The new stopping methods,or pseudo-declivity mining,upper entry forging ahead and lower entry forging ahead extraction methods,are adopted to recover triangle coal for the purpose of reducing the loss of coal and enhancing the recovery ratio,which has ensured to reduce the loss amount of coal to the minimum and raised economy benefits for Xinli mine.

Based on the actual state in Fengshuigou Coal Mine, provides the technology ways of lifting coal extracion rate, which are reforming coal winning machine, reducing thickness loss, adjusting mining triangle coal, reducing area loss, reforming extraction process and extracting goaf.

This paper has studied the top coal caving below roof and floor for horizontal section top coal caving in steep seam,and has analyzed the losing of triangular coal below roof and floor,and has researched the boundary state between coal and rock.

Based on theory analysis and practical survey in testing ground,had studied influence factors such as caving height,work resistance of supports,coal seam rupture angle,main roof rotary angle and stopping mining time.