Rock burst and sound monitoring system based on optical fiber vibration sensing and construction method of rock burst and sound monitoring system

Abstract

The invention discloses a rock burst rock noise monitoring system based on optical fiber vibration sensing and a construction method thereof, and the monitoring system comprises a plurality of optical fiber sensors which are arranged in a coal body of a stope face at intervals along the trend direction of a roadway, the multi-frequency acoustic wave sensor is configured to collect multi-frequency acoustic wave signals generated by coal rock fracture and convert the multi-frequency acoustic wave signals into optical signals; the underground optical fiber signal base station is coupled with the plurality of optical fiber sensors and is configured to be used for receiving the optical signals; the distributed optical fiber signal demodulator is coupled with the underground optical fiber signal base station and is configured to be used for converting the optical signal into a voltage signal; and the ground monitoring center is coupled with the distributed optical fiber signal demodulator and is configured to be used for receiving the voltage signal and analyzing and processing the voltage signal.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mining, and in particular to an impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing and a construction method thereof. Background Art

[0002] With the continuous increase in coal mining depth and mining intensity, the stress environment of deep coal rock has changed, the mine pressure has intensified, and the danger, scale and intensity of rock burst disasters have increased, posing a major threat to the safe and efficient mining of deep coal resources and seriously affecting the normal production of coal resources and the sustainable development of the coal industry.

[0003] "How to achieve intelligent, safe and efficient mining of coal seams with rock burst?" has always been a very important industrial technology issue. Rock burst is the result of the spatiotemporal evolution of multi-scale fissures from deformation and rupture of surrounding rocks to instability disasters under the coupling of high ground stress, engineering activities and external dynamic loads. In the process of disaster preparation and disaster-causing, there must be the initiation, development and expansion of fissures, which will generate acoustic signals of different frequency bands at different stages of the disaster. Microseismic, geoacoustic and acoustic emission systems monitor acoustic signals of different frequency bands in a targeted manner, which can effectively characterize the dynamic evolution process of rock burst and are an effective geophysical means to achieve reliable early warning of rock burst.

[0004] Traditional microseismic, ground sound and acoustic emission systems need to be arranged independently due to the limitation of sensor frequency monitoring range, and the cost of vibration and acoustic wave monitoring in different frequency bands is relatively high. At the same time, traditional multi-frequency acoustic wave monitoring equipment has many shortcomings, such as explosion risk, short electrical signal transmission distance, large background noise, and susceptibility to electromagnetic interference. Technically, it is impossible to meet the application requirements of high sensitivity and wide-band response of multi-frequency acoustic wave monitoring in coal mines. In order to ensure the safe production of coal mines and efficient early warning of rock burst disasters, it is urgent to introduce advanced optical fiber technology, tackle and develop a new multi-frequency acoustic wave monitoring system for monitoring rock burst hazards, and further strengthen the source control of rock burst.

[0005] Based on the above analysis, it can be found that there is currently a lack of multi-frequency acoustic wave monitoring systems for coal mine rock burst pressure based on optical fiber sensing technology, and the existing technology in coal mines cannot meet the actual needs of full-band waveform monitoring of rock burst pressure. In order to solve the above problems, the present invention innovatively constructs a multi-frequency acoustic wave monitoring system for rock burst pressure based on distributed optical fiber sensing based on optical fiber sensing technology. Summary of the invention

[0006] In response to the problems and needs raised above, this solution proposes an impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing. Due to the adoption of the following technical features, it can achieve the above technical objectives and bring about many other technical effects.

[0007] An object of the present invention is to provide an impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing, comprising:

[0008] A plurality of optical fiber sensors are arranged at intervals in the mining face along the direction of the roadway, and are configured to collect multi-frequency acoustic wave signals generated by coal and rock fractures and convert the multi-frequency acoustic wave signals into optical signals;

[0009] A downhole optical fiber signal base station, coupled to the plurality of optical fiber sensors, configured to receive the optical signal;

[0010] A distributed optical fiber signal demodulator, coupled to the downhole optical fiber signal base station, configured to convert the optical signal into a voltage signal;

[0011] The well monitoring center is coupled to the distributed optical fiber signal demodulator and is configured to receive the voltage signal and analyze and process the voltage signal.

