A coal and rock mass stress monitoring device and system

Abstract

The present invention discloses a coal and rock mass stress monitoring device and system, which includes a multi-directional stress sensing hydraulic cylinder and a pressure transmitter; the multi-directional stress sensing hydraulic cylinder includes a cylindrical cylinder body, a hydraulic chamber is arranged axially inside the cylindrical cylinder body, an oil injection port communicating with the hydraulic chamber is arranged at the tail end of the cylindrical cylinder body, a plurality of hydraulic hole groups are evenly arranged circumferentially on the cylindrical cylinder body, each hydraulic hole group includes a plurality of hydraulic holes, each hydraulic hole communicates with the hydraulic chamber, a hydraulic plunger is arranged in each hydraulic hole, a plurality of arc-shaped pressing plates respectively corresponding to each hydraulic hole group are arranged circumferentially on the outer side of the cylindrical cylinder body, the hydraulic plungers in each hydraulic hole group are connected to the corresponding arc-shaped pressing plates, and a displacement sensor is arranged between each arc-shaped pressing plate and the cylindrical cylinder body; the input end of the pressure transmitter is connected to the oil injection port through a hydraulic oil pipe. The present invention can adapt to the monitoring of pressure coming from different directions, improve the monitoring effect, can be fully coupled with the drilling wall, improve the monitoring accuracy, and ensure the stability and accuracy of long-term monitoring.

Description

Technical Field

[0001] The present invention relates to the technical field of coal and rock mass stress monitoring, and particularly to a coal and rock mass stress monitoring device and system. Background Art

[0002] With the increase in the depth of coal resource mining and the improvement of mining intensity, coal and rock dynamic disasters such as rock bursts, coal and gas outbursts, and large-area roof collapses occur frequently, seriously restricting the safe and efficient production of coal mines. The stress of coal and rock mass is the basic data for the design and maintenance of roadways, the design of working face spacing, etc. in underground engineering design and construction, and is also the fundamental acting force causing the deformation and failure of geotechnical engineering excavations such as mining. Therefore, stress monitoring of coal and rock mass is crucial for preventing coal and rock dynamic disasters, evaluating the danger of working face areas, roof control, and roadway support.

[0003] At present, the most commonly used equipment for coal and rock mass stress monitoring is the liquid-filled expansion pillow type borehole stress gauge improved from the Glotzi pressure cell. It consists of upper and lower clamping plates and a pressure pillow, and is fixedly installed by drilling and probing. When the stress around the borehole changes, it causes the liquid pressure in the pressure pillow to change, and the liquid pressure is converted into an electrical signal or a frequency signal through a pressure transmitter to achieve stress monitoring. However, this monitoring method has certain limitations in practical applications, mainly manifested in:

[0004] ① The liquid-filled expansion pillow type borehole stress gauge usually can only perform one-way monitoring. When the principal stress direction is not clear or there are multi-directional stress changes in the mine pressure environment, the installation of the stress gauge is blind, and the monitoring effect is limited;

[0005] ② The outer diameter of the stress gauge is smaller than the borehole diameter. Due to the limited expansion deformation amount of the oil pressure pillow, the stress gauge cannot fit fully with the borehole wall, and the coupling effect is poor, affecting the monitoring accuracy.

[0006] ③ The pressure pillow is prone to deformation after a long time of pressurization, resulting in pressure relief, and pressure supplementation is required, affecting the stability and accuracy of long-term monitoring. Summary of the Invention

[0007] The purpose of the present invention is to provide a coal and rock mass stress monitoring device and system to solve the problems existing in the above-mentioned prior art, which can adapt to the monitoring of in-coming pressure in different directions, improve the monitoring effect, can be fully coupled with the borehole wall, improve the monitoring accuracy, and can ensure the stability and accuracy of long-term monitoring.

