Experiment on mining upper limit improvement for fully mechanized longwall top coal caving mining face with thin overburden bedrock in Yangcun Mine

A borehole water injection method was applied to probe the mining failure height of the strata after the coal mining operation of the fully mechanized longwall caving mining face in Yangcun Mine and also to probe the bedrock pillar thickness in the direct roof No.305 coal mining face.A radio wave gateway perspective method was applied to predict the hidden small faults and the extension condition in the coal mining face.Based on those circumstances,the safety sand prevention coal pillar of No.305 coal mining face was designed as 30 m in wide and the related safety mining plan was made.With the experiment obtained,the fully mechanized coal caving mining face in No.3 seam was successfully increased the upper mining limit in the mine.