Research on location optimization and application of the gob-side entry retaining by roof cutting in close-distance coal seams

Compared to traditional long-wall mining, the gob-side entry retaining by roof-cutting (GERRC) technology reduces the amount of entry excavation by 50%, and recovers the previously wasted coal pillar resources, which has obvious superiority in mining efficiency and economic benefits. In response to the problem of reasonable entry location of the GERRC in close-distance coal seams, this paper takes the 9105 Working face in Longmenta Coal Mine as the engineering background and conducts an in-depth study by using methods such as theoretical analysis, numerical simulation and field tests. Firstly, the structural characteristics of the overburden rock for GERRC in the close-distance coal seam are analyzed, based on which a method for determining the reasonable location of the GERRC in close-distance coal seams is proposed; secondly, a mechanical model for load transfer and rock mass damage of the upper coal seam floor was established to analyze the floor damage characteristics and stress distribution law, forming the theoretical analysis of the reasonable entry location; Finally, the optimal entry location (22.5 m from the center of the upper remaining coal pillar) was used for field test of GERRC at the 9105 Working face of Longmenta Coal Mine. It has achieved good on-site application results.