A magnetic force-based pressure relief hole deformation and stress concentration monitoring device and method

Abstract

This invention relates to a magnetically based device and method for monitoring the deformation and stress concentration of pressure relief holes. The invention proposes a series-connected, layered monitoring sensing structure: the core of the device consists of multiple monitoring units connected in series via gradually varying outer diameter spiral drill rods. Each unit uses a mounting ring as a carrier, and a constant-pressure airbag with a rotatable mounting ball is arranged on the mounting ring. Each mounting ball has a magnetically fixed base corresponding to a displacement detection unit with a magnetic baffle and a Fabry-Perot cavity optical fiber. The airbag is equipped with a constant-pressure inflation structure with a bidirectional differential pressure explosion-proof valve. The accompanying monitoring method uses magnetic repulsion to drive changes in the Fabry-Perot cavity length, analytically obtaining the deformation and stress concentration coefficient of the pressure relief hole. This invention can adaptively conform to the inner wall of the pressure relief hole, has high sensing accuracy and strong anti-interference ability, and can be recycled and reused as a whole, significantly reducing monitoring costs. It is suitable for large-scale downhole rock mass stress monitoring applications.

Description

Technical Field

[0001] This invention belongs to the field of disaster prevention and control technology in mining engineering, and particularly relates to a device and method for monitoring the deformation and stress concentration of pressure relief holes based on magnetic force. Background Technology

[0002] To prevent rock bursts from damaging personnel and equipment underground, drilling is used to relieve pressure on site. Due to its ease of construction and excellent results, it has become the most common pressure relief measure in coal mines.

[0003] Currently, after borehole decompression, the borehole may experience radial deformation or even closure and compaction due to the surrounding rock stress. However, over time, the surrounding rock stress in the decompressed area may increase again, necessitating secondary decompression to reduce the impact of mine pressure. To accurately monitor the stress concentration within the borehole and fulfill the requirement for secondary decompression, borehole stress concentration monitoring devices have become crucial for the safety of mining engineering. The monitoring accuracy and reusability of these devices directly impact the mine's coal mining efficiency and economic returns.

[0004] For current monitoring instruments used inside stress relief holes in mining engineering, one approach is to employ various pressure sensors to monitor stress concentration within the hole via air pressure, water pressure, or metal deformation. However, these ordinary sensors suffer from drawbacks such as poor moisture resistance, water resistance, and anti-interference performance, and cannot perform distributed sensing monitoring, thus failing to adequately meet the need for real-time stress monitoring inside stress relief holes. Another approach utilizes fiber optic monitoring technology, enabling the cascading use of multiple sensors. Leveraging the high precision, remote capability, and real-time dynamic capabilities of fiber optics, effective monitoring of the entire drilling and stress relief process can be achieved. However, current fiber optic sensing requires flexible tubing and filler material to ensure accurate reflection of internal stress concentration. Excessive borehole deformation can prevent the sensor from being removed, wasting the cost of the fiber optic sensor and creating difficulties for secondary stress relief. Summary of the Invention

[0005] (a) Purpose of the invention To overcome the above shortcomings, the present invention aims to provide a device and method for monitoring the deformation and stress concentration of pressure relief holes based on magnetic force, so as to solve the above technical problems.

[0006] (II) Technical Solution To achieve the above objectives, the technical solution provided in this application is as follows: A magnetically-based device for monitoring the deformation and stress concentration of pressure relief holes. The device includes a mounting ring, on which at least one airbag is provided. Multiple mounting balls are evenly distributed on the airbag. The mounting balls are rotatably mounted on the airbag through a fixed base. A displacement detection unit is correspondingly provided on the radial mounting ring of the fixed base of the airbag. The displacement detection unit includes a magnetic baffle. The fixed base has magnetism that repels the magnetic baffle. Adjacent mounting rings are connected by a spiral drill rod.

