关键词: 切顶留巷, 贯通采空区, 瓦斯富集区, 覆岩裂隙, Y型通风

Abstract:

To investigate the effect of Y-type ventilation in a gob-side entry retained by roof cutting on gas enrichment and distribution characteristics in a connected goaf, a high-gas mining face in the Huangling mining area was selected as the engineering background.. The overburden fracture distribution after goaf connection under gob-side entry retaining by roof cutting was simulated and analyzed using 3 Dimension Distinct Element Code(3DEC). A geometric model of the connected goaf was established. The effects of different air volumes under Y-type ventilation on gas enrichment zones in the connected goaf were investigated using Fluent. Based on the fracture characteristics, efficient gas extraction zones were determined. A directional long-borehole gas extraction scheme across the working face was designed. The results show that the caving zone on the roof-cutting side and the fracture zone on the non-cutting side of the 1009 goaf exhibit a high degree of fracture development. After the 1010 working faces is mined out, the two goafs are connected and form a connected goaf. The overburden subsidence further increases. When the air volume in No. 2 roadway is increased alone, the length of the low-gas zone along the strike of the goaf increases. The gas on the roof-cutting side along the dip direction is less disturbed. When the air-volume ratio between the main intake roadway and the auxiliary intake roadway is 2∶1, the length of the low-gas zone at different levels of the connected goaf increases 51.5-76.2 m with increasing air volume.During mining, the directional long boreholes across the working face enter a stable high-volume-fraction stage when they lag 178.3-190.5 m behind the working face. The average gas extraction volume fractions drilling sites are 52.6% and 48.3%, respectively. The overall gas extraction effect is good.

Key words: roof cutting and roadway retaining, connecting goaf, gas enrichment area, overburden fissures, Y-type ventilation method