Method and system for monitoring rock burst in ultra-thin coal seams

Abstract

A method for monitoring a rock burst in ultra-thin coal seams, which method belongs to the technical field of fully mechanized coal mining in ultra-thin coal seams. The method comprises: respectively recording the acquired propagation times and propagation velocities of attenuated seismic waves from artificial seismic sources and the acquired propagation time and propagation velocity of a rock burst, and comparing different seismic wave signals and real-time rock burst signals passing through a mining area; converting the different seismic wave signals and the real-time rock burst signals into digital signals, and determining via comparison whether the digital signals have waveforms during the rock burst; when the digital signals have waveforms during the rock burst, identifying the waveforms of micro-seismic events, and determining the energy intensity of the rock burst; locating rock burst sources, and obtaining an intersection area of the rock burst sources, so as to obtain a seismic source position after a delineated range is reduced; and on the basis of acquired real-time pressure data in underground rock or coal seams, obtaining the positions of the maximum pressure and maximum pressure changes of a seismic source, and the numerical values thereof by means of analyzing a real-time pressure value and a real-time strain change rate. By means of the method, potential hazardous areas can be monitored. The present invention further relates to a system for monitoring a rock burst in ultra-thin coal seams.

Description

A method and system for monitoring rock burst in extremely thin coal seams Technical Field

[0001] The present invention relates to the technical field of fully mechanized mining of ultra-thin coal seams, and more particularly to a method and system for monitoring rock burst in ultra-thin coal seams based on a multi-parameter model. Background Art

[0002] Rock burst refers to the sudden release of energy accumulated within coal rock during the mining process. Rock burst can damage underground facilities and tunnels, and even cause casualties among mine workers. As mining depths in my country increase year by year, the deeper coal and rock layers, compared to shallower layers, exhibit a more complex geomechanical structure with a long geological history and modern geological environment. Rock burst can also increase the probability of other mine disasters, and even trigger major accidents such as gas explosions and roof water inrush, resulting in damage and collapse of surface buildings. Therefore, in order to better prevent and control rock burst, further research is needed into the mechanism and monitoring process of rock burst.

[0003] Currently, with the substantial increase in the degree of comprehensive mechanization in coal mines and the resulting ultra-intensive mining, the reserves of thick and medium-thick coal seams are decreasing. However, thin coal seams, due to their small thickness and inconvenient mining, have relatively large reserves. Extremely thin coal seams are widely distributed in my country, particularly in southern mines, where they are numerous, possess considerable absolute reserves, and possess excellent coal quality. Furthermore, the complex distribution and confined space of extremely thin coal seams make them difficult for workers to operate, unlike thick coal seams. Therefore, intelligent monitoring of mine pressure in extremely thin coal seams is a key technology to be explored.

[0004] Existing support equipment has low reliability and automation levels. Ultra-thin coal seams are thin and support conditions are poor. These conditions often make effective support measures difficult to implement, leading to rock bursts and difficulty meeting the requirements for mining in these seams. The limited space in these seams presents challenges for the installation and layout of monitoring equipment. The limited space in these seams limits the type and quantity of equipment that can be used for monitoring. This spatial limitation makes comprehensive and frequent monitoring impossible, preventing the monitoring of all potentially hazardous areas, thus impacting monitoring reliability. Summary of the Invention

[0005] In response to the problems existing in the above-mentioned fields, the present invention proposes a method and system for monitoring rock burst pressure in extremely thin coal seams, which can solve the technical problems that are caused by the spatial limitations of extremely thin coal seams, resulting in the inability to carry out comprehensive and high-frequency monitoring, and the inability to cover all potential danger areas within the monitoring range, thereby affecting the reliability of monitoring.

[0006] To solve the above technical problems, the present invention discloses a method for monitoring rock burst in an extremely thin coal seam, comprising the following steps:

[0007] Obtain seismic waves after artificial source attenuation, rock burst pressure, and real-time pressure data in underground rocks or coal seams;

[0008] Record the propagation time and speed of the seismic waves and rock burst after the artificial source is attenuated, and compare the different seismic wave signals and real-time rock burst signals passing through the mining area;

[0009] The arrival time, amplitude, and frequency of different seismic wave signals and real-time rock burst signals are converted into digital signals, and the waveforms of the digital signals with and without rock burst are compared. When the digital signal has a rock burst waveform, the waveform of the microseismic event is identified, and the rock burst energy intensity is determined by analyzing the increase or decrease in the amplitude of the waveform.

[0010] The time difference and propagation speed of seismic waves are used to locate the rock burst pressure source; the intersection area of ​​the rock burst pressure source is taken to obtain the source position after the narrowed range;

[0011] Based on the real-time pressure data in underground rocks or coal seams, the real-time pressure value and strain change rate are obtained; based on the real-time pressure value and strain change rate, the maximum pressure position and maximum pressure change position of the earthquake source and their values ​​are obtained.

[0012] Preferably, the method further includes obtaining a series of threshold values ​​of relevant indicators at the mining point based on the energy intensity of the rock burst, the location of the maximum pressure, the location of the maximum pressure change, and the location information of the rock burst source, with reference to historical data;

[0013] By analyzing the location information of the rock burst source and its corresponding rock burst energy intensity, the energy intensity value after the rock burst is transmitted to the mining location is calculated, and the energy intensity value is compared with the set threshold to determine whether the energy intensity value exceeds the threshold;

[0014] The difference between the energy intensity value and the set threshold is used as a basis to set the first, second and third level warning signals respectively; according to the level of the warning signal, the degree of danger of mining is determined;

[0015] The level of the warning signal is determined based on the thresholds of a series of relevant indicators at the mining point.