[0007] Preferably, the mounting ring is provided with a radial moving groove, the magnetic baffle is installed in the moving groove by a spring, an optical fiber is provided on the inner side of the magnetic baffle, the optical fiber and the inner surface of the magnetic baffle form a Fabry-Perot cavity, the inner surface of the magnetic baffle is polished to serve as the reflective surface of the optical fiber, and the inner surface of the magnetic baffle and the optical fiber are kept perpendicular to each other.

[0008] Preferably, the mounting ring is provided with multiple air channels, and a rubber tube is slidably arranged in the air channels. One end of the rubber tube is connected to the airbag, and the other end of the rubber tube is provided with an explosion-proof valve. The airbag is inflated through the explosion-proof valve and the rubber tube.

[0009] Preferably, the rubber tube is slidably installed within the air duct, and the explosion-proof valve is a bidirectional differential pressure conducting structure, connected to the inner surface of the steel tube via two limiting springs with preset pre-tension; the pre-tension of the limiting springs matches the stable air pressure value required by the airbag. When the pressure relief hole contracts, causing the airbag volume to shrink and the internal air pressure to be higher than the preset average value, the internal air pressure thrust overcomes the spring preload tension, pushing the explosion-proof valve to open outward, expelling excess nitrogen and reducing the air pressure inside the airbag. When the pressure relief hole expands, causing the airbag volume to increase and the internal air pressure to be lower than the preset average value, the external atmospheric pressure pushes the explosion-proof valve to open inward, replenishing gas and causing the air pressure inside the airbag to rise again. The automatic opening and closing of the explosion-proof valve maintains the air pressure inside the airbag within a preset range, allowing the airbag to adapt to the deformation of the pressure relief hole and always remain tightly attached to the inner wall of the pressure relief hole.

[0010] Preferably, the outer diameter of the auger drill rod gradually increases from the front end to the rear end, the inner diameter of the auger drill rod is the same as the inner diameter of the mounting ring, the minimum diameter of the auger drill rod is the same as the outer diameter of the mounting ring, and the outer diameter of the auger drill rod is greater than or equal to the sum of the diameter of the mounting ring and the diameter of the mounting ball.

[0011] Preferably, the device also includes a microprocessor for signal acquisition and data calculation. The output of the optical fiber is input to the input terminal of the microprocessor after passing through a spectral measurement module and a signal processing circuit. The output terminal of the microprocessor is connected to an information display module. The microprocessor is also connected to a power module and a control button module.

[0012] A method for monitoring deformation and stress concentration of pressure relief holes based on magnetic force, specifically including the following steps: Step 1: Place the entire magnetically based pressure relief hole deformation and stress concentration monitoring device into the pressure relief hole to be monitored, and fill the air bladder of the monitoring device with nitrogen to inflate the air bladder, thus completing the device setup. Step 2: When the pressure relief hole undergoes radial deformation, the deformation area compresses the airbag and the mounting ball, causing the fixed base inside the airbag to shift, reducing the distance between the fixed base and the magnetic baffle. By utilizing the change in repulsive force generated by the magnetic poles of the fixed base and the magnetic baffle, the magnetic baffle is pushed to overcome the spring force and move inward along the moving groove, changing the length of the Fabry-Perot interference cavity between the lower surface of the magnetic baffle and the end of the optical fiber. Step 3: Acquire the interference signal of the Fabry-Perot interferometer cavity, analyze the interference signal to obtain the cavity length change, calculate the repulsive force change by combining the spring coefficient, and then deduce the real-time strain measurement value inside the pressure relief hole. Step 4: Based on the real-time strain measurements from multiple measuring points, calculate the stress concentration factor of the rock mass to obtain the stress concentration at different locations of the pressure relief hole.

