1.Introduction
The northern boundary of Qinglong Coal Mine second mining area and the adjacent area of Tuomeihe River have a wide area of surface carbonate rocks, most of which are exposed or semi- exposed. Karst depressions, karst buckets, karst pools and karst springs are well developed. Karst caves are locally developed underground. Thus, potential underground rivers are not excluded. In 2017, the mine side constructed 6 water exploration and drainage boreholes near the bottom contact roadway of No.2 Mining Area, of which 4 boreholes produced water about 60m after construction, with the maximum water yield of about 150m3/h and the water pressure of about 2.5MP. The possibility of communication with the surface river Tuomeihe reservoir is not ruled out. Therefore, the exploration of Changxing Limestone Water Bearing/rich and low resistance abnormal area with water channel characteristics in the circle section and the research on the water rich characteristics and control technology of karst development in the second mining area are urgently needed. The research is related to the safety production of Qinglong Coal Mine. Ground transient electromagnetic method is used to detect the water bearing/rich abnormal area of Changxing Limestone within the specified range, and to predict the potential water channel, which can provide reference for the research of this subject.
2.Treatment solution
Due to the limitation of different topographical and geological conditions, water carrying structures and discharge conditions, the distribution of water bearing and water rich properties is uneven. Therefore, it is necessary to use the transient electromagnetic method which is sensitive to water bearing body to explore the above areas.
3.Construction situation
The exploration area is about 1.2km²。In this exploration, 1698 TEM physical points were actually collected, including 26 test points and 51 quality inspection points, with a control area of 1.2km².
Digital topographic map of exploration area
4.Achieved accomplishment
Based on the processing of TEM data, combined with drilling, related maps and other geological data of each layer, the low resistivity abnormal area in the target layer is comprehensively analyzed. On the basis of inversion resistivity data, the distribution range of low resistivity abnormal area in the target layer is explained, and the water bearing/rich property of low resistivity abnormal area in the target layer is summarized and inferred. The main results are as follows.
a).Six low resistivity anomaly areas were found in Changxing Limestone Formation. It is inferred that the anomaly are related to water bearing/rich karst fissure.
Abnormal plannar of main aquifer
C-1 low resistivity anomaly area is located in a large area in the southwest of the survey area, with strong anomaly intensity and obvious banded characteristics. It can be divided into two branches in the process of extending to the southeast. According to the hydrogeological data collected from the second mining area of the mine, it is known that the drilling fluid leakage is large during borehole surface drilling process in the area. In addition, there are 6 water exploration and drainage boreholes near the bottom connecting roadway of the second mining area in the abnormal area. Among them, water inrush were encountered when drilling at about 60m, with 150m3/h maximum water output and 2.5MP pore water pressure. The water comes from the Changxing Limestone layer, which indicated that the abnormal area might be supplied by the water from Tuomeihe River. Moreover, in the southeast of the strong anomaly area, the drilling fluid leakage during drilling z4-2 is more than 15m3/h, and the exposure shows that karst and fracture are developed in the anomaly area.
For C-2 to C-6 low resistivity anomaly area, it is inferred that it may be related to the relative development of karst and fracture, and local water bearing/rich.
Resistivity anomaly stereogram of main aquifer
b).Six low resistivity abnormal areas were found in the abnormal plane 30 m above the top boundary of Changxing Limestone Formation, and six low resistivity abnormal areas were also found in the abnormal plane 80 m above the top boundary of Changxing Limestone Formation. Compared with the plane abnormal characteristics of the above two horizons, the downward abnormal range has the trend of increasing and the intensity of increasing. It is inferred that the downward water abundance has increasing trendency.
c).Combined with the results of cross-section and upper & lower level plane anomaly, the low resistivity anomaly area with the characteristics of water channel is inferred and interpreted.
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