CN-116819609-B - Microseism positioning method based on fiber bragg grating acoustic emission sensing technology

CN116819609BCN 116819609 BCN116819609 BCN 116819609BCN-116819609-B

Abstract

The invention discloses a microseismic positioning method based on a fiber bragg grating acoustic emission sensing technology, which comprises the steps of (a) selecting at least four monitoring points in an underground mine to be detected, arranging a fiber bragg grating acoustic emission sensor on each monitoring point, arranging four fiber bragg gratings on the fiber bragg grating acoustic emission sensor at equal intervals, (b) solving the propagation speed of acoustic emission signals on paths from all the fiber bragg grating acoustic emission sensors to a seismic source, (c) processing coordinate data of each fiber bragg grating acoustic emission sensor and time data of acoustic emission signals received to obtain corresponding data on the corresponding monitoring points, and (d) substituting the calculated propagation speed, the coordinate data of the monitoring points and the time data of acoustic emission signals received into a seismic source calculation equation set to obtain the coordinates of the seismic source. The invention can accurately position the seismic source in the underground mine, provide reliable technical guidance for targeted measures such as reinforcement and support, and ensure the safe production and exploitation of the underground mine.

Inventors

ZHU ZEQI
PANG XIN
Wan Daochun
XIA LUQING
ZHANG SHAOJUN
CHEN HAONAN

Assignees

中国科学院武汉岩土力学研究所
攀钢集团矿业有限公司

Dates

Publication Date: 20260512
Application Date: 20230606

Claims (4)

1. A microseismic positioning method based on a fiber bragg grating acoustic emission sensing technology is characterized by comprising the following steps: (a) Selecting at least four monitoring points in an underground mine to be detected, arranging a fiber grating acoustic emission sensor at each monitoring point, and arranging four fiber gratings on each fiber grating acoustic emission sensor at equal intervals; (b) Solving the propagation speed of acoustic emission signals on the paths from all the fiber bragg grating acoustic emission sensors to the seismic source; (c) Processing the coordinate data of each fiber bragg grating acoustic emission sensor and the time data of receiving the acoustic emission signals to obtain corresponding data on corresponding monitoring points; (d) Substituting the calculated propagation speed, the coordinate data of the monitoring point and the time data of the received acoustic emission signal into a seismic source calculation equation set to obtain the coordinate of a seismic source; Solving the propagation speed of acoustic emission signals on the paths from all the fiber bragg grating acoustic emission sensors to the seismic source in the step (b), wherein the method comprises the following steps of: One monitoring point is selected to be marked as P A , an acoustic emission sensor of the fiber bragg grating distributed by the monitoring point P A is marked as A, the distance between the fiber bragg gratings is l, and the coordinates of the four fiber bragg gratings on the acoustic emission sensor A of the fiber bragg grating are respectively marked as (x A1 ,y A1 ,z A1 )、(x A2 ,y A2 ,z A2 )、(x A3 ,y A3 ,z A3 )、(x A4 ,y A4 ,z A4 ); Assuming that after the vibration of the vibration source q, the time when the fiber bragg grating acoustic emission sensor A receives four acoustic signals is respectively recorded as T A1 、T A2 、T A3 、T A4 , and the distance between the fiber bragg grating sensor A and the vibration source q is respectively recorded as S A1 、S A2 、S A 、S A4 ; assuming that the coordinate of the seismic source q is (x 0 ,y 0 ,z 0 ), the seismic source starting moment is T 0 , and the equation set for solving the acoustic emission signal propagation speed V A from the fiber grating acoustic emission sensor A to the seismic source q path is as follows: The time difference between the time T A2 、T A3 、T A4 and the time T A1 of the four acoustic signals of the fiber grating acoustic emission sensor A is recorded as delta T a 、Δt b 、Δt c , and the following steps are adopted According to the time difference delta t a 、Δt b 、Δt c and the distance l between the fiber gratings, the following steps are obtained: the above equation set is solved as: Thus, the unknowns are V A 、t A , n, m, and the known amounts are Deltat a 、Δt b 、Δt c , l; the propagation speed V A of the acoustic emission signal on the path from the optical fiber grating acoustic emission sensor A to the seismic source q is calculated as follows: and the propagation speed V i of acoustic emission signals on the paths from all the fiber bragg grating acoustic emission sensors i to the seismic source q is obtained by analogy, i= A, B, C.
2. The microseismic positioning method based on the fiber bragg grating acoustic emission sensing technology according to claim 1, wherein the fiber bragg grating acoustic emission sensor in the step (a) is arranged at a monitoring point in a plumb or horizontal mode.
3. The method for locating a microseismic based on fiber bragg grating acoustic emission sensing technology of claim 1, wherein the set of source calculation equations in step (d) is: Wherein S i is the distance from each monitoring point to the seismic source point, T i is the moment when the acoustic emission signal is received at each monitoring point, and V i is the propagation speed of the acoustic emission signal on the path from each fiber grating acoustic emission sensor to the monitoring point.
4. The microseismic locating method based on the fiber bragg grating acoustic emission sensing technology according to claim 1, wherein the data of each monitoring point is processed as follows: Where x i represents the x-direction coordinate represented by the monitoring point P i , y i represents the y-direction coordinate represented by the monitoring point P i , z i represents the z-direction coordinate represented by the monitoring point P i , T i represents the time when the monitoring point P i receives the acoustic emission signal, j=1, 2,3,4; i= A, B, C.