[0016] Preferably, the acquisition of rock burst pressure comprises the following steps:

[0017] According to the scope of the ground where the mining area is located, the entire mining area is divided into multiple rectangular areas by determining the center point of the entire mining area, and the center point of each rectangular area is determined;

[0018] Determine the layout position of each seismic wave transmitting device according to the center point of each rectangular area;

[0019] By detecting the attenuated seismic waves generated by artificial sources launched on the ground, the impact ground pressure generated by underground microseismic activities is passively monitored in real time when no artificial sources are launched on the ground.

[0020] Preferably, determining the rock burst energy intensity comprises the following steps:

[0021] The energy of rock burst is determined based on the amplitude of the seismic wave. The amplitude of the seismic wave is proportional to the seismic energy, so the energy of rock burst can be calculated.

[0022] By comparing the artificial seismic wave signals of different intervals and the real-time rock burst signals monitored by the monitoring devices deployed at different locations in the mining area, the different amplitudes, change frequencies, and energy sizes are recorded to obtain the rock burst energy intensity.

[0023] Preferably, the positioning of the impact ground pressure source comprises the following steps:

[0024] By comparing the attenuated seismic waves emitted by artificial seismic sources throughout the mining area, and using the difference in propagation velocities between the attenuated seismic waves of each artificial seismic source and the propagation time difference between the shear and longitudinal waves of the attenuated seismic waves of the same artificial seismic source, the spatial location of high stress concentration in extremely thin coal seams and the spatial location of the seismic source can be preliminarily delineated.

[0025] And based on the spatial location of the earthquake source, the time when the earthquake source occurred can be determined by tracing back in time and space.

[0026] Preferably, the preliminary delineation of the spatial location of high stress concentration in the extremely thin coal seam specifically includes:

[0027] When the seismic waves emitted by the ground seismic wave transmitting station are propagating, if they encounter rock bursts, the shear wave waveform of the artificial seismic wave will be disturbed for a moment, and the waveform will change to varying degrees. If they encounter macroscopic damage such as cracks, cavities, and faults during the propagation process, the shear wave energy of the artificial seismic wave will decay instantly, which is reflected in the instantaneous decrease in amplitude and the absence of waveform.

[0028] When there is no rock burst, the energy of the artificial seismic wave will attenuate as it travels from the ground to the underground. This is manifested as a decrease in the amplitude of the waveform. However, the decrease is uniform and there is no sudden change.

[0029] When encountering a squeezed coal seam, the dense and sparse parts and amplitude of the longitudinal wave waveform of the artificial seismic wave will increase, but the dense part will be more obvious; the longitudinal wave velocity will increase, and it will be more significant in the stress concentration area.

[0030] Preferably, obtaining the earthquake source position after narrowing the scope comprises the following steps:

[0031] Based on the propagation time and speed of seismic waves, positioning is performed using the time difference positioning method. On a map, multiple monitoring devices are used as a reference. Based on the seismic wave signals and rock burst signals after attenuation of different artificial earthquake sources, a time difference curve is drawn using the seismic wave time difference and propagation speed. Three monitoring devices in the multiple monitoring devices are grouped together. The three intersection points of the inverse time difference curve drawn from the seismic wave and rock burst signals after attenuation of the same artificial earthquake source are found. The three obtained intersection points are circled to obtain the location of a rock burst source.

[0032] Similarly, all deployed monitoring devices are grouped into groups of three, and the seismic wave signals and rock burst signals after attenuation of different artificial seismic sources are analyzed and processed to obtain multiple rock burst source locations;

[0033] The intersection area of ​​the multiple rock burst source locations is used as the earthquake source location after the demarcation range is narrowed down.

[0034] Preferably, obtaining the maximum pressure position and the maximum pressure change position of the earthquake source and their values ​​comprises the following steps:

[0035] According to the real-time pressure data in underground rocks or coal seams, real-time pressure data and real-time strain data are obtained through sensor monitoring, and the data are processed, stored and analyzed in turn to obtain real-time pressure values ​​and stress change rates;

[0036] The real-time pressure value and stress change rate obtained through data analysis and processing are used to obtain the maximum pressure position and maximum pressure change position of the earthquake source and their values.

[0037] Preferably, a monitoring system for an ultra-thin coal seam rock burst monitoring system is also included, comprising:

[0038] A data acquisition unit, used to acquire seismic waves after attenuation of the artificial seismic source, rock burst pressure, and real-time pressure data in underground rocks or coal seams;

[0039] Seismic wave signal acquisition unit, used to record the propagation time and speed of seismic waves and rock burst after the artificial source is attenuated, and compare different seismic wave signals and real-time rock burst signals passing through the mining area;

[0040] The rock burst energy intensity acquisition unit is used to convert the arrival time, amplitude, and frequency of different seismic wave signals and real-time rock burst signals into digital signals, and compare the digital signals with the waveforms of rock burst and the waveforms of rock burst. When the digital signals have the waveform of rock burst, the waveform of the microseismic event is identified, and the rock burst energy intensity is determined by analyzing the increase or decrease in the amplitude of the waveform.

[0041] The earthquake source location determination unit is used to locate the rock burst pressure source by using the time difference and propagation speed of the seismic waves; the intersection area of ​​the rock burst pressure source is taken to obtain the earthquake source location after the narrowed range is demarcated;

[0042] The stress concentration position acquisition unit is used to obtain the real-time pressure value and strain change rate based on the real-time pressure data in the underground rock or coal seam; based on the real-time pressure value and strain change rate, the maximum pressure position and maximum pressure change position of the earthquake source and their values ​​are obtained.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The monitoring method proposed in the present invention breaks through the technical defects of being unable to carry out comprehensive and high-frequency monitoring due to the spatial limitations of extremely thin coal seams and being unable to cover all potential dangerous areas within the monitoring range. The method analyzes the increase or decrease of the amplitude in the waveform, compares and records the seismic wave signals passing through the mining area and the real-time impact ground pressure signals, and obtains the maximum pressure position and the maximum pressure change point of the seismic wave waveform after the attenuation of the artificial seismic source and the seismic wave waveform generated by underground microseismic activity, thereby making up for the monitoring defects when no artificial seismic waves are emitted from the ground, so that the spatial position, occurrence time and vibration energy of the seismic source can be more comprehensively located. According to the real-time pressure change data in the underground rock or coal seam, the real-time maximum pressure change point and the maximum pressure change point are obtained. Further, the intersection of the waveform maximum pressure position and the maximum pressure change point and the real-time maximum pressure change point and the maximum pressure change point are taken to obtain the maximum pressure position and the maximum pressure change point of the integrated dangerous point, thereby narrowing the monitoring range of the dangerous point and improving the accuracy of monitoring.

