Surrounding rock control mechanism in the gob-side retaining entry in thin coal seams, and its application

Gob-side entry retention can decrease mine driveage ratio and eliminate the adverse effect of stress concentration on coal pillars that support a roadway in a thin coal seam.Gobside entry retention is an important development for non-coal pillar mining in China, since it decreases the stress reduction area to achieve a Y-ventilation system for the working face, which the transfinite gas problem at the face (Xie, Zhang, and Gao, 2016.The yield and mining efficiency in thin coal seams can be improved by increasing the mining rate, in situ gangue backfilling, and relieving lifting and transportation pressure on the mine (Li, Yang, and Liang, 2011).Many researchers have conducted longterm and in-depth investigations of gob-side entry retention.Roadside filling bodies have been developed from gangue picking for wall building, dense individual props, and concrete blocks to novel support materials such as high-and ultrahigh-water materials and pasty fluid materials (Mohammad, Reddish, and Stace, 1997; Golshani et al., 2007).Support modes in roadways have developed from shedtype support systems, like I-beams and Ushaped steels, into the present high-strength anchor bolt support system, which has been successfully applied in many mining regions in China (Mark et al., 2007; Schumacher and Kim, 2014).The retention roadway along the gob is influenced by the intensive mining of the working face and the next working face.Stress from extensive mining causes failure of the roadside filling body and intense deformation of the roadway, and complicates maintenance (Chen, 1994).In addition, a high driveage ratio and large gangue content are prominent problems that restrict the mining of thin coal seams that are developed along geological structures such as faults.