[0012] In this technical solution, the vibration waves generated by the sound wave signals of different frequencies in the coal rock mass are transmitted to the optical fiber sensor with coal rock as the medium. The sensitive optical fiber in the optical fiber sensor is affected by the vibration wave, and the optical phase changes, converting the vibration wave signal into an optical signal. The optical signal is then transmitted through the downhole transmission optical cable via the optical fiber signal base station to the distributed optical fiber signal demodulator on the well. The optical information is converted into a voltage signal by the distributed optical fiber signal demodulator, and the voltage signal output is then analyzed by the well monitoring center.

[0013] The monitoring system uses optical fiber as the signal transmission medium. The underground operation part does not need power supply, and the signal monitoring will not be interrupted due to power failure, which ensures the continuous monitoring of the acoustic signal during the mining process of the working face. At the same time, the monitoring system based on optical fiber sensing also has the technical advantages of strong anti-interference ability, high sensitivity, wide monitoring range and intrinsic safety of the system.

[0014] The rock burst acoustic wave monitoring system based on the Michelson fiber optic interferometry principle can monitor multi-band acoustic wave signals, provide more comprehensive acoustic wave data for rock burst monitoring and early warning, and improve the accuracy of the monitoring system.

[0015] Compared with the traditional rock burst mine monitoring system which requires the installation of microseismic monitoring system and ground sound monitoring system, the rock burst multi-band acoustic wave monitoring system proposed by this monitoring system combines the collection of acoustic wave signals by microseismic and ground sound systems, thus reducing the cost of rock burst monitoring in mines.

[0016] The monitoring system buries the fiber optic sensor in a 5-10m borehole, which can effectively reduce environmental noise interference and enhance the coupling between the sensor and the inner wall of the coal rock, ensuring the effectiveness of multi-frequency acoustic wave signal monitoring.

[0017] In addition, the impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing according to the present invention may also have the following technical features:

[0018] In one example of the present invention, a plurality of boreholes are provided in the working face inclination direction of the coal body of the mining working face and are spaced apart in the direction of the tunnel to form a borehole group, and an optical fiber sensor is correspondingly arranged in each of the boreholes, wherein cement slurry is injected into the borehole to achieve coupling and fixation between the optical fiber sensor and the borehole wall.

[0019] In one example of the present invention, the drilling groups include two, and are respectively arranged on both sides of the coal body of the mining face in the inclination direction of the working face, wherein the drill holes in each drilling group correspond one to one in the inclination direction of the working face.

[0020] In one example of the present invention, the cement slurry is expansive cement.

[0021] In one example of the present invention, the depth of the borehole is 5m-10m, and the distance L between two adjacent boreholes in the direction of the tunnel does not exceed 50m.

[0022] Another object of the present invention is to provide a construction method of an impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing, comprising the following steps:

[0023] S10: According to the size of the optical fiber sensor, a suitable diameter of the construction drill bit is selected, and a plurality of boreholes are provided in the working face inclination direction of the coal body of the mining working face and in the direction of the roadway to form a borehole group, and an optical fiber sensor is correspondingly placed in each borehole, and the optical fiber sensor is encapsulated in the borehole using cement slurry so that the coal rock body and the optical fiber sensor are completely fitted;

[0024] S20: Using mining optical cables to sequentially connect the optical fiber sensor, the downhole optical fiber signal base station, the distributed optical fiber signal demodulator and the uphole monitoring center, and transmit the optical fiber sensor monitoring optical signal to the uphole monitoring center via the downhole optical fiber signal base station and the distributed optical fiber signal demodulator for processing;

[0025] S30: After the monitoring system is connected, a mining vibrator is used to send a vibration signal with a fixed frequency and amplitude at a certain distance from each fiber optic sensor. The installation and coupling quality of the fiber optic sensor is judged based on the signal amplitude and optical path power received by the monitoring system, and each fiber optic sensor is accurately calibrated.

[0026] In one example of the present invention, in step S10, encapsulating the optical fiber sensor in the borehole using cement slurry specifically includes the following steps:

[0027] The fiber optic sensor is sent to the bottom of the borehole through a push rod, a grouting pipe and a grouting pipe are placed in the borehole, the borehole mouth is sealed tightly with sealing materials, and a grouting pump is used to inject cement slurry into the borehole through the grouting pipe. When grouting flows out of the grouting pipe, the grouting pipe is closed so that the cement slurry couples and fixes the fiber optic sensor to the borehole wall. When the pressure of the grouting pump reaches 2.5MPa, the grouting is stopped to allow the cement slurry to fill the new cracks and primary cracks caused by drilling.