[0008] To achieve the above purpose, the present invention provides the following scheme:

[0009] The present invention provides a coal and rock mass stress monitoring device, including a multi-directional stress induction hydraulic cylinder and a pressure transmitter;

[0010] The multi-directional stress-sensing hydraulic cylinder includes a cylindrical cylinder body. Inside the cylindrical cylinder body, a hydraulic chamber is provided along the axial direction. An oil injection port communicating with the hydraulic chamber is provided at the tail end of the cylindrical cylinder body. A plurality of hydraulic hole groups are evenly provided on the cylindrical cylinder body along the circumferential direction. Each hydraulic hole group includes a plurality of hydraulic holes spaced apart along the axial direction. Each hydraulic hole is arranged along the radial direction and communicates with the hydraulic chamber. A hydraulic plunger is slidably sealed in each hydraulic hole. A plurality of arc-shaped pressing plates corresponding to each hydraulic hole group one by one are provided on the outer side of the cylindrical cylinder body along the circumferential direction. The hydraulic plungers in each hydraulic hole group are connected to the corresponding arc-shaped pressing plates. A displacement sensor is provided between each arc-shaped pressing plate and the cylindrical cylinder body for detecting the real-time displacement of the hydraulic plunger;

[0011] The input end of the pressure transmitter is connected to the oil injection port through a hydraulic oil pipe.

[0012] In one embodiment, an elastic protective sleeve is wrapped outside the multi-directional stress-sensing hydraulic cylinder.

[0013] In one embodiment, the arc-shaped pressing plate is fixedly connected to the hydraulic plunger through a fastening screw.

[0014] In one embodiment, the pressure transmitter includes a support seat, a pressure sensing mechanism, a first fiber Bragg grating, a second fiber Bragg grating, an optical fiber coupler, and a pigtail. A hydraulic oil path is provided inside the support seat. One end of the hydraulic oil path is connected to the oil injection port through a hydraulic oil pipe. The pressure sensing mechanism includes a pressure-receiving diaphragm, a force transmission rod, a sensitivity-enhancing lever structure, and a cantilever beam. The pressure-receiving diaphragm is arranged at the other end of the hydraulic oil path and fixed on the support seat. One end of the force transmission rod is fixed to the middle of the pressure-receiving diaphragm, and the other end is connected to the first free end of the sensitivity-enhancing lever structure. The second free end of the sensitivity-enhancing lever structure abuts against the upper surface of the free end of the cantilever beam. The force arm corresponding to the force exerted by the force transmission rod on the sensitivity-enhancing lever structure is the first force arm, and the force arm corresponding to the force exerted by the cantilever beam on the sensitivity-enhancing lever structure is the second force arm. The length of the first force arm is greater than the length of the second force arm. The first fiber Bragg grating and the second fiber Bragg grating are respectively attached to the upper surface and the lower surface of the same position of the cantilever beam. The transmission optical fibers connected to the first fiber Bragg grating and the second fiber Bragg grating are coupled and connected to the pigtail through the optical fiber coupler.

[0015] In one embodiment, the sensitivity-enhancing lever structure includes a first connecting rod and a second connecting rod fixedly connected in an L shape. The rotation fulcrum of the sensitivity-enhancing lever structure is arranged at the joint of the first connecting rod and the second connecting rod. The length of the first connecting rod is greater than the length of the second connecting rod. The force transmission rod is connected to the free end of the first connecting rod, and the free end of the second connecting rod abuts against the upper surface of the free end of the cantilever beam.

[0016] In one embodiment, one end of the support base is connected to the hydraulic oil pipe through a quick hydraulic joint.

[0017] In one embodiment, an outer shell is sleeved on the support base in a sealed manner, and the pressure sensing mechanism, the first fiber Bragg grating, the second fiber Bragg grating and the fiber optic coupler are all arranged inside the outer shell, and the pigtail extends out from the tail end of the outer shell through a pigtail protection sleeve.

[0018] In one embodiment, the support base and the outer shell are sealed by an O-ring.

[0019] The present invention also provides a coal and rock mass stress monitoring system, which includes the coal and rock mass stress monitoring device described above, and also includes a three-way pipe, a displacement data collector and an oil pump; the three-way pipe is arranged on the hydraulic oil pipe, two ports of the three-way pipe are respectively connected to the hydraulic oil pipe through a first valve and a second valve, and the other port is connected to the oil pump through a third valve, and the displacement data collector is in signal connection with the displacement sensor.

