Study on Overlying Rocks' Movement Laws of Ascending Mining Thin Coal Seam in Closed Distance Coal Seam Group

In order to upward mine abandoned coal resources securely and effectively,according to the coal seam occurrence condition and present mining situation of Zhangjiazhuang coal mine in Fenxi,failure and movement laws of overlying rocks were studied by theoretical analysis and UDEC discrete element numerical software simulation when 10^# coal seam and 9^# thin coal seam were mined respectively.Overlying rocks' movement and deformation laws of two kinds of typical lithologic structures mudstone and limestone were contrasted and analyzed.By monitoring overlying rocks' displacement changes as excavation goes when coal seams were mined,the paper draws a conclusion that the mining stable time of mudstone lithologic structure overlying rock is shorter than the time of limestone lithologic structure overlying rock,which is consistent with the real situation.