Coal seam drilling deformation endoscopic monitor and rock burst early warning critical value determination method

Abstract

The invention provides a coal seam borehole deformation endoscopic monitor and a rock burst early warning critical value determination method, and relates to the technical field of mine safety monitoring, the coal seam borehole deformation endoscopic monitor comprises a borehole endoscopic monitoring probe, a cable and a host; according to the rock burst early warning method based on the borehole aperture variation, a mathematical model between borehole aperture convergence parameters and rock burst risk assessment is determined, and effective prediction and timely early warning of potential risks of rock burst are achieved. The device can meet the requirement of high-precision and real-time monitoring of coal seam drilling convergence deformation with different strengths.

Description

Technical Field

[0001] The present invention relates to the technical field of mine safety monitoring, and particularly to a coal seam borehole deformation endoscope monitoring instrument and a method for determining the critical value of rock burst warning. Background Art

[0002] Coal mine rock burst refers to the phenomenon that coal and rock masses suddenly become unstable and break under high stress conditions, releasing a large amount of impact energy. This problem has been recognized as a world-class problem by the international mining community and the rock mechanics community. With the continuous deepening of coal mining in China, the frequency and intensity of rock bursts are increasing day by day, posing a severe challenge to mine safety. Precise monitoring and early warning of the danger of rock bursts are important bases for the scientific prevention and control of rock bursts.

[0003] At present, generally, a coal body borehole stress sensor (stress gauge) is used to directly monitor the magnitude of the coal body stress. As the most commonly used monitoring and early warning technology for predicting the occurrence of rock bursts, this method mainly focuses on the stress level of the coal body. This technology has problems with the coupling between the stress gauge and the coal and rock masses, resulting in errors in the monitoring results of the stress gauge, and the mutual feedback response change of the stress gauge to hard coal is not obvious. Therefore, directly monitoring the change amount of the coal seam borehole diameter and the crack conditions of the coal and rock on the inner wall of the borehole can provide more accurate information for the prediction of rock bursts. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a coal seam borehole deformation endoscope monitoring instrument and a method for determining the critical value of rock burst warning; the present invention designs a coal seam borehole deformation endoscope monitoring instrument, which can meet the requirements of high-precision and real-time monitoring of the convergence deformation amount of coal seam boreholes with different strengths, and can capture the crack conditions of the borehole wall and the convergence change amount of the borehole diameter in real time, so as to reflect the change of the force source of the surrounding rock of the roadway during the rock burst gestation period, so as to achieve the purpose of warning the danger of rock bursts. The present invention further proposes a rock burst warning method based on the change amount of the borehole diameter, establishes a mathematical model between the borehole diameter convergence parameter and the rock burst risk assessment, combines image observation and data processing technologies, and analyzes the borehole convergence deformation amount in real time, provides a more accurate prediction for the rock burst danger, and realizes the effective prediction and timely warning of the potential danger of rock bursts.

[0005] A coal seam borehole deformation endoscope monitoring instrument includes a borehole endoscope monitoring probe, a cable and a mainframe;

[0006] The borehole endoscope monitoring probe includes a fuselage, an ultrasonic sensor, a rotating device, a panoramic camera, a lighting system, a control center, a safety shell, a top structure and a collision protection system, an interface adapter, and a centering device;

[0007] The fuselage is a cylindrical hollow structure with the control center placed inside. At one end of the fuselage, the ultrasonic sensor, panoramic camera, and lighting system are provided. At the other end of the fuselage, the interface adapter is provided, and the interface adapter is connected to the host through a cable.

[0008] The centering device is provided outside the fuselage. On the side of the fuselage equipped with the ultrasonic sensor, the ultrasonic sensor is fixedly arranged through a rotating device, and the safety shell covers the ultrasonic sensor and the panoramic camera. The safety shell is made of a sound-transmitting material.

[0009] An annular lighting system is arranged around the panoramic camera, and a reinforced top structure and a collision protection system are provided at the top of the panoramic camera.

[0010] The control center integrates an ultrasonic signal processing device, receives the acquisition signals of the ultrasonic sensor, and preprocesses the acquisition signals through the built-in ultrasonic signal processor to eliminate the signal interference invading the coal body interior. The processed signals are transmitted to the host through the interface adapter, and the host will present the borehole deformation amount. In addition, the control center is also used to transmit the borehole wall images recorded by the panoramic camera to the host through the interface adapter for real-time monitoring to observe the crack conditions of the borehole wall.

