Research on the mechanism and control of roof deformation in gob-side entry retaining of close-distance coal seams

Abstract

Multiple mining operations in close-distance coal seams (CDCSs) can reduce the integrity and bearing capacity of the surrounding rock, leading to roof fracturing and widespread subsidence in gob-side entry retaining (GER). This highlights the critical need for research on roof control technology. For this purpose, adopting the panel of the Xinchazhuang Coal Mine (the distance between two coal seams is 7.3 m) as the engineering background, a theoretical model of GER of CDCSs was established on the basis of the surrounding rock structure and roof rock movement characteristics, and the roof failure deformation mechanism was examined. The roof failure deformation encompasses two parts: rotational sinking of roof rock blocks and roof separation deformation. To achieve roof control, a strategy involving optimized roof cutting and higher preload cables was suggested. The impacts of key roof control parameters on roadway deformation were examined and compared by numerical simulation studies. The findings showed that optimized roof cutting resulted in a 21.1 % reduction in the roof stress, whereas the use of roof cables with higher preload levels resulted in a 55.1 % decrease in roadway deformation, effectively mitigating rotational sinking and roof separation deformation. The field tests demonstrated that the optimized scheme facilitated roof integrity preservation, and the maximum deformation of the roof reached 98 mm, a decrease of 68.5 % on average from that in the original scheme. These research results could provide a reference for roof support in CDCSs roadways under similar geological conditions.