Majority of the coal seams in Urumqi coal field, located in Xinjiang Province, China, are dipping about or above 45 degrees, called steeply dipping coal seams. The maximum width of the coal seams group is about 50m, and the minimum width is only 20m. and the vertical height is more than 400m. At present, the mining method used for these seams is the horizontal section top-coal caving mining. In this paper, the caving effect of steeply dipping and thick coal seams after weakening are studied with numerical simulation. The migration path and the falling quantity of discrete coal particles are analyzed and the distribution characteristics of hinged force between flowing blocks are intuitively presented. The load change of supports in the process of topcoal caving is monitored in real time, and the expression equation for caving space in flow model is established. The mining practice shows that the coal mass can be separated by using the advance pre-blasting method, which improves the top-coal recovery rate and reduces the loss of resource.

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