Multi-parameter coupled evaluation device and method for pressure relief effect of large-diameter boreholes in coal and rock

Abstract

This invention discloses a multi-parameter coupled evaluation device and method for pressure relief effect in large-diameter coal and rock boreholes, relating to the field of coal and rock pressure relief effect monitoring and evaluation technology. The device includes a hollow monitoring probe, a radon gas collection and monitoring component, and a fiber optic grating monitoring component. The hollow monitoring probe is arranged along the borehole axis. The radon gas collection and monitoring component includes a radon gas collection channel and a radon meter for collecting radon gas within the borehole. The fiber optic grating monitoring component includes a monitoring unit and a fiber optic demodulator for acquiring data on borehole wall radial deformation, circumferential deformation, and stress changes at corresponding locations within the borehole. This invention constructs a coupled evaluation index for pressure relief effect by calculating and analyzing stress attenuation, borehole wall deformation, radon gas release, dual-hole consistency, and borehole closure state. This index can continuously reflect the entire process of borehole pressure relief from initial effectiveness and stable pressure relief to closure failure, significantly improving the real-time performance and accuracy of pressure relief effect evaluation.

Description

Technical Field

[0001] This invention relates to the field of monitoring and evaluation technology of coal and rock pressure relief effect, specifically to a multi-parameter coupled evaluation device and method for the pressure relief effect of large-diameter coal and rock boreholes. Background Technology

[0002] With the increasing depth of coal mining, the surrounding rock of roadways is often subjected to a superimposed environment of high ground stress, high tectonic stress, and strong mining disturbance, significantly increasing the risk of dynamic disasters such as rock bursts, spalling, floor heave, and coal blasting. Large-diameter borehole stress relief technology is a commonly used local stress relief method in coal mine roadway rockfill prevention and surrounding rock control. It promotes the transfer of high stress to deeper layers by creating large-scale free surfaces and fractured loosening zones within the coal and rock mass, thereby reducing the energy accumulation in the shallow surrounding rock. Therefore, accurately evaluating the stress relief effect of large-diameter boreholes is of great significance for ensuring the stability of roadway surrounding rock and preventing dynamic disasters.

[0003] Existing methods for evaluating the pressure relief effect of large-diameter boreholes largely rely on drill cuttings volume, single-point stress gauges, microseismic events, borehole inspection, or manual experience. However, these methods typically suffer from technical limitations, such as using only one monitoring parameter, poor spatial correspondence, and difficulty in continuously reflecting the entire process of borehole closure failure. For example, a single stress index can only reflect local stress changes and is insufficient to determine the development of borehole fractures and the state of gas migration; while a single deformation index can reflect borehole wall convergence or deformation, it is difficult to distinguish between effective pressure relief deformation and borehole closure failure; borehole inspection and manual interpretation are greatly affected by coal dust, water vapor, and borehole wall fracture, making long-term continuous online monitoring difficult; furthermore, the pressure relief effect of a borehole is not constant during mining disturbances and mining advances, and the borehole may experience different stages such as effectiveness, stable pressure relief, borehole wall convergence, partial closure, or even failure.

[0004] Therefore, there is an urgent need to invent a multi-parameter coupled evaluation device and method for stress monitoring, deformation monitoring, and continuous monitoring of gas migration in fractures to overcome the shortcomings of existing technologies and ensure safe and efficient production in deep mining faces. Summary of the Invention

[0005] To address the aforementioned problems, this invention discloses a multi-parameter coupled evaluation device and method for the pressure relief effect of large-diameter coal and rock boreholes. By integrating stress, deformation, and radon gas monitoring components in two adjacent boreholes, the coupled evaluation of the borehole pressure relief effect is achieved, which has the advantages of reliable evaluation results, accurate monitoring data, and continuous monitoring capability.

[0006] The multi-parameter coupled evaluation device for pressure relief effect of large-diameter coal and rock boreholes proposed according to the present invention includes a hollow monitoring probe, a radon gas collection and monitoring component, and a fiber optic grating monitoring component. The hollow monitoring probe is arranged along the borehole axis and is fixedly connected to the borehole sealing structure. A flexible airbag is sleeved on the outer wall of one end of the hollow monitoring probe near the borehole opening, and the flexible airbag is connected to an external air pump. The radon gas collection and monitoring component includes a radon gas collection channel and a radon detector. The radon gas collection channel is arranged inside the hollow monitoring probe, with one end extending into the borehole to collect radon gas and the other end connected to the radon detector outside the borehole. The fiber optic grating monitoring component includes a monitoring unit and a fiber optic demodulator. The monitoring unit includes a deformation monitoring unit and a stress monitoring unit. Both the deformation monitoring unit and the stress monitoring unit are arranged on the outer wall of the hollow monitoring probe and are connected to the external fiber optic demodulator via optical fibers to acquire data on radial deformation, circumferential deformation, and stress changes of the borehole wall at corresponding locations.

[0007] Preferably, the end of the hollow monitoring probe near the orifice is fixedly connected to an orifice flange, and the orifice sealing structure is a T-shaped sealing positioning sleeve, which is fitted onto the orifice end of the hollow monitoring probe. The orifice flange and the sealing positioning sleeve are fixedly connected by bolts, and a sealing gasket is also provided between the orifice flange and the sealing positioning sleeve.

[0008] Preferably, the radon gas collection channel is formed by the hollow cavity of the hollow monitoring probe; the radon gas collection and monitoring component further includes a deep sieve gas collection component, a desiccant, and a filter. The deep sieve gas collection component includes a sieve tube and a conical end cap. One end of the sieve tube is fixedly connected to the end of the hollow monitoring probe that extends into the borehole, and the other end is fixedly connected to the conical end cap. The outer wall of the sieve tube is covered with a dustproof filter, and the inner wall is covered with a waterproof and breathable membrane. The conical end cap has a guide hole at the end away from the sieve tube. The desiccant and the filter are sequentially installed on the air inlet pipe between the radon detector and the radon gas collection channel.

