Experimental Study on Creep Behavior of Unloading-Cracked Beishan Granite

In order to investigate the long-term behavior of host rock after excavation unloading, the creep tests under dry and saturated conditions were carried out on unloading-cracked granite, based on the mechanical parameters obtained from triaxial compression tests on unloading-cracked granite. The unloading-cracked granite were produced from triaxial unloading tests on intact rock. The full processes of stress and strain were monitored in real time by the three-dimensional acoustic emission monitoring system. The test results indicate that the creep deformation and steady state creep strain rate in lateral direction were found to be greater than in axial direction. Meanwhile, the ratio of creep strain to total strain and steady state creep strain rate were shown to be degraded by the saturation. The critical stress value corresponding to the accelerated development of damage was about 90% of the compressive strength of unloading-cracked specimen. What’s more, the acoustic emission ringing counts during the last step of creep test had the same trendline of change with lateral strain. It is suggested that the degeneracy effects of saturation on the deformation and strength of host rock should be considered in the stability analysis of underground engineering.