In order to understand the top-coal movement law influenced by caving sequence in steeply dipping seam, taking NO. 1201 working face of Shanxi Dayuan coal Ltd. as engineering background, established the PFC2D numerical model and simulated caving process under three different caving sequences: caving from top to bottom, caving from bottom to top and mixed caving sequence. The characteristic of recovery ratio, top-coal draw body and the boundary of coal and rock under the condition of steeply dipping seam are obtained from the simulation. The results show that the recovery ratio is the lowest when caving from top to bottom, while it is the highest when caving from bottom to top; the top-coal draw body has the tendency of developing towards the top of working face; the boundary of coal and rock shows significant asymmetry during the developing process; under the condition of steep coal seam, the top-coal at the top-of working face left blank seriously, which has a significant impact on the stability of the air-return way, so special measures are suggested to reinforce the top-coal above the air-return way.
With the exhaustion of the eastern mining area's coal resources, the focus of coal mining in our country gradually shifted to the west part of China, and the occurrence conditions of coal seams in west part of China are complex, the steeply dipping and steep seam are widely distributed in western China (Wu 2001). Therefore, the research which focuses on the top-coal movement law of steeply dipping seam caving mining technique has important significance to ensure the security and efficiency in the caving mining and to improve the resource recovery ratio. At present, many scholars have conducted researches on the law of top-coal movement under the steeply dipping seam condition and the failure mechanism of the top-coal (Wang et al. 2006, Wang et al. 2013). However, the former researches on the top-coal movement law under steeply dipping seam conditions always place extra emphasis on the analysis of top-coal recovery ratio, while rare researches have been conducted on the aspect of combination with top-coal caving pattern and evolution about boundary of coal and rock (Wang et al. 2005, Yang et al. 2010).