Study on the structural characteristics of the overburden under thick loose layer and thin-bed rock for safety of mining coal seam

The geological conditions of the first working face at the Baodian Coal Mine of the Yanzhou mining district in China are examined to determine the feasibility of modifying coal pillars that prevent water seepage to those that prevent sand flow. The coal pillars are under a thick loose layer of sediment and thin layer of bedrock. After analyzing the structure of the rock and soil mass above the coal seam, the thickness of the bedrock, bottom clay layer and bottom aquifer of two detecting roadways are discussed. At the center of the Xingxing anticline, the thinnest of the bedrock is only about 30 m. However, the thickness of the bottom clay layer is at least 10 m and more, and the Jurassic rock (sandstone) is the thinnest with low levels of water and a layer of weathered material. The bottom aquifer has low water yield with no pressure. The similarity theory is used to construct a prototype with 30-m-high bedrock. The conclusion is that the height of the caved zone height is about 21.3 m after the complete extraction of no. 3 coal seam, and the results are in agreement with the experimental data. The results show that it is feasible for the first working face to use a coal pillar to prevent sand flow. Moreover, the findings in this study can act as an important reference source for predicting the height of the overburden that would cause damage and reasonable advancement of mining that is considered to be safe under similar geomining conditions.