[0011] The fuselage is of an integrated design, and its material is stainless steel. The interface adapter is located at a position far from the ultrasonic sensor.

[0012] The centering device adopts telescopic rods with position sensors thereon. Two mutually perpendicular diameters are selected at the center of the cross-section of the fuselage, and there is a telescopic device at each end of the two diameters, a total of four, which constitute the centering device with sensors thereon to detect the telescopic length of the telescopic rods and make their telescopic lengths consistent, so that the ultrasonic borehole endoscopy monitoring probe is centered inside the borehole.

[0013] The ultrasonic sensor is a transceiver integrated ultrasonic sensor. The ultrasonic sensor rotates 360° through a rotating device to obtain the real-time change of the borehole radius.

[0014] The lighting system is annularly distributed around the panoramic camera.

[0015] The cable has scales to locate the position of the borehole endoscopy monitoring probe in the borehole.

[0016] The host is used to present the internal images of the borehole recorded by the panoramic camera, display the parameters and information transmitted back by the ultrasonic sensor, and store and record the data. Specifically, it includes a display screen and buttons. The buttons include: image area adjustment button, observation screen size adjustment button, centering device on / off button, power on / off button, and connector.

[0017] The image area adjustment button is used to adjust the observed image area, the observed picture size adjustment button is used to adjust the size of the observed picture, the centering device on / off button is used to turn on and off the centering device, the power button is used to switch on and off the drilling endoscope monitoring probe, and the connector is used to connect the cable, the host and the drilling endoscope monitoring probe;

[0018] On the other hand, the present invention also provides a method for determining the critical value of rock burst warning, which is realized by the aforementioned coal seam drilling deformation endoscope monitor, and includes the following steps:

[0019] Step S1: Turn on the host and the drilling deformation endoscope monitor, connect one end of the cable to the host and the other end to the drilling endoscope monitoring probe;

[0020] Step S2: Through the transmission device, put the drilling endoscope monitoring probe into the drilling hole. When reaching the position to be monitored, turn on the centering device, and the four telescopic rods on the fuselage start to open and continuously adjust their lengths until the telescopic lengths of the four telescopic rods are the same. At this time, the drilling endoscope monitoring probe is located at the central position of the drilling hole;

[0021] Step S3: The ultrasonic sensor rotates 360° and emits ultrasonic signals;

[0022] Step S4: The ultrasonic sensor receives the ultrasonic signals;

[0023] Step S5: The control center processes the ultrasonic signals;

[0024] Step S5.1: Use a filter to perform preprocessing on the ultrasonic signals;

[0025] Specifically:

[0026] The system function of the high-pass filter is where s is the complex frequency variable, and w p is the cut-off frequency of the high-pass filter. The system function of the low-pass filter is where w l is the cut-off frequency of the low-pass filter.

[0027] Step S5.2: Use signal segmentation technology to distinguish reflected signals and intrusion signals:

[0028] In the signal segmentation technology, the signal segmentation is based on a time criterion where d penetration is the distance of intrusion into the coal and rock mass, ν is the wave velocity, and when the time t > t tdhrehol it is an intrusion signal, otherwise it is a reflected signal.

[0029] Step S5.3: Perform short-time Fourier transform on the extracted reflected signals:

[0030] Where x(t) is the time-domain signal, ω(t - τ) is the window function, τ is the time delay, f is the frequency; t is the time

[0031] Step S5.4: Filter the signal processed in Step S5.3 through a band-pass filter:

[0032] Where f l is the low-frequency cut-off frequency filtered by the band-pass filter, f h is the low-frequency cut-off frequency filtered by the band-pass filter.

[0033] Step S5.5: Enhance the envelope of the signal by calculating the analytic representation of the signal;

[0034] Where P.V. is the Cauchy principal value

[0035] Step S5.6: Use the autocorrelation function to identify periodic components or repeating patterns in the signal;

[0036] Where R(τ) is the autocorrelation function, τ is the time delay;

[0037] Step S6: Calculate the distance d between the ultrasonic sensor and the hole wall through the time difference between ultrasonic emission and reception,

[0038] Where v is the ultrasonic wave speed; t is the time difference between ultrasonic emission and reception;

[0039] Step S7: When the signal is transmitted to the host, the internal situation of the drilled hole wall recorded by the panoramic camera appears on the host display screen. At this time, adjust the observation area through the image area adjustment button and the viewing screen size adjustment button. At the same time, the distance from the ultrasonic sensor to the drilled hole wall recorded by the ultrasonic wave will be displayed on the display, and observe the situation of the drilled hole wall;

[0040] Step S8: After observing a moment, repeat the above Steps S3 - S7, continue to observe and record the image of the drilled hole wall and the ultrasonic signal at another moment, and obtain d' at time t'. Then the deformation u = d' - d;

[0041] Step S9: After the operator completes the operation, turn off the ultrasonic sensor and the panoramic camera;

[0042] Step S10: Disconnect the cable from the interface adapter and the host, and then tidy up the cable.

