Selection of Rational Mining Height in Shallow Coal Seam With Thin Bedrock

In order to determine the reasonable mining height in shallow coal seam with thin bedrock, the article analyzed different mining height effect on Shendong trial coal mining face which the shallow buried depth of coal thickness is 5.7 m by theoretical calculations and numerical simulation method. Analysis results demonstrate that mining height is small, the roof is prone to sliding instability, but with the mining height increases, the instability of the rotation angle increases and caving and fractured zone expansion is upward, loose sand overlying layer can not form a stable structure after the bedrock breaking, and eventually lead to "pressure frame" accident. Finally it got that the rational mining height of this working face is 4.5 to 5.0 m.