Generalized Cyclic-Degradation-Pore-Pressure Generation Model for Clays

A model for the behavior of fully saturated normally consolidated and overconsolidated marine clays subjected to uniform cyclic strain-controlled and staged cyclic loading under simple shear conditions is proposed. Staged cyclic testing with several levels of different uniform cyclic strains was used to simulate a clay response similar to the one that occurs during true irregular cyclic loading during earthquakes, ocean storms, and other natural cyclic loading phenomena. The model incorporates cyclic degradation, cyclic pore-water pressure generation, and cyclic threshold shear strain defined as the cyclic strain amplitude below which neither significant (positive or negative) pore-water pressure develops nor significant degradation occurs. The model was verified by staged cyclic direct simple shear testing of five marine clays. Practical applications of the model are addressed.