[0045] The monitoring method proposed in this application can combine the ground monitoring of the impact ground pressure of extremely thin underground coal seams with the underground monitoring of the underground impact ground pressure, and combine the ground monitoring of the location of high stress concentration with the underground monitoring of the location of high stress concentration, thereby obtaining more accurate impact ground pressure energy intensity, source location, maximum pressure location of the source, maximum pressure change and their values. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] FIG1 is a flow chart of the monitoring method proposed by the present invention;

[0047] FIG2 is a schematic diagram showing the location layout of the seismic wave transmitting stations of the present invention throughout the mining area;

[0048] FIG3 is a waveform diagram of the artificial seismic wave of the present invention before encountering rock burst;

[0049] FIG4 is a waveform diagram of the artificial seismic wave of the present invention after encountering rock burst;

[0050] FIG5 is a flowchart of the method of each subsystem of the active monitoring system, stress monitoring system and passive monitoring system provided by the present invention. DETAILED DESCRIPTION

[0051] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with Figures 1 to 5 of the embodiments of the present invention. It should be understood that the terms used in the present invention are only used to describe specific implementation methods and are not intended to limit the present invention.

[0052] As shown in FIG1 , the rock burst monitoring method for an extremely thin coal seam proposed in this application includes the following steps:

[0053] S1: Acquire seismic waves after artificial source attenuation, rock burst pressure, and real-time pressure data in underground rocks or coal seams;

[0054] S2: Record the propagation time and velocity of the seismic wave and rock burst after the artificial source is attenuated, and compare the different seismic wave signals and real-time rock burst signals passing through the mining area;

[0055] S3: Convert the arrival times, amplitudes, and frequencies of different seismic wave signals and real-time rock burst signals into digital signals, and compare the digital signals with and without rock burst waveforms. If the digital signals have rock burst waveforms, identify the waveforms of microseismic events and determine the rock burst energy intensity by analyzing the increase or decrease in amplitude in the waveforms.

[0056] S4: Using the time difference and propagation speed of seismic waves, locate the rock burst pressure source; take the intersection area of ​​the rock burst pressure source to obtain the source position after narrowing the scope;

[0057] S5: Based on the real-time pressure data in the underground rock or coal seam, the real-time pressure value and strain change rate are obtained; based on the real-time pressure value and strain change rate, the maximum pressure position and the maximum pressure change position of the earthquake source and their values ​​are obtained.

[0058] It also includes obtaining a series of threshold values ​​of relevant indicators at the mining point based on the energy intensity of the rock burst, the location of the maximum pressure and the location of the maximum pressure change, and the location information of the rock burst source, with reference to historical data;

[0059] By analyzing the location information of the rock burst source and its corresponding rock burst energy intensity, the energy intensity value after the rock burst is transmitted to the mining location is calculated, and the energy intensity value is compared with the set threshold to determine whether the energy intensity value exceeds the threshold;

[0060] The difference between the energy intensity value and the set threshold is used as a basis to set the first, second and third level warning signals respectively; according to the level of the warning signal, the degree of danger of mining is determined;

[0061] The level of the warning signal is determined based on the thresholds of a series of relevant indicators at the mining point.

[0062] In step S1, obtaining rock burst pressure includes the following steps:

[0063] According to the scope of the ground where the mining area is located, the entire mining area is divided into multiple rectangular areas by determining the center point of the entire mining area, and the center point of each rectangular area is determined;

[0064] Determine the layout position of each seismic wave transmitting device according to the center point of each rectangular area;

[0065] By detecting the attenuated seismic waves generated by artificial sources launched on the ground, the impact ground pressure generated by underground microseismic activities is passively monitored in real time when no artificial sources are launched on the ground.

[0066] In step S3, determining the rock burst energy intensity includes the following steps:

[0067] The energy of rock burst is determined based on the amplitude of the seismic wave. The amplitude of the seismic wave is proportional to the seismic energy, so the energy of rock burst can be calculated.

[0068] By comparing the artificial seismic wave signals of different intervals and the real-time rock burst signals monitored by the monitoring devices deployed at different locations in the mining area, the different amplitudes, change frequencies, and energy sizes are recorded to obtain the rock burst energy intensity.

[0069] In step S4, locating the rock burst pressure source includes the following steps:

[0070] By comparing the attenuated seismic waves emitted by artificial seismic sources throughout the mining area, and using the difference in propagation velocities between the attenuated seismic waves of each artificial seismic source and the propagation time difference between the shear and longitudinal waves of the attenuated seismic waves of the same artificial seismic source, the spatial location of high stress concentration in extremely thin coal seams and the spatial location of the seismic source can be preliminarily delineated.

[0071] And based on the spatial location of the earthquake source, the time when the earthquake source occurred can be determined by tracing back in time and space.

[0072] Among them, the spatial location of high stress concentration in extremely thin coal seams was preliminarily identified, including:

[0073] When the seismic waves emitted by the ground seismic wave transmitting station are propagating, if they encounter rock bursts, the shear wave waveform of the artificial seismic wave will be disturbed for a moment, and the waveform will change to varying degrees. If they encounter macroscopic damage such as cracks, cavities, and faults during the propagation process, the shear wave energy of the artificial seismic wave will decay instantly, which is reflected in the instantaneous decrease in amplitude and the absence of waveform.