[0009] Preferably, the hollow monitoring probe is composed of multiple sections of rod spliced ​​together, with adjacent sections threaded together and a sealing structure provided at the connection.

[0010] Preferably, one or more sets of monitoring units are arranged along the axial direction of the hollow monitoring probe; the stress monitoring unit includes an arc-shaped wall-adhering pressure block, an elastic force transmission component, a pre-tightening airbag, and a stress fiber optic grating. The arc-shaped wall-adhering pressure block is disposed on the outside of the hollow monitoring probe, and its outer arc surface is adapted to the shape of the borehole wall. A support component is disposed on the side of the arc-shaped wall-adhering pressure block near the hollow monitoring probe. The elastic force transmission component is disposed between the support component and the hollow monitoring probe. The stress fiber optic grating is attached to the elastic force transmission component and is used to sense the elastic strain caused by the contact stress of the borehole wall. The pre-tightening airbag is disposed between the arc-shaped wall-adhering pressure block and the hollow monitoring probe. The pre-tightening airbag is connected to an external air pump; the deformation monitoring unit includes a circumferential fiber grating and a radial fiber grating. The circumferential fiber grating is fixedly installed on the outer wall of the arc-shaped wall-fitting block along the circumference of the hollow monitoring probe; the radial fiber grating is encapsulated on an elastic measuring plate, which is arranged radially along the hollow monitoring probe, with one end fixedly connected to the arc-shaped wall-fitting block and the other end fixedly connected to the outer wall of the hollow monitoring probe; the stress fiber grating, the radial fiber grating, and the circumferential fiber grating are all connected to the fiber demodulator via optical fibers. The outer wall of the hollow monitoring probe has an axial fiber protection groove, and the optical fibers are arranged within the fiber protection groove.

[0011] Preferably, the stress monitoring unit further includes a guide limiting connector, which includes a fixed seat and a guide post. The fixed seat is a hollow structure and is fixedly installed on the outer wall of the hollow monitoring probe. The guide post has an outer shape that matches the hollow part of the fixed seat. One end of the guide post extends into the hollow part of the fixed seat and is fixedly connected to the fixed seat through a spring provided at the end. The other end is fixedly installed on the inner wall of the arc-shaped wall-adhering pressure block.

[0012] Preferably, each set of monitoring units consists of three stress monitoring units and three deformation monitoring units evenly distributed along the circumference of the hollow monitoring probe.

[0013] A method for evaluating the pressure relief effect using the aforementioned multi-parameter coupled evaluation device for large-diameter coal and rock boreholes, proposed according to the present invention, includes the following steps: S1. Determine the location, diameter, depth and spacing of two adjacent boreholes within the test section to be evaluated, and determine the location of the peak area of ​​the support pressure measured on site. S2. After assembling the hollow monitoring probe, the deep screen hole gas collection component and the fiber optic grating monitoring component, send them into two adjacent boreholes and install and fix them. Use an air pump to inflate the flexible airbag and the pre-tightening airbag through the corresponding airbag channel so that the flexible airbag and the arc-shaped wall-adhering pressure block are in contact with the borehole wall. S3. Connect the fiber optic demodulator and the radon gas collection and filter assembly, perform zero-point calibration on them, and collect the initial stress, initial hole wall deformation and initial radon gas concentration at the beginning of installation as reference values. S4. During the borehole activation, mining disturbance, and mining advance, simultaneously collect the borehole wall contact stress, radial fiber grating deformation, circumferential fiber grating deformation, and radon concentration in two adjacent boreholes. S5. Normalize the collected multi-parameter data and calculate the stress attenuation coefficient, borehole wall deformation coefficient, radon gas release coefficient, dual-hole consistency coefficient and borehole closure coefficient respectively to obtain the coupled evaluation index of pressure relief effect. S6. Based on the pressure relief effect coupled evaluation index, judge the pressure relief effect of the borehole, and optimize the borehole parameters accordingly.

[0014] Preferably, in S5, the stress attenuation coefficient is determined by the degree of reduction in the contact stress of the hole wall relative to the initial contact stress, and its calculation formula is as follows: In the formula: σ i0 - The average initial contact stress of the borehole wall in the i-th borehole; σ it - The average contact stress of the borehole wall at time t for the i-th borehole; The hole wall deformation coefficient is determined by the radial convergence, circumferential strain, and the degree of ellipticization of the hole wall relative to the effective deformation threshold. Its calculation formula is as follows: In the formula: μ it -The average radial convergence at time t for the i-th borehole; μ i0 - Average initial radial convergence of the i-th borehole; ν it -The average circumferential strain at time t in the i-th borehole; ν i0 -The average value of the initial circumferential strain of the i-th borehole; ω it - The average degree of ellipticity of the borehole wall at time t for the i-th borehole, where D i(x)t D i(y)t These are the equivalent apertures in the horizontal and vertical directions, D. i0 This is the initial aperture; μ th -Effective radial deformation threshold; ν th -Effective circumferential strain threshold; ω th - Ellipticization threshold; The radon release coefficient is determined by the increase in radon release concentration in the deep fracture gas of the borehole relative to the initial concentration, and its calculation formula is as follows: In the formula: C it - Radon concentration at time t in the i-th borehole; C i0 - Radon concentration at the initial stage of installation in the i-th borehole; The dual-hole consistency coefficient is determined by the similarity of the trends in stress, deformation, and radon release between two adjacent boreholes, and its calculation formula is as follows: The borehole closure coefficient refers to the degree to which borehole wall convergence reduces the effective pressure relief space of the borehole. A larger coefficient indicates a higher degree of borehole closure. The calculation formula is as follows: In the formula: D i0 - Initial borehole diameter for the i-th borehole; The formula for calculating the pressure relief effect coupled evaluation index E is: In the formula: K σ - The average stress attenuation coefficient between two adjacent boreholes; K ε - The average value of the borehole wall deformation coefficient between two adjacent boreholes; K Rn - The average radon release coefficient of two adjacent boreholes; K α -Dual-hole consistency coefficient; K β - The average borehole closure coefficient of two adjacent boreholes; a, b, c, d, e - Weighting coefficients, all ≥ 0 and a+b+c+d+e =1; K σ , K ε , K Rn , K α , K β All values ​​have been normalized and range from 0 to 1.