[0020] The present invention also provides a coal and rock mass stress monitoring system, which includes the coal and rock mass stress monitoring device described above, and also includes a three-way pipe, a displacement data collector, an oil pump and a fiber Bragg grating demodulator; the three-way pipe is arranged on the hydraulic oil pipe, two ports of the three-way pipe are respectively connected to the hydraulic oil pipe through a first valve and a second valve, and the other port is connected to the oil pump through a third valve, and the displacement data collector is in signal connection with the displacement sensor; the fiber Bragg grating demodulator is connected to the pigtail.

[0021] The present invention has achieved the following technical effects compared with the prior art:

[0022] For the coal and rock mass stress monitoring device and system provided by the present invention, the multi-directional stress induction hydraulic cylinder pushes the hydraulic plunger through hydraulic oil, so that the arc-shaped pressing plate is in close contact with the borehole wall, can be fully coupled with the borehole wall, improves the monitoring accuracy, and can effectively transmit the stress in all directions of the borehole, adapts to the monitoring of the pressure coming from different directions, and improves the monitoring effect; a displacement sensor is arranged between the arc-shaped pressing plate and the cylindrical cylinder body, which can real-time monitor the displacement data of the hydraulic plunger, and judge the pressure coming direction according to the displacement change amplitude and trend in each direction; the present invention has a high anti-deformation ability after pressurization, a strong pressure holding ability, will not have a pressure relief phenomenon, and can ensure the stability and accuracy of long-term monitoring.

[0023] Furthermore, the pressure transmitter uses a sensitivity-enhancing lever structure and a cantilever beam to amplify tiny stress changes. The wavelength drift of the fiber Bragg grating corresponds to the pressure change. The stress change is measured by a fiber Bragg grating demodulator. It also has good temperature self-compensation ability, anti-electromagnetic interference ability, and high sensitivity, meeting the requirements of intrinsic safety explosion protection and being able to work stably in a complex mine environment. Brief Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a schematic diagram of a partial cross-sectional structure of a multi-directional stress sensing hydraulic cylinder in an embodiment of the present invention;

[0026] Figure 2 It is a schematic diagram of the structure of a multi-directional stress sensing hydraulic cylinder in an embodiment of the present invention;

[0027] Figure 3 It is a schematic diagram of the structure of a pressure transmitter in an embodiment of the present invention;

[0028] Figure 4 It is a schematic diagram of the structure of a pressure sensing mechanism in an embodiment of the present invention;

[0029] Figure 5 It is a schematic diagram of a multi-directional stress sensing hydraulic cylinder in a borehole before pressurization in an embodiment of the present invention;

[0030] Figure 6 It is a schematic diagram of a multi-directional stress sensing hydraulic cylinder in a borehole after pressurization in an embodiment of the present invention;

[0031] Figure 7 It is a static simulation nephogram of a compressed diaphragm in an embodiment of the present invention;

[0032] Figure 8 It is a modal simulation nephogram of a compressed diaphragm in an embodiment of the present invention;

[0033] Figure 9 It is a schematic diagram of a coal and rock mass stress monitoring system in an embodiment of the present invention.

[0034] In the figure: 1 - multi - directional stress - sensing hydraulic cylinder, 101 - cylindrical cylinder body, 102 - hydraulic chamber, 103 - oil injection port, 104 - hydraulic hole, 106 - sealing sleeve, 107 - hydraulic plunger, 108 - fastening screw, 109 - arc - shaped pressing plate, 110 - displacement sensor; 2 - three - way pipe, 201 - first valve, 202 - second valve, 203 - third valve; 3 - pressure transmitter, 301 - pressure - receiving diaphragm, 302 - force - transmitting rod, 303 - sensitivity - enhancing lever structure, 3031 - first connecting rod, 3032 - second connecting rod, 304 - rotating shaft, 305 - cantilever beam, 306 - first fiber - optic grating, 307 - second fiber - optic grating, 308 - transmission optical fiber, 309 - fiber - optic coupler, 310 - tail - fiber protection sleeve, 311 - tail - fiber, 312 - O - ring seal, 313 - oil - pressure quick - connector, 314 - outer shell, 315 - support seat, 316 - hydraulic oil circuit; 4 - displacement data collector, 5 - oil pump, 6 - fiber - optic grating demodulator; 701 - drill - hole wall, 702 - void. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0036] The purpose of the present invention is to provide a coal - rock mass stress monitoring device and system to solve the problems existing in the prior art, be able to adapt to the monitoring of in - coming pressure in different directions, improve the monitoring effect, be able to be fully coupled with the drill - hole wall, improve the monitoring accuracy, and ensure the stability and accuracy of long - term monitoring.

