ABSTRACT
Loading and strain rates play a significant role in soil viscous response that was investigated with little effort in the past. In the present paper, experimental investigations of shear viscosity of clayey soil are emphasized. The investigation centers on nonlinear viscosity in response to strain rates and different time scales. To do so, three types of shear tests are conducted with multiple axial shear systems, including static triaxial shear, dynamic triaxial, and dynamic torsional shear tests. Moreover, soil skeletal frame is assumed to behave as a non-Newtonian fluid. A new constitutive relation of nonlinear viscosity, therefore, is introduced to describe viscous forces on and deformation of soil skeletal frame. Constitutive parameters are calibrated from results of three types of shear tests. This is the first attempt to discuss soil nonlinear viscosity over different time scales that are investigated with three different shear devices. The testing results from three different devices indicate similar trends when soil viscosity changes with strain rate and enhance our understanding of soil viscous responses and effects of time scales on viscous behaviours.
