Time-Dependent Stress-Strain Behavior of Soft Hong Kong Marine Deposits

To investigate the time-dependent stress-strain behavior of Hong Kong marine deposits (HKMD), three types of triaxial tests have been conducted under both compression and extension states. The first is conventional undrained shear tests at different strain rates ranging from 0.0025 to 0.25%/min. The second type is stress relaxation tests. The last type is undrained creep tests. The results are reported in this paper. One order increment of logarithmic strain rate causes about 5 to 9% increase of undrained shear strength. In stress relaxation tests, the pore-water pressure increase is about 10% of the consolidation pressure under extension states. A power law equation is presented to calculate the decay of the deviator stress in relaxation. In multi-stage triaxial creep tests, the log(strain rate)-log(t) relationship of the lower stress level is linear. The slopes of these lines are dependent on current deviator stress as well as stress history.