Overlying Strata Removing Regulationg Of Unstable Thick Soil Layer Thin Bedrocks Shallow Coal Seam And Support Resistance Confirmation

Based on the typical occurrence character, shallow depth, thin bedrock and overlying thick epipedon, in Shendong coal mine, the paper analyzed systematically the overlying rock movement law and coalface support resistance under different combined conditions of bedrock and overlying epipedon thickness by theoretical analysis, numerical analysis, physical simulation and the analysis of field measurement etc.The results show that first caving interval of immediate roof and first weight interval of main roof(the former is about 65 meters, the latter is about 103 meters) are quite large during the mining of thick soil layer(20～80 meters) shallow seam coalface, which brings large threat to coalface safety production; and with the increment of the bedrock thickness, the first caving interval of immediate roof , first weight and periodic weight interval of main roof all will increase, and ground pressure behavior will becomes more stronger. If the thickness of roof bedrock was less than 70 m, the thick soil layer easily appears bed separation with bedrock in some advance distance. But, with the coalface going on advancing, mining fissure constantly develops and reaches ground surface quickly; If the thickness of roof bedrock was than 70 m, mining fissure can't reach surface, ground pressure of unstable thick soil layer thin bedrock shallow seam coalface appears relatively alleviation, under enough support resistance, the coalface will not appear bench subsidence along the coal wall. At the same time, theory analyses thick soil layer shallow seam structure, considers that it can not use voussoir beam theory to compute the force of supports. By studying on equilibrium condition of key rock in the fracture rockpillare, the mechanical model of key rock structure is established, theoretical formulas of rational support resistance during the mining of thick soil layer shallow seam coalface is obtained and verified by field practice.This research results were successfully applied in 6-2101 large mining height first coalface of Na Linmiao NO.2 coal mine in Yitai group, which supplies some theoretical basis and practical guidance for mining overall height in one times in thick coal seam in similar conditions.