[0028] In one example of the present invention, the length of the grouting pipe is smaller than the length of the reverse grouting pipe, and both the grouting pipe and the reverse grouting pipe are penetrated by the plugging material and extend to the cement slurry area of ​​the borehole; wherein, the grouting pipe in the cement slurry area is located at one end close to the plugging material, and the reverse grouting pipe in the cement slurry area is located at one end away from the plugging material.

[0029] In an example of the present invention, in step S10, the drilling groups include two, and are respectively arranged on both sides of the coal body of the mining face in the inclination direction of the working face, wherein the drill holes in each drilling group correspond one to one in the inclination direction of the working face.

[0030] In an example of the present invention, in step S10, the depth of the borehole is 5m-10m, and the distance between two adjacent boreholes in the extension direction does not exceed 50m.

[0031] The best embodiment for carrying out the present invention will be described in more detail below with reference to the accompanying drawings so that the features and advantages of the present invention can be easily understood. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention, wherein the drawings are only used to illustrate some embodiments of the present invention, but not to limit all embodiments of the present invention thereto.

[0033] Figure 1 Schematic diagram of the structure of an impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing according to an embodiment of the present invention;

[0034] Figure 2 is a schematic diagram of the structure of an optical fiber sensor in a borehole according to an embodiment of the present invention;

[0035] Figure 3 Flow chart of a method for monitoring rock pressure and ground sound based on optical fiber vibration sensing according to an embodiment of the present invention;

[0036] Figure 4 A time domain waveform diagram and a frequency domain diagram of a microseismic acoustic wave signal collected by a monitoring system according to an embodiment of the present invention;

[0037] Figure 5A time domain waveform diagram and a frequency domain diagram of a ground sound wave signal collected by a monitoring system according to an embodiment of the present invention;

[0038] Figure 6 The monitoring system according to the embodiment of the present invention collects the time domain waveform diagram and frequency domain diagram of the acoustic emission sound wave signal.

[0039] List of reference numerals:

[0040] Monitoring system 100;

[0041] Optical fiber sensor 110;

[0042] Downhole optical fiber signal base station 120;

[0043] Distributed optical fiber signal demodulator 130;

[0044] Well Monitoring Center 140;

[0045] User terminal 150;

[0046] Coal body 200;

[0047] Drilling group 210;

[0048] Drilling 211;

[0049] Cement slurry 220;

[0050] plugging material 230;

[0051] Grouting pipe 240;

[0052] Anti-slurry pipe 250;

[0053] Crack 260;

[0054] Working face inclination direction H;

[0055] The direction of the roadway is V;

[0056] The distance L between two adjacent bore holes. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the technical solution of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described in conjunction with the drawings of specific embodiments of the present invention. The same figure marks in the drawings represent the same parts. It should be noted that the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] Unless otherwise defined, the technical terms or scientific terms used herein shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar words used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "one" do not necessarily indicate a quantity limitation. Words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0059] According to a first aspect of the present invention, an impact ground pressure and ground sound monitoring system 100 based on optical fiber vibration sensing is provided. Figure 1 and Figure 2 Shown, shown, including:

[0060] A plurality of optical fiber sensors 110 are arranged at intervals in the mining face along the direction V of the tunnel, and are configured to collect multi-frequency acoustic wave signals generated by coal and rock fractures and convert the multi-frequency acoustic wave signals into optical signals;

[0061] A downhole optical fiber signal base station 120, coupled to the plurality of optical fiber sensors 110, configured to receive the optical signal;

[0062] A distributed optical fiber signal demodulator 130, coupled to the downhole optical fiber signal base station 120, configured to convert the optical signal into a voltage signal;

[0063] The well monitoring center 140 is coupled to the distributed optical fiber signal demodulator 130 and is configured to receive the voltage signal and analyze and process the voltage signal.

[0064] The vibration waves generated by the acoustic signals of different frequencies in the coal rock mass are transmitted to the optical fiber sensor 110 with the coal rock as the medium. The optical phase of the sensitive optical fiber in the optical fiber sensor 110 changes due to the vibration waves, and the vibration wave signal is converted into an optical signal. The optical signal is then transmitted through the downhole transmission optical cable via the optical fiber signal base station to the distributed optical fiber signal demodulator 130 on the well. The optical information is converted into a voltage signal by the distributed optical fiber signal demodulator 130, and the voltage signal output is analyzed by the well monitoring center 140.

