In a coal mine in Huaibei Coal Mining Field, a total of 10 faults were exposed during construction of roadway, interconection and maingate of Ⅲ633 working face, with a drop of 0.4-5m. Among which FⅢ63-16 and SF14 faults have a greater impact on mining.A microseismic monitoring system is installed by CCTEG Xi'an Research Institute (Group) Co., Ltd., on the Ⅲ633 working face to conduct real-time, continuous, and full-space dynamic monitoring of the working face, evaluate and find out the development of hidden water-guiding structures under the working face along with the development of mining fissures, and provide reference for early warning of water inrush in coal mines in accordance with.Through setting up the microseismic monitoring system in the III633 working face of Zhuzhuang Coal Mine, and the microseismic monitoring during the mining period and one month after the end of mining, accurate microseismic events were obtained. The microseismic monitoring data collected during the monitoring period are carefully processed, analyzed and summarized, providing strong technical support for safe and efficient mining of coal mines.
(1) Plane distribution of microseismic events
Figure 1 shows the distribution of all microseismic event location results on the XY plane during the monitoring period. It can be seen from the figure that the microseismic events are mainly concentrated in the mining area in the direction of the roadway (X direction), that is, from the mining line to the mining area on February 9. Between the working lines, and in the middle part of the area, the event density is higher; the microseismic events are mainly concentrated on the wind tunnel side of the working face in the direction of the roadway inclination (Y), and extend to the goaf side of the III631 working face. According to the plane distribution of microseismic events, microseismic events are mainly concentrated in the mining area during mining, and the number of microseismic events on the side of the wind tunnel of the working face is relatively more, which may be caused by the proximity of the wind tunnel to the goaf of III631 working face.
Fig. 1 XY plane density nephogram of microseismic event
(2) Distribution of floor microseismic events
Figure 2 is the XY plane distribution diagram of floor microseismic events. It can be seen from the figure that the density distribution of microseismic events is relatively uniform, and there is no concentrated development in a local area. The analysis of the floor damage is relatively uniform, and there is no crack development concentrated in a small area.
Fig. 2 XY plane density nephogram of microseismic event in floor
Figure 3 and Figure 4 are the event density maps of floor microseismic events along the XZ direction of the coal seam strike and along the YZ direction of the coal seam dip. From the perspective of the XZ plane, the microseismic events on the floor of the III633 working face are relatively evenly developed, mainly occurring less than 40m below the floor, and mainly concentrated within the range of 90-220m from the stop production line; There are more microseismic events in the tunnel than in the machine roadway. The deepest microseismic events develop to 40m below the floor, but most of them are concentrated within 25-30m below the floor (red dotted line in the figure), and there are far more floor microseismic events inside the working face than outside the working face. Through the comprehensive analysis of the floor microseismic events, it is believed that the depth of floor damage during mining is about 25-30m, and the number of microseismic events is significantly reduced when it starts within 50m from the production line.
Fig. 3 Density nephogram in XZ direction of microseismic event in floor(along the strike direction of working face)
Fig. 4 Density nephogram in YZ direction of microseismic event in floor(along the inclined direction of working face)
(3) Distribution of roof microseismic events
Figure 5 is the XY plane distribution diagram of microseismic events on the roof. It can be seen from the figure that microseismic events are distributed throughout the working face, especially concentrated near the wind lane of III633 working face, and relatively few near the machine lane of III633 working face. Analysis may be due to the fact that the wind tunnel of the III633 working face is closer to the goaf of the III631 working face, and the elevation is higher than that of the machine tunnel, so the development of roof cracks is more obvious, and there are more and more concentrated microseismic events.
Fig. 5 XY plane density nephogram ofmicroseismic event in roof
As shown in Figure 6 and Figure 7, they are the XZ and YZ plane distribution diagrams of the location results of roof microseismic events during the monitoring period. From the perspective of the XZ plane, the distribution of microseismic events on the roof of the III633 working face is relatively even, mainly concentrated on the roof at a depth of 35-40m (marked by the red dotted line in the figure), and the highest development is about 80m on the roof; from the YZ plane, the III633 working face There are more microseismic events in the wind tunnel than in the machine tunnel. It is speculated that the wind tunnel is closer to the III631 gob and its elevation is higher than that of the machine tunnel. From the Z direction, the height of the cracks on the roof is 80m above the roof In the following range, the microseismic events are also concentrated on the roof at a depth of 35-40m. Combining the microseismic event density cloud map and the event distribution interval, it is estimated that the maximum height of the crack zone on the roof is about 37m. Calculated based on the average coal thickness of 2.8m, the cracking ratio is 13.2.
Fig. 6 Density nephogram in XZ direction of microseismic event in roof(along the strike direction of working face)
Fig. 7 Density nephogram in YZ direction of microseismic event in roof(along the inclined direction of working face)
