Anisotropic conditions prevail in the natural clay deposits and many of them exhibit time-dependent behavior when subject to external loading. In this paper, a bounding surface model developed by the authors was extended to include the rate dependent effects, such as creep and stress relaxation. The rate dependent formulation was based on Kaliakin-Dafalias approach, which used Perzyna's viscoplasticity theory. A total of 15 parameters are required to completely describe this model. The predictive capability of the model was examined by comparing the simulation with the laboratory test results of San Francisco Bay Mud.
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