[0065] The monitoring system 100 uses optical fiber as the signal transmission medium. The underground operation part does not need power supply, and the signal monitoring will not be interrupted due to power failure, which ensures the continuous monitoring of the acoustic wave signal during the mining process of the working face. At the same time, the monitoring system 100 based on optical fiber sensing also has the technical advantages of strong anti-interference ability, high sensitivity, wide monitoring range and intrinsic safety of the system.

[0066] The monitoring system 100 is based on the Michelson fiber optic interference principle and can monitor multi-band acoustic wave signals, provide more comprehensive acoustic wave data for rock burst monitoring and early warning, and improve the accuracy of the monitoring system 100.

[0067] Compared with the traditional rock burst mine monitoring system 100 which requires the installation of a microseismic monitoring system 100 and a ground sound monitoring system 100, the rock burst multi-band acoustic wave monitoring system 100 proposed by the monitoring system 100 combines the collection of acoustic wave signals by the microseismic and ground sound systems, thus reducing the cost of monitoring rock burst in mines.

[0068] The monitoring system 100 buries the optical fiber sensor 110 in a borehole 211 of 5-10 m, which can effectively reduce environmental noise interference, enhance the coupling between the sensor and the inner wall of the coal rock, and ensure the effectiveness of multi-frequency acoustic wave signal monitoring.

[0069] In one example of the present invention, a plurality of boreholes 211 are provided in the working face inclination direction H extending from the coal body 200 of the mining working face and are spaced apart in the direction V of the tunnel to form a borehole 211 group 210, and an optical fiber sensor 110 is correspondingly arranged in each of the boreholes 211, wherein cement slurry 220 is injected into the boreholes 211 to achieve coupling and fixation between the optical fiber sensor 110 and the wall of the borehole 211; wherein the working face inclination direction H and the tunnel direction V are perpendicular to each other.

[0070] That is to say, by setting up boreholes 211 at intervals in the mining working face to ensure the effective collection of multi-frequency acoustic wave signals generated by coal rock fractures within the monitoring range, and injecting cement slurry 220 into the borehole 211, the optical fiber sensor 110 can be fixed in the borehole 211 to achieve complete fit between the coal rock and the optical fiber sensor 110, so as to more accurately sense the multi-frequency acoustic wave signals in the coal rock.

[0071] In one example of the present invention, the drilling group 210 includes two, and is respectively arranged on both sides of the coal body 200 of the mining working face in the working face inclination direction H, wherein the drilling holes 211 in each drilling group 210 correspond one to one in the working face inclination direction H;

[0072] In other words, the drilling group 210 is divided into an upward drilling group 210 and a downward drilling group 210, and the optical fiber sensor 110 is arranged inside the coal rock mass to ensure that the sensor is arranged in the coal rock layer section with less crack development. By setting up two drilling groups 210, the multi-frequency acoustic wave signals in the coal rock can be sensed more accurately.

[0073] In one example of the present invention, the cement slurry 220 is expansive cement.

[0074] In one example of the present invention, the depth of the borehole 211 is 5m-10m, and the distance L between two adjacent boreholes in the tunnel direction V does not exceed 50m;

[0075] The depth of borehole 211 is 5-10m, ensuring that the sensor is arranged in the coal rock layer section with less crack development. The multi-frequency fiber optic sensor 110 is arranged in the area with higher impact ground pressure risk in the coal mining face. The number of probes is arranged according to the regional range, and the probe spacing does not exceed 50m to ensure the effective collection of multi-frequency acoustic wave signals generated by coal rock fractures within the monitoring range.

[0076] In an example of the present invention, it further includes: a user terminal 150 , which is coupled to the uphole monitoring center 140 and is configured to view data information in the uphole monitoring center 140 in real time through the user terminal 150 .

