Experimental research on creep properties of limestone under fluid-solid coupling

Water is one of the important factors influencing the long-term stability of underground construction. Water becomes a huge threat to the safe operation of underground construction because of the increasing hydraulic pressure in deep stratum. In the present study, compression creep tests of limestone not covered by rubber jacket under different hydraulic confining pressures were carried out by using the self-developed YSL-200 multi-channel rock creep testing system. Based on the analysis of test data, the creep properties of limestone under fluid-solid coupling were studied. Then the effect of water and hydraulic confining pressure on the failure mechanism and creep properties were discussed. The results show that the hydraulic confining pressure has a significant influence on the rock creep properties. Compared with the confining pressure in conventional triaxial creep test, under the long-term effect of hydraulic confining pressure, water seeps into the rock through fissures or cracks and applies splitting effects on the crack surface, which promotes crack propagation, increases the damage of rock and accelerates the rock failure process. Both the value of strain and the creep strain rate increase with the increasing of hydraulic confining pressure, but the increase magnitude of the creep strain rate is much smaller. The results can provide a reference for the study of long-term stability of underground structure under fluid-solid coupling.