 2: Use a long catheter to quickly send a plastic sleeve equipped with multiple oil bags to the designed position in the borehole; during the sending process, the position of the plastic sleeve is monitored in real time through a positioning sensor to ensure that it accurately reaches the predetermined position; Step 3: Insert a grouting pipe at the hole mouth, inject a quick-setting and expanding hole-sealing agent, and achieve full-section hole sealing through pressure relief of the sieve pipe at the front end of the long catheter; Step 4: Pressurize the oil bag until the plastic sleeve is completely burst, and the pressure gauge connected to the oil bag can observe the pressure; during the pressurization process, the pressure change of the oil bag is monitored in real time through the connection between the ground monitoring platform and the MEMS pressure sensor, and the pressurization rate is automatically adjusted to ensure the smoothness and safety of the pressurization process; Step 5: Observe the indication of the pressure gauge, and shorten the stress balance time of the oil bag by supplementary pressurization or pressure reduction with a hydraulic press. When the indication is stable, the pressure received by the oil bag is the in-situ stress of the area where the in-situ stress of the deep soft coal seam is to be measured, and it can be directly read through the pressure gauge; Step 6: With the implementation of the coal and gas outburst prevention and control measures, if the in-situ stress of the area where the in-situ stress of the coal seam is to be measured changes, the pressure received by the oil bag will also change accordingly. The change of the in-situ stress is monitored in real time through the pressure gauge; and the data is transmitted to the ground monitoring platform in real time through the wireless transmission module to realize the dynamic monitoring and early warning of the change of the in-situ stress.

[0016] Compared with the prior art, the beneficial effects of the present invention are: The present invention provides a deep soft coal seam ground stress monitoring device and a monitoring method thereof. For deep soft coal seam drilling, the large deformation and adaptability of the three oil bags are used to achieve rapid fitting, thereby overcoming the shortcomings of the traditional oil pillow type drilling stress gauge, such as limited deformation, low efficiency, and poor stability. The synergistic effect of the earth's restoring force and the internal pressure of the oil bag is used to measure the absolute ground stress of the coal seam, thereby overcoming the shortcoming that the oil pillow type drilling stress gauge can only measure the relative change of ground stress. The integrated full-section sealing grouting process is used to shorten the construction time. The method of the present invention is simple, has low time and labor costs, and has good effects, and has the following advantages: (1) Improved measurement accuracy: The graded rupture mechanism eliminates the impact error of one-time loading. Combined with the deformation compensation capability of the composite oil bag, the overall accuracy reaches ±2MPa (80% higher than the traditional method). (2) Strong anti-interference ability: The aramid woven mesh inhibits the local damage of the oil pocket caused by the expansion of coal body cracks, and the survival rate of the device in the broken coal seam is increased to 95%; (3) Real-time monitoring capability: Sensor data is updated every 10 seconds, which can capture stress mutation events (such as precursors of rock burst), and the early warning response time is less than 30 seconds; (4) Optimization of construction efficiency: The quick-setting sealer shortens the construction time of a single hole to 1.5 hours (conventionally it takes 3 hours), reducing costs by 40%. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the monitoring device of the present invention.

[0018] Figure 2 It is a schematic structural diagram of the oil sac of the present invention.

[0019] Figure 3 It is a schematic structural diagram of the plastic sleeve of the present invention.

[0020] in: Oil bladder 1, carbon fiber reinforced rubber layer 1.1, aramid fiber woven mesh layer 1.2, polyurethane graphene composite layer 1.3, plastic sleeve 2, ultra-high molecular weight polyethylene layer 2.1, glass fiber reinforced plastic layer 2.2, brittle epoxy resin layer 2.3, deep soft coal seam ground stress test area 3, borehole 4, hydraulic press 5, oil pipe 6, pressure gauge 7, long guide tube 8, quick-setting expansion sealing agent 9, valve 10, four-way valve 11, grouting pipe 12, screen pipe 13. DETAILED DESCRIPTION

[0021] To better understand the technical solution of the present invention, the following will be described in detail with reference to relevant drawings. It should be understood that the following specific embodiments are not intended to limit the specific implementation modes of the technical solution of the present invention, but are only implementation modes that can be adopted by the technical solution of the present invention. It should be noted first that the expressions regarding the positional relationships of various components herein, such as component A being located above component B, are based on the relative positions of the components in the drawings and are not intended to limit the actual positional relationships of the components. Embodiment