[0077] According to the second aspect of the present invention, a construction method of an impact ground pressure and ground sound monitoring system 100 based on optical fiber vibration sensing is as follows: Figure 3 As shown, the following steps are included:

[0078] S10: According to the size of the optical fiber sensor 110, a suitable construction drill bit diameter is selected, and a plurality of boreholes 211 are provided in the working face inclination direction H of the coal body 200 of the mining working face and are spaced apart in the direction V of the tunnel to form a borehole group 210, and an optical fiber sensor 110 is correspondingly placed in each of the boreholes 211, and the optical fiber sensor 110 is encapsulated in the borehole using cement slurry 220, so that the coal rock body and the optical fiber sensor 110 are completely fitted;

[0079] S20: Using a mining optical cable to sequentially connect the optical fiber sensor 110, the downhole optical fiber signal base station 120, the distributed optical fiber signal demodulator 130 and the uphole monitoring center 140, the optical fiber sensor 110 monitoring optical signal is transmitted to the uphole monitoring center 140 via the downhole optical fiber signal base station 120 and the distributed optical fiber signal demodulator 130 for processing;

[0080] S30: After the monitoring system is connected, a mining vibrator is used to emit a vibration signal with a fixed frequency and amplitude at a certain distance from each optical fiber sensor 110. The installation and coupling quality of the optical fiber sensor 110 is determined based on the signal amplitude and optical path power received by the monitoring system, and each optical fiber sensor 110 is accurately calibrated.

[0081] The monitoring system 100 construction method uses optical fiber as the signal transmission medium. The monitoring system 100 does not need power supply when it is running underground, and the signal monitoring will not be interrupted due to power failure, which ensures the continuous monitoring of the acoustic wave signal during the mining process of the working face. At the same time, the monitoring system 100 based on optical fiber sensing also has the technical advantages of strong anti-interference ability, high sensitivity, wide monitoring range and intrinsic safety of the system.

[0082] The monitoring system 100 construction method is based on the Michelson fiber optic interference principle. The rock burst acoustic wave monitoring system 100 can realize the monitoring of multi-band acoustic wave signals, provide more comprehensive acoustic wave data for rock burst monitoring and early warning, and improve the accuracy of the monitoring system 100.

[0083] Compared with the traditional rock burst mine monitoring system 100 which requires the installation of a microseismic monitoring system 100 and a ground sound monitoring system 100, the rock burst multi-band acoustic wave monitoring system 100 proposed by the monitoring system 100 combines the collection of acoustic wave signals by the microseismic and ground sound systems, thus reducing the cost of monitoring rock burst in mines.

[0084] The construction method of the monitoring system 100 buries the optical fiber sensor 110 in a 5-10m borehole 211, which can effectively reduce environmental noise interference, enhance the coupling between the sensor and the inner wall of the coal rock, and ensure the effectiveness of multi-frequency acoustic wave signal monitoring.

[0085] In one example of the present invention, in step S10, encapsulating the optical fiber sensor 110 in the borehole using cement slurry 220 specifically includes the following steps:

[0086] The optical fiber sensor 110 is sent to the bottom of the borehole 211 by a push rod, a grouting pipe 240 and a reverse grouting pipe 250 are placed in the borehole 211, and the borehole 211 is tightly sealed with a plugging material 230. A grouting pump is used to inject cement slurry 220 into the borehole 211 through the grouting pipe 240, and the reverse grouting pipe 250 is closed after the grouting 220 flows out of the reverse grouting pipe 250, so that the cement slurry 220 couples and fixes the optical fiber sensor 110 to the wall of the borehole 211, and when the pressure of the grouting pump reaches 2.5 MPa, the grouting is stopped to allow the cement slurry 220 to fill the new cracks 260 and the original cracks 260 caused by drilling the borehole 211;

[0087] Through the above packaging steps, the optical fiber sensor 110 can be effectively packaged in the borehole 211 , which is beneficial to improving the monitoring accuracy of the optical fiber sensor 110 .

[0088] For example, the optical fiber sensor 110 is connected to the underground optical fiber signal base station 120 via a mining optical cable. In order to protect the portion of the mining optical cable in the borehole 211 , a casing may be provided outside the mining optical cable in the borehole 211 .

[0089] For example, the sealing material 230 is a common polyurethane sealing agent AB material.

[0090] In one example of the present invention, the length of the grouting pipe 240 is smaller than the length of the reverse slurry pipe 250, and both the grouting pipe 240 and the reverse slurry pipe 250 penetrate the plugging material 230 and extend to the cement slurry 220 area of ​​the borehole 211; wherein, the grouting pipe 240 in the cement slurry 220 area is located at one end close to the plugging material 230, and the reverse slurry pipe 250 in the cement slurry 220 area is located at one end away from the plugging material 230.

