Creep and Control of the Deep Soft Rock Roadway (DSRR): Insights from Laboratory Testing and Practice in Pingdingshan Mining Area

Coal mines in Pingdingshan mining area, Henan province, China, are commonly mined at a great depth up to 1000 m, and inevitably reside in high temperature, high pressure, high permeability, strong mining disturbance, and strong time effect environment. Support structures of the mines in the area are vulnerable to failure and destruction while roadway stability has been a long-standing issue in the region. Based on the specimens collected from the roof of the return-air rise at Pingdingshan No.1 coal mine, here, we investigated the creep characteristics of sandy mudstone under triaxial conditions and developed a constitutive relationship to predict the creep behavior. Parameter identification and sensitivity analysis were performed to determine the influential factors of creep deformation. We showed that the creep deformation and steady-state creep rate at Pingdingshan coal region grow as axial stress is elevated while descend with increased confining pressure. However, the maximum creep deformation of sandy mudstone increases with a higher confining pressure. Thereby, stress difference, elastic modulus and coefficient of viscosity are the major parameters controlling creep deformation. Hence, it is important to enhance the support strength and mechanical properties of the surrounding rock, to better the roadway stability. In addition, numerical simulation was also conducted for simple excavation geometries to analyze different support structures. On this basis, the “cable bolts steel arch, deep and shallow reinjection, floor pressure relief and local reinforcement” scheme was proposed and field practice showed promising results. The findings in this study can be used to guide the support design for the deep soft rock roadway (DSRR).