[0015] Preferably, in S6, the borehole pressure relief effect is judged based on the coupling evaluation index E: K βWhen the borehole temperature is ≥ the field experience threshold, it is determined that the borehole is at risk of closure or is approaching failure, requiring borehole cleaning, repair, adjustment of borehole parameters, and reinforcement of support; when K β If the pressure relief effect is below the field experience threshold, and E ≥ 0.80, the pressure relief effect is considered excellent; if 0.50 ≤ E < 0.80, the pressure relief effect is considered effective; if 0.20 ≤ E < 0.50, the pressure relief effect is considered average, and it is suggested that monitoring should be strengthened; if E < 0.20, the pressure relief effect is considered to be at risk, the borehole is prone to failure, and support should be strengthened and the pressure relief plan should be reviewed in time.

[0016] Compared with existing technologies, the advantages of the multi-parameter coupled evaluation device and method for pressure relief effect of large-diameter coal and rock boreholes disclosed in this invention are: (1) This invention innovatively combines stress monitoring, deformation monitoring and radon concentration monitoring, which can evaluate the borehole pressure relief effect from three dimensions of parameters: mechanical response, structural deformation and fracture gas migration, and the evaluation results are more comprehensive and objective.

[0017] (2) The present invention adopts a synchronous monitoring method for adjacent boreholes, which can identify the difference between local anomalies in a single borehole and the overall response of the pressure relief zone, and can also continuously reflect the entire process of borehole from effective start-up, stable pressure relief to closure failure, thus eliminating the randomness error of single borehole monitoring.

[0018] (3) This invention can realize long-term monitoring downhole and quantify the pressure relief effect by calculating the pressure relief effect coupled with evaluation indicators. It can directly serve on-site decision-making such as hole filling, hole spacing adjustment and support strengthening, which is convenient for engineering promotion and application. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the overall layout of the multi-parameter coupled evaluation device for the pressure relief effect of large-diameter coal and rock boreholes disclosed in this invention.

[0021] Figure 2 This is a schematic diagram showing the installation of the hollow monitoring probe in conjunction with the fiber optic grating monitoring assembly and the deep sieve gas collection assembly.

[0022] Figure 3 For sealing and positioning.

[0023] Figure 4 Schematic diagram of the deep sieve gas collection assembly structure Figure 5 This is a schematic diagram of the radon gas collection and filtration component.

[0024] Figure 6 This is a schematic diagram of the installation structure for the monitoring unit and the hollow monitoring probe.

[0025] Figure 7 for Figure 6 Enlarged view of section I in the middle.

[0026] Figure 8 This is a schematic diagram illustrating the graded depressurization effects.

[0027] In the diagram: 1-Hollow monitoring probe; 11-Orifice flange; 12-Bolt; 13-Sealing gasket; 14-Flexible airbag; 15-Sealing positioning sleeve; 16-Sealing plug; 2-Fiber Bragg grating monitoring assembly; 21-Arc-shaped wall-adhering pressure block; 22-Radial fiber Bragg grating; 23-Circumferential fiber Bragg grating; 24-Fiber optic cable; 25-Fiber optic demodulator; 26-Stressed fiber Bragg grating; 27-Elastic force transmission component; 28-Pre-tightening airbag; 29-Support component ; 210-Guide limiting connector; 3-Radon gas collection and monitoring component; 31-Radon gas collection channel; 32-Deep sieve gas collection component; 321-Dustproof filter; 322-Sieve tube; 323-Waterproof and breathable membrane; 324-Conical end cap; 325-Flow guide hole; 326-Hollow connector; 33-Radon meter; 331-Air inlet; 332-Exhaust outlet; 34-Desiccant; 35-Filter; 4-Air pump; 5-Drill hole. Detailed Implementation

[0028] The specific embodiments of the present invention will be briefly described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] Figures 1-8 A preferred embodiment of the present invention is shown and analyzed in detail.

[0030] like Figure 1 The multi-parameter coupled evaluation device for the pressure relief effect of large-diameter coal and rock boreholes shown includes a hollow monitoring probe 1, a radon gas collection and monitoring component 3, and a fiber optic grating monitoring component 2.

