Elastic Anisotropic Viscoplastic Modeling of the Strain-Rate-Dependent Stress–Strain Behavior of K0-Consolidated Natural Marine Clays in Triaxial Shear Tests

Abstract

This paper presents a new three-dimensional (3D) anisotropic elastic viscoplastic (EVP) model for the time-dependent stress-strain behavior of Ko-consolidated marine clays. A nonlinear creep function with a limit for the creep volumetric strain under an isotropic or odometer Ko-consolidated stressing condition and a nonsymmetrical elliptical loading locus are incorporated in the 3D anisotropic EVP model. An alpha-line defines the inclination of the nonsymmetrical elliptical loading locus in the p'-q plane and is commonly used for natural soils. All model parameters are determined from the results of one set of consolidated undrained compression tests and an isotropic consolidation/creep test. With the parameters determined, the 3D anisotropic EVP model is used to simulate the behavior of Ko-consolidation tests and the strain-rate-dependent stress-strain behaviors of the Ko-consolidated triaxial compression and extension tests on natural Hong Kong marine deposit clay specimens. These triaxial Ko-consolidated specimens were sheared at step-changed axial strain rates from +2 to +0.2, +20, -2 (unloading) and +2%/h (reloading) for compression tests; or from -2 to -0.2, -20, +2 (unloading), and -2%/h (reloading) for extension tests, all in an undrained condition. The simulation results of all these tests are compared with the test results. The validation and limitations of the model are then evaluated and discussed.