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ABSTRACT: Time-Dependent Deformations of Marine Clays on Submarine Slopes

A. J. Silva, H. Brandes, M. H. Sadd, W-M. Tian

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.< P>

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 of such a continuum, we 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.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990