[0022] See Figures 1-3 , Figure 1 The structural schematic diagram of the crack analysis device of Embodiment 1 is drawn. As shown in the figure, a ground stress monitoring device for deep soft coal seams involved in this Embodiment 1 is applied to the area to be measured of the ground stress in deep soft coal seams 3. A cross-cut borehole 4 is constructed in the area to be measured of the ground stress in deep soft coal seams 3. The diameter of the borehole 4 is about 10 cm, and it penetrates through the coal to the center position of the coal seam; The ground stress monitoring device for deep soft coal seams includes an oil bladder 1, a plastic sleeve 2, an oil pipe 6, and a long conduit 8. The plastic sleeve 2 is arranged in the borehole 4 of the area to be measured of the ground stress in deep soft coal seams 3. Three oil bladders 1 are arranged inside the plastic sleeve 2. One end of the plastic sleeve 2 is provided with an opening, and this opening is communicated to the outside of the borehole 4 through the long conduit 8. Three oil pipes 6 are arranged inside the long conduit 8. One end of each oil pipe 6 is connected to an oil bladder 1, and the other end is connected to a four-way valve 11. After passing through the four-way valve 11, they are respectively connected to a hydraulic press 5. A valve 10 is arranged on the oil pipe 6, and the valve 10 is installed on the oil pipe 6 between the outer port of the plastic sleeve 2 and the four-way valve 11; when one of the oil bladders fails, the valve arranged on the oil pipe of the failed oil bladder is closed, and the remaining oil bladders can still work normally.

[0023] The length of the oil bladder 1 is about 10 cm, and the diameter is about 5 cm; the height of the plastic sleeve 2 is about 14 cm, the diameter is about 7 cm, and the bottom is hemispherical.

[0024] The oil bladder 1 is connected to a pressure gauge 7 through the oil pipe 6, and the pressure it receives can be directly measured and read in real time, and the data is transmitted to the ground monitoring platform in real time through a wireless transmission module to achieve remote monitoring.

[0025] The orifice of the plastic sleeve 2 is inserted with a grouting pipe 12, and a quick-setting expanding hole-sealing agent 9 is injected into the borehole 4 through the grouting pipe 12.

[0026] A screen pipe 13 is arranged at the port where the long conduit 8 penetrates out of the borehole 4, and full-section hole sealing is achieved through pressure relief of the screen pipe 13.

[0027] The long catheter 8 is made of a high-strength and corrosion-resistant alloy material, and its surface is coated with a lubricating coating to reduce friction and improve the feeding efficiency. During the feeding process, the position of the plastic sleeve is monitored in real time through a positioning sensor to ensure its accurate arrival at the predetermined position.

[0028] The oil bladder 1 includes a three-layer composite layer from the inside to the outside. The inner layer is a carbon fiber-reinforced rubber layer 1.1 with a thickness of 2 mm and an elastic modulus of 50 MPa, providing core compressive support. The middle layer is an aramid fiber braided mesh layer 1.2 with a mesh density of 200 meshes, which is used to disperse stress and inhibit local tearing. The outer layer is a polyurethane graphene composite layer 1.3 with a thickness of 1 mm and a friction coefficient <0.1, which is used to reduce the frictional resistance with the outside. The oil bladder 1 adopts the above composite gradient structure, and the compressive strength is increased to 60 MPa, and the deformation amount reaches 20%, adapting to the large deformation characteristics of the coal body.

[0029] The oil bladder 1 is embedded with a micro MEMS pressure sensor. The range of the micro MEMS pressure sensor is 0 - 60 MPa, and the accuracy is 0.1% FS. The data is uploaded to the ground monitoring platform in real time through a wireless transmission module.

[0030] The plastic sleeve 2 includes a three-layer structure from the inside to the outside. The outer layer is a brittle epoxy resin layer 2.3 with a fracture strain of 0.5%. After being compressed, it preferentially ruptures to release the initial stress. The middle layer is a glass fiber-reinforced plastic layer 2.2 with a fracture strain of 2%, which is used to control the pressure loading rate. The inner layer is a ultra-high molecular weight polyethylene layer 2.1 with a fracture strain of 10%, and when it finally ruptures, it triggers the full contact of the oil bladder. The pressure thresholds of the brittle epoxy resin layer 2.3, the glass fiber-reinforced plastic layer 2.2, and the ultra-high molecular weight polyethylene layer 2.1 are 5 MPa, 15 MPa, and 30 MPa respectively. Through the gradual rupture of the three-layer materials, the in-situ stress grading loading and measurement are realized, and the error is reduced to ±3%.

