ABSTRACT
During the mining process of the first mined coal seam of loose and soft gassy coal seam groups with low air permeability, fractures due to caving and shifting of the rock strata of roof and floor lead to pressure relieving and desorption of a great deal of gas in the mining coal seam and the adjacent coal seam. Due to the buoyant characteristic of the coexisting gas seepage flow and the surrounding air, the great low pressure gas accumulates into the fully developed zone of the fracture and forms a accumulation pool in the annular fracture ring. In this paper, we discuss the location method of the position of the annular fracture ring, analyze the accumulation process of the gas bulk in the fracture ring and give the highly effective drainage technology with drainage drills and roadways laid in the annular fracture ring of the first mined coal seam.
