Study on space-time evolution mechanism of deformation and failure of lower roadway in close residual coal pillar area based on deviatoric stress field distribution

This study investigates the deformation and failure mechanisms of a ventilation roadway beneath residual coal pillars during close-distance coal seam mining at Tashan Coal Mine. Field observations via roof drilling and peeping confirmed an overall asymmetric failure pattern in the roadway roof. Using FLAC3D numerical simulation and the second invariant of deviatoric stress (J 2 ), this paper analyzes the distribution of deviatoric stress fields, plastic zones, and deformation characteristics at different mining stages and roadway locations. The results indicate that the magnitude and distribution of deviatoric stress are positively correlated with the severity of deformation and failure. After upper seam extraction, sections of the lower retreat roadway fall within the influence of the mining-induced deviatoric stress field. Subsequent lower seam mining generates intense superimposed deviatoric stress on the roadway side adjacent to the residual coal pillar (A-side), leading to greater strain and damage depth than the side near the working face (B-side). We conclude that the asymmetric deformation and failure of the roadway is primarily caused by the superimposed effect of deviatoric stress fields generated by upper and lower coal seam mining. This study clarifies the asymmetric failure mechanism induced by superimposed deviatoric stress fields, providing a theoretical basis for roadway stability control under similar mining conditions.