[0043] Step S11: Press the on / off button of the centering device, retract the centering device, and take out the endoscopic detection probe from the drilled hole through the transfer device;

[0044] Step S12: Establish the relationship among the borehole deformation u, the radius ρ of the borehole plastic zone, and the borehole radius a where ε c is the strain value corresponding to the peak value of the uniaxial compressive stress of the coal body;

[0045] Step S13: Establish the stress field of a circular borehole under non-uniform pressure:

[0046]

[0047] where, σ r is the radial stress at any point, σ θ is the circumferential stress at any point, τ rθ is the shear stress at any point, r is the distance from any point around the borehole to the borehole center, the azimuth angle is θ, λ is the coefficient of lateral pressure, and p is the surrounding rock pressure

[0048] Step S14: When the distance r from any point around the borehole to the borehole center is r = ρ, the stress at the elastic-plastic interface satisfies the following relational expression:

[0049] σ θ +σ τ =(1 + λ)p + 2(1 - λ)pcosθ

[0050] Step S15: Establish the stress expression in the plastic zone:

[0051]

[0052]

[0053] τ rθ = 0

[0054] where, is the internal friction angle;

[0055] Step S16: Establish the relationship among the radius ρ of the borehole plastic zone, the external load p, the internal friction angle and the cohesion c m :

[0056] where λ is the coefficient of lateral pressure.

[0057] Step S17: Substitute the theoretical formula for rock burst occurrence where k is the impact energy index, into the formula in Step S16 to obtain the convergence deformation of the borehole surrounding rock, and then predict the risk of rock burst;

[0058]

[0059] where ε cis the impact energy index, and σ c is the uniaxial compressive strength of coal.

[0060] The beneficial effects of adopting the above technical solutions are as follows:

[0061] The present invention can achieve high-precision monitoring of the convergence deformation of boreholes in coal seams with different strengths, and simultaneously capture the fissure conditions of the borehole wall in real time. However, traditional coal seam borehole stress sensors (stress gauges) have monitoring errors due to coupling problems and are not obvious in the response to hard coal; the early warning accuracy is greatly improved. By establishing a mathematical model of the borehole diameter convergence parameter and the rock burst risk assessment, and combining image observation and data processing technologies, accurate prediction and real-time analysis of rock burst hazards are realized. Traditional methods mostly rely on a single monitoring index and are difficult to accurately reflect precursor information; in addition, the present invention has a wide range of applicability and can adapt to coal seams with different strengths and various monitoring conditions, solving the installation and monitoring problems of traditional sensors under complex conditions; finally, it has good real-time performance and can timely monitor and give early warning of rock burst hazards. Compared with the deficiencies of traditional methods in data real-time performance, it can better capture rock burst precursors, providing an important basis for the scientific prevention and control of coal mine rock bursts and effectively improving the safety of mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 is a schematic external structure diagram of a rock burst coal seam borehole deformation endoscope monitoring probe provided by an embodiment of the present invention;

[0063] Figure 2 is a sectional view of a rock burst coal seam borehole deformation endoscope monitoring probe provided by an embodiment of the present invention;

[0064] Figure 3 is a schematic structure diagram of a cable storage device of a rock burst coal seam borehole deformation endoscope monitoring instrument provided by an embodiment of the present invention;

[0065] Figure 4 is a schematic outer contour diagram of the main body of a rock burst coal seam borehole deformation endoscope monitoring instrument provided by an embodiment of the present invention;

[0066] Figure 5 is a schematic diagram after the connection of a rock burst coal seam borehole deformation endoscope monitoring probe, a cable and a main body provided by an embodiment of the present invention;

[0067] Figure 6 is a schematic diagram of the state of a rock burst coal seam borehole deformation endoscope monitoring probe centered by a centering device inside the borehole provided by an embodiment of the present invention;

[0068] Figure 7 is a force model diagram of a rock burst coal seam borehole provided by an embodiment of the present invention;

