Long-term, drained triaxial creep and direct simple shear creep tests were conducted on undisturbed marine specimens from the Gulf of Mexico and the north-central Pacific. Results indicated that time-dependent deformations can be represented by a power law equation, and the creep strain rate can be represented by an equation similar to that suggested earlier by other researchers. However, it was found that the m parameter suggested by these scientists was not a constant but dependent on stress level and sediment plasticity. Ageing effects were evidenced in triaxial specimens by the increase of shear strength with both test duration and stress level. The results provided a guide for the development of mathematical stress–strain–time relationships that will be developed in a separate paper. Key words : drained triaxial creep, simple shear creep, stress–strain–time behavior.
Evidence from geological and geophysical records indicates that time-dependent deformations occur on or within many submarine slopes. Laboratory studies on marine clays from the slope/rise and the ocean's basin have shown that these clays are generally quite viscous and therefore can be expected to deform in the field even under such small stresses as those caused by the downslope component of gravity on relatively gentle slopes. The nature and extent of these deformations has important geologic and engineering applications and depends on a number of factors. A research program at the University of Rhode Island is under way to study these factors, make predictions on rates of displacement, and identify environmental conditions that may lead to catastrophic mass failures. A laboratory testing program on the time-dependent characteristics of marine clays has been under way for a number of years. The data include, among others, long-term drained triaxial, one-dimensional, and direct simple shear creep tests. These results along with practical considerations are used to select a constitutive model for inclusion in the numerical code. Sediment deposits encountered on the continental slope and rise can vary substantially both in composition and behavior over relatively short distances. To analyze the integrated behavior ofmore » such a continuum, the authors have selected the finite element method. The code being developed will initially include a numerical model proposed by other investigators. With the aid of the developed methodology, creep deformations can be studied for a number of field cases of interest.« less
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