Description

Microseism positioning method based on fiber bragg grating acoustic emission sensing technology Technical Field The invention belongs to the technical field of microseism focus positioning, and particularly relates to a microseism positioning method based on a fiber bragg grating acoustic emission sensing technology. Background In recent years, with the continuous growth of population and the rapid development of industry, the national demand for metal ores having underground reserves is increasing, and exploitation of underground metal mines is also an important economic activity. With the deepening of the mine depth and the increase of exploitation difficulty, the unstable geological environment brings higher safety risks to exploitation and production of mineral resources. Therefore, improving the ability to accurately evaluate and predict disasters in the geological environment of a mine is one of the urgent tasks of the production safety of the underground mine at present. The accurate seismic source positioning technology is an important foundation for developing mine disaster prediction, and can provide technical support for early warning, monitoring, accident emergency and the like for mine safety production and exploitation. Because the solid material is subjected to external forces (mechanical loads, temperature changes, etc.), an internal stress concentration zone is created. When the high-energy state is transited to the low-energy state, the strain energy is rapidly released in the form of elastic waves, namely, an acoustic emission phenomenon is generated. The acoustic emission phenomenon between 10Hz and 300Hz is called microseismic, and is a tiny signal that the inside of a solid substance is deformed or broken. Microseismic monitoring is a method for researching mechanical behaviors and dynamic processes of underground nonlinear materials by recording changes of microseismic signals. The microseism monitoring technology is based on acoustic emission science and seismology, and the purpose of evaluating the effect of the microseism monitoring technology on the underground environment and engineering structures is achieved by monitoring and analyzing the occurrence of microseism events in exploitation and production activities. The technology generally predicts whether an accident will occur by analyzing the position distribution of the seismic source points, the seismic source mechanism (shear fracture or tensile fracture) and other characteristics. Thus, the core of this technique is to accurately determine the source location to eliminate or mitigate the potential environmental and safety hazards of the mining and production activities. Because the acoustic emission signals carry rich information required by the damage and destruction conditions in the underground mine materials, the positions, properties and expansion conditions of cracks can be monitored in time, accurate early warning of damage positions and degrees is realized, accidents are effectively prevented, and therefore, how to accurately detect the acoustic emission signals is an important ring in microseism monitoring. The traditional acoustic emission signal measurement adopts a piezoelectric ceramic sensor, and has the problems that electromagnetic interference is plagued, real-time long-term monitoring cannot be realized, and the like. For this reason, fiber grating acoustic emission sensors are commonly used in the production of mined material to measure acoustic emission signals. The fiber grating acoustic emission sensor is favored because of the advantages of high sensitivity, small volume, immune electromagnetic interference, long distance between electronic equipment and the sensor, and the like, and particularly, under the condition that a sensing signal is modulated by wavelength, the measuring signal can be realized without being influenced by fiber loss, connection loss, light source floating, detector aging and the like, and the requirements are difficult to reach by contrary to the traditional piezoelectric ceramic sensor. In addition, the fiber grating acoustic emission sensor can combine a plurality of gratings in one transmission fiber, further a wavelength division multiplexing technology is used for realizing distributed measurement, and for a plurality of acoustic emission signals, data processing is performed after measurement and acquisition based on the method, so that more accurate signal data can be obtained. However, the conventional micro-seismic source positioning calculation method based on the fiber bragg grating acoustic emission sensing technology has a plurality of limitations in underground mine application, is large in error and lacks sufficient accuracy and stability, so that reliable technical guidance and prediction cannot be provided, and the safety production exploitation of the underground mine is affected. The main reason is that the microseismic positioning calculation method is too