Abstract
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.
Highlights
Occurrence of ultra-thick coal seam is a common phenomenon
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
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
Summary
Occurrence of ultra-thick coal seam is a common phenomenon. Coalfields with single seam thickness of more than 20 m distribute in major coal-mining countries and regions such as China, United States, Russia, Eastern Europe and Southeast Asia. Wu et al [14] studied genesis of ultra-thick coal seam in typical fault basins, and believed that the allochthonous accumulation of peat caused by storms, gravity flow and underwater debris flow played a very important role in the development of ultra-thick coal seam. They established the genetic model of allochthonous accumulation in deep water environment of ultra-thick coal seam. Based on distribution and occurrence characteristic of ultra-thick coal seam in Xinjiang, this paper theoretically analyses the variation characteristic of the support load under different roof bearing structures, classifies ultra-thick coal seams according to the occurrence conditions, and puts forward the appropriate mining technology. The results will provide a guideline for the mining area construction and coal mining method selection under similar mining conditions
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