[0031] like Figure 2 , 3As shown, the hollow monitoring probe 1 is axially arranged along the borehole 5 and fixedly connected to the borehole sealing structure. Specifically, a borehole flange 11 is fixedly connected to the end of the hollow monitoring probe 1 near the borehole opening. The borehole sealing structure is a T-shaped sealing positioning sleeve 15, which is fitted onto the borehole end of the hollow monitoring probe 1. The borehole flange 11 and the sealing positioning sleeve 15 are fixedly connected by bolts 12, and a sealing gasket 13 is also provided between the borehole flange 11 and the sealing positioning sleeve 15 for sealing. After the sealing positioning sleeve 15 is fixedly connected to the hollow monitoring probe 1 through the borehole flange 11, it is then fixed to the borehole opening of the borehole 5 by grouting, thereby achieving axial and radial positioning of the hollow monitoring probe 1. The hollow monitoring probe 1 is composed of multiple sections of rod spliced ​​together, with adjacent sections threaded together and O-rings provided at the joints for sealing to ensure airtightness during long-term downhole monitoring. The splicing length of the hollow monitoring probe 1 is determined according to the actual hole depth, ensuring that the deep screen hole gas collection component 32 is located 1-2m deep from the peak support pressure zone. This position is more sensitive to changes in gas release and avoids the closure of the hole wall by debris at the peak position. If this position is close to the bottom of the hole, a 0.2-0.5m anti-clogging gap is reserved between it and the bottom of the hole. A flexible airbag 14 is fitted on the outer wall of the end of the hollow monitoring probe 1 near the hole opening. The flexible airbag 14 is connected to the air pump 4 outside the hole through an inflation pipe set in the inner cavity of the hollow monitoring probe 1. After the flexible airbag 14 is inflated by the air pump 4, it fits tightly against the hole wall of the borehole 5, so that the hollow monitoring probe 1 is stably centered in the hole and forms a sealed space. After the hole opening is sealed, it can prevent fresh air from the roadway from directly entering the borehole 5 and causing radon dilution, and it can also prevent coal dust and water vapor from entering the hole opening and affecting the accuracy of the data. For long-term monitoring, a removable protective cover can be set around the hole opening. The orifice end of the hollow monitoring probe 1 is sealed by a multi-channel sealing plug 16. The inflation lines connecting the flexible airbag 14 and the pre-tensioned airbag 28 pass through the sealing plug 16 and are connected to the air pump 4. The air inlet line on the radon detector 33 connects to the corresponding channel on the sealing plug 16, thus connecting to the radon gas collection channel 31. Each channel on the sealing plug 16 is sealed with sealant after being connected to the corresponding pipeline. A through hole is provided on the orifice flange 11 for the optical fiber 24 to pass through; the hole is also sealed with sealant after the optical fiber 24 passes through.

[0032] The radon gas collection and monitoring component 3 includes a radon gas collection channel 31, a deep sieve gas collection component 32, and a radon gas collection and filtration component, such as... Figure 5 As shown, the radon gas collection and filtration assembly includes a radon detector 33, a desiccant 34, and a filter 35. The radon gas collection channel 31 is formed by the hollow cavity of the hollow monitoring probe 1, with one end extending into the borehole 5 to collect radon gas, and the other end connected to the radon detector 33 outside the borehole 5 via an air inlet pipe. The radon detector 33 is equipped with an air inlet 331 and an air outlet 332. Figure 4As shown, the deep sieve-hole gas collection assembly 32 includes a sieve tube 322 and a conical end cap 324. One end of the sieve tube 322 is threadedly connected to the end of the hollow monitoring probe 1 that penetrates into the borehole 5 via a hollow connecting seat 326. The other end is integrally formed with the conical end cap 324. The conical end cap 324 facilitates the smooth entry of the entire device into the depth of the borehole 5. Multiple rows of sieve holes are evenly distributed on the sieve tube 322 to increase the gas collection area. The outer wall of the sieve tube 322 is covered with a dust filter 321 to block larger coal dust and debris, while the inner wall is covered with a waterproof and breathable membrane 323 to block liquid water, water mist, and fine particles while allowing gas to pass through. The end of the conical end cap 324 away from the sieve tube 322 is provided with a guide hole 325 to allow the gas from the fracture in the borehole 5 to continuously enter the radon gas collection channel 31. Desiccant 34 and filter 35 are sequentially installed on the air inlet pipe between radon detector 33 and radon gas collection channel 31. Filter 35 is used to further remove dust and particulate matter from the gas, and desiccant 34 is used to remove moisture and reduce the humidity of the collected gas. In use, radon detector 33 collects radon gas from borehole 5 through negative pressure extraction. Radon gas enters radon detector 33 after passing through air inlet 331, desiccant 34, and filter 35, and the radon concentration and change rate are obtained in real time. Finally, it is discharged to the ventilation position through exhaust port 332 to avoid radon gas backflow or local accumulation.

[0033] like Figure 6 , 7 As shown, the fiber optic grating monitoring component 2 includes a monitoring unit and a fiber optic demodulator 25. The monitoring unit includes a deformation monitoring unit and a stress monitoring unit. Both the deformation monitoring unit and the stress monitoring unit are installed on the outer wall of the hollow monitoring probe 1 and are connected to the external fiber optic demodulator 25 through an optical fiber 24 to obtain data on the radial deformation, circumferential deformation and stress change of the borehole wall at the corresponding position of the borehole 5.