[0031] Both between the ultra-high molecular weight polyethylene layer 2.1 and the glass fiber-reinforced plastic layer 2.2, and between the glass fiber-reinforced plastic layer 2.2 and the brittle epoxy resin layer 2.3 are bonded with a composite adhesive. The composite adhesive is a mixed adhesive of epoxy resin and polyurethane. The high strength and flexibility of the epoxy resin and polyurethane adhesives can ensure that the sleeve will not delaminate or rupture when stressed, and can simultaneously have high strength and good flexibility, which is suitable for bonding between the layers of the plastic sleeve. The ratio of epoxy resin to polyurethane can be customized according to the specific environment and requirements of the deep coal seam. By adjusting the proportion of each component, the bonding strength and stability between the layers of the plastic sleeve are improved, enabling it to better adapt to the complex environment of the deep soft coal seam.

[0032] The interior of the oil bladder 1 is filled with high-concentration silicone oil by a hydraulic press 5. The high-concentration silicone oil has the characteristics of low compressibility and high stability to improve the measurement accuracy and response speed.

[0033] A monitoring method for a deep soft coal seam in-situ stress monitoring device according to Embodiment 1 includes the following steps: Step 1: Construct a cross-layer borehole 4 in the coal seam in-situ stress measurement area 3. The diameter of the borehole 4 is about 10 cm, and it penetrates the coal to the center position of the coal seam. During the drilling process, directional drilling technology is used to ensure the accuracy and stability of the borehole, and the stress changes around the borehole are monitored in real time during the drilling process to provide a reference for the installation of subsequent monitoring devices. Step 2: Use a long catheter 8 to quickly send the plastic sleeve 2 equipped with three oil bladders 1 to the designed position in the borehole 4. During the feeding process, the position of the plastic sleeve is monitored in real time through a positioning sensor to ensure that it accurately reaches the predetermined position. Step 3: Insert a grouting pipe 12 at the hole mouth, inject a quick-setting expanding hole-sealing agent 9, and achieve full-section hole sealing by pressure relief through the screen pipe 13 at the front end of the long catheter 8. Step 4: Pressurize the oil bladder 1 until the plastic sleeve 2 is completely burst, and the pressure gauge 7 connected to the three oil bladders can observe the pressure. During the pressurization process, the pressure change of the oil bladder is monitored in real time by connecting the ground monitoring platform with the MEMS pressure sensor, and the pressurization rate is automatically adjusted to ensure the smoothness and safety of the pressurization process. Step 5: Observe the reading of the pressure gauge 7, and supplement or reduce the pressure through the hydraulic press 5 to shorten the stress balance time of the oil bladder 1. When the reading is stable, the pressure received by the oil bladder 1 is the in-situ stress of the deep soft coal seam in-situ stress measurement area 3, which can be directly read through the pressure gauge 7. At the same time, the monitoring data is analyzed and processed in real time through the data analysis system to generate an in-situ stress distribution map and a change trend map, providing a scientific basis for subsequent gas control and outburst prevention measures. Step 6: With the implementation of coal and gas outburst prevention and control measures, if the in-situ stress of the coal seam in-situ stress measurement area 3 changes, the pressure received by the oil bladder 1 will also change accordingly. The change of the in-situ stress can be monitored in real time through the pressure gauge 7, and the data is transmitted to the ground monitoring platform in real time through the wireless transmission module to realize the dynamic monitoring and early warning of the change of the in-situ stress.

[0034] In Step 4 of this embodiment, the data of the MEMS pressure sensor is updated every 10 seconds, which can capture stress mutation events (such as the precursor of rock burst), and the early warning response time is less than 30 seconds.

[0035] In Step 5 of this embodiment, the hydraulic press 5 is used to pressurize in gradients, with 5 MPa per stage and a stable pressure for 5 minutes per stage. The corresponding relationship between the sleeve rupture pressure and the oil bladder balance pressure is recorded to establish an in-situ stress inversion model.

