EXPERIMENTAL STUDY ON PERMEABILITY OF SANDSTONE DURING POST-PEAK UNLOADING OF THE CONFINING PRESSURE

In order to understand the permeability of surrounding rock during post peak unloading of the confining pressure caused by coal mining,the authors conducted permeability test of sandstone using instantaneous permeating method with the electro-hydraulic servo controlled rock mechanics testing system(MTS-815.02).The curves of permeability-axial strain and stress-axial strain before the peak point were obtained.The curves of permeability-confining pressure and principal stress difference-confining pressure during post-peak unloading of confining pressure under a constant axial strain were also obtained.The permeability of sandstone during post-peak unloading of the confining pressure was evaluated by fitting relationship curve of the post-peak permeability-effective confining pressure.The results provide guidelines for solving the problem caused by coupling stress field and seepage field of rock mass in underground engineering.