[0069] Figure 8 It is a flowchart for rock burst warning provided by an embodiment of the present invention;

[0070] Figure 9 It is a theoretical distribution diagram of the critical displacement of the convergence of the borehole surrounding rock provided by an embodiment of the present invention;

[0071] In the figure, 1 - fuselage, 2 - interface adapter, 3 - centralizer, 4 - control center, 5 - ultrasonic sensor, 6 - panoramic camera, 7 - rotating device, 8 - top structure and collision protection system, 9 - safety housing, 10 - display screen, 11 - key, 12 - connector; Specific embodiments

[0072] The following will further describe in detail the specific embodiments of the present invention in conjunction with the accompanying drawings and embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0073] A coal seam borehole deformation endoscope monitoring instrument includes a borehole endoscope monitoring probe, a cable and a host;

[0074] The borehole endoscope monitoring probe is as Figure 1 , Figure 2 shown, and includes a fuselage 1, an ultrasonic sensor 5, a rotating device 7, a panoramic camera 6, a lighting system, a control center 4, a safety housing 9, a top structure and a collision protection system 8, an interface adapter 2, and a centralizer 3;

[0075] The fuselage 1 is a cylindrical hollow structure, and the control center 4 is placed inside; one end of the fuselage 1 is provided with the ultrasonic sensor 5, the panoramic camera 6 and the lighting system, and the other end of the fuselage 1 is provided with the interface adapter 2. The interface adapter 2 is connected to the host through a cable; the ultrasonic signal and the picture recorded by the panoramic camera 6 are transmitted to the host and generate images and data, so as to judge the situation of the borehole wall and the change amount of the borehole diameter.

[0076] The centralizer 3 is arranged outside the fuselage 1, and the centralizer 3 is used to ensure the stable positioning of the borehole endoscope monitoring probe at the geometric center of the borehole to achieve uniform monitoring of the internal shape of the borehole. On one side of the fuselage 1 equipped with the ultrasonic sensor 5, the ultrasonic sensor 5 is fixedly arranged through the rotating device 7 to realize 360° rotation to comprehensively record the situation inside the borehole; the safety housing 9 covers the ultrasonic sensor 5 and the panoramic camera 6; the safety housing 9 is made of a sound-transmitting material, allowing the ultrasonic signal to penetrate without attenuation, so as to ensure that the efficiency and accuracy of ultrasonic transmission and reception are not affected.

[0077] A ring-shaped lighting system is arranged around the panoramic camera 6 to provide sufficient light, ensuring high-definition image acquisition inside the borehole. To enhance the durability of the device, especially in the case of collisions that may occur during borehole operations, a reinforced top structure and a collision protection system 8 are provided on the top of the panoramic camera 6. These devices are designed to protect the sensitive ultrasonic sensor 5 and the panoramic camera 6 from damage, ensuring stable operation of the device under harsh working conditions.

[0078] The control center 4 serves as the control center of the entire borehole endoscope monitoring probe, integrating an ultrasonic signal processing device. It receives the acquisition signals from the ultrasonic sensor 5 and preprocesses the acquisition signals through the built-in ultrasonic signal processor to eliminate signal interference from inside the coal body. The processed signals are transmitted to the host through the interface adapter 2 for further data analysis. The host will present accurate data on the borehole deformation, providing a scientific basis for the risk assessment of rock bursts. In addition, the control center 4 is also used to transmit the borehole wall images recorded by the panoramic camera 6 to the host through the interface adapter 2 for real-time monitoring to observe the fissure conditions of the borehole wall.

[0079] The fuselage 1 is of an integrated design, that is, it does not require multi-segment connection, which can improve the strength of the fuselage. Its material is stainless steel. There is an interface adapter 2 at a position away from the ultrasonic sensor 5.

[0080] The centering device 3 uses telescopic rods with position sensors. Two mutually perpendicular diameters are selected at the center of the cross-section of the fuselage 1. There is a telescopic device at each end of the two diameters, a total of four, which constitute the centering device 3. It is equipped with sensors to detect the telescopic length of the telescopic rods and make their telescopic lengths consistent, so that the ultrasonic borehole endoscope monitoring probe is centered inside the borehole.

[0081] The ultrasonic sensor 5 is a transceiver integrated ultrasonic sensor; the ultrasonic sensor 5 rotates 360° through the rotating device 7 to obtain the real-time change of the borehole radius.