[0074] When there is no rock burst, the energy of the artificial seismic wave will attenuate as it travels from the ground to the underground. This is manifested as a decrease in the amplitude of the waveform. However, the decrease is uniform and there is no sudden change.

[0075] When encountering a squeezed coal seam, the dense and sparse parts and amplitude of the longitudinal wave waveform of the artificial seismic wave will increase, but the dense part will be more obvious; the longitudinal wave velocity will increase, and it will be more significant in the stress concentration area.

[0076] Obtaining the earthquake source location after narrowing the scope includes the following steps:

[0077] Based on the propagation time and speed of seismic waves, positioning is performed using the time difference positioning method. On a map, multiple monitoring devices are used as a reference. Based on the seismic wave signals and rock burst signals after attenuation of different artificial earthquake sources, a time difference curve is drawn using the seismic wave time difference and propagation speed. Three monitoring devices in the multiple monitoring devices are grouped together. The three intersection points of the inverse time difference curve drawn from the seismic wave and rock burst signals after attenuation of the same artificial earthquake source are found. The three obtained intersection points are circled to obtain the location of a rock burst source.

[0078] Similarly, all deployed monitoring devices are grouped into groups of three, and the seismic wave signals and rock burst signals after attenuation of different artificial seismic sources are analyzed and processed to obtain multiple rock burst source locations;

[0079] The intersection area of ​​the multiple rock burst source locations is used as the earthquake source location after the demarcation range is narrowed down.

[0080] In step S5, the maximum pressure position and the maximum pressure change position of the earthquake source and their values ​​are obtained, including the following steps:

[0081] According to the real-time pressure data in underground rocks or coal seams, real-time pressure data and real-time strain data are obtained through sensor monitoring, and the data are processed, stored and analyzed in turn to obtain real-time pressure values ​​and stress change rates;

[0082] The real-time pressure value and stress change rate obtained through data analysis and processing are used to obtain the maximum pressure position and maximum pressure change position of the earthquake source and their values.

[0083] This application also proposes an ultra-thin coal seam rock burst monitoring system based on this monitoring method, including:

[0084] The data acquisition unit includes a seismic wave transmitting device, an underground seismic wave receiving device and a sensor, wherein:

[0085] Seismic wave transmitting devices are arranged at the center point of each block in the area covered by the extremely thin coal seam on the ground, and are used to transmit artificial seismic sources from the ground to the underground;

[0086] Underground seismic wave receiving devices are all deployed in the coal seam coverage area or tunnel of the divided extremely thin coal seam. They are used to detect the seismic waves after attenuation of artificial seismic sources generated by artificial transmission on the ground. They are also used for real-time passive monitoring of the impact ground pressure generated by underground microseismic activities when no artificial seismic sources are transmitted on the ground.

[0087] Sensors are installed on the roof surface and tunnel of the hydraulic support to monitor real-time pressure change data in underground rocks or coal seams;

[0088] The seismic wave signal acquisition unit is used to record the propagation time and speed of the seismic waves and rock burst after the artificial source is attenuated, and to compare the different seismic wave signals and real-time rock burst signals passing through the mining area.

[0089] The rock burst energy intensity acquisition unit is used to convert the arrival time, amplitude and frequency of different seismic wave signals and real-time rock burst signals into digital signals.

[0090] The ground-based central monitoring station analyzes and processes digital signals. It compares the waveforms of rock bursts with those of real-time pressure change data based on attenuated seismic waves from artificial sources. When a rock burst waveform is detected in the digital signal, the system identifies the waveform of the microseismic event and determines the rock burst energy intensity by analyzing the increase or decrease in amplitude within the waveform. It also locates the rock burst source using the time difference and propagation velocity of seismic waves. The intersection of these sources is used to narrow down the source location. It also analyzes stored pressure data based on real-time pressure change data within underground rock or coal seams to obtain real-time pressure values ​​and real-time strain change rates. Based on these real-time pressure values ​​and real-time strain change rates, it determines the location of the maximum pressure and the point of maximum pressure change, along with their values.

[0091] Among them, the seismic wave transmitting device, including the seismic source / vibration vehicle, is used to generate high-frequency seismic waves. The propagation speed of seismic waves in the rock layer is 3-4 km / s for shear waves and 5-7 km / s for longitudinal waves. The propagation time of seismic waves from the ground to the underground coal seam is a moment.

[0092] The underground seismic wave receiving device includes seismometers and seismic geophones, which are the core components of the monitoring system.

[0093] Sensors include pressure sensors and strain sensors, which are used to detect underground pressure changes caused by earthquakes, underground explosions or other underground activities, and are also used to monitor underground stress status and underground activities.

[0094] The rock burst energy intensity acquisition unit is used to receive and preliminarily process the signals collected by the sensor to generate analog signals; convert the analog signals into digital signals, and use them to preliminarily filter and amplify the data.

[0095] It also includes communication equipment, including 5G communication, radio, Wi-Fi or satellite, which is used to transmit the data processed by the data acquisition unit to the ground central monitoring station.

[0096] The ground central monitoring station is equipped with computers and storage devices, which are used to process and interpret microseismic data through professional data analysis software, determine the location of high stress concentration and maximum stress change, the spatial location of the earthquake source and the time of occurrence.

[0097] The monitoring method and monitoring system proposed in this application can accurately monitor all potential danger areas.

[0098] Example

[0099] The embodiment of the present invention provides a method for monitoring rock burst in an extremely thin coal seam based on a multi-parameter model, comprising the following steps:

[0100] Figure 2 shows the layout of ground seismic wave transmitters. By determining the extent of the mining area, the center point of Mining Area 1 is found, and small rectangle 1 is obtained in Mining Area 2. The center point of small rectangle 1 in Mining Area 2 is found as 2 in Mining Area 3. Similarly, center points are found in other locations, such as those shown in Mining Area 4, and seismic wave transmitters are deployed at each center point.

