Abstract:
In order to grasp the composite deformation characteristics of multiple mining overburden of coal group and its influence on the stability of vertical gas well through coal seam, taking the cross-mining area of Xiaobaodang No.2 coal mine as the engineering background, a similar simulation test was carried out to study the composite fracture characteristics, fracture distribution and settlement rule of overburden under the influence of multiple mining of coal group.The influence of shear dislocation between hard and soft rock strata at different working distances on gas well stability is analyzed.The results show that the strata between multiple mining strata are seriously damaged, and the initial caving and periodic caving steps of lower coal seam are smaller than those of upper coal seam.The complex movement of overlying rock in lower coal seam spreads to the key layer and the surface, and the mining distance is shorter than that of the mining face in upper coal seam.The settlement curve of overlying rock in each coal seam is in the shape of “basin bottom”,which is symmetrical about the center of the goaf.With the increase of the distance of the working face pushed through the gas well, the shear stress between the soft and hard rocks along the axial direction of the gas well increases gradually, and the maximum shear stress finally appears between the soft and hard rocks near the key layer and the sub-key layer.The shear stress caused by the first slip dislocation between the rock strata caused by the first mining movement is larger than that caused by the repeated shear dislocation of the compacted overburden rock caused by the multiple mining movements, but the shear deformation of the gas well caused by the multiple mining groups is more frequent, but the intensity is weakened.The research results can provide useful reference for optimizing coal seam group mining design and ensuring the stability of gas wells through coal seam groups in coal-natural gas cross-mining area.