[0091] By designing the length of the grouting pipe 240 to be smaller than the length of the slurry pipe 250, the cement slurry 220 can be gradually filled from one end close to the plugging material 230 to the end away from the plugging material 230. This filling method is conducive to filling the borehole 211 densely and can effectively fill the new cracks 260 and the original cracks 260.

[0092] It should be noted that stop valves can be provided on both the grouting pipe 240 and the anti-slurry pipe 250, and the grouting pipe 240 and the anti-slurry pipe 250 can be closed by the stop valves.

[0093] In an example of the present invention, in step S10, the drilling group 210 includes two, and is respectively arranged on both sides of the coal body 200 of the mining working face in the working face inclination direction H, wherein the boreholes 211 in each drilling group 210 correspond one to one in the working face inclination direction H;

[0094] In other words, the drilling group 210 is divided into an upward drilling group 210 and a downward drilling group 210, and the optical fiber sensor 110 is arranged inside the coal rock mass to ensure that the sensor is arranged in the coal rock layer section with less crack development. By setting up two drilling groups 210, the multi-frequency acoustic wave signals in the coal rock can be sensed more accurately.

[0095] In an example of the present invention, in step S10, the depth of the borehole 211 is 5m-10m, and the distance L between two adjacent boreholes in the extension direction does not exceed 50m;

[0096] The depth of borehole 211 is 5-10m, ensuring that the sensor is arranged in the coal rock layer section with less crack development. The multi-frequency fiber optic sensor 110 is arranged in the area with higher impact ground pressure risk in the coal mining face. The number of probes is arranged according to the regional range, and the probe spacing does not exceed 50m to ensure the effective collection of multi-frequency acoustic wave signals generated by coal rock fractures within the monitoring range.

[0097] It should be noted that regarding the arrangement of the optical fiber sensor 110, since the multi-frequency acoustic wave signal is attenuated when propagating in the coal rock mass, based on the sensitivity of the optical fiber sensor 110, the multi-frequency optical fiber sensor 110 is evenly arranged in the area with the risk of impact ground pressure on the basis of ensuring that a relatively high-quality multi-frequency acoustic wave signal can be picked up. Through on-site attenuation tests, it is found that the high-frequency acoustic wave signal is severely attenuated when the distance between the rupture source and the optical fiber sensor is greater than 100m, which is not conducive to the monitoring of high-frequency signals.

[0098] In one example of the present invention, in step S30: the multi-frequency fiber optic sensor 110 is calibrated, and after the geosound monitoring system 100 is arranged, a mining vibrator is used to vibrate 3 times at intervals of 10 m at a distance greater than 50 m from the fiber optic sensor 110, and a vibration signal with a fixed frequency and amplitude is emitted. The frequency and amplitude of the vibration signal monitored by the system are compared to check the attenuation coefficient and correct the sensor monitoring sensitivity.

[0099] Specific examples

[0100] A mining face with impact hazard in a deep mine in Liaoning Province was selected. The average mining depth of the face was 727.9m, and the average mineable thickness of the coal seam was about 11m. Due to the large mining depth of the face and the presence of residual coal pillars above the face, the high stress concentration phenomenon leads to a high risk of rock burst at the face. Therefore, this embodiment selects the range with high impact hazard of the face (about 500m in the direction) as the monitoring object, and a total of 10 multi-frequency optical fiber sensors 110 are arranged. Since the transmission distance of high-frequency and low-amplitude acoustic emission sound wave signals is short, in order to ensure that the full-band sound wave information during the mining process of the face can be monitored, the spacing between the optical fiber sensors 110 is set to 50m, that is, 5 sensors are arranged in the transport lane and the return air lane of the face, and each sensor arrangement point selects an area with a small degree of coal body 200 and marks it.