[0013] Preferably, step three specifically includes: The incident light propagates in the optical fiber, and returns to the optical fiber after passing through the first reflection surface between the optical fiber and the air and the second reflection surface between the air and the inner surface of the magnetic baffle. Interference signal Represented as: ; In the formula, and The light intensities of the reflected light input to the two reflecting surfaces are respectively; The refractive index of the intermediate medium (air); The length of the Fabry-Perot interferometer cavity; Wavelength; The phase difference between the two reflected beams; The distance between the inner surface of the magnetic baffle and the optical fiber is the distance in the above equation. The length of the Fabry-Perot interferometer cavity.

[0014] Preferably, the rock mass stress concentration factor in step four is: The calculation formula is as follows: ; In the formula, n This indicates the total number of test points on the sensor. For the first i Strain measurements during secondary coal seam mining It is the first i1 Strain measurements during secondary coal seam mining.

[0015] Beneficial effects: 1. Environmental adaptability and service life advantages: This invention uses optical fiber as the sensing core, with no internal electronic components, and naturally has the advantages of anti-electromagnetic interference and corrosion resistance, making it suitable for the harsh underground working environment of mining engineering; at the same time, the overall structure is simple and reusable, which effectively extends the service life of the sensor, reduces the frequency of maintenance, and lowers the maintenance cost of long-term monitoring.

[0016] 2. Improved accuracy and cost advantages of the coupling structure: This invention achieves complete coupling between the device and the inner wall of the pressure relief hole by using an airbag with a constant pressure explosion-proof valve, which can ensure that the deformation of the pressure relief hole is completely transmitted to the fiber optic sensor. Compared with the traditional method of coupling with slurry filling, it significantly improves the accuracy of stress deformation monitoring, while eliminating the need for slurry materials and filling process, and reducing the cost of using the fiber optic sensor per use.

[0017] 3. The reusable design offers cost-reducing advantages. This invention utilizes a threaded drill rod in conjunction with a steel ball structure on the airbag to smoothly remove the core sensing component after the pressure relief hole has been completely deformed. This enables the reuse of the fiber optic sensor and effectively reduces the operational cost of batch monitoring of multiple pressure relief holes.

[0018] 4. The dynamic monitoring advantages of the network layout: This invention supports flexible expansion layout, allowing multiple sets of centrally symmetrical monitoring points to be arranged in the same area, or multiple monitoring sensors to be connected in series in the vertical direction. This facilitates the construction of a regional monitoring network, enabling real-time dynamic monitoring of the strain concentration inside the pressure relief hole, and can meet the needs of large-scale, long-term underground stress monitoring. 5. Performance improvement advantages of optimized measurement principle: This invention uses the Fabry-Perot interferometry principle combined with magnetic pole repulsion to realize strain signal conversion. The strain inside the pressure relief hole is sequentially converted into airbag deformation, magnetic baffle displacement, and finally into the change of Fabry-Perot cavity length to complete the measurement. This reduces the measurement deviation caused by physical wear in traditional fiber optic pressure relief hole monitoring, further improves the measurement accuracy, and expands the measurement range. In addition, by setting a display screen connected to the microprocessor, the strain measurement value can be directly output and displayed, which is convenient for on-site observation. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the device structure of the present invention; Figure 2 This is a top view of the present invention; Figure 3 This is a schematic diagram showing the matching result between the displacement detection unit and the mounting ball of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the following detailed embodiments are described in conjunction with the appendix. Figure 1-3The present invention will be described in further detail below. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0021] This invention provides a magnetic force-based device for monitoring deformation and stress concentration in pressure relief holes. The device is arranged along the axial direction of the pressure relief hole and consists of multiple independent monitoring units, a connecting structure, and a signal acquisition and processing system. Each monitoring unit's basic supporting component is a mounting ring 5, with adjacent mounting rings 5 ​​connected by a spiral drill rod 1. The outer diameter of the spiral drill rod 1 gradually increases from the front to the rear, while its inner diameter matches that of the mounting ring 5. The minimum outer diameter of the spiral drill rod is the same as that of the mounting ring 5, and the maximum outer diameter of the spiral drill rod 1 is greater than or equal to the sum of the diameter of the mounting ring 5 and the diameters of the two mounting balls 3. In use, the number of monitoring units can be connected in series via the spiral drill rod 1 according to the required depth of the pressure relief hole, flexibly adjusting the number of monitoring layers to meet the needs of layered monitoring at different depths. The gradually changing outer diameter design ensures that the entire device can be smoothly pushed into the pressure relief hole while preventing protruding parts from scraping against the hole wall and causing damage, thus improving the smoothness of the device's lowering and installation.

