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1 mining engineering background
Vantown lead zinc mine located in the middle of the border zone Wolf Hetao Plain. The ore body starts from the 0 line and the west line to the 19th line. The main ore body is above 850m elevation. The overall orientation of the ore body is northeast-southwest, tending to northwest, and the inclination is 12°~60°. The ore body is layered and lenticular, ranging in thickness from a few meters to tens of meters. The ore is dominated by dolomite marble , Jinyun graphite schist and graphite dolomite marble. The relative influence of fault structure is small, the surrounding rock alteration is not developed, and the mining technical conditions are good. The mining method is a segmental empty-field mining method. The mine was put into operation in 2004, with an annual production capacity of 700,000 tons. The middle-stage pillars were not retained during the interval of room and column separation, forming a super-large goaf with an empty area of ​​about 1.3 million m3. The exposed area of ​​the goaf exceeds 3,500 m2, and only four tall continuous pillars are supported. The vertical height of the pillars of the 19, 15, 11 and 7 exploration lines is about 40-110 m, as shown in Figure 1 and Table 1.
The stability of the pillars of the Wancheng lead-zinc mine and the stability of the goaf are prominent. Once the goaf is unstable, the potential damage of the mining area is greatly affected, which brings serious safety hazards to the mining of the lower ore body.
2 Microseismic monitoring system introduction
In response to the stability of the extra-large pillars and goafs in the Wancheng lead-zinc mine, an 18-channel microseismic monitoring system was established in 2013. The sensors are arranged in the middle of the 960m section of the 7-, 11-, 15- and 19-line pillars. The middle section of 930m, the middle section of 890m and the 873m layer. The system is mainly composed of three parts: the surface main server, the underground data acquisition base station and the sensor. The micro-seismic signal is received by the inner cylinder sensor and amplified by the preamplifier. After the data acquisition base station performs A/D conversion, the optical cable is transmitted to the surface. The main server has established an 18-channel microseismic monitoring system to achieve real-time monitoring of the stability of the pillars and goafs, as shown in Figure 2.
3 Microseismic monitoring and incentive analysis of ground pressure in dynamic mining process
Micro-seismic monitoring analysis of 3.115 line pillar stability
A total of five sensors are arranged on the 15-line pillar, which are 6#, 7#, 12#, 17# and 18# sensors. The sensor arrangement is shown in Figure 3.
In May 2015, the 15-seismite sensor microseismic event was active, and the number of 17# sensor microseismic events in the middle of 873m exceeded the warning value. Figure 4 and Figure 5 show the typical rock burst waveform of the 15-line ore sensor and the May 2015 microseismic. The trend of event level changes, it can be seen that the number of 12#, 17#, 18# sensor events in the 890m middle segment and the 873m middle segment on the 15th line has been active. On May 15th, the 17# sensor microseismic event exceeded the warning value. Changsha Mine Research The hospital and the Wancheng lead-zinc mine issued a warning of ground pressure disasters, prohibiting the entry of personnel and equipment. Since then, the number of microseismic events has been at a high level.
Through the actual exploration of the 15-line pillar, it is found that local rock mass cracking and collapse occurred in the side of the -8m mined column near the 3-4 goaf. At the same time, it was found that the rock in the upper plate fell, and even piled up to block some roadways. In the middle of the 873m middle section, the edge of the 3-4 mining area along the vein lane, the exploration found that there was a crack in the upper part of the roadway, and the obvious rock mass cracking and flake phenomenon were found in the 3-4 mining area near the 15-line pillar. .
Analysis of the cause of the ground pressure of 3.215 line pillar
Both the microseismic monitoring data and the ground pressure phenomenon show that the microseismic data and the ground pressure phenomenon on the upper or lower plate of the 15-line pillar are prominent, and the rock mass damage along the vein is more significant. The activity is pressed on the 15-line pillar. According to the investigation of production operations, the 15-line pillar rock pressure activity is caused by the mining of 3-4 stope, especially in mid-April 2015, in the middle of the 530-850m east 5 stope. In the middle and deep hole blasting, on the one hand, the static height of the 15-line pillar near the upper plate increases and the lateral limit decreases. On the other hand, the mining of the ore body in this area leads to the loss of support on the upper plate, which is the direct occurrence of the ground pressure activity of the 15-line pillar. Incentives. The following countermeasures have been developed for this mine:
(1) Improve the ground pressure monitoring and disaster early warning system, establish an emergency plan, and find that the abnormality immediately withdraws from the underground personnel in the area and adjacent mining areas;
(2) Temporarily stop the blasting operation of 3-4 stope until the microseismic monitoring data returns to normal level;
(3) speed up the filling speed, adjust the filling plan, and preferentially fill the 3-4 empty areas;
(4) Strengthen microseismic monitoring. At this stage, the monthly report will be changed to weekly report. If necessary, it can be changed to daily report. At the same time, the local pressure management work will be strengthened, and problems will be reported to relevant leaders and departments in a timely manner.
4 Conclusion
In this paper, based on the 18-channel all-digital microseismic monitoring system, the 18-channel all-digital microseismic monitoring system is used to monitor and analyze the ground pressure activities of the dynamic mining process of the 15-line mine in the high-strength pillar and goaf stability of Wancheng lead-zinc mine. The reasons for the occurrence of ground pressure and the corresponding measures have been formulated, which have important guiding significance for the safe production of mines.
references:
[1] Peng Fuhua, Cheng Jianyong, Jia Baoshan, et al. Feasibility study of multi-channel microseismic monitoring in D mining area of ​​Sandaozhuang Open-pit Mine [J]. Mining Technology, 2013, 13(1): 33-36.
[2] Peng Fuhua, Li Yulin, Cheng Jianyong, et al. Microseismic test study on stress wave propagation characteristics of mesoscale complex rock mass [J]. Chinese Journal of Geotechnical Engineering, 2014, 36(2): 312-319.
[3]Peng F, lin F, Hu J, etc. Indexes of mine microseismic and their application in safety assessment by statistiacl e valuation at Luomu mine [J] . The 13th Internatio nal Symposium on Rock Mechanics. Montreal, Canada, May 2015.
[4] Li Yulin. Discussion on the application of microseismic monitoring technology in underground engineering [J]. Journal of Underground Space and Engineering, 2009, 5(1): 122-128.
[5] Feng Xiaodong, Yang Shun. Multi-channel microseismic monitoring system of Wancheng lead-zinc mine and its research [J]. Mining Technology, 2014, 14(4): 54-57.
[6] Yuan Jieping. Discussion on the necessity of multi-channel microseismic monitoring technology in Shizhuyuan [J]. Mining Technology, 2009, 9(1): 66-69.
[7] Fu Zhanyu, Peng Fuhua. Feasibility study on acoustic emission monitoring of overburden stability in goaf [J]. Mining Technology, 2011, 11 (4): 77-79.
Peng Fuhua, Yang Shun; Changsha Mining Research Institute Co., Ltd., Changsha 410012, China;
Source: Mining Technology: 2016, 16(2);
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