[0082] Preferably, the panoramic camera preferably uses a high-resolution lens that can adapt to the dark environment, which can completely record the situation inside the borehole and transmit it to the host screen, enabling the operator to intuitively see the borehole wall conditions for more intuitive observation of the borehole wall conditions.

[0083] The lighting system is annularly distributed around the panoramic camera, providing a relatively good environment and brightness for the recording of the lens.

[0084] Preferably, the control center can be regarded as the processing unit of the borehole endoscopy monitoring probe, responsible for coordinating and executing the data acquisition, processing, and decision-making functions in the monitoring task. It is equipped with an ultrasonic signal processing device and various complex circuits to support the operation of the borehole endoscopy monitoring probe.

[0085] Preferably, the top structure and the collision protection system are designed to protect the borehole endoscopy monitoring probe from damage when it hits the bottom of the borehole, which may cause damage to the ultrasonic borehole endoscopy monitoring probe.

[0086] Preferably, the interface adapter 2 transmits the signals processed by the host to the host through a cable, enabling better monitoring of the situation in the borehole.

[0087] Preferably, the cable can also connect the circuits of the borehole endoscopy monitoring probe and the host, and conduct the control center signals of the borehole endoscopy monitoring probe to the host; the cable has scales to locate the position of the borehole endoscopy monitoring probe in the borehole.

[0088] The host is used to present the internal image of the borehole recorded by the panoramic camera, display the parameters and information transmitted back by the ultrasonic sensor, and store and record the data. Specifically, it includes a display screen 10 and buttons 11; among them, the buttons 11 include: an image area adjustment button, an observation screen size adjustment button, a centering device on / off button, a power on / off button, and a connector 12;

[0089] The image area adjustment button is used to adjust the observation image area, the observation screen size adjustment button is used to adjust the size of the observation screen, the centering device on / off button is used to turn on and off the centering device, the power on / off button is used to turn on and off the borehole endoscopy monitoring probe, and the connector is used to connect the cable, the host, and the borehole endoscopy monitoring probe;

[0090] On the other hand, the present invention also provides a method for determining the critical value of rock burst warning, which is realized based on the aforementioned coal seam borehole deformation endoscopy monitor, and includes the following steps:

[0091] Step S1: Turn on the host and the borehole deformation endoscopy monitoring probe to make them operate. Connect one end of the cable to the host and the other end to the borehole endoscopy monitoring probe, as Figure 5 shown;

[0092] Step S2: Through the transmission device, place the borehole endoscopy monitoring probe into the borehole. When it reaches the position to be monitored, turn on the centering device, and the four telescopic rods on the fuselage start to open and continuously adjust their lengths until the telescopic lengths of the four telescopic rods are the same. At this time, the borehole endoscopy monitoring probe is located at the central position of the borehole;

[0093] Step S3: The ultrasonic sensor rotates 360° and emits ultrasonic signals;

[0094] Step S4: The ultrasonic sensor receives ultrasonic signals;

[0095] Step S5: The control center processes the ultrasonic signals;

[0096] Step S5.1: Preprocess the ultrasonic signals using a filter: This is used to remove unwanted frequency components in the signals to reduce noise and interference.

[0097] Specifically:

[0098] The system function of the high-pass filter is where s is the complex frequency variable, and w p is the cut-off frequency of the high-pass filter. The system function of the low-pass filter is where w l is the cut-off frequency of the low-pass filter.

[0099] Step S5.2: Use signal segmentation technology to distinguish reflected signals and intrusion signals: This can improve the accuracy of signal analysis.

[0100] In the said signal segmentation technology, signal segmentation is based on a time criterion where d penetration is the distance of intrusion into the coal and rock mass, ν is the wave velocity. When the time t > t tdhrehol it is an intrusion signal, otherwise it is a reflected signal.

[0101] Step S5.3: Perform a short-time Fourier transform on the extracted reflected signals: This analysis technique can reveal the frequency components of the signals at different time points and provide important information for the time-frequency analysis of the signals.

[0102] where x(t) is the time-domain signal, ω(t - τ) is the window function, τ is the time delay, f is the frequency; t is the time

[0103] Step S5.4: Filter the signals processed in Step S5.3 through a band-pass filter: This strategy aims to eliminate non-target frequency components and only retain the signals related to the reflection on the coal and rock surface to enhance the effective information of the signals.

[0104] where f l is the low-frequency cut-off frequency filtered by the band-pass filter, and f h is the high-frequency cut-off frequency filtered by the band-pass filter.