[0037] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0038] Embodiment 1

[0039] As Figures 1 - 6 shown, this embodiment provides a coal - rock mass stress monitoring device, including a multi - directional stress - sensing hydraulic cylinder 1 and a pressure transmitter 3;

[0040] The multi-directional stress-sensing hydraulic cylinder 1 includes a cylindrical cylinder block 101. Inside the cylindrical cylinder block 101, a hydraulic chamber 102 is provided axially for containing hydraulic oil. An oil injection port 103 communicating with the hydraulic chamber 102 is provided at the tail end of the cylindrical cylinder block 101, through which hydraulic oil can be injected into the hydraulic chamber 102. A plurality of hydraulic hole groups are evenly arranged circumferentially on the cylindrical cylinder block 101. Each hydraulic hole group includes a plurality of hydraulic holes 104 spaced apart in the axial direction. In this embodiment, there are six hydraulic hole groups, and each hydraulic hole group includes four hydraulic holes 104. Each hydraulic hole 104 is arranged radially and communicates with the hydraulic chamber 102. A hydraulic plunger 107 is slidably and sealingly arranged in each hydraulic hole 104. A sealing sleeve 106 is provided at the end of the hydraulic plunger 107. The hydraulic plunger 107 can reciprocate in the hydraulic hole 104 and form a sliding seal structure with the hydraulic hole 104 through the sealing sleeve 106. The movement of the hydraulic plunger 107 is pushed by the oil pressure in the hydraulic chamber 102. The movements of the hydraulic plungers 107 in each group do not affect each other, and the hydraulic plungers in each group share a hydraulic chamber 102. Six arc-shaped pressing plates 109 corresponding to each hydraulic hole group one by one are arranged circumferentially on the outside of the cylindrical cylinder block 101. The hydraulic plungers 107 in each hydraulic hole group are connected to the corresponding arc-shaped pressing plates 109. The arc-shaped pressing plates 109 are evenly distributed in the circumferential direction of the cylindrical cylinder block 101. When the internal pressure of the hydraulic chamber 102 increases, it pushes the hydraulic plunger 107, and the hydraulic plunger 107 pushes the arc-shaped pressing plate 109 to move radially outward. A displacement sensor 110 is provided between each arc-shaped pressing plate 109 and the cylindrical cylinder block 101 for detecting the real-time displacement of the hydraulic plunger 107 and providing the real-time displacement data of the hydraulic plunger 107;

[0041] The input end of the pressure transmitter 3 is connected to the oil injection port 103 through a hydraulic oil pipe.

[0042] In this embodiment, to prevent impurities such as rock particles and dust from entering the hydraulic plunger assembly during installation and use, the outside of the multi-directional stress-sensing hydraulic cylinder 1 is wrapped with an elastic protective sleeve, and the elastic protective sleeve can be a rubber sleeve.

[0043] In this embodiment, the arc-shaped pressing plate 109 is fixedly connected to the hydraulic plunger 107 through a fastening screw 108.

