Experimental research on time-dependent behavior of crack propagation in Jinping deep marble

The long-term stability of underground engineering is closely related to the time-dependent behavior in brittle rock. Jinping deep marble will appear initial damage when subjected to high stress unloading. The no damaged rock sample is obtained by sampling without damage and tested by acoustic emission. The effect of initial damage on test result is rejected. A series of long-term static-fatigue tests are carried out to test the time-dependent behavior of Jinping deep marble. The marble in Jinping shows the strength degradation with time. When the driving-stress ratio is rather lower, the failure time is longer. The static-fatigue limit is 0.48. The creep curve can also be divided into three phases when brittle rock under long-term loading and the strain ratio shows corresponding change trend. The deformation characteristics and failure mode in static-fatigue test are analyzed by dilatancy index. The stress relaxation zone and concentration zone caused by excavation are calculated by FLAC(3D). The result indicates that the buried depth affects the test. When the rock samples contain joints, the strength is rather lower. Numerical test is performed by smooth joint model in the particle flow code (PFC). The numerical result meets well with the test. The existence of joints impacts the strength of rock. The rock will be compacted closely in initial loading stage and show the hardening effect and ductility behavior in residual stage.