[0101] The ground-based seismic wave transmitter station intermittently transmits seismic waves underground, covering the entire mining area. An underground seismic wave receiver (microseismic monitoring device) receives the attenuated artificial seismic waves. An underground data acquisition unit records the arrival time, amplitude, and frequency of the artificial seismic waves. The signal is differentially amplified and filtered, and the waveform is converted into a digital signal. This is transmitted via 5G communication to the ground-based central processing station, where specialized software analyzes and processes the digital signal, including digital filtering, waveform analysis, frequency domain analysis, and time domain analysis, to understand the signal's characteristics and information.

[0102] Figures 3 and 4 show the changes in artificial seismic waves before and after encountering a high stress concentration. When seismic waves transmitted from a ground-based seismic transmitter encounter rock burst during propagation, the shear waveform of the artificial seismic wave is momentarily disturbed. The waveform may exhibit varying degrees of change, including irregularities, sudden increases in amplitude, and chaotic signals that may indicate energy release. If the propagation encounters macroscopic damage such as cracks, voids, or faults, the shear energy of the seismic wave is instantly attenuated, manifesting as a momentary decrease in amplitude and waveform gaps. If there is no rock burst, the artificial seismic wave experiences energy attenuation during its transmission from the surface to the underground, manifested as a decrease in amplitude. However, this decrease is uniform, without sudden changes. When encountering a compressed coal seam, the amplitude of the artificial seismic wave's longitudinal waveform increases in both dense and sparse areas, but this increase is more pronounced in the dense areas. The longitudinal wave velocity also increases, becoming more pronounced in areas of stress concentration.

[0103] By comparing the attenuated seismic waves emitted by artificial sources throughout the mining area, and utilizing the propagation velocity differences between the attenuated seismic waves from each artificial source and the propagation time differences between the shear and longitudinal waves of the attenuated seismic waves from the same artificial source, we can preliminarily delineate the spatial location of high stress concentrations in extremely thin coal seams. The spatial location of the earthquake source can then be preliminarily delineated. Based on the approximate location of the earthquake source, we can then determine the approximate time of its occurrence through time and space tracing back. In other words, the active monitoring system can roughly delineate the spatial location of the earthquake source, make a preliminary estimate of the time of its occurrence, and preliminarily identify areas of high stress concentration in extremely thin coal seams.

[0104] The underground microseismic monitoring device is installed in the tunnel or coal seam working face. It is the same device as the seismic wave receiving device in the active monitoring system. When artificial seismic waves are intermittently emitted on the ground, the microseismic monitoring device mainly performs intermittent active monitoring of the signals transmitted to the underground by the artificial seismic waves. After collecting the data, it is transmitted to the ground central processing station for analysis and processing of the collected data. When no artificial seismic waves are emitted on the ground, the underground microseismic monitoring device is responsible for real-time passive monitoring of the impact ground pressure. After collecting the data, it is transmitted to the ground central processing station for analysis and processing of the collected data.

[0105] Because rock burst pressure in extremely thin coal seams is easily variable and the elastic energy of the coal seams is low due to their thinness, the microseismic energy generated is smaller than that in thicker coal seams. However, the microseismic signal changes more frequently than in thicker coal seams, and the frequency of microseisms is higher than in ordinary coal seams. Therefore, microseismic monitoring focuses on small vibrations. Therefore, underground microseismic monitoring devices are needed to passively monitor rock burst pressure in real time and accurately locate the spatial location of the earthquake source, the time of occurrence, and the vibration energy.

[0106] The microseismic events caused by rock burst are similar to artificial seismic waves, and the analysis and processing methods used are roughly the same. The difference is that artificial seismic waves are not generated in real time, but intermittent seismic waves generated by seismic sources or vibrating vehicles, while the microseismic events caused by rock burst are real-time, and there will be vibrations at any time, even if the vibrations are very small; secondly, the duration is different. The duration of artificial seismic waves will not be very long, but rock burst seismic waves will produce long-term microseisms based on continuous or repeated rock burst events; the waveform characteristics are different. The waveform of artificial seismic waves is controllable and relatively regular. The waveform of seismic waves caused by rock burst is more complex, and will include sudden high energy and irregular amplitude changes. The area radiated by the artificial seismic wave transmitting station deployed in this application is the entire mining area, which can monitor a large area, while the seismic waves caused by rock burst can only be received by working faces, tunnels, etc., and the monitoring range is smaller.

[0107] Underground microseismic monitoring devices monitor rock bursts in real time, generating a series of microseismic signals caused by rock bursts. The underground data acquisition unit collects data including: the arrival time of natural seismic waves, recording the arrival time of shear and longitudinal waves at each sensor; the amplitude and frequency of natural seismic wave vibrations; the waveform shape and characteristics of each natural seismic wave, including duration and periodicity; and estimates of the energy release and local magnitude of the microseismic event. The rock burst energy intensity acquisition unit roughly processes this data, performing simple filtering and feature extraction, before converting it into a digital signal. This data is transmitted via 5G communications to a ground-based central processing station, where it is analyzed and processed using specialized software.

[0108] Compare each microseismic event, analyze and process the data, and proceed according to the following steps as shown in the method flow chart of each subsystem in Figure 5.

[0109] Data preprocessing: Clean and preprocess the collected micro-vibration data to remove noise and interference signals, and then perform digital filtering, differential amplification, baseline adjustment, etc. on the data to ensure data quality.

[0110] Waveform analysis: Identify and analyze the waveform of microseismic events, including amplitude, frequency, wave velocity, duration, etc., and determine the arrival time of different types of seismic waves.

[0111] Event location: Locate the spatial position of the earthquake source based on the propagation time difference of the earthquake source, and then determine the time when the event occurred.

[0112] Microseismic Characterization: Estimation of the energy and local magnitude of microseismic events.

[0113] Using these processing and analysis methods, the earthquake source is spatially located again and the time period of occurrence is recorded.

