Feasibility study on fully mechanized large mining height long wall top-coal caving mining in ultra-thick (20-30 m), parting-rich coal seams: A case study of the Laosangou mining field in China

To analyze the feasibility of fully mechanized large mining height long wall top-coal caving mining (LLTCC) in ultra-thick (20-30 m), parting-rich coal seams, a case study on No. 6 coal seam of the Laosangou mining field was conducted. First, the distribution pattern of the coal-seam structure was mastered and generalized based on the coal-seam thickness, parting thickness, and parting horizon. On this basis, physical simulation and UDEC simulation were performed to analyze the top-coal fracture characteristic and the impact of partings. The top-coal caving of No. 6 coal seam was systematically evaluated with statistical results of coal-seam recovery height (hre) and mining-caving ratio (Rmc). Finally, the range of mining height (h) at LLTCC faces was determined as an indicator for the division of LLTCC feasible regions in the Laosangou mining field, which is based on the Rmc, hre, coal-wall stability, and equipment selection. The results show that the top-coal caving structure of LLTCC faces can be divided into four layers which were effected by top-coal thickness and upper-horizon partings. LLTCC in ultra-thick (20-30 m), parting-rich coal seams was highly feasible. The top-coal cavability of No. 6 coal seam was good overall, and the Rmc was about 1:2.89-1:3.91. Direct mining regions (h = 4.0-5.3 m) and buffer mining regions (h = 5.3-6.0 m) of LLTCC were 52.66% and 42.96%, respectively. This study can be used as a reference for the design of LLTCC in similar coal mines.