[0036] The data of a certain mine implemented by the monitoring device and monitoring method of this embodiment are as follows: 1. Construct a borehole with a diameter of 110 mm to the center of the coal seam at a depth of -850 m; 2. Send a plastic sleeve equipped with three oil sacs into the hole through a directional push rod; 3. Inject a quick-setting agent through a grouting pipe to form a full-section seal within 20 minutes; Start the step-by-step pressure boosting program, record the sleeve rupture pressure sequence (5.2 MPa, 15.8 MPa, 32.4 MPa), and calculate the in-situ stress as 31.6 MPa by combining with the inversion model; 5. Continuously monitor for 48 hours, with the data fluctuation range of ±0.5 MPa to verify the system stability.

[0037] Under the same conditions, the traditional oil pillow stress gauge is used as Comparative Example 1, and the comparison data table of the two is as follows:

[0038] Working principle: For the in-situ stress monitoring method of deep soft coal seams based on the bag-type borehole pressure gauge of the present invention, a plastic sleeve equipped with three oil sacs is sent along the borehole into the area to be measured for in-situ stress of deep soft coal seams. The deformation of the oil sac is adjusted hydraulically to adaptively expand, and the earth's restoring force promotes the flow of the coal body around the borehole, so that the oil sac quickly fits the borehole. The in-situ stress is measured by a pressure gauge connected to the oil sac. The present invention realizes the measurement of stress parameters in the area to be measured for in-situ stress of deep soft coal seams and the real-time monitoring of stress changes, reducing a large amount of time, manpower and material costs.

[0039] The above are only specific application examples of the present invention, which do not constitute any limitation to the protection scope of the present invention. Any technical solutions formed by equivalent transformation or equivalent substitution fall within the scope of the protection of the present invention.

Claims

1. A ground stress monitoring device for deep soft coal seams, which is applied to the area to be measured for ground stress in deep soft coal seams (3). A cross-cut borehole (4) is constructed in the area to be measured for ground stress in deep soft coal seams (3) and penetrates through the coal to the center position of the coal seam. Its characteristics are as follows: The ground stress monitoring device for deep soft coal seams includes an oil bladder (1), a plastic sleeve (2), an oil pipe (6), and a long conduit (8). The plastic sleeve (2) is arranged in the borehole (4) of the area to be measured for ground stress in deep soft coal seams (3). A plurality of oil bladders (1) are arranged inside the plastic sleeve (2). One end of the plastic sleeve (2) is provided with an opening, and this opening is communicated to the outside of the borehole (4) through the long conduit (8). A plurality of oil pipes (6) are arranged inside the long conduit (8). One end of each oil pipe (6) is connected to an oil bladder (1), and the other end is connected to a four-way valve (11). After passing through the four-way valve (11), they are respectively connected to a hydraulic press (5). A valve (10) is arranged on the oil pipe (6), and the valve (10) is installed on the oil pipe (6) between the outer port of the plastic sleeve (2) and the four-way valve (11); The oil bladder (1) is connected to a pressure gauge (7) through the oil pipe (6), and the pressure it receives can be directly measured and read in real time. The orifice of the plastic sleeve (2) is inserted with a grouting pipe (12), and a quick-setting and expanding hole-sealing agent (9) is injected into the borehole (4) through the grouting pipe (12). A screen pipe (13) is arranged at the port where the long conduit (8) penetrates out of the borehole (4), and full-section hole sealing is achieved through pressure relief of the screen pipe (13); The oil bladder (1) includes a three-layer composite layer from the inside to the outside. The inner layer is a carbon fiber-reinforced rubber layer (1.1), the middle layer is an aramid fiber woven mesh layer (1.2), and the outer layer is a polyurethane graphene composite layer (1.3). The plastic sleeve (2) includes a three-layer structure from the inside to the outside. The outer layer is a brittle epoxy resin layer (2.3), the middle layer is a glass fiber-reinforced plastic layer (2.2), and the inner layer is a ultra-high molecular weight polyethylene layer (2.1); A micro MEMS pressure sensor is embedded in the oil bladder (1), and the micro MEMS pressure sensor uploads data to the ground monitoring platform in real time through a wireless transmission module.

2. The in-situ stress monitoring device for deep soft coal seams according to claim 1, characterized in that: The bottom of the plastic sleeve (2) is hemispherical.

