The reasonable layer selection is the main influencing factors for gas drainage by high level borehole, the borehole parameters is based on the caving & fracture zone height of gob.
高位钻孔抽放最主要的影响因素是合理层位选择，其钻孔参数应根据采空区冒落带及裂隙带高度来设计。
2
Based on this case, through filling the gob area by means of chamber blasting, the requirement of protective top - layer for slicing and caving can be achieved.
针对这一情况，从药室爆破放顶充填采空区，从而达到分层崩落法采矿的护顶层要求。
3
Nitrogen injection to the gob with buried pipes is used in 7235 full-mechanized caving mining face in Xuzhuang Colliery to prevent the left coal oxidizing and self-igniting.