| Rich water in limestone of coal seam floor is a major hidden danger that affects the safety of coal mine production.When there are hidden structures such as fractures,karst caves,collapse columns and faults in limestone,it is easy to develop into a hidden water channel.Under the influence of mining conditions,the water pressure on the bottom plate also increases,which is prone to flooding accidents,causing casualties and production equipment damage,seriously threatening the safety of coal mine production.At 13:00 p.m.on September 6,2017,the water and gas injection accident occurred when the drainage water from the drilling hole to the ash water of the 2 # drilling field of the East Wing bottom drainage lane in the fourth mining area of Hexi coal mine of Shanxi Coking Coal Fenxi Mining Group was constructed to 14.5m.Therefore,it is necessary to detect the water content of floor limestone.This paper is to study this.On the basis of summarizing the principles,methods and characteristics of mine TEM,GPR and HDE,combined with the geophysical characteristics of the strata in the study area,the paper has carried out the comprehensive geophysical exploration tests of three methods: Mine TEM,GPR and HDE.According to the field test,TEM is not feasible because L5 limestone in the main target layer is in the detection blind area,so the comprehensive geophysical exploration technology of GPR and high-density electrical method is determined.Based on the theory and software of GPR and high-density forward modeling,and according to the existing geological data in the study area,the stratigraphic model of the area is established,on the basis of which the geological body model of karst cave,fracture fracture and fault fracture zone is established,and the forward modeling is carried out respectively.The GPR forward image characteristics of the model and the low and high resistance response of high-density electrical method are analyzed and summarized.According to the simulation results,the GPR can identify the structure and horizon by image features,and preliminarily identify the water bearing property;the high-density electrical method can determine the water bearing property by low resistance and high resistance response,and has insufficient ability to identify the structure.Based on the response characteristics of GPR and high-density electrical method forward simulation,combined with geological data,the data processing results of the two methods are analyzed comprehensively,and three anomalies of water-free karst cave,water-bearing fault and water-free fracture development are explained.The results show that the underground comprehensive geophysical prospecting method combined with GPR and HDE is an effective geophysical prospecting method for detecting water rich limestone in short distance coal seam floor. |
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