[0034] The stress monitoring unit includes an arc-shaped wall-adhering pressure block 21, an elastic force transmission component 27, a pre-tightening airbag 28, and a stress fiber optic grating 26. The arc-shaped wall-adhering pressure block 21 is located on the outside of the hollow monitoring probe 1, and its outer arc surface is adapted to the shape of the borehole wall 5, which can increase the contact area with the borehole wall and reduce the risk of local crushing. A support component 29 is fixedly installed on the side of the arc-shaped wall-adhering pressure block 21 near the hollow monitoring probe 1. The elastic force transmission component 27 is located between the support component 29 and the hollow monitoring probe 1 and is fixed to the support component 29. The stress fiber optic grating 26 is attached to the elastic force transmission component 27 and is used to sense the elastic strain caused by the contact stress of the borehole wall. The pre-tightening airbag 28 is located between the arc-shaped wall-adhering pressure block 21 and the hollow monitoring probe 1. The pre-tightening airbag 28 is connected to the external air pump 4. After inflation, it is used to push the arc-shaped wall-adhering pressure block 21 to adhere tightly to the borehole wall 5, forming a stable borehole wall contact stress transmission interface. Specifically, there are two symmetrically arranged support members 29, and the pre-tensioning airbag 28 is placed between the two support members 29. Stress monitoring process: When the stress on the borehole wall changes, the force acting on the borehole wall is transmitted to the elastic force transmission member 27 through the arc-shaped wall-adhering pressure block 21. This causes the elastic force transmission member 27 to generate elastic strain corresponding to the contact stress on the borehole wall, which in turn causes a change in the central reflection wavelength of the stress fiber optic grating 26. The generated optical signal enters the external fiber optic demodulator 25 through the fiber optic cable 24. The fiber optic demodulator 25 demodulates the wavelength change into a strain signal, which is ultimately converted into the contact stress on the borehole wall.

[0035] The stress monitoring unit also includes a guide and limiting connector 210, which comprises a fixed base and a guide post. The fixed base is a hollow structure and is fixedly installed on the outer wall of the hollow monitoring probe 1. The guide post's shape matches the hollow part of the fixed base. One end of the guide post extends into the hollow part of the fixed base and is fixedly connected to the fixed base via a spring at its end. The other end is fixedly installed on the inner wall of the arc-shaped wall-adhering pressure block 21. The guide and limiting connector 210 allows the arc-shaped wall-adhering pressure block 21 to undergo slight displacement while preventing it from falling off or deflecting. Two guide and limiting connectors 210 are symmetrically arranged.

[0036] The deformation monitoring unit includes a circumferential fiber grating 23 and a radial fiber grating 22. The circumferential fiber grating 23 is fixedly installed circumferentially along the hollow monitoring probe 1 within a circumferential encapsulation groove on the outer wall of the arc-shaped wall-mounting block 21 using epoxy resin. It is used to monitor the circumferential strain and ellipticity of the borehole wall 5. The radial fiber grating 22 is encapsulated on an elastic measuring plate and is used to measure the closure degree of the borehole 5. The elastic measuring plate is arranged radially along the hollow monitoring probe 1, with one end fixedly connected to the arc-shaped wall-mounting block 21 and the other end fixedly connected to the outer wall of the hollow monitoring probe 1. It is used to generate corresponding strain when the arc-shaped wall-mounting block 21 displaces as the borehole wall converges radially. The stress fiber grating 26, the radial fiber grating 22, and the circumferential fiber grating 23 are all connected to the fiber demodulator 25 via optical fibers 24 to convert the optical signals into corresponding physical data. An axial fiber protection groove is opened on the outer wall of the hollow monitoring probe 1, and the optical fibers 24 are arranged within the fiber protection groove to reduce wear during installation and extraction.

[0037] The monitoring unit is set in the monitoring section corresponding to the peak area of ​​the support pressure. The length of the monitoring section along the axial direction of the hollow monitoring probe 1 is 0.2m to 1.0m, preferably 0.3m to 0.5m. One or more monitoring units are set along the axial direction of the hollow monitoring probe 1. When one monitoring unit is set, it is used to evaluate the local pressure relief effect; when multiple monitoring units are set, it is used to form a comprehensive evaluation result for the entire monitoring section. Each monitoring unit contains three stress monitoring units and three deformation monitoring units evenly distributed along the circumference of the hollow monitoring probe 1. Specifically, the flexible airbag 14 and the pre-tensioning airbag 28 are connected by independent pipelines, and the corresponding pre-tensioning airbags 28 in multiple monitoring units are also connected by independent pipelines. The three pre-tensioning airbags 28 in the same monitoring unit are connected by the same pipeline.

[0038] Another method disclosed in this invention for evaluating the pressure relief effect using the aforementioned multi-parameter coupled evaluation device for large-diameter coal and rock boreholes includes the following steps: S1. Under the same pressure relief zone and consistent parameters, select any two directly adjacent boreholes 5 for monitoring. Based on the surrounding rock conditions, support parameters, and pressure relief design, determine the location, diameter, depth, and spacing of the two adjacent boreholes 5, and determine the location of the peak support pressure area measured on-site. Clean the floating coal, accumulated water, and loose coal dust inside the boreholes. Determining the location of borehole 5 is to determine whether the two adjacent boreholes 5 are located within the same pressure relief zone to be evaluated, providing a basis for the consistency coefficient of the two boreholes. Determining the borehole diameter is to determine the outer arc surface dimensions of the arc-shaped wall-mounted pressure block 21, the pushing stroke of the pre-tightening airbag 28, the calculation benchmark for the borehole wall convergence, and the initial borehole diameter benchmark for the borehole closure coefficient. Determining the borehole depth is to determine the splicing length of the hollow monitoring probe 1 and the installation depth of the deep screen hole gas collection component 32. Determining the borehole spacing is to determine whether the pressure relief influence zones of the two adjacent pressure relief holes have an interaction relationship, serving as a basis for subsequent borehole consistency coefficient and borehole spacing optimization. Determining the peak support pressure area is to monitor the most critical location for parameters such as stress, deformation, and fracture gas.