[0044] In this embodiment, the pressure transmitter 3 includes a support base 315, a pressure sensing mechanism, a first fiber Bragg grating 306, a second fiber Bragg grating 307, an optical fiber coupler 309, and a pigtail 311. A hydraulic oil passage 316 is provided in the support base 315. One end of the hydraulic oil passage 316 is connected to the oil injection port 103 through a hydraulic oil pipe. The pressure sensing mechanism includes a pressure-receiving diaphragm 301, a force transmission rod 302, a sensitivity-enhancing lever structure 303, and a cantilever beam 305. The pressure-receiving diaphragm 301 is arranged at the other end of the hydraulic oil passage 316 and fixed to the support base 315. The pressure-receiving diaphragm 301 is fixed to the support base 315 in a fixed manner with peripheral fixation. One end of the force transmission rod 302 is fixed to the middle of the pressure-receiving diaphragm 301, and the other end is connected to the first free end of the sensitivity-enhancing lever structure 303. The second free end of the sensitivity-enhancing lever structure 303 abuts against the upper surface of the free end of the cantilever beam 305. The lever arm corresponding to the force exerted by the force transmission rod 302 on the sensitivity-enhancing lever structure 303 is the first lever arm, and the lever arm corresponding to the force exerted by the cantilever beam 305 on the sensitivity-enhancing lever structure 303 is the second lever arm. The length of the first lever arm is greater than the length of the second lever arm. The first fiber Bragg grating 306 and the second fiber Bragg grating 307 are respectively attached to the upper surface and the lower surface of the same position of the cantilever beam 305. When the cantilever beam 305 undergoes bending deformation, the central wavelengths of the first fiber Bragg grating 306 and the second fiber Bragg grating 307 shift. The transmission optical fibers 308 connected to the first fiber Bragg grating 306 and the second fiber Bragg grating 307 are coupled and connected to the pigtail 311 through the optical fiber coupler 309.

[0045] In this embodiment, the sensitivity-enhancing lever structure 303 includes a first connecting rod 3031 and a second connecting rod 3032 that are fixedly connected in an L shape. The rotation fulcrum of the sensitivity-enhancing lever structure 303 is arranged at the connection of the first connecting rod 3031 and the second connecting rod 3032. The sensitivity-enhancing lever structure 303 can freely rotate around the rotating shaft 304 at its rotation fulcrum. The length of the first connecting rod 3031 is greater than the length of the second connecting rod 3032. The force transmission rod 302 is connected to the free end of the first connecting rod 3031, and the free end of the second connecting rod 3032 abuts against the upper surface of the free end of the cantilever beam 305.

[0046] In this embodiment, one end of the support base 315 is connected to the hydraulic oil pipe through a quick oil pressure joint 313, which is convenient and fast to install.

[0047] In this embodiment, an outer shell 314 is hermetically sleeved outside the support base 315. The pressure sensing mechanism, the first fiber Bragg grating 306, the second fiber Bragg grating 307, and the optical fiber coupler 309 are all arranged inside the outer shell 314. The pigtail 311 extends out from the tail end of the outer shell 314 through a pigtail protection sleeve 310.

[0048] In this embodiment, the support base 315 and the outer shell 314 are sealed by an O-ring 312.

[0049] The first fiber Bragg grating 306 and the second fiber Bragg grating 307 are located on the upper and lower surfaces of the same position of the cantilever beam 305 and are in the same temperature field. The deformations generated on the upper and lower surfaces of the cantilever beam 305 are equal in magnitude and opposite in direction, which can eliminate the temperature influence during measurement and achieve temperature self-compensation.

[0050] The principle of temperature self-compensation is as follows:

[0051] When the first fiber Bragg grating 306 pasted on the cantilever beam 305 is simultaneously affected by strain and temperature, the drift of its reflection wavelength can be expressed as:

[0052] ,

[0053] When the second fiber Bragg grating 307 pasted under the cantilever beam 305 is simultaneously affected by strain and temperature, the drift of its reflection wavelength can be expressed as:

[0054] ,

[0055] In the formula: is the initial central wavelength of the first fiber Bragg grating 306; is the drift of the reflection wavelength of the first fiber Bragg grating 306; is the initial central wavelength of the second fiber Bragg grating 307; is the drift of the reflection wavelength of the second fiber Bragg grating 307; is the effective elasto-optic coefficient of the optical fiber; is the axial strain suffered by the first fiber Bragg grating 306; is the axial strain suffered by the second fiber Bragg grating 307; is the thermal expansion coefficient of the optical fiber; is the thermo-optic coefficient of the optical fiber; is the temperature change of the first fiber Bragg grating 306; is the temperature change of the second fiber Bragg grating 307.