[0105] Step S5.5: Enhance the envelope of the signals by calculating the analytic representation of the signals to highlight potential useful information.

[0106] where P.V. is the Cauchy principal value

[0107] Step S5.6: Use the autocorrelation function to identify the periodic components or repeating patterns in the signal for further analysis of the signal's structural characteristics.

[0108] where R(τ) is the autocorrelation function and τ is the time delay;

[0109] Step S6: Calculate the distance d between the ultrasonic sensor and the hole wall through the time difference between ultrasonic emission and reception,

[0110] where v is the ultrasonic wave velocity; t is the time difference between ultrasonic emission and reception;

[0111] Step S7: When the signal is transmitted to the host, the internal situation of the borehole wall recorded by the panoramic camera appears on the host display screen. At this time, adjust the observation area through the image area adjustment button and the viewing screen size adjustment button. The operator can hold it as needed. At the same time, the distance from the ultrasonic sensor to the borehole wall recorded by the ultrasonic wave will be displayed on the monitor, and the situation of the borehole wall will be observed;

[0112] Step S8: After observing a moment, repeat the above steps S3 - S7 to continue observing and recording the borehole wall image and ultrasonic signal at another moment. When d' at time t' is obtained, the deformation amount u = d' - d;

[0113] Step S9: After the operator completes the operation, turn off the ultrasonic sensor and the panoramic camera;

[0114] Step S10: Disconnect the cable from the interface adapter and the host, and then tidy up the cable, as Figure 3 shown.

[0115] Step S11: Press the centering device on / off button, retract the centering device, and take out the endoscopic detection probe from the borehole through the transfer device;

[0116] Step S12: Establish the relationship between the borehole deformation amount u, the radius ρ of the borehole plastic zone, and the borehole radius a where ε c is the strain value corresponding to the peak value of the uniaxial compressive stress of the coal body;

[0117] Step S13: Establish the stress field of a circular borehole under non-uniform pressure:

[0118]

[0119] where, σ r is the radial stress at any point, σθ is the circumferential stress at any point, τ rθ is the shear stress at any point, r is the distance from any point around the borehole to the center of the borehole, the azimuth angle is θ, λ is the coefficient of lateral pressure, and p is the surrounding rock pressure

[0120] Step S14: When the distance r from any point around the borehole to the center of the borehole is r = ρ, the stress at the elastoplastic interface satisfies the following relationship:

[0121] σ θ +σ τ =(1 + λ)p + 2(1 - λ)pcosθ

[0122] Step S15: Establish the stress expression in the plastic zone:

[0123]

[0124] τ rθ = 0

[0125] where is the angle of internal friction;

[0126] Step S16: Establish the relationship between the radius ρ of the borehole plastic zone, the external load p, the angle of internal friction and the cohesion c m :

[0127] where λ is the coefficient of lateral pressure.

[0128] Step S17: Substitute the theoretical formula for the occurrence of rock bursts where k is the impact energy index, into the formula in Step S16 to obtain the convergence deformation amount of the borehole surrounding rock, and then predict the risk of rock bursts;

[0129]

[0130] where ε c is the impact energy index, and σ c is the uniaxial compressive strength of the coal.

[0131] In actual operation, connect one end of the cable connector to the borehole endoscopic monitoring probe, and the other end to the main unit, as Figure 4 shown. Press the main unit switch to start powering on, and the borehole endoscopic monitoring probe will immediately enter the working state. Place the endoscopic monitoring probe into the borehole and press the centering device on button to make the borehole endoscopic monitoring probe roughly centered in the borehole, as Figure 6As shown. Then, press the on-switch of the borehole endoscopic monitoring probe. At this time, the ultrasonic sensor and the panoramic camera start to work, recording the situation inside the borehole. The collected data is transmitted to the host through the cable and the interface adapter for the operator to observe the situation inside the borehole and record the parameters of the borehole. In this embodiment, as Figure 7 As shown is the force model diagram of the borehole in the coal seam with rock burst provided by the embodiment of the present invention; as Figure 8 As shown is the flow chart of the rock burst early warning provided by the embodiment of the present invention; as Figure 9 As shown is the theoretical distribution diagram of the critical displacement of the convergence of the surrounding rock of the borehole provided by the embodiment of the present invention.

