An innovative approach for gob-side entry retaining in deep coal mines: A case study

Abstract

Due to the complex geostress and mining conditions in the coal seam with depth of 800 m, stability of surrounding rock for gob-side entry retaining is very difficult to achieve. In this paper, we firstly propose an innovative bolt-grouting controlled roof-cutting for gob-side entry retaining (BCR-GER) approach for deep coal mines. Secondly, a mechanical model of “surrounding rock-supporting body” for BCR-GER is constructed, which consists of coal wall, roadside props, and gangues in gob (the whole supporting body). Thirdly, the key parameters (ie, cutting height, cutting angle, grouting cable length, and row of roadside props) are designed. Finally, field practice was applied at the No. 31120 haulage roadway of the Suncun coal mine in China, and in situ investigations were conducted for verification. Field measurement results show that maximum convergences of roof-to-floor and side-to-side were 264 mm and 113 mm, respectively. What is more, the maximum support resistance of roadside props was reduced by approximately 58%. The deformation and failure of surrounding rock were effectively controlled, and the pressure on roadside props was greatly reduced. This research fully considers the bearing properties of gangues in gob, eliminates the secondary disasters caused by borehole blasting, and provides guidance and reference for deep surrounding rock control of the same or similar gob-side entry.