Experimental Study On The Regularity Of Crack In Loess Slope Induced By Underground Coal Mining

China’s loess area is rich in coal resources.Loess geo-hazards induced by underground coal mining occurred frequently.Landslide is the most common type of geological hazard.Previous study results show that the surface deformation and the strength deterioration of fissured loess caused by coal mining are main cause of landslide formation.However,the laws of cracking of loess slopes caused by underground coal mining is still unclear.Therefore,the fissure development laws in loess slope under different mining depth and thickness ratio are studied combining numerical simulation and physical model test.The research results will provide theoretical support for the formation mechanism research of loess landslide caused by underground coal mining.Research result indicates:(1)The mining depth-to-thickness ratio is the most important factor affecting the fissure development in loess slope.The smaller the mining-thickness ratio,the higher the degree fissure development.However the mining depth-to-thickness ratio is less than a certain value,the slope shape will become the main factor,because the key layer of the bedrock overlying the coal layer is destructed caused by the underground coal mining.(2)The fissures in loess slope caused by underground coal mining exists in two forms: near perpendicular to the slope surface and near horizontal to the slope surface.When the mining depth-to-thickness ratio is smaller,with the increase of slope gradient and the erosion of slope,the vertical cracks with the slope surface increased obviously.When the mining depth-tothickness ratio is larger,with the increase of slope gradient and the erosion of slope,the horizontal cracks with the slope surface increased obviously and the vertical cracks with the slope surface decreased.(3)The maximum displacement of the loess slope caused by underground coal mining is located near the slope surface.As the slope becomes steeper,the maximum displacement of the linear slope transferred from the middle of the slope to the slope and shoulder.For the gentle convex slope,the maximum displacement of the slope body occurs at the convex part of the slope.(4)After the key layer of the bedrock overlying the coal layer destructed by the underground coal mining,the gradient change of convex slope is larger than that of straight slope.