[0132] In this example, for a borehole with a diameter of 140 mm in a working face, the mechanical parameters of the surrounding coal and rock, including the uniaxial compressive strength σ c , the peak value of uniaxial compressive strain ε c , the cohesion c m , the internal friction angle The impact energy index k is as follows:

[0133]

[0134] Substitute into the formula to obtain the critical borehole convergence deformation amount when predicting the occurrence of rock burst;

[0135] u cr = 12.1[(0.24 + 6.13×10 -2 ×(2.5 - cos2θ)] 0.67 (mm)

[0136] Compare the actual measured value of the device with it to predict rock burst.

[0137] The above description is only the preferred embodiment of the present disclosure and the explanation of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above inventive concept. For example, the technical solutions formed by mutually replacing the above features with the (but not limited to) technical features with similar functions disclosed in the embodiments of the present disclosure.

Claims

1. A coal seam drilling deformation endoscopic monitoring instrument, characterized in that: Including borehole endoscopy monitoring probe, cables and host; The borehole endoscopy monitoring probe includes a fuselage, an ultrasonic sensor, a rotating device, a panoramic camera, a lighting system, a control center, a safety shell, a top structure and a collision protection system, an interface adapter, and a centering device; The fuselage is a cylindrical hollow structure, in which the control center is placed; the ultrasonic sensor, the panoramic camera and the lighting system are arranged at one end of the fuselage, and the interface adapter is arranged at the other end of the fuselage, and the interface adapter is connected to the host through a cable; The centering device is arranged outside the fuselage, on one side of the fuselage equipped with an ultrasonic sensor, the ultrasonic sensor is fixedly arranged by a rotating device, and the safety shell covers the ultrasonic sensor and the panoramic camera; the safety shell is made of sound-transmitting material; A ring lighting system is arranged around the panoramic camera, and a reinforced top structure and a collision protection system are arranged on the top of the panoramic camera; The control center integrates an ultrasonic signal processing device, receives the collected signals of the ultrasonic sensor, and pre-processes the collected signals through the built-in ultrasonic signal processor to eliminate the signal interference that invades the coal body; the processed signals are transmitted to the host through the interface adapter, and the host will present the borehole deformation. In addition, the control center is also used to transmit the borehole wall image recorded by the panoramic camera to the host through the interface adapter for real-time monitoring and observation of the borehole wall cracks; The fuselage is of integrated design and is made of stainless steel. An interface adapter is provided at a position far away from the ultrasonic sensor.

2. The coal seam drilling deformation endoscopic monitoring instrument according to claim 1 is characterized in that: The centerer adopts a telescopic rod with a position sensor on it. Two mutually perpendicular diameters are selected at the center of the circle of the cross section of the fuselage, and there is a telescopic device at each end of the two diameters, a total of four, which constitute the centerer. The centerer is equipped with a sensor to detect the telescopic length of the telescopic rod. When the telescopic length is consistent, the ultrasonic drilling endoscopic monitoring probe is centered inside the borehole.

3. The coal seam drilling deformation endoscopic monitoring instrument according to claim 1 is characterized in that: The ultrasonic sensor is a transceiver integrated ultrasonic sensor; the ultrasonic sensor is rotated 360 degrees by a rotating device to obtain real-time changes in the drilling radius.

4. The coal seam drilling deformation endoscopic monitoring instrument according to claim 1 is characterized in that: The lighting system is distributed in a ring around the panoramic camera.

5. The coal seam drilling deformation endoscopic monitoring instrument according to claim 1 is characterized in that: The cable is provided with a scale for locating the position of the borehole endoscopy monitoring probe in the borehole.

6. The coal seam drilling deformation endoscopic monitoring instrument according to claim 1, characterized in that: The host is used to present the internal image of the borehole recorded by the panoramic camera, display the parameters and information sent back by the ultrasonic sensor, and store and record the data, and specifically includes a display screen and buttons; wherein the buttons include: an image area adjustment button, an observation screen size adjustment button, a centerer on and off button, a switch key, and a connector.

7. The coal seam drilling deformation endoscopic monitoring instrument according to claim 6 is characterized in that: The image area adjustment button is used to adjust the observation image area, the observation screen size adjustment button is used to adjust the observation screen size, the centralizer on and off button is used to turn the centralizer on and off, the switch key is used to turn on and off the drilling endoscopy monitoring probe, and the connector is used to connect the cable, the host and the drilling endoscopy monitoring probe.