[0022] At least one airbag 2 is provided on the mounting ring 5, and multiple mounting balls 3 are evenly arranged on the airbag 2. The mounting balls 3 are sealed and rotated on the airbag 2 through the fixed base 4. All fixed bases 4 are correspondingly arranged in the radial position of the mounting ring 5, and a displacement detection unit is correspondingly provided at the radial mounting ring position of each fixed base 4.

[0023] The displacement detection unit includes a magnetic baffle 6. The fixed base 4 itself has magnetism that repels the magnetic baffle 6. A radially extending movable groove is provided on the mounting ring 5. The magnetic baffle 6 is installed in the movable groove by a spring 11. The magnetic baffle is not gapped with the inner wall of the movable groove and is pre-lubricated. An optical fiber 7 is provided on the inner side of the magnetic baffle 6. The optical fiber is set on the mounting ring [please confirm that this is correct]. The optical fiber 7 and the inner surface of the magnetic baffle 6 together form a Fabry-Perot cavity. The inner surface of the magnetic baffle 6 is polished and serves as the reflective surface of the optical fiber, and is always kept perpendicular to the optical fiber.

[0024] During use, the pressure relief hole deforms and squeezes the airbag. After being squeezed, the airbag drives the fixed base 4 to move radially toward the center of the mounting ring 5. Since the fixed base 4 and the magnetic baffle 6 repel each other, as the fixed base 4 approaches, the magnetic repulsion will push the magnetic baffle 6 to compress the spring and move inward along the moving groove. Ultimately, this changes the length of the Fabry-Perot cavity between the reflective surface of the magnetic baffle 6 and the optical fiber 7. The deformation and stress concentration of the pressure relief hole can be inferred from the change in cavity length.

[0025] This structure transmits strain signals through magnetic-mechanical displacement conversion. Compared to traditional structures that directly bond optical fibers, it reduces measurement deviations caused by physical wear, resulting in better measurement stability. Combined with the Fabry-Perot interferometry principle, it naturally possesses advantages in high measurement accuracy and a wide measurement range. Furthermore, with the rotatable pulling structure of the auger rod, when monitoring is complete or the pressure relief hole is completely deformed and the component needs to be retrieved, the entire device can be pulled out by rotating and pulling the auger rod 1. The protruding mounting ball 3 on the airbag can scrape off debris attached to the hole wall to prevent jamming, allowing the sensor to be smoothly removed as a whole, meeting the requirements for reuse, and effectively reducing the monitoring cost of multiple pressure relief holes.

[0026] To ensure stable coupling between the airbag and the inner wall of the pressure relief hole, the mounting ring 5 is provided with multiple air guide channels. A rubber tube 8 is slidably installed in the air guide channels. One end of the rubber tube 8 is connected to the inside of the airbag 2, and the other end is equipped with an explosion-proof valve 9. Nitrogen can be injected into the airbag 2 through the explosion-proof valve 9 and the rubber tube 8 to complete the inflation.

[0027] The explosion-proof valve 9 is a bidirectional differential pressure conduction structure. It is connected to the inner surface of the mounting ring on the outside of the air guide channel by two limiting springs 10 with preset pre-tightening force. The pre-tightening force of the limiting springs 10 is matched with the stable air pressure value required by the airbag 2.