[0039] S2. Assemble the hollow monitoring probe 1 according to the peak area of ​​the support pressure and the hole depth, so that it extends to the position of the peak area of ​​the support pressure. After assembling the hollow monitoring probe 1, the deep screen hole gas collection component 32 and the fiber optic grating monitoring component 2, insert them into two adjacent boreholes 5 and install and fix them. Use the air pump 4 to inflate the flexible airbag 14 and the pre-tightening airbag 28 through the corresponding airbag channel, so that the flexible airbag 14 and the arc-shaped wall-adhering pressure block 21 are in contact with the borehole wall of the borehole 5. Then, complete the orifice sealing through the orifice flange 11, bolts 12, sealing gasket 13 and sealing positioning sleeve 15. After the device is installed and sealed, check its sealing status.

[0040] S3. Connect the fiber optic demodulator 25 and the radon gas collection and filter assembly, perform zero-point calibration on them, and after standing for a period of time, collect the initial stress, initial hole wall deformation and initial radon gas concentration at the beginning of installation as reference values.

[0041] S4. During the activation of borehole 5, mining disturbance, and mining advance, the contact stress of the borehole wall, the deformation of the radial fiber grating 22, the deformation of the circumferential fiber grating 23, and the radon concentration in two adjacent boreholes 5 are collected simultaneously.

[0042] S5. Normalize the collected multi-parameter data and calculate the stress attenuation coefficient, borehole wall deformation coefficient, radon gas release coefficient, dual-hole consistency coefficient and borehole closure coefficient respectively to obtain the coupled evaluation index of pressure relief effect. The stress attenuation coefficient is determined by the degree of reduction in the contact stress of the hole wall relative to the initial contact stress, and its calculation formula is as follows: In the formula: σ i0-The average initial contact stress of the hole wall in the i-th borehole; σ it - The average contact stress of the borehole wall at time 5t for the i-th borehole; The hole wall deformation coefficient is determined by the radial convergence, circumferential strain, and the degree of ellipticization of the hole wall relative to the effective deformation threshold. Its calculation formula is as follows: In the formula: μ it - Average radial convergence at time 5t for the i-th borehole; μ i0 - Average initial radial convergence of the i-th borehole; ν it -Average circumferential strain at time 5t for the i-th borehole; ν i0 -The average value of the initial circumferential strain of the i-th borehole; ω it - The average degree of ellipticity of the borehole wall at time 5t for the i-th borehole, where D i(x)t D i(y)t These are the equivalent apertures in the horizontal and vertical directions, D. i0 This is the initial aperture; μ th - The effective radial deformation threshold refers to the baseline value when the radial convergence of the borehole wall reaches the effective pressure relief deformation response. It is determined based on the average borehole diameter reduction of five historical borehole inspection results under the same conditions. D j0 Let D be the initial borehole diameter of the j-th historical borehole 5. j,e The effective pressure relief equivalent aperture determined by inspection of borehole 5 in the j-th historical borehole 5; ν th - The effective circumferential strain threshold, which refers to the baseline value at which the circumferential strain of the borehole wall reaches an effective deformation response, is calculated using the following formula: D i0 This is the initial aperture; ω th - Ellipticization threshold, refers to the baseline value at which the borehole wall deforms from an approximately circular shape to a distinct ellipse. It is determined based on the average degree of ellipticization of five historical borehole inspection results under five similar conditions. D j(x),e D j(y),e These are the effective pressure relief level and the equivalent vertical borehole diameter determined by inspection of borehole 5 in the j-th historical borehole.

[0043] The radon release coefficient is determined by the increase in radon release concentration in the deep fracture gas of borehole 5 relative to the initial concentration, and its calculation formula is as follows: In the formula: C it - Radon concentration at time 5t in the i-th borehole; C i0 - Radon concentration at the initial stage of installation in the i-th borehole; The consistency coefficient of the two boreholes is determined by the similarity of the trends in stress, deformation, and radon release between two adjacent boreholes 5. The calculation formula is as follows: The borehole closure coefficient refers to the degree to which borehole wall convergence reduces the effective pressure relief space of borehole 5. A larger coefficient indicates a higher degree of closure of borehole 5. The calculation formula is as follows: In the formula: D i0 - Initial diameter of the i-th borehole; The formula for calculating the pressure relief effect coupled evaluation index E is: In the formula: K σ - The average stress attenuation coefficient of two adjacent boreholes 5; K ε - The average value of the borehole wall deformation coefficient of two adjacent boreholes 5; K Rn - The average radon release coefficient of two adjacent boreholes 5; K α -Dual-hole consistency coefficient; K β - The average borehole closure coefficient of two adjacent boreholes 5; K σ , K ε , K Rn , K α , K β All values ​​have been normalized and range from 0 to 1. a, b, c, d, e - Weighting coefficients, all ≥ 0 and a+b+c+d+e=1. The weighting coefficients are determined based on field calibration tests, historical pressure relief effect evaluation data, expert experience, mine anti-scour requirements, and evaluation objectives. The preferred values ​​are a=0.30, as stress attenuation is the core of the pressure relief effect and has the highest weight; b=0.20, c=0.20, deformation response and radon release reflect structural response and fracture gas response respectively, each with a certain weight; d=0.10, dual-hole consistency is used to correct local anomalies and has a lower weight; e=0.20, closure of borehole 5 will lead to failure of the pressure relief space.

[0044] S6, such as Figure 8 As shown, based on the coupled evaluation index of pressure relief effect, the pressure relief effect of borehole 5 is judged, and the parameters of borehole 5 and the timing of re-drilling are optimized accordingly. Specifically, K β When the borehole temperature is ≥ the on-site experience threshold, it is determined that borehole 5 has a risk of closure or is approaching failure, requiring borehole cleaning, repair, adjustment of borehole 5 parameters, and reinforcement of support; when K β If the pressure relief effect is below the field experience threshold, and E ≥ 0.80, the pressure relief effect is considered excellent; if 0.50 ≤ E < 0.80, the pressure relief effect is considered effective; if 0.20 ≤ E < 0.50, the pressure relief effect is considered average, and it is suggested that monitoring should be strengthened; if E < 0.20, the pressure relief effect is considered to be at risk, borehole 5 is approaching failure, and support should be strengthened and the pressure relief plan should be reviewed in time.

