The scientific and efficient mining of ultra-thick coal seam in Xinjiang, China is faced with the problems of low exploration level and lack of theoretical research on underground mining. This paper studied occurrence characteristic of ultra-thick coal seams in Xinjiang, using field investigation and drilling exploration. Based on the variation law of support load under different roof bearing structure form and development height in multi-layer mining, classification method and mining technology selection of ultra-thick coal seam were put forward. The results indicate that: 1) The ultra-thick coal seams in Xinjiang have a distribution characteristic of more north and less south, more east and less west, mainly concentrate in East Junggar and Turpan-Harmi coalfields. The form of the ultra-thick coal seam has the remarkable characteristic of coal seams merging and bifurcating. 2) The mechanical model of the relationship between the support and surrounding rock under different roof bearing structures is established. At the early stage of multi-layer mining, the support load includes the load caused by rotary subsidence of the blocks that formed the near-stope roof bearing structure and the gravity load of rock blocks under roof bearing structure. At the later stage, the support load is mainly gravity load of loose blocks below the far-stope roof bearing structure. 3) According the roof bearing structure form, ultra-thick coal seam can be divided into three types: no stable bearing structure, (higher) beam bearing structure and arch bearing structure. In order to ensure the stability of near-stope roof bearing structure, backfill mining, longwall mining, and longwall mining early and backfill mining later should be adopted in three types ultra-thick coal seams mining respectively.
Monitoring strata behavior due to multi-slicing top coal caving longwall mining in steeply dipping extra thick coal seam