[0028] Before use, the preload of the limiting spring 10 can be adjusted according to monitoring needs. After inflating the airbag 2 to the preset pressure, the device installation is complete. During operation, when the pressure relief hole contracts and deforms, causing the airbag 2 to shrink in volume and the internal pressure to be higher than the preset average, the thrust of the internal pressure will overcome the preload of the limiting spring 10, pushing the explosion-proof valve outward to release excess nitrogen and lower the air pressure inside the airbag. When the pressure relief hole expands and deforms, causing the airbag volume to increase and the internal pressure to be lower than the preset average, the external atmospheric pressure will... Push the explosion-proof valve inward to open, replenishing gas and causing the air pressure inside the airbag to rise; [Please confirm if this is correct] This structure can maintain the air pressure inside the airbag within a preset range through the automatic opening and closing of the explosion-proof valve, allowing the airbag to adapt to the deformation of the pressure relief hole and always remain tightly attached to the inner wall of the pressure relief hole. This ensures that the deformation of the pressure relief hole can be completely transmitted to the sensing unit. Compared with the traditional solution that uses slurry filling to achieve coupling, this not only improves the measurement accuracy but also saves the slurry filling process and material costs, resulting in lower monitoring costs.

[0029] This device is also equipped with a signal acquisition and processing system, including a microprocessor for signal acquisition and data processing. The optical signal output from the fiber optic cable is processed sequentially by a spectral measurement module and a signal processing circuit before being input to the microprocessor. The output of the microprocessor is connected to an information display module. The microprocessor is also connected to a power supply module and a control button module. During operation, the microprocessor can convert the acquired cavity length changes into corresponding strain and stress values ​​at the pressure relief holes, which are then directly displayed through the information display module. This allows on-site personnel to easily read the monitoring data in real time, eliminating the need for additional external processing equipment and making on-site use more convenient.

[0030] A method for monitoring deformation and stress concentration of pressure relief holes based on magnetic force, specifically including the following steps: Step 1: Place the entire magnetically based pressure relief hole deformation and stress concentration monitoring device into the pressure relief hole to be monitored, and fill the air bladder of the monitoring device with nitrogen to inflate the air bladder, thus completing the device setup. Step 2: When the pressure relief hole undergoes radial deformation, the deformation area compresses the airbag and the mounting ball, causing the fixed base inside the airbag to shift, reducing the distance between the fixed base and the magnetic baffle. By utilizing the change in repulsive force generated by the magnetic poles of the fixed base and the magnetic baffle, the magnetic baffle is pushed to overcome the spring force and move inward along the moving groove, changing the length of the Fabry-Perot interference cavity between the lower surface of the magnetic baffle and the end of the optical fiber. Step 3: Acquire the interference signal of the Fabry-Perot interferometer cavity, analyze the interference signal to obtain the cavity length change, calculate the repulsive force change by combining the spring coefficient, and then deduce the real-time strain measurement value inside the pressure relief hole. Step 4: Based on the real-time strain measurements from multiple measuring points, calculate the stress concentration factor of the rock mass to obtain the stress concentration at different locations of the pressure relief hole.

[0031] Preferably, step three specifically includes: The incident light propagates in the optical fiber, and returns to the optical fiber after passing through the first reflection surface between the optical fiber and the air and the second reflection surface between the air and the inner surface of the magnetic baffle. Interference signal Represented as: ; In the formula, and The light intensities of the reflected light input to the two reflecting surfaces are respectively; The refractive index of the intermediate medium (air); The length of the Fabry-Perot interferometer cavity; Wavelength; The phase difference between the two reflected beams; The distance between the inner surface of the magnetic baffle and the optical fiber is the distance in the above equation. The length of the Fabry-Perot interferometer cavity.

[0032] Preferably, the rock mass stress concentration coefficient in step four is , and its calculation formula is: ; In the formula, n represents the total number of test points on the sensor, is the strain measurement value during the i th coal seam mining, is the strain measurement value during the i1 th coal seam mining.

