Analysis of stress evolution law and large deformation mechanism in surrounding rock of gob-side entry retaining

Aiming at the serious deformation of surrounding rock in gob-side retaining due to the redistribution of stress caused by two working face during its service period, the deformation characteristics of the surrounding and the stress evolution law were investigated by finite analysis based on the case study conducted in Qinxin mine. The reasons for the large deformation of surrounding rock were summarized based on the damage effect of rock by loading and unloading cycles. Combined with this research, two conclusions have been drawn as following: ① in order to adapt to the roof collapse of the first working face and form a stable bearing structure, the continuous deformation of surrounding rock caused by the difference of mechanical properties between roadside support and integrated coal beside roadway was the main component of the large deformation of gob side entry retaining surrounding rock; ② the surrounding rock experienced three times loading and unloading cycles in axial direction for gob-side entry retaining in whole service period. Deformation and destruction of surrounding rock were intensified as consecutive loading-unloading cycles under unloading confining pressure, and which was also a process of accumulation of surrounding rock deformation. This was the key reason that caused the large deformation of gob-side entry retaining surrounding rock as well.