[0114] Stress sensors are used to measure the stress at the deployment location in real time. The seismic wave signal acquisition unit records the collected stress data, including stress values ​​and corresponding times, and transmits them to the ground central processing station via 5G communication. The data is processed as necessary and then analyzed to obtain the patterns and trends of stress changes.

[0115] Compare the pressure values, analyze and process the data, and follow the steps below.

[0116] The collected data is processed, including filtering, denoising and calibration; the specific stress values ​​are analyzed to obtain the stress distribution in each area, and the stress change rate is obtained based on the time corresponding to the stress value; using these processing and analysis steps, the high stress concentration location under the extremely thin coal seam, the location of maximum stress change, and the location of continuous stress change are obtained.

[0117] Ground monitoring of underground extremely thin coal seam impact pressure is combined with underground monitoring of underground impact pressure, and ground monitoring of high stress concentration locations is combined with underground monitoring of high stress concentration locations.

[0118] The active monitoring system provides a rough delineation of the spatial location of the earthquake source and a preliminary estimate of its occurrence time. The passive monitoring system provides the spatial location of the earthquake source and the recorded time period. By integrating the information from these two systems, a more precise spatial location of the earthquake source and the time period of the microseismic occurrence are obtained. The active monitoring system has preliminarily delineated areas of high stress concentration in extremely thin coal seams.

[0119] The stress monitoring system obtains the high stress concentration location and the location of maximum stress change under the extremely thin coal seam; the data of the two systems are integrated to obtain more accurate high stress concentration location points, the location of maximum stress change, and the location of continuous stress change.

[0120] The monitoring method proposed in this application reduces the layout of equipment in extremely thin underground coal seams based on the characteristics of extremely thin coal seams, and introduces a method that combines ground monitoring underground with underground monitoring underground to improve the sensitivity of the overall system.

[0121] Based on this monitoring method, an embodiment of the present application also provides an ultra-thin coal seam rock burst monitoring system based on a multi-parameter model.

[0122] The layout of the system's seismic wave transmitters is shown in Figure 2, with each monitoring station interconnected. Multiple sets of seismic wave receivers (microseismic monitoring devices) are deployed underground. Multiple sets of high-precision ground pressure sensors are deployed on the roof surface of the hydraulic support and in the roadways. Data acquisition units are deployed at the coal mining face, and data is transmitted to the surface using 5G communication cables. A central monitoring station is established on the ground to process the received data, including:

[0123] The seismic wave transmitting device, which generates a seismic source by a seismic source or a vibrating vehicle, can generate high-frequency seismic waves and is used to transmit artificial seismic sources from the ground to the underground. The propagation speed of seismic waves in the rock layer can reach 3-4km / s for shear waves and 5-7km / s for longitudinal waves. The propagation time from the ground to the underground coal seam can be completed in an instant.

[0124] Seismic wave receiving devices (microseismic monitoring devices), consisting of seismometers and geophones, are the core of the system, used to detect rock bursts generated by artificial transmission above ground and microseismic activity underground. These sensors are typically very sensitive and can capture tiny seismic fluctuations.

[0125] High-precision pressure sensors are used to measure pressure changes in underground rock or coal seams. These sensors can detect changes in underground pressure caused by earthquakes, underground explosions, or other underground activities, allowing for monitoring of underground stress and activity. These sensors can be pressure sensors, strain sensors, and other types of sensors.

[0126] The rock burst energy intensity acquisition unit is used to receive and preliminarily process the signals collected by the sensor, is responsible for converting the analog signals into digital signals, and preliminarily filters and amplifies the data.

[0127] Communication equipment is used to transmit the data processed by the impact ground pressure energy intensity acquisition unit to the central monitoring station through a wired (such as 5G communication) or wireless (such as radio, Wi-Fi or satellite) communication system.

[0128] The central monitoring station on the ground further analyzes and stores the received data using analysis and processing software. It is usually equipped with high-performance computers and large-capacity storage devices to process and record large amounts of data.

[0129] Analysis and processing software, specialized software for data analysis, capable of processing and interpreting microseismic data, including determining the location, magnitude, timing, and possible causes of seismic events.

[0130] In order to further clarify the functions and connections between the various subsystems, this application associates the various subsystems. FIG5 is a flowchart of the method of the passive monitoring system, the active monitoring system, and the stress monitoring system, wherein:

[0131] The passive monitoring system consists of an underground seismic wave receiving device (microseismic monitoring device), a data acquisition unit, a communication device (data transmission equipment), and a ground central monitoring station (data storage and analysis equipment and terminal software).

[0132] The active monitoring system consists of seismic wave transmitting instruments, underground seismic wave receiving devices (microseismic monitoring devices), data acquisition units, communication equipment (data transmission equipment), and ground central monitoring stations (data storage and analysis equipment and terminal software).

[0133] Multiple groups of high-precision pressure sensors, data acquisition units, communication equipment (data transmission equipment), and ground central monitoring stations (data processing and analysis equipment) constitute the stress monitoring system.

[0134] The active monitoring system and the passive monitoring system share the same microseismic monitoring device, the same data acquisition unit, and the same terminal processing software, but use different data transmission equipment and data storage units.

[0135] The pressure monitoring system is independent of the active and passive monitoring systems, and the pressure sensor, data acquisition unit, data transmission equipment, and data processing and analysis equipment are all independent devices.

