Deviatoric stress evolution and time step control technology of retreat roadway surrounding rock in fully mechanized working face

The distribution characteristics of the deviatoric stress tensor (DST) field in the surrounding rock of the end-mining retreat roadway (ERR) are intricate, exerting a substantial influence on the stability of the ERR's surrounding rock. Taking the fully mechanized working face and its retreat roadway in Wutong Coal Mine as the engineering backdrop, initially, a numerical model of the DST in the end-mining coal pillar (ECP) was established to analyze its evolutionary pattern. Based on the response surface methodology (RSM) model, the significance of each influencing factor was examined. Subsequently, the three dimensional stress expression above the ECP was deduced, and the invariants and distortion energy (DE) of the DST at any position within the ECP were ascertained. Then, the expressions for the cutting height and cutting angle were derived, and a novel time step control technology (TSCT) for the ERR's surrounding rock was put forward, based on the real-time evolution characteristics of DST, dynamic matching of support strategies and roof cutting parameters is achieved through two stages of passive reinforcement and active roof cutting to achieve collaborative control. Compared with traditional static design or single time step methods, this technology reduces the deformation rate of surrounding rock by about 84% through step-by-step and timely application of support and cutting. Ultimately, according to the field measured data, it was demonstrated that this technology can effectively mitigate the deformation of the ERR's surrounding rock.