[0045] The above description of the disclosed embodiments enables those skilled in the art to make and use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit and scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-parameter coupled evaluation device for the pressure relief effect of large-diameter coal and rock boreholes, characterized in that, The system includes a hollow monitoring probe (1), a radon gas collection and monitoring component (3), and a fiber optic grating monitoring component (2). The hollow monitoring probe (1) is arranged along the axial direction of the borehole (5) and is fixedly connected to the borehole sealing structure. A flexible airbag (14) is fitted on the outer wall of the hollow monitoring probe (1) near the borehole opening. The flexible airbag (14) is connected to an external air pump (4). The radon gas collection and monitoring component (3) includes a radon gas collection channel (31) and a radon meter (33). The radon gas collection channel (31) is arranged on the hollow monitoring probe. Inside the rod (1), one end is inserted into the borehole (5) to collect radon gas, and the other end is connected to the radon detector (33) outside the borehole (5); the fiber optic grating monitoring component (2) includes a monitoring unit and a fiber optic demodulator (25). The monitoring unit includes a deformation monitoring unit and a stress monitoring unit. The deformation monitoring unit and the stress monitoring unit are both set on the outer wall of the hollow monitoring probe (1) and connected to the fiber optic demodulator (25) outside the borehole through an optical fiber (24) to obtain the radial deformation, circumferential deformation and stress change data of the borehole wall at the corresponding position of the borehole (5).

2. The multi-parameter coupled evaluation device for the pressure relief effect of large-diameter coal and rock boreholes according to claim 1, characterized in that, The hollow monitoring probe (1) is fixedly connected to a flange (11) at one end near the orifice. The orifice sealing structure is a T-shaped sealing positioning sleeve (15), which is fitted onto the orifice end of the hollow monitoring probe (1). The flange (11) and the sealing positioning sleeve (15) are fixedly connected by bolts (12). A sealing gasket (13) is also provided between the flange (11) and the sealing positioning sleeve (15).

3. The multi-parameter coupled evaluation device for pressure relief effect of large-diameter coal and rock boreholes according to claim 1, characterized in that, The radon gas collection channel (31) is formed by the hollow cavity of the hollow monitoring probe (1); the radon gas collection and monitoring component (3) also includes a deep sieve gas collection component (32), a desiccant (34) and a filter (35). The deep sieve gas collection component (32) includes a sieve tube (322) and a conical end cap (324). One end of the sieve tube (322) is fixedly connected to the end of the hollow monitoring probe (1) that is inserted into the borehole (5), and the other end is fixedly connected to the conical end cap (324). The outer wall of the sieve tube (322) is covered with a dustproof filter (321), and the inner wall is covered with a waterproof and breathable membrane (323). The conical end cap (324) is provided with a guide hole (325) at the end away from the sieve tube (322). The desiccant (34) and the filter (35) are sequentially installed on the air inlet pipe between the radon meter (33) and the radon gas collection channel (31).

4. The multi-parameter coupled evaluation device for pressure relief effect of large-diameter coal and rock boreholes according to claim 1, characterized in that, The hollow monitoring probe (1) is composed of multiple sections of rods, with threaded connections between adjacent sections and a sealing structure at the connection.

5. The multi-parameter coupled evaluation device for pressure relief effect of large-diameter coal and rock boreholes according to claim 1, characterized in that, The monitoring unit is provided in one or more sets along the axial direction of the hollow monitoring probe (1); the stress monitoring unit includes an arc-shaped wall-attaching pressure block (21), an elastic force transmission component (27), a pre-tightening airbag (28), and a stress fiber optic grating (26). The arc-shaped wall-attaching pressure block (21) is located on the outside of the hollow monitoring probe (1), and its outer arc surface is adapted to the shape of the borehole wall (5). A support component (29) is provided on the side of the arc-shaped wall-attaching pressure block (21) close to the hollow monitoring probe (1). The elastic force transmission component (27) is located between the support component (29) and the hollow monitoring probe (1). The stress fiber optic grating (26) is attached to the elastic force transmission component (27) and is used to sense the elastic strain caused by the contact stress of the borehole wall. The pre-tightening airbag (28) is located between the arc-shaped wall-attaching pressure block (21) and the hollow monitoring probe (1). The pre-tightening airbag (28) is connected to the external air pump (4); the deformation monitoring unit includes a circumferential fiber grating (23) and a radial fiber grating (22). The circumferential fiber grating (23) is fixedly installed on the outer wall of the arc-shaped wall-fitting block (21) along the circumference of the hollow monitoring probe (1); the radial fiber grating (22) is encapsulated on an elastic measuring plate. The elastic measuring plate is arranged radially along the hollow monitoring probe (1), with one end fixedly connected to the arc-shaped wall-fitting block (21) and the other end fixedly connected to the outer wall of the hollow monitoring probe (1); the stress fiber grating (26), the radial fiber grating (22) and the circumferential fiber grating (23) are all connected to the fiber demodulator (25) through optical fibers (24). The outer wall of the hollow monitoring probe (1) has an axial fiber protection groove, and the optical fiber (24) is arranged in the fiber protection groove.