[0033] In summary, the decompression hole deformation and stress concentration monitoring device and method based on magnetism of the present invention, aiming at the actual needs of stress concentration monitoring of decompression holes in mining engineering, through structural design innovation and sensing principle optimization, solve the industry pain points of poor anti-interference ability, insufficient coupling accuracy, and non-recyclable sensors in traditional monitoring schemes.

[0034] The present invention adopts an all-fiber sensing architecture as a whole, without electronic components inside, and naturally has the characteristics of anti-electromagnetic interference and corrosion resistance. It can adapt to the complex and harsh underground working environment, effectively extending the service life of the device; through the design of a constant-pressure airbag with a two-way pressure-difference conducting explosion-proof air valve, it can adaptively follow the deformation of the decompression hole and always maintain a tight fit with the hole wall, ensuring that the deformation of the decompression hole is completely transmitted to the sensing unit. Compared with the traditional coupling scheme of filling slurry, it not only significantly improves the monitoring accuracy, but also saves the process and material costs of slurry filling, simplifying the on-site installation process;配合渐变外径螺旋钻杆与可转动安装球的结构设计,可在监测完成后顺畅拉出整套装置,实现核心传感部件的完整回收与重复利用,大幅降低了多测点、多卸压孔的批量监测成本。

[0035] The monitoring method supporting the present invention completes strain analysis by means of step-by-step signal conversion of magnetism-mechanical displacement-Fabry-Perot cavity length and combines the Fabry-Perot interference principle. The signal conversion process is stable, effectively reducing the measurement deviation caused by physical wear of traditional structures, and having the advantages of a large measurement range and high measurement accuracy; at the same time, it supports the axial series connection of multiple monitoring units and the layout of multiple measurement points on the same layer, and can build a monitoring network covering the entire depth and area of the decompression hole.配合内置的数据采集处理与显示模块,能够直接输出得到卸压孔不同位置的应力集中系数,实现应力状态的实时动态监测,完全满足井下大规模岩体应力监测的工程需求,具备良好的现场应用与推广价值。

[0036] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0037] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A magnetically-based device for monitoring the deformation and stress concentration of a pressure relief hole, characterized in that, The device includes a mounting ring, on which at least one airbag is provided. Multiple mounting balls are evenly distributed on the airbag. The mounting balls are rotatably mounted on the airbag through a fixed base. A displacement detection unit is correspondingly provided on the radial mounting ring of the fixed base of the airbag. The displacement detection unit includes a magnetic baffle. The fixed base has magnetism that repels the magnetic baffle. Adjacent mounting rings are connected by a spiral drill rod.

2. The magnetic force-based pressure relief hole deformation and stress concentration monitoring device according to claim 1, characterized in that, The mounting ring has a radial moving groove. The magnetic baffle is installed in the moving groove by a spring. An optical fiber is provided on the inner side of the magnetic baffle. The optical fiber and the inner surface of the magnetic baffle form a Fabry-Perot cavity. The inner surface of the magnetic baffle is polished to serve as the reflective surface of the optical fiber. The inner surface of the magnetic baffle and the optical fiber are kept perpendicular to each other.

3. The magnetic force-based pressure relief hole deformation and stress concentration monitoring device according to claim 1, characterized in that, The mounting ring is provided with multiple air channels, and a rubber tube is slidably installed in the air channels. One end of the rubber tube is connected to the airbag, and the other end of the rubber tube is provided with an explosion-proof valve. The airbag is inflated through the explosion-proof valve and the rubber tube.