8. A method for determining a critical value of rock burst warning, based on the coal seam drilling deformation endoscopic monitoring device according to claim 1, characterized in that: The following steps are involved: Step S1: Turn on the host and the borehole deformation endoscopic monitoring probe, connect one end of the cable to the host, and connect the other end to the borehole endoscopic monitoring probe; Step S2: The borehole endoscope monitoring probe is placed into the borehole through a conveying device. When the probe reaches the position to be monitored, the centering device is opened, and the four telescopic rods on the body begin to open and continuously adjust their lengths until the four telescopic rods have the same telescopic length. At this time, the borehole endoscope monitoring probe is located in the center of the borehole. Step S3: The ultrasonic sensor rotates 360° and emits an ultrasonic signal; Step S4: The ultrasonic sensor receives the ultrasonic signal; Step S5: The control center processes the ultrasonic signal; Step S6: Calculate the distance d between the ultrasonic sensor and the hole wall by the time difference between ultrasonic emission and reception. Where v is the ultrasonic wave velocity; t is the time difference between ultrasonic emission and reception; Step S7: When the signal is transmitted to the host, the internal situation of the borehole wall recorded by the panoramic camera appears on the host display screen. At this time, the observation area is adjusted by the image area adjustment button and the observation screen size adjustment button. At the same time, the display will show the distance from the ultrasonic sensor to the borehole wall recorded by the ultrasonic wave, and the situation of the borehole wall is observed; Step S8: After observing a moment, repeat the above steps S3-S7 to continue observing and recording the borehole wall image and ultrasonic signal at another moment to obtain the time t, d , , then the deformation u=d , -d; Step S9: After the operator completes the operation, the ultrasonic sensor and the panoramic camera are turned off; Step S10: disconnect the cable from the interface adapter and the host, and then tidy up the cable; Step S11: Press the centering device on / off button to retract the centering device, and take the endoscope detection probe out of the borehole through the conveying device; Step S12: Construct the relationship between the drilling deformation u, the drilling plastic zone radius ρ and the drilling radius a where ε c is the strain value corresponding to the peak value of uniaxial compression stress of coal body; Step S13: Establish the stress field of the circular borehole under non-isostatic pressure: Among them, σ r is the radial stress at any point, σ θ is the hoop stress at any point, τ rθ is the shear stress at any point, r is the distance from any point around the borehole to the center of the borehole, the azimuth is θ, λ is the lateral pressure coefficient, and p is the surrounding rock pressure Step S14: When the distance r from any point around the borehole to the center of the borehole is r=ρ, the stress at the elastic-plastic interface satisfies the following relationship: s θ +s τ =(1+λ)p+2(1-λ)pcosθ Step S15: Establish the plastic zone stress expression: t rθ =0 in, is the internal friction angle; Step S16: Establish the borehole plastic zone radius ρ, external load p, and internal friction angle and cohesion c m The relationship between: Where λ is the lateral pressure coefficient; Step S17: Theoretical formula for rock burst Where k is the impact energy index, which is substituted into the formula of step S16 to obtain the convergence deformation of the surrounding rock of the borehole, and then predict the danger of rock burst; where ε c is the impact energy index, σ c is the uniaxial compressive strength of coal.

9. The method for determining a critical value of rock burst warning according to claim 8, characterized in that: The step S5 specifically comprises the following steps: Step S5.1: pre-processing the ultrasonic signal using a filter; Specifically: The system function of the high-pass filter is Where s is a complex frequency variable, w p is the cutoff frequency of the high-pass filter; the system function of the low-pass filter is where w l is the cut-off frequency of the low-pass filter; Step S5.2: Use signal segmentation technology to distinguish between reflected signals and intrusion signals: In the signal segmentation technology, signal segmentation is based on the time standard where d penetration is the distance of invasion into the coal rock mass, ν is the wave velocity, when time t>t tdhrehol When , it is an intrusion signal, otherwise it is a reflection signal; Step S5.3: Perform short-time Fourier transform on the extracted reflection signal: Where x(t) is the time domain signal, ω(t-τ) is the window function, τ is the time delay, f is the frequency; t is the time Step S5.4: Filter the signal processed in step S5.3 by a bandpass filter: where f l is the low frequency cutoff frequency of the bandpass filter, f h The low frequency cutoff frequency filtered by the bandpass filter; Step S5.5: enhancing the envelope of the signal by calculating an analytical representation of the signal; Where PV is the Cauchy principal value Step S5.6: using the autocorrelation function to identify periodic components or repetitive patterns in the signal; where R(τ) is the autocorrelation function and τ is the time delay.

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