Study on Movement and Failure Law of Overlying Strata of Fully Mechanized Top Coal Caving Face in Shallow Medium-hard Extremely Thick Coal Seam

Taking Suancigou coal mine as test mine,deep base point and numerical simulation test was conducted to study the movement and failure law of overlying strata under mining effect. The results show that,the heights of overburdentwo zones,in top coal caving of Suancigou coal mine,were 49m and 133m; from coal seam to earth surface,as the depth decreases,the starting time of rock movement lags,and except some basis points,the absolute displacement of base points shows a decreasing trend; during overlying strata movement,most of the base points shows 1 to 4 wave peaks,among all of the three boreholes,the absolute speed of ZS1drilling overlying strata is the biggest,implying there are two forms of sinking,the rapid sinking in short period,and the staged non-uniform sinking in long period.