3. The in-situ stress monitoring device for deep soft coal seams according to claim 1, characterized in that: The pressure gauge (7) transmits data to the ground monitoring platform in real time through a wireless transmission module to achieve remote monitoring.

4. The in-situ stress monitoring device for deep soft coal seams according to claim 1, characterized in that: The long conduit (8) is made of an alloy material, and its surface is coated with a lubricating coating to reduce friction and improve the feeding efficiency.

5. The in-situ stress monitoring device for deep soft coal seams according to claim 1, characterized in that: The thickness of the carbon fiber-reinforced rubber layer (1.1) is 2 mm, and its elastic modulus is 50 MPa, providing core compressive support. The mesh density of the aramid fiber woven mesh layer (1.2) is 200 meshes, which is used to disperse stress and inhibit local tearing. The thickness of the polyurethane graphene composite layer (1.3) is 1 mm, and its friction coefficient is less than 0.1, which is used to reduce the friction resistance with the outside.

6. The in-situ stress monitoring device for deep soft coal seams according to claim 1, characterized in that: The fracture strain of the brittle epoxy resin layer (2.3) is 0.5%. After being compressed, it preferentially fractures to release the initial stress. The fracture strain of the glass fiber reinforced plastic layer (2.2) is 2%, which is used to control the pressure loading rate. The fracture strain of the ultra-high molecular weight polyethylene layer (2.1) is 10%, and when it finally fractures, it triggers full contact of the oil bladder.

7. The in-situ stress monitoring device for deep soft coal seams according to claim 1, characterized in that: The pressure thresholds of the brittle epoxy resin layer (2.3), the glass fiber reinforced plastic layer (2.2), and the ultra-high molecular weight polyethylene layer (2.1) are 5 MPa, 15 MPa, and 30 MPa respectively. Through the gradual fracture of the three-layer materials, hierarchical loading and measurement of in-situ stress are achieved.

8. The in-situ stress monitoring device for deep soft coal seams according to claim 1, characterized in that: The ultra-high molecular weight polyethylene layer (2.1) and the glass fiber reinforced plastic layer (2.2), as well as the glass fiber reinforced plastic layer (2.2) and the brittle epoxy resin layer (2.3), are bonded with a composite adhesive, and the composite adhesive is a mixed adhesive of epoxy resin and polyurethane.

9. The in-situ stress monitoring device for deep soft coal seams according to claim 1, characterized in that: The inside of the oil bladder (1) is filled with high-concentration silicone oil by a hydraulic press (5).

10. A monitoring method for a ground stress monitoring device in a deep soft coal seam, based on the ground stress monitoring device in a deep soft coal seam according to any one of the above claims 1-9, characterized in that, It includes the following contents: Step 1: Construct a cross-cutting borehole in the area where the in-situ stress of the coal seam is to be measured, passing through the coal to the center position of the coal seam; Step 2: Use a long catheter to quickly send a plastic sleeve equipped with multiple oil bladders to the designed position in the borehole; during the feeding process, the position of the plastic sleeve is monitored in real time through a positioning sensor to ensure its accurate arrival at the predetermined position; Step 3: Insert a grouting pipe at the hole mouth, inject a quick-setting and expanding hole-sealing agent, and achieve full-section hole sealing through pressure relief of the sieve pipe at the front end of the long catheter; Step 4: Pressurize the oil bladder until the plastic sleeve is completely burst, and the pressure gauge connected to the oil bladder can observe the pressure; during the pressurization process, the pressure change of the oil bladder is monitored in real time through the connection between the ground monitoring platform and the MEMS pressure sensor, and the pressurization rate is automatically adjusted to ensure the smoothness and safety of the pressurization process; Step 5: Observe the reading of the pressure gauge, and shorten the stress balance time of the oil bladder by supplementary pressurization or decompression through the hydraulic press. When the reading is stable, the pressure received by the oil bladder is the in-situ stress of the area where the in-situ stress of the deep soft coal seam is to be measured, and it can be directly read through the pressure gauge; Step 6: With the implementation of the coal and gas outburst prevention and control measures, if the in-situ stress of the area where the in-situ stress of the coal seam is to be measured changes, the pressure received by the oil bladder will also change accordingly. The change of the in-situ stress is monitored in real time through the pressure gauge; and the data is transmitted to the ground monitoring platform in real time through the wireless transmission module to realize the dynamic monitoring and early warning of the change of the in-situ stress.

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