3-D elastic viscoplastic modeling analysis of a diatomaceous soft rock

Based on Perzyna's fundamental assumptions of the elastic viscopalstic theory, a viscoplastic flow rule, and Yin and Graham's 3-D elastic viscoplastic constitutive model (3-D EVP model), the formulation under a triaxial stress state is obtained. Yin and Graham's model proposed new concepts such as equivalent time, instant time line, reference time line and limit time line. The derived formulation is used to simulate the time-dependent stress-strain behavior of consolidated undrained triaxial tests of a soft rock. The simulated results are compared with the triaxial test results. The comparison of the results shows that agreement between the model predictions and measured results is good. This demonstrates that the EVP model can be used to describe the time-dependent stress-strain behavior of the diatomaceous soft rock.