[0136] This monitoring method and system overcomes the technical defects of being unable to conduct comprehensive and high-frequency monitoring due to the spatial limitations of extremely thin coal seams, and being unable to cover all potential danger areas within the monitoring range. By analyzing the increase or decrease in amplitude in the waveform and comparing the recorded seismic wave signals passing through the mining area with the real-time impact ground pressure signals, the maximum pressure position and the point of maximum pressure change of the seismic wave waveform after the artificial source is attenuated and the seismic wave waveform generated by underground microseismic activity are obtained, which makes up for the monitoring defects when no artificial seismic waves are emitted from the ground, so that the spatial position, occurrence time and vibration energy of the source can be more comprehensively located. Based on the real-time pressure change data in the underground rock or coal seam, the real-time maximum pressure change point and the point of maximum pressure change are obtained. Furthermore, the intersection of the waveform maximum pressure position and the point of maximum pressure change and the real-time maximum pressure change point and the point of maximum pressure change is taken to obtain the integrated maximum pressure position and the point of maximum pressure change of the dangerous point, thereby narrowing the monitoring range of the dangerous point and improving the accuracy of monitoring.

[0137] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

[0138] In addition, unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods related to the documents. In the event of any conflict with any incorporated document, the content of this specification shall prevail.

Claims

1. A method for monitoring rock burst in an extremely thin coal seam, characterized in that: The following steps are involved: Obtain seismic waves after artificial seismic source attenuation, rock burst pressure and real-time pressure data in underground rocks or coal seams; Record the propagation time and speed of the seismic waves and rock burst after the artificial source is attenuated, and compare the different seismic wave signals and real-time rock burst signals passing through the mining area; The arrival time, amplitude and frequency of different seismic wave signals and real-time rock burst signals are converted into digital signals, and the waveforms of the digital signals with and without rock burst are compared; when the digital signals have the waveform of rock burst, the waveform of the microseismic event is identified, and the energy intensity of the rock burst is determined by analyzing the increase or decrease of the amplitude in the waveform; The time difference and propagation speed of seismic waves are used to locate the rock burst pressure source; the intersection area of ​​the rock burst pressure source is taken to obtain the source position after the demarcation range is narrowed; According to the real-time pressure data in the underground rock or coal seam, the real-time pressure value and strain change rate are obtained; according to the real-time pressure value and strain change rate, the maximum pressure position and the maximum pressure change position of the earthquake source and their values ​​are obtained; It also includes obtaining a series of thresholds of relevant indicators at the mining point based on the energy intensity of rock burst, the location of the maximum pressure, the location of the maximum pressure change, and the location information of the rock burst source, with reference to historical data; By analyzing the location information of the rock burst pressure source and its corresponding rock burst pressure energy intensity, the energy intensity value after the rock burst pressure is transmitted to the mining location is calculated, and the energy intensity value is compared with the set threshold to determine whether the energy intensity value exceeds the threshold; The difference between the energy intensity value and the set threshold is used as a basis to set the first, second and third level warning signals respectively; according to the level of the warning signal, the degree of danger of mining is determined; The level of the warning signal is determined according to the threshold values ​​of a series of relevant indicators at the mining point; The acquisition of rock burst pressure comprises the following steps: According to the scope of the ground where the mining area is located, the entire mining area is divided into multiple rectangular areas by determining the center point of the entire mining area, and the center point of each rectangular area is determined; Determine the layout position of each seismic wave transmitting device according to the center point of each rectangular area; By detecting the attenuated seismic waves generated by artificial sources emitted on the ground, when no artificial sources are emitted on the ground, the impact ground pressure generated by underground microseismic activities is passively monitored in real time; The method of locating the rock burst pressure source comprises the following steps: By comparing the seismic waves emitted from the artificial seismic sources in the entire mining area after attenuation, and using the difference in propagation speed between the seismic waves after attenuation of each artificial seismic source and the propagation time difference between the shear wave and the longitudinal wave of the seismic wave after attenuation of the same artificial seismic source, the spatial location of the high stress concentration in the extremely thin coal seam and the spatial location of the seismic source are preliminarily delineated; And according to the spatial location of the earthquake source, the time of its occurrence can be determined by tracing back through time and space; The preliminary delineation of the spatial location of high stress concentration in extremely thin coal seams specifically includes: When the seismic waves emitted by the ground seismic wave transmitting station are propagating, if they encounter impact ground pressure, the shear wave waveform of the artificial seismic wave will be disturbed in an instant, and the waveform will change to varying degrees; if the propagation process encounters macroscopic damage such as cracks, cavities and faults, the energy of the shear wave of the artificial seismic wave will decay instantly, which is reflected in the instantaneous decrease of amplitude and the absence of waveform; When there is no rock burst, the energy of the artificial seismic wave will decay when it is transmitted from the ground to the underground, which is manifested as a decrease in the amplitude of the waveform. However, the decrease process is uniform without sudden changes. When encountering a compressed coal seam, the dense and sparse parts of the longitudinal wave waveform and the amplitude of the artificial seismic wave will increase, but the dense part will be more obvious; the longitudinal wave velocity will increase, which will be more significant in the stress concentration area; The step of obtaining the earthquake source position after the demarcation range is reduced comprises the following steps: According to the propagation time and speed of seismic waves, the positioning is carried out by using the time difference positioning method. On the map, multiple monitoring devices are used as the reference. According to the seismic wave signals and rock burst signals after attenuation of different artificial seismic sources, the time difference curve is drawn using the time difference of seismic waves and the propagation speed. Three monitoring devices in the multiple monitoring devices are grouped together. The three intersection points of the inverse time difference curve drawn by the seismic wave and rock burst signals after attenuation of the same artificial seismic source are found, and the three intersection points are circled to obtain a rock burst source location. Similarly, all deployed monitoring devices are grouped into groups of three, and the seismic wave signals and rock burst signals after attenuation of different artificial seismic sources are analyzed and processed to obtain multiple rock burst source locations; The intersection area of ​​the multiple rock burst source locations is used as the earthquake source location after the demarcation range is narrowed down.

2. The method for monitoring rock burst in an ultra-thin coal seam according to claim 1, characterized in that: Determining the rock burst energy intensity comprises the following steps: The energy of rock burst is determined based on the amplitude of the seismic wave. The amplitude of the seismic wave is proportional to the seismic energy, so the energy of rock burst can be calculated. By comparing the artificial seismic wave signals of different intervals and the real-time rock burst signals monitored by the monitoring devices arranged at different locations in the mining area, the different amplitudes, changing frequencies and energy sizes are recorded to obtain the rock burst energy intensity.