[0101] Drill holes 211 are drilled at each of the proposed sensor layout points. The diameter of the drill hole 211 is slightly larger than the diameter of the sensor. The height of the drill hole 211 is 1 to 2 meters from the bottom plate of the tunnel. The depth of the drill hole 211 is 5 to 10 meters. The construction of the upward hole of the drill hole 211 is convenient for drainage and slag removal. After the construction of the drill hole 211 is completed, the optical cable at the tail end of the sensor is passed through the sensor push rod, and the sensor push rod and the sensor are connected by threads. Then the sensor is pushed into the bottom of the drill hole 211, and the grouting pipe and the anti-grouting pipe are placed in the drill hole 211. The drill hole 211 is tightly sealed with the drill hole 211 plugging material 230, and then cement is injected into the drill hole 211 through the grouting pipe until the cement slurry flows out of the anti-grouting pipe and the stop valve is closed. Grouting is continued until the grouting pump pressure reaches 2.5Mpa and then the grouting is stopped. This step is to allow the cement slurry to fill the new cracks and primary cracks caused by drilling, which is more conducive to the monitoring of the sensor, ensuring that the sensor is fully coupled with the coal rock mass, and more conducive to the transmission of sound waves.

[0102] After the sensor is stably installed in the borehole 211, the mine armored optical cable is pulled from the underground optical fiber signal base station 120 to each sensor deployment point, and the optical cable at the tail of the sensor is fused with the pulled optical cable using an optical fiber fusion splicer. The multi-band acoustic wave signal monitored by the sensor is transmitted to the underground signal base station through the mine optical cable, and then further transmitted to the above-ground optical fiber signal demodulator and the ground monitoring system 100 through the optical cable.

[0103] After the fiber optic multi-frequency acoustic wave monitoring system 100 is arranged, the multi-frequency acoustic wave sensor needs to be calibrated. The specific calibration steps are: at a distance of more than 50m from the sensor, use a mining vibrator to vibrate 3 times every 10m to send out a vibration signal with a fixed frequency and amplitude, compare the frequency and amplitude of the vibration signal monitored by the system, check the attenuation coefficient, and correct the sensor monitoring sensitivity.

[0104] During the mining process of the working face, the different frequency sound waves generated by the coal rock fracture caused by mining disturbance are transmitted to the sensor, causing the phase of the optical signal to change. The calculation formula is:

[0105]

[0106] Where β is the sensor constant, L is the length of the interferometer fiber in the sensor, and P 11 and P 12 is an element of the strain-optical tensor. The light beam with phase modulation information is demodulated by the Michelson interferometer into light intensity changes, and the calculation formula is:

[0107]

[0108] Where I0 is the output light intensity of the laser. The light intensity change is converted into an electrical signal by a photoelectric converter and transmitted to the analysis system.

[0109] like Figures 4 to 6 As shown in the figure, different frequency bands of acoustic wave signals monitored by a sensor during the working face mining process were selected, and the acoustic wave signals were processed by Fourier transform underground to convert the time series waveform information into frequency domain information, so that the main frequency range of the acoustic wave signal can be seen more intuitively. It was found that the main frequency of the monitored microseismic acoustic wave example was 121.1Hz, and its waveform showed the characteristics of large signal amplitude and long waveform duration; the main frequency of the monitored ground sound wave example was 510.5Hz, and its waveform showed the characteristics of large signal amplitude and long waveform duration; the main frequency of the monitored acoustic emission sound wave example was 3821.9Hz, and its waveform showed the characteristics of small signal amplitude and short waveform duration, which verified the accuracy of the system in monitoring acoustic wave signals of different frequency bands.

[0110] The exemplary implementation scheme of the impact ground pressure and ground sound monitoring system 100 based on optical fiber vibration sensing proposed in the present invention is described in detail above with reference to the preferred embodiments. However, those skilled in the art will appreciate that, without departing from the concept of the present invention, various modifications and variations can be made to the above-mentioned specific embodiments, and various technical features and structures proposed in the present invention can be combined in various ways without exceeding the protection scope of the present invention, which is determined by the attached claims.

Claims

1. An impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing, characterized in that: include: A plurality of optical fiber sensors (110) are arranged at intervals in a coal body (200) of a mining face along a tunnel strike direction (V), and are configured to collect multi-frequency acoustic wave signals generated by coal rock fracture and convert the multi-frequency acoustic wave signals into optical signals; A downhole optical fiber signal base station (120), coupled to the plurality of optical fiber sensors (110), configured to receive the optical signal; A distributed optical fiber signal demodulator (130), coupled to the downhole optical fiber signal base station (120), configured to convert the optical signal into a voltage signal; The well monitoring center (140) is coupled to the distributed optical fiber signal demodulator (130) and is configured to receive the voltage signal and analyze and process the voltage signal.