[0056] When the cantilever beam 305 is bent under force, the strains of the fiber Bragg gratings on the upper and lower surfaces are equal in magnitude and opposite in direction, that is ; and the two fiber Bragg gratings are in the same temperature field, that is , it can be obtained that

[0057] ,

[0058] That is

[0059] ,

[0060] Eliminate the temperature influence during measurement.

[0061] Such as Figure 7As shown in the figure, a static simulation analysis is carried out on the pressure-receiving diaphragm 301. As the pressure load increases, the displacement of the diaphragm shows an increasing trend. The displacement at the center of the diaphragm is the largest and gradually decreases along the radial direction. Therefore, the force transmission rod 302 should be fixed at the center position of the diaphragm to ensure uniform force and maximum effect of load transmission.

[0062] As Figure 8 shown in the figure, a modal simulation analysis is carried out on the pressure-receiving diaphragm 301. The first natural frequency has the largest deformation at the center of the diaphragm. The structure of the pressure-receiving diaphragm 301 has good dynamic characteristics and is suitable for the measurement of high-frequency pressure changes. Moreover, the natural frequency is relatively high and will not resonate with the coal and rock mass to cause signal distortion.

[0063] When the pressure-receiving diaphragm 301 is subjected to pressure, the acting force is transmitted through the force transmission rod 302 to the first connecting rod 3031 of the sensitivity-enhancing lever structure 303. According to the moment conservation formula, the force is amplified and then transmitted through the second connecting rod 3032 of the sensitivity-enhancing lever structure 303 to the end of the cantilever beam 305. The force transmitted from the pressure-receiving diaphragm 301 to the cantilever beam 305 is effectively amplified, improving the ability to perceive minute pressure changes.

[0064] The relevant formulas are as follows:

[0065] The pressure received by the pressure-receiving diaphragm 301 acts on its effective area and the generated force

[0066] is:

[0067] This force is transmitted through the force transmission rod 302 to the first connecting rod 3031 of the sensitivity-enhancing lever structure 303, causing the sensitivity-enhancing lever structure 303 to rotate around the axis, driving the second connecting rod 3032 to apply a force to the top of the cantilever beam 305, causing the cantilever beam to bend.

[0068] From the moment balance, we can obtain

[0069] where

[0070] In the formula, is the length of the first force arm, is the length of the second force arm.

[0071] The force is amplified by

[0072] times. times.

[0073] The force analysis of the cantilever beam 305 and the calculation process of the fiber Bragg grating wavelength drift are as follows:

[0074] Here, taking the cantilever beam 305 as an isosceles triangle as an example for illustration, its base is the fixed end;

[0075] When the force acts on the free end of the cantilever beam 305, the strain at the x position on the surface of the cantilever beam 305 is:

[0076] ,

[0077] In the formula, is the length of the cantilever beam, is the distance from the x position to the fixed end, is the elastic modulus of the cantilever beam, A x is the cross-sectional area of the cantilever beam at the x position, is the thickness of the cantilever beam.

[0078] The cross-sectional area of the cantilever beam at the x position A x can be expressed as:

[0079] ,

[0080] In the formula, is the width of the cantilever beam at the x position, is the width of the fixed end of the cantilever beam.

[0081] It can be obtained that:

[0082] ,

[0083] When the cantilever beam 305 bends, the fiber grating pasted on the cantilever beam 305 undergoes a cooperative deformation, and the deformation of the fiber grating is approximately the same as that of the cantilever beam. At this time:

[0084] ,

[0085] Combining with the above fiber grating formula, the relationship between the pressure on the pressure diaphragm 301 and the wavelength drift of the fiber grating can be obtained as:

[0086] .

