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Microseismic Monitoring System

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(Microseismic Monitoring Techniquefor short MS)It is a new cross-disciplinary and cross-industry technology developed from seismic exploration industry in recent years. Mainly used in coal mines, metal mines, highway tunnels, oil depots, rock slopes and other safety areas. The microseismic monitoring technology is to use microseismic sensors to monitor the vibration caused by rock mass rupture or other objects, receive the data through the microseismic monitoring sub-station, and process the data by the ground data processing server. The location, magnitude, energy, seismic moment, inelastic deformation and focal mechanism of rock mass microfracture are obtained. Then the stress-strain state of surrounding rock is analyzed in combination with seismological principle, and the purpose of monitoring and warning of coal and rock mass stability is achieved.

According to the classification of mine disasters, microseismic monitoring technology has the following applications:
1) Mine rock burst monitoring (rock mass stability monitoring).
Rock burst is also called ” rock burst”, ” mine impact”, ” rock burst” and so on. Usually when the mechanical system of coal and rock reaches the strength limit, the energy accumulated in the coal and rock mass around the mine roadway and stope is suddenly and sharply released. The generated power throws the coal and rock mass to the roadway, and at the same time, strong noise occurs, causing vibration and damage of coal mass, damage of supports and equipment, collapse and damage of some roadways, casualties and so on. In serious cases, it causes ground vibration and damage of buildings and so on.

Positioning result Display\analysis

Real-time waveform data

During the process of propulsion, the CG1302 working face occurred in the process of mining. At 19:48 on the evening of July 28, 2017, the roof subsidence and roadway shrinkage occurred. The site verification confirmed the fault activation.

2) Advanced detection of coal seam roadways with tunneling.
At present, the advanced detection methods for coal mine roadway include drilling, electric method and traditional seismic method.
Coal roadway accidents have become one of the most important threats to coal mine safety in production. In order to effectively reduce or even avoid the occurrence of dynamic disasters, the distribution of geological anomalies in front of the heading head should be identified in advance so as to make reasonable planning and targeted treatment in advance. In the process of coal roadway excavation, a lot of seismic wave signals will be generated, which contain rich geological anomaly information such as structure and gas bag. By taking the seismic echo signal generated by coal cutting machine cutting coal as the seismic source excitation signal for advancing detection along the roadway, a triaxial array microseismic sensor is arranged in the roadway, and the travel time, amplitude, phase and frequency of seismic waves are analyzed through real-time recording of the advancing seismic waveform. Based on the relevant interference theory, advancing detection along the roadway along the roadway in coal seam is carried out in real time.

Pre-exploration with excavation

Coal seam roadway with advanced exploration
From May 17th to May 24th, 2018, the 15110 working face of the Sijiazhuang Coal Mine was surveyed by the excavation. The head position was 1139m, and the gas area in front of the head was predicted to be 1169m-1174m. On May 28th, the K1 value and the amount of cuttings were measured through the field hole, indicating that the gas exceeded the standard, K1 value: 0.83 (mL•(g•min1/2)-1), and cuttings value: 2.8 (kg/m). Which is consistent with the results of the lead detection.

3) Mine water control monitoring.
The formation and occurrence of mine water disasters have a change process from gestation, development to occurrence, and there are corresponding precursors at different stages in this change process. Microseismic monitoring is to find out the specific parameters of water channel, including space-time location, energy and channel type, and then to carry out advance prediction and early warning of mine water inrush. The microseismic monitoring technology adopts the global optimization positioning technology when monitoring the coal mine water inrush danger, fully considers the different influence factors of the internal and external seismic source positioning, and combines the correction technologies of velocity structure, sensor consistency and the like to realize the high stability and high precision positioning of the microseismic source, optimize the arrangement of the microseismic monitoring network, and carry out real-time monitoring on concealed structures such as large faults, collapse columns and the like. through the three- dimensional display and analysis of the positioning results, the actual measurement parameters such as the activation rule of geological structures, the bottom plate rupture depth, the roof rupture height, the reasonable coal pillar size and the like are obtained, so as to realize the prediction and prediction of the water inrush danger.

4) Monitoring of cross-border mining.

This case is a frequent occurrence of civil mining activities in a mine production process, and the goaf has caused great safety hazards to mine production. The project plan adopts the installation of sensors on the ground in the mining area to form a micro-seismic monitoring network to monitor the mining activities in real time. Realize timely detection and timely stop, thus ensuring mine safety production.

5) Surrounding rock stability monitoring of mine goaf.
For years of mining and other historical reasons, many mines in our country have left large and complicated mined-out areas that have not been treated. As the stress balance in the mined-out areas is broken, the stability of surrounding rocks in the mined-out areas will be destroyed with the passage of time, such as roof collapse, which will pose certain risks to the top of the mined-out areas, buildings and roads nearby, and some mined- out areas will also pose certain threats to underground working faces. Therefore, monitoring and early warning of the stability of mined-out areas is the focus of mine safety production.

Using microseismic system to monitor the stability of salt cavern roof

Collapse signal

6) Coalbed methane hydraulic fracturing monitoring.
At present, hydraulic fracturing technology is widely used in a large number of coal mines, such as Songzao in Chongqing, Huainan in Anhui, Pingdingshan in Henan, Shanxi, etc., but the evaluation methods of hydraulic fracturing effect are limited. Coal seam is soft rock, joint fissure and has strong non – uniformity, so the microseismic waveform signal generated by coal fracture caused by hydraulic fracturing has unique characteristics. However, the microseismic monitoring technology realizes the microseismic real-time monitoring and evaluation of the hydraulic fracturing effect of underground coal seams through microseismic signal characteristics, microseismic event identification and microseismic positioning imaging processing of hydraulic fractures.
Application case – surface

Application case – in the mine

7) Slope stability monitoring.
In order to fully ensure the safety of slope engineering in open pit mines, grasp the changes in slope stability and slope risk level in time, and give early warning of possible large-area landslide events in advance. Therefore, by setting up a microseismic monitoring system on the mine slope, the safety of the slope can be analyzed and forewarned in real time.

In order to fully guarantee the safety of open pit slope engineering, timely grasp the slope stability change and slope risk grade, and forecast the large-area landslide events that may occur in advance. By installing a microseismic monitoring system on the slope of the mine, the slope safety analysis and early warning are carried out in real time.

8) Rockburst monitoring in tunnel excavation.
For long tunnels under high ground stress, disasters caused by dynamic ground pressure or engineering
construction blasting, such as rockburst and large caving, often occur in the construction stage. These disasters will seriously threaten the safety of construction personnel and equipment and affect the construction progress.