6. The multi-parameter coupled evaluation device for pressure relief effect of large-diameter coal and rock boreholes according to claim 5, characterized in that, The stress monitoring unit also includes a guide limiting connector (210), which includes a fixed seat and a guide column. The fixed seat is a hollow structure and is fixedly installed on the outer wall of the hollow monitoring probe (1). The shape of the guide column matches the hollow part of the fixed seat. One end of the guide column extends into the hollow part of the fixed seat and is fixedly connected to the fixed seat through a spring at the end. The other end is fixedly installed on the inner wall of the arc-shaped wall-adhering pressure block (21).

7. The multi-parameter coupled evaluation device for pressure relief effect of large-diameter coal and rock boreholes according to claim 6, characterized in that, Each monitoring unit consists of three stress monitoring units and three deformation monitoring units evenly distributed along the circumference of the hollow monitoring probe (1).

8. A method for evaluating the pressure relief effect using the multi-parameter coupled evaluation device for large-diameter coal and rock borehole pressure relief effect according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Determine the location, diameter, depth and spacing of two adjacent boreholes (5) in the test section to be evaluated, and determine the location of the peak area of ​​the support pressure measured on site. S2. After assembling the hollow monitoring probe (1), the deep screen hole gas collection component (32) and the fiber optic grating monitoring component (2), send them into two adjacent boreholes (5) and install and fix them. Use the air pump (4) to inflate the flexible airbag (14) and the pre-tightening airbag (28) through the corresponding airbag channel so that the flexible airbag (14) and the arc-shaped wall-adhering pressure block (21) fit against the borehole wall (5). S3. Connect the fiber optic demodulator (25) and the radon gas collection and filter assembly, perform zero-point calibration on them, and collect the initial stress, initial hole wall deformation and initial radon gas concentration at the beginning of installation as reference values. S4. During the period of borehole (5) activation, mining disturbance and mining advance, the contact stress of the borehole wall, the deformation of the radial fiber grating (22), the deformation of the circumferential fiber grating (23) and the radon concentration in two adjacent boreholes (5) are collected simultaneously. S5. Normalize the collected multi-parameter data and calculate the stress attenuation coefficient, borehole wall deformation coefficient, radon gas release coefficient, dual-hole consistency coefficient and borehole closure coefficient respectively to obtain the coupled evaluation index of pressure relief effect. S6. Based on the pressure relief effect coupled evaluation index, judge the pressure relief effect of borehole (5) and optimize the parameters of borehole (5) accordingly.

9. The method according to claim 8, characterized in that, In S5, the stress attenuation coefficient is determined by the degree of reduction in the contact stress of the hole wall relative to the initial contact stress, and its calculation formula is as follows: In the formula: σ i0 - Average initial borehole wall contact stress of the i-th borehole (5); σ it - The average contact stress of the borehole wall at time t for the i-th borehole (5); The hole wall deformation coefficient is determined by the radial convergence, circumferential strain, and the degree of ellipticization of the hole wall relative to the effective deformation threshold. Its calculation formula is as follows: In the formula: μ it - Average radial convergence at time t for the i-th borehole (5); μ i0 - Average value of the initial radial convergence of the i-th borehole (5); ν it -The average circumferential strain at time t of the i-th borehole (5); ν i0 -The average initial circumferential strain of the i-th borehole (5); ω it - The average value of the ellipticity of the borehole wall at time t for the i-th borehole (5), where D i(x)t D i(y)t These are the equivalent apertures in the horizontal and vertical directions, respectively, D. i0 This is the initial aperture. μ th -Effective radial deformation threshold; ν th -Effective circumferential strain threshold; ω th - Ellipticization threshold; The radon release coefficient is determined by the degree of increase in radon release concentration in the deep fracture gas of borehole (5) relative to the initial concentration, and its calculation formula is as follows: In the formula: C it - Radon concentration at time t in the i-th borehole (5); C i0 - Radon concentration at the initial stage of installation of the i-th borehole (5); The dual-hole consistency coefficient is determined by the similarity of the trends in stress, deformation, and radon release between two adjacent boreholes (5), and its calculation formula is as follows: The borehole closure coefficient refers to the degree to which the effective pressure relief space of the borehole (5) is reduced due to borehole wall convergence. The larger the coefficient, the higher the degree of borehole (5) closure. The calculation formula is as follows: In the formula: D i0 - Initial diameter of the i-th borehole (5); The formula for calculating the pressure relief effect coupled evaluation index E is: In the formula: K σ - The average stress attenuation coefficient of two adjacent boreholes (5); K ε - The average value of the hole wall deformation coefficient of two adjacent boreholes (5); K Rn - The average radon release coefficient of two adjacent boreholes (5); K α -Dual-hole consistency coefficient; K β - The average borehole closure coefficient of two adjacent boreholes (5); a, b, c, d, e - Weighting coefficients, all ≥ 0 and a+b+c+d+e =1; K σ , K ε , K Rn , K α , K β All values ​​have been normalized and range from 0 to 1.

10. The method according to claim 8, characterized in that, In S6, the pressure relief effect of borehole (5) is judged based on the coupling evaluation index E of the pressure relief effect: K β When the value is ≥ the field experience threshold, it is determined that the borehole (5) has a risk of closure or is approaching failure, and it is necessary to clean the hole, fill the hole, adjust the borehole (5) parameters, and strengthen the support; when K β If the pressure relief effect is below the threshold of field experience, if E≥0.80, the pressure relief effect is considered excellent; if 0.50≤E<0.80, the pressure relief effect is considered effective; if 0.20≤E<0.50, the pressure relief effect is considered average, and it is suggested that monitoring should be strengthened; if E<0.20, the pressure relief effect is considered to be at risk, the borehole (5) tends to fail, and support should be strengthened and the pressure relief plan should be reviewed in time.

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