Study on the safety pillars under water-bearing strata using fully mechanized sub-level caving method in Taiping coal mine, Shandong province, China

The engineering geological model and numerical simulation models for fully mechanized sublevel caving under thick unconsolidated water-bearing strata, are, constructed to predict and simulate the stress distribution and the extent of failure zones in the overlying rook mass. The distribution of the principal stresses in overburden rock mass is divided into three types. The failure conditions of overburden are classified into tensile cracked area, tensile-Assured area, and plastic deformation or shear fractured area. The extent and height. of water flowing fractured zone can be determined on the stress distributions and failure conditions. Based on the calculation results and comprehensive engineering geological and hydrogeological evaluation, the height of safety pillars under water body of mining thick coal seam No. 3 in Taiping coal mine is then defined to be 60m, which is the minimum size of pillars in similar geological and mining conditions in Yanzhou coalfield.