Study On Damage Mechanics Of Mining Cracks And Control Methods In Shallow Coal Seam

The mining area locates in the transition zone of Maowusu desert and hill ravine of loess plateau in Shanbei of China. There are thick loose beds, droughty, short of the rain and little vegetation, more aeolian sands on the ground surface in the mining area. The groundwater resource is very rich, most of which lie above the bedrock of the roofs. The seam of the mining area that has the characteristics of shallow imbedding, thick mining, thin bedrock and thick loose beds is a typical shallow seam. In this condition, mining will result in a series of geology and environment calamity. For example, the surface cracks and the cave-in pits, the aquifers leaking, the destroyed water resource, the serious soil erosion and the desertification, etc. The problems, which badly harm the property of nation and people, are researched and solved to the continuable development of the mining area.In this paper, by investigation of engineering geology condition and summarizing of mining damage actuality about shallow seam in the Yushen mining area, the physical mechanics characteristic of overburden rock and the rules of mining damage are analyzed. Based on the key strata theory of the ground control and analyzing the condition of geology and mine in the shallow coal seam, the characteristic parameters of the key strata are educed. By FLAC^3D numerical analysis, the characteristic parameters of the key strata and the control mechanism of the key strata to the overburden rocks are discussed. The position of key stratum and the rules of the displacement and deformation are presented by numerical analysis. It is indicated that the method of the numerical analysis is simple and effective. Its simulation results tally with the theory calculation.Based on the spot observation, the mechanic analysis model and UDEC numerical analysis model are founded. The condition of the sliding instability and the gyration instability is analyzed. The surface crack and the step subsidence are caused by the block...