4. The magnetic force-based pressure relief hole deformation and stress concentration monitoring device according to claim 3, characterized in that, The rubber tube is slidably installed within the air passage. The explosion-proof valve is a bidirectional differential pressure conducting structure, connected to the inner surface of the steel tube via two small limiting springs with preset pre-tension. The pre-tension of the limiting springs matches the stable air pressure value required by the airbag. When the pressure relief hole contracts, causing the airbag volume to shrink and the internal air pressure to be higher than the preset average value, the internal air pressure thrust overcomes the spring preload tension, pushing the explosion-proof valve to open outward, expelling excess nitrogen and reducing the air pressure inside the airbag. When the pressure relief hole expands, causing the airbag volume to increase and the internal air pressure to be lower than the preset average value, the external atmospheric pressure pushes the explosion-proof valve to open inward, replenishing gas and causing the air pressure inside the airbag to rise again. The automatic opening and closing of the explosion-proof valve maintains the air pressure inside the airbag within a preset range, allowing the airbag to adapt to the deformation of the pressure relief hole and always remain tightly attached to the inner wall of the pressure relief hole.

5. The magnetic force-based pressure relief hole deformation and stress concentration monitoring device according to claim 1, characterized in that, The outer diameter of the auger drill rod gradually increases from the front end to the rear end. The inner diameter of the auger drill rod is the same as the inner diameter of the mounting ring. The smallest part of the auger drill rod is the same as the outer diameter of the mounting ring. The outer diameter of the auger drill rod is greater than or equal to the sum of the diameter of the mounting ring and the diameter of the mounting ball.

6. The magnetic force-based pressure relief hole deformation and stress concentration monitoring device according to claim 1, characterized in that, It also includes a microprocessor for signal acquisition and data calculation. The output of the optical fiber is input to the input terminal of the microprocessor after passing through the spectral measurement module and the signal processing circuit. The output terminal of the microprocessor is connected to an information display module. The microprocessor is connected to a power module and a control button module.

7. A method for monitoring deformation and stress concentration of a pressure relief hole based on magnetic force, characterized in that, Specifically, the following steps are included: Step 1: Place the entire magnetic stress relief hole deformation and stress concentration monitoring device according to any one of claims 1-6 into the stress relief hole to be monitored, and fill the air bladder of the monitoring device with nitrogen to inflate the air bladder, thus completing the device setup. Step 2: When the pressure relief hole undergoes radial deformation, the deformation area compresses the airbag and the mounting ball, causing the fixed base inside the airbag to shift, reducing the distance between the fixed base and the magnetic baffle. By utilizing the change in repulsive force generated by the magnetic poles of the fixed base and the magnetic baffle, the magnetic baffle is pushed to overcome the spring force and move inward along the moving groove, changing the length of the Fabry-Perot interference cavity between the lower surface of the magnetic baffle and the end of the optical fiber. Step 3: Acquire the interference signal of the Fabry-Perot interferometer cavity, analyze the interference signal to obtain the cavity length change, calculate the repulsive force change by combining the spring coefficient, and then deduce the real-time strain measurement value inside the pressure relief hole. Step 4: Based on the real-time strain measurements from multiple measuring points, calculate the stress concentration factor of the rock mass to obtain the stress concentration at different locations of the pressure relief hole.

8. The method for monitoring deformation and stress concentration of a magnetically-based pressure relief hole according to claim 7, characterized in that, Step three specifically includes: The incident light propagates in the optical fiber, and returns to the optical fiber after passing through the first reflection surface between the optical fiber and the air and the second reflection surface between the air and the inner surface of the magnetic baffle. Interference signal Represented as: ； In the formula, and The light intensities of the reflected light input to the two reflecting surfaces are respectively; The refractive index of the intermediate medium (air); The length of the Fabry-Perot interferometer cavity; Wavelength; The phase difference between the two reflected beams; The distance between the inner surface of the magnetic baffle and the optical fiber is the distance in the above equation. The length of the Fabry-Perot interferometer cavity.

9. The method for monitoring deformation and stress concentration of a magnetically-based pressure relief hole according to claim 7, characterized in that, The rock mass stress concentration factor in step four is: The calculation formula is as follows: ； In the formula, n This indicates the total number of test points on the sensor. For the first i Strain measurements during secondary coal seam mining It is the first i1 Strain measurements during secondary coal seam mining.

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