Top coal cracking and migration law of fully mechanized top coal caving mining face in steep inclined and thick seam strike

In order to keep the stability of the support system in the fully mechanized top coal caving mining face in the steep inclined and strike seam and to improve the top coal recovery rate,the UDEC2D program and site observation and measurement method were applied to the research on the top coal cracking and migration.The results showed that the coal and rock in the top and meddle section of the coal mining face were failed in a large area,seriously cracking,far to the initial start area.The top coal movement at the front of the coal wall were a complex movement with the horizontal displacement and vertical displacement along the strike of the seam.Above the hydraulic powered supports,the movement was the complex displacement with the horizontal along strike,inclined level and vertical level.In the production,the measures to prevent the falling and sliding of the hydraulic powered supports in the top and middle section of the coal mining face shall be enhanced and the downward section of the coal mining face,the top coal caving operation shall be enhanced.The top coal recovery rate shall be improved.