2. The impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing according to claim 1 is characterized in that: A plurality of boreholes (211) are provided in a working face inclination direction (H) of the coal body (200) of the mining working face and are spaced apart in the direction (V) of the tunnel to form a borehole group (210), wherein an optical fiber sensor (110) is correspondingly arranged in each of the boreholes (211), wherein cement slurry (220) is injected into the boreholes (211) to achieve coupling and fixation between the optical fiber sensor (110) and the wall of the borehole (211).

3. The impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing according to claim 2 is characterized in that: The drilling groups (210) include two, and are respectively arranged on both sides of the coal body (200) of the mining working face in the working face inclination direction (H), wherein the drilling holes (211) in each drilling group (210) correspond one to one in the working face inclination direction (H).

4. The impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing according to claim 2 is characterized in that: The cement slurry (220) is expansive cement.

5. The impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing according to claim 2 is characterized in that: The depth of the borehole (211) is 5m-10m, and the distance between two adjacent boreholes (211) in the tunnel direction (V) does not exceed 50m.

6. A construction method of an impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing, characterized in that: The steps include: S10: According to the size of the optical fiber sensor (110), a suitable construction drill bit diameter is selected, and a plurality of boreholes (211) are provided in the working face inclination direction (H) of the coal body (200) of the mining working face and are spaced apart in the direction (V) of the tunnel to form a borehole group (210), wherein an optical fiber sensor (110) is correspondingly arranged in each borehole (211), and cement slurry (220) is used to encapsulate the optical fiber sensor (110) in the borehole (211), so that the coal rock body and the optical fiber sensor (110) are completely fitted together; S20: using a mining optical cable to sequentially connect the optical fiber sensor (110), the downhole optical fiber signal base station (120), the distributed optical fiber signal demodulator (130) and the uphole monitoring center (140), and transmitting the monitoring optical signal of the optical fiber sensor (110) to the uphole monitoring center (140) via the downhole optical fiber signal base station (120) and the distributed optical fiber signal demodulator (130) for processing; S30: After the monitoring system is connected, a mining vibrator is used to emit a vibration signal with a fixed frequency and amplitude at a certain distance from each optical fiber sensor (110). The installation and coupling quality of the optical fiber sensor (110) is judged based on the signal amplitude and optical path power received by the monitoring system, and each optical fiber sensor (110) is accurately calibrated.

7. The construction method of the impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing according to claim 6 is characterized in that: In step S10, the process of encapsulating the optical fiber sensor (110) in the borehole (211) using cement slurry (220) specifically includes the following steps: The optical fiber sensor (110) is sent to the bottom of the borehole (211) by a push rod, a grouting pipe (240) and a grouting pipe (250) are placed in the borehole (211), and the borehole (211) mouth is tightly sealed with a plugging material (230). A grouting pump is used to inject cement slurry (220) into the borehole (211) through the grouting pipe (240), and when grouting (220) flows out of the grouting pipe (250), the grouting pipe (250) is closed, so that the cement slurry (220) couples and fixes the optical fiber sensor (110) to the wall of the borehole (211), and when the pressure of the grouting pump reaches 2.5 MPa, the grouting is stopped to allow the cement slurry (220) to fill the new cracks and primary cracks caused by drilling the borehole (211).

8. The construction method of the impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing according to claim 7 is characterized in that: The length of the grouting pipe (240) is shorter than that of the reverse grouting pipe (250), and both the grouting pipe (240) and the reverse grouting pipe (250) penetrate the plugging material (230) and extend to the cement slurry (220) region of the borehole (211); wherein the grouting pipe (240) in the cement slurry (220) region is located at one end close to the plugging material (230), and the reverse grouting pipe (250) in the cement slurry (220) region is located at one end away from the plugging material (230).

9. The construction method of the impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing according to claim 6 is characterized in that: In step S10, the drilling groups (210) include two, and are respectively arranged on both sides of the coal body (200) of the mining working face in the working face inclination direction (H), wherein the drill holes (211) in each drilling group (210) correspond one to one in the working face inclination direction (H).

10. The construction method of the impact ground pressure and ground sound monitoring system based on optical fiber vibration sensing according to claim 6, characterized in that: In step S10, the depth of the borehole (211) is 5m-10m, and the distance between two adjacent boreholes (211) in the extension direction does not exceed 50m.

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