Abstract: To solve the security problem of fully mechanized mining with sub-level caving in the super-thick coal seam under the reservoir, by the flushing fluid leakage measurement in surface borehole and detection of EH-4 continuous conductivity profile instrument, the overburden failure features and water filling states before and after N1S1 Coal Face mining in Daping Coal Mine were detected, and the deformation and failure features of overburden were retrieved and simulated by using RFPA2D Software. The results show that the permeable fractured zone is developed in the vertical pressure-relief and horizontal tensile zone of rock stratum above goaf, while the top interface depth is 220.92 m, and the average flushing water leakage in borehole is 0.50~0.71 L/(s•m).Meanwhile, the weak water-bearing section in the lower part of Cretaceous sandstone and sandy conglomerate confined aquifer is located in the fracture zone, while the rock strata below the depth of 200 m are in the state of water filling, and the apparent resistivity is 20~40 Ω•m. In addition, the rock strata which are above the permeable fractured zone, and below the depth of about 120 m, are in the states of vertical pressure-relief and horizontal compression, as well as bed separation development, and no water filling. Thus, the coal mining under the reservoir is safety and reliable.

Key words: coal mining with sub-level caving, overburden failure, permeable fractured zone, flushing fluid leakage, apparent resistivity