Evolution of damage and permeability characteristics in roadways under mining disturbance

The mining works in underground coal mines induce the changes in stress state of rock mass in front of mining face, which can lead to rock mass damage, form groundwater seepage channel, and then cause disasters such as water inrush and surrounding rock collapse. In view of this situation, three stress loading paths are designed to simulate the stress state of rock mass under mining disturbance in different regions: conventional triaxial compression test(CTCT), loading axial pressure and unloading lateral pressure test(IUT), and keeping axial pressure and unloading lateral pressure test(KUT) for triaxial compression tests, and creep tests of two loading modes are designed: the creep test involving step loading and unloading confining pressure are conducted to investigate the evolutionary characteristics of rock damage and permeability and their time-dependent mechanisms. The damage to limestone during creep and creep unloading processes is characterized through theoretical analysis. The results show that:(1) Limestone exhibits significant differences in mechanical and permeability properties, such as yield characteristics and permeability, under different stress paths. However, shear failure dominates its failure mode in all cases. (2) As confining pressure gradually increases, the stress paths corresponding to the maximum permeability growth rate are CTCT, IUT, and KUT respectively. This indicates that the evolution of limestone permeability is closely related to in-situ stress levels and stress states. (3) Damage primarily occurs during axial loading and confining pressure unloading processes. The rate of damage accumulation and failure in limestone is faster under confining pressure unloading paths than under conventional loading paths. (4) A modified Nishihara model was developed, and its reliability was successfully validated. The research results can provide reference for the construction stability research in underground engineering, such as roadways and tunnels.