Experimental and numerical investigations on crack development and mechanical behavior of marble under uniaxial cyclic loading compression

Rock masses in underground excavations are exposed to cyclic loading due to several factors, such as blasting and mechanical excavation, etc. However, the understanding for the effect of cyclic loadings on rock damage remains not completely clear. To this end, we have investigated the crack development and mechanical behavior of marble under three different cyclic loadings. The results showed that the crack closure threshold can be improved by cyclic loadings. The crack initiation threshold, crack damage threshold, cohesion and elastic modulus initially increase with the cycles, followed by a decrease as the rock heads toward failure. The cohesion is proportional to the elastic modulus before the latter reaches its maximum value. Further, additional cyclic loadings exhibited evident compaction effect on the rock. Meanwhile, the cyclic loadings caused simultaneous strengthening and damage effect of rocks. The proposed strengthening principle is implemented in the well-established rock failure process analysis (RFPA) code. The model is then validated by comparing the simulation and experiment results. Based on the experiment results, the cohesion weakening and frictional strengthening (CWFS) model is amended as the cohesion variation and frictional strengthening (CVFS) model.