3. The method for monitoring rock burst in an ultra-thin coal seam according to claim 2, characterized in that: The method of obtaining the maximum pressure position and the maximum pressure change position of the earthquake source and their values ​​comprises the following steps: According to the real-time pressure data in underground rocks or coal seams, the real-time pressure data and real-time strain data are obtained through sensor monitoring, and the data are processed, stored and analyzed in turn to obtain the real-time pressure value and stress change rate; The real-time pressure value and stress change rate obtained through data analysis and processing can be used to obtain the maximum pressure position and maximum pressure change position of the earthquake source and their values.

4. A monitoring system for rock burst monitoring system of an extremely thin coal seam, characterized in that: include: A data acquisition unit, used to acquire seismic waves after attenuation of artificial seismic sources, rock burst pressure, and real-time pressure data in underground rocks or coal seams; A seismic wave signal acquisition unit, used to record the propagation time and speed of the seismic wave and rock burst after the attenuation of the artificial source, and to compare different seismic wave signals and real-time rock burst signals passing through the mining area; The rock burst energy intensity acquisition unit is used to convert the arrival time, amplitude and frequency of different seismic wave signals and real-time rock burst signals into digital signals, and compare the waveform of the digital signal with or without rock burst; when the digital signal has the waveform of rock burst, it identifies the waveform of the microseismic event, and determines the rock burst energy intensity by analyzing the increase or decrease of the amplitude in the waveform; The earthquake source location determination unit is used to locate the rock burst pressure source by using the time difference and propagation speed of the seismic wave; the intersection area of ​​the rock burst pressure source is taken to obtain the earthquake source location after the demarcation range is narrowed; The stress concentration position acquisition unit is used to obtain the real-time pressure value and strain change rate according to the real-time pressure data in the underground rock or coal seam; and obtain the maximum pressure position and the maximum pressure change position of the earthquake source and their values ​​according to the real-time pressure value and strain change rate; It also includes a signal warning unit, which is used to obtain a series of thresholds of relevant indicators at the mining point according to the energy intensity of the rock burst, the maximum pressure position and the maximum pressure change position as well as the location information of the rock burst source, with reference to historical data; by analyzing the location information of the rock burst source and its corresponding rock burst energy intensity, the energy intensity value after the rock burst is transmitted to the mining position is calculated, and the energy intensity value is compared with the set threshold value to determine whether the energy intensity value exceeds the threshold value; The difference between the energy intensity value and the set threshold is used as a basis to set the first, second and third level warning signals respectively; according to the level of the warning signal, the danger level of mining is determined; wherein, the level of the warning signal is determined according to the threshold of a series of related indicators at the mining point; The acquisition of rock burst in the data acquisition unit includes the following steps: according to the range of the ground where the mining area is located, by determining the center point of the entire mining area, the entire mining area is divided into a plurality of rectangular areas, and the center point of each rectangular area is determined; according to the center point of each rectangular area, the layout position of each seismic wave transmitting device is determined; by detecting the seismic wave attenuated by the artificial source generated by artificial emission on the ground, when no artificial source is emitted on the ground, the rock burst generated by the underground microseismic activity is passively monitored in real time; The positioning of the rock burst pressure source in the earthquake source position determination unit includes the following steps: comparing the attenuated seismic waves of the artificial earthquake sources emitted in the entire mining area, using the difference in propagation speed between the attenuated seismic waves of each artificial earthquake source, and the propagation time difference between the shear wave and the longitudinal wave of the attenuated seismic wave of the same artificial earthquake source, preliminarily delineating the spatial position of the extremely thin coal seam with high stress concentration, and preliminarily delineating the spatial position of the earthquake source; and determining the time of occurrence of the earthquake source through time and space backtracking according to the spatial position of the earthquake source; The preliminary delineation of the spatial position of high stress concentration in the extremely thin coal seam specifically includes: when the seismic waves emitted by the ground seismic wave transmitting station are propagating, when encountering rock burst, the shear wave waveform of the artificial seismic wave will be disturbed in an instant, and the waveform will change to varying degrees; if the propagation process encounters macroscopic damage such as cracks, cavities and faults, the energy of the shear wave of the artificial seismic wave will decay instantly, which is reflected in the instantaneous decrease in amplitude and waveform vacancies; when there is no rock burst, the process of the artificial seismic wave from the ground to the underground will experience energy attenuation, which is specifically manifested in the decrease in the amplitude of the waveform, but the decrease process is uniform without mutation; when encountering a squeezed coal seam, the dense part, sparse part and amplitude of the longitudinal wave waveform of the artificial seismic wave will all increase, but the dense part is more obvious; the longitudinal wave velocity will increase, which will be more significant in the stress concentration part; The earthquake source position determination unit obtains the earthquake source position after the demarcation range is narrowed, including the following steps: positioning by the time difference positioning method according to the propagation time and speed of the earthquake wave, taking multiple monitoring devices deployed on the map as a reference, and drawing a time difference curve according to the earthquake wave signals and rock burst signals after attenuation of different artificial earthquake sources by using the time difference of the earthquake wave and the propagation speed, dividing three monitoring devices among the multiple monitoring devices into one group, finding the three intersection points of the inverse time difference curve drawn by the earthquake wave and rock burst signals after attenuation of the same artificial earthquake source, demarcating the obtained three intersection points, and obtaining a rock burst source position; and so on, grouping all the deployed monitoring devices into threes, analyzing and processing the earthquake wave signals and rock burst signals after attenuation of different artificial earthquake sources, and obtaining multiple rock burst source positions; and using the intersection area of ​​the obtained multiple rock burst source positions as the earthquake source position after the demarcation range is narrowed.

Images