[0087] Example Two

[0088] As Figure 9As shown in the figure, this embodiment provides a coal and rock mass stress monitoring system, which includes the coal and rock mass stress monitoring device described in Embodiment 1, and further includes a tee 2, a displacement data collector 4, an oil pump 5, and a fiber Bragg grating demodulator 6. The tee 2 is arranged on the hydraulic oil pipe. The two ports of the tee 2 are respectively connected to the hydraulic oil pipe through a first valve 201 and a second valve 202, and the other port is connected to the oil pump 5 through a third valve 203. The displacement data collector 4 is in signal connection with the displacement sensor 110. The fiber Bragg grating demodulator 6 is connected to the pigtail 311.

[0089] During application, the multi-directional stress induction hydraulic cylinder 1 is horizontally installed in the borehole using a mounting rod equipped with an inclination sensor. At this time, as Figure 5 shown, there is a gap 702 between the multi-directional stress induction hydraulic cylinder 1 and the borehole wall 701, and it cannot be fully coupled with the borehole wall 701. Then, open the first valve 201, the second valve 202, and the third valve 203, start the oil injection pump 5, and inject hydraulic oil into the hydraulic chamber 102 of the multi-directional stress induction hydraulic cylinder 1. Use the action of the high-pressure oil to push the hydraulic plunger 107 on the multi-directional stress induction hydraulic cylinder 1. The hydraulic plunger 107 pushes the arc-shaped pressing plate 109 to move radially outward until it is in close contact with the borehole wall 701, as Figure 6 shown, to achieve effective coupling of the arc-shaped pressing plates 109 in six directions with the borehole wall 701, and better transmit the full-direction stress of the borehole. As the hydraulic oil continues to be injected, the oil pressure gradually increases. When the oil pressure reaches the set value, turn off the oil injection pump 5 and close the third valve 203 to ensure that the pressure remains in a stable state.

[0090] The high-pressure hydraulic oil gives a uniform pressure to the pressure-receiving diaphragm 301 of the pressure transmitter 3, and is transmitted to the cantilever beam 305 with fiber Bragg gratings pasted on both the upper and lower surfaces through the force transmission rod 302 and the sensitivity enhancement lever structure 303, causing the cantilever beam 305 to bend and deform, and the central wavelength of the fiber Bragg grating to shift. Subsequently, the wavelength shift amount is detected by the fiber Bragg grating demodulator 6 to establish a pressure-wavelength shift amount correspondence relationship.

[0091] When the stress around the borehole changes, the borehole wall 701 exerts a radially inward pressure on the arc-shaped pressing plate 109, which is transmitted to the hydraulic chamber 102, and the hydraulic oil pressure in the hydraulic chamber 102 changes, and the liquid pressure is converted into an optical signal by the pressure transmitter.

[0092] The displacement data collector 4 monitors the feedback of each displacement sensor 110 in real time, and can judge the weighting direction by comparing the displacement change amplitude and trend in each direction.

[0093] The coal and rock mass stress monitoring device and system provided by the present invention can adapt to the monitoring of inrushes from different directions, can be fully coupled with the borehole wall, has improved sensitivity, has high anti-deformation ability after pressurization, strong pressure-holding ability, can ensure the stability and accuracy of long-term monitoring, and has intrinsic safety and explosion-proof characteristics and anti-electromagnetic interference ability, and has good temperature compensation ability.

