Experimental investigation on the movement mechanism of top coal in steeply inclined ultra-thick coal seams

The pre-blasting zones have a significant influence on the coal broken and the recovery rate of the top coal caving mining.This paper explores the coal movement mechanism in the top coal with pre-blasting zones based on the geological parameters of Jiangcang No.1 mine in the western of China.The steeply inclined ultra-thick coal seam was mined by using the sublevel top-coal caving mining method.The geo-image process system(GIPS)software was used to track the mark points on the coal and roof.The support was used to record the load on the top of the support during the caving mining process.The results show that the horizontal coal is moved to the shield window and the vertical coal is moved downward in the first level,while that in the second level shows consistency for the integrity of the coal.The vertical displacements of the corresponding points in the first level are lairger than that in the second level.However,the load on the top of the support in the first level is smaller than that in the second level.It indicated that the pre-blasting zones will give a more loosen top-coal and a small degree of difficulty in the top coal caving.