Fracture Characteristics and Mining Height of Overlying Strataunder Water Rich Extra Thick Sand Conglomerate

In order to determine the safe mining height of 2601 working face in Gangou Coal Mine under the influence of water rich extra thick sand conglomerate,the height of hydraulic fracture zone of the working face was studied by using the method of field measurement,theoretical analysis,numerical simulation and similar simulation experiment.The results show that the measured split ratio of overlying strata of the working face in Gangou Coal Mine is 7.5,the hydraulic fracture height of the overlying strata of 2601 working face under different mining heights is calculated with the split ratio 7.5,and the upper limit of the safe mining height of the working face is set as 5.0 m;under the condition of set mining height of 5.0 m,numerical simulation and similar simulation experiments are used to further verify that the overlying strata failure height is 40.0 m and 37.0 m respectively,the result is similar to that predicted by using the split ratio of 7.5,indicating that it is feasible to determine the mining height of 2601 working face as 5.0 m.