[0094] Specific examples are used in the present invention to illustrate the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A coal rock mass stress monitoring device, characterized in that: Includes a multi-directional stress-sensing hydraulic cylinder and a pressure transmitter; The multi-directional stress sensing hydraulic cylinder comprises a cylindrical cylinder body, a hydraulic chamber is axially arranged inside the cylindrical cylinder body, an oil filling port connected to the hydraulic chamber is arranged at the tail end of the cylindrical cylinder body, a plurality of hydraulic hole groups are evenly arranged along the circumferential direction on the cylindrical cylinder body, each of the hydraulic hole groups comprises a plurality of hydraulic holes spaced apart along the axial direction, each of the hydraulic holes is arranged along the radial direction and connected to the hydraulic chamber, a hydraulic plunger is provided in each of the hydraulic holes for sliding sealing, a plurality of arc-shaped pressure plates corresponding to each of the hydraulic hole groups are circumferentially arranged on the outer side of the cylindrical cylinder body, the hydraulic plungers in each of the hydraulic hole groups are connected to the corresponding arc-shaped pressure plates, the arc-shaped pressure plates are fixedly connected to the hydraulic plungers by fastening screws, and a displacement sensor is provided between each of the arc-shaped pressure plates and the cylindrical cylinder body for detecting the real-time displacement of the hydraulic plungers; The input end of the pressure transmitter is connected to the oil filling port through a hydraulic oil pipe; The pressure transmitter includes a support seat, a pressure sensing mechanism, a first fiber grating, a second fiber grating, a fiber coupler and a pigtail. A hydraulic oil circuit is provided in the support seat. One end of the hydraulic oil circuit is connected to the oil filling port through a hydraulic oil pipe. The pressure sensing mechanism includes a pressure-bearing diaphragm, a force transmission rod, a sensitivity-enhancing lever structure and a cantilever beam. The pressure-bearing diaphragm is arranged at the other end of the hydraulic oil circuit and fixed on the support seat. One end of the force transmission rod is fixed to the middle of the pressure-bearing diaphragm, and the other end is connected to the first free end of the sensitivity-enhancing lever structure. The second free end of the cantilever beam is against the upper surface of the free end of the cantilever beam, the force arm corresponding to the force of the force transmission rod acting on the sensitivity-enhancing lever structure is the first force arm, the force arm corresponding to the force of the cantilever beam acting on the sensitivity-enhancing lever structure is the second force arm, the length of the first force arm is greater than the length of the second force arm, the first fiber grating and the second fiber grating are respectively attached to the upper surface and the lower surface of the same position of the cantilever beam, and the transmission optical fibers connected to the first fiber grating and the second fiber grating are coupled to the pigtail through the optical fiber coupler; The sensitivity enhancement lever structure includes a first connecting rod and a second connecting rod fixedly connected in an L shape, the rotation fulcrum of the sensitivity enhancement lever structure is arranged at the junction of the first connecting rod and the second connecting rod, the length of the first connecting rod is greater than the length of the second connecting rod, the force transmission rod is connected to the free end of the first connecting rod, and the free end of the second connecting rod is abutted against the upper surface of the free end of the cantilever beam.

2. The coal rock mass stress monitoring device according to claim 1, characterized in that: The multi-directional stress sensing hydraulic cylinder is externally wrapped with an elastic protective sleeve.

3. The coal rock mass stress monitoring device according to claim 1, characterized in that: One end of the support seat is connected to the hydraulic oil pipe through a hydraulic quick connector.

4. The coal rock mass stress monitoring device according to claim 1, characterized in that: The outer sealing sleeve of the support seat is provided with a shell, the pressure sensing mechanism, the first fiber grating, the second fiber grating and the fiber coupler are all arranged in the shell, and the pigtail extends from the rear end of the shell through the pigtail protective cover.

5. The coal rock mass stress monitoring device according to claim 4, characterized in that: The support seat and the housing are sealed by an O-ring.

6. A coal rock mass stress monitoring system, characterized in that: The coal rock stress monitoring device comprises any one of claims 1 to 5, and also comprises a tee, a displacement data collector and an oil pump; the tee is arranged on the hydraulic oil pipe, the two ports of the tee are connected to the hydraulic oil pipe through a first valve and a second valve respectively, the other port is connected to the oil pump through a third valve, and the displacement data collector is connected to the displacement sensor signal.

7. A coal rock mass stress monitoring system, characterized in that: The coal rock stress monitoring device comprises the device described in any one of claims 1 to 5, and further comprises a tee, a displacement data collector, an oil pump and a fiber optic Bragg grating demodulator; the tee is arranged on the hydraulic oil pipe, the two ports of the tee are connected to the hydraulic oil pipe through a first valve and a second valve respectively, the other port is connected to the oil pump through a third valve, the displacement data collector is connected to the displacement sensor signal; the fiber optic Bragg grating demodulator is connected to the pigtail.

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