Resilient and permanent strain behavior of soft clay under cyclic loading

Considering the characteristics of traffic loading, undrained high-cycle loading (50000 cycles) triaxial tests under different initial confining pressures and cyclic stress ratios were conducted on natural Wenzhou soft clay through dynamic triaxial test system (DYNTTS) manufactured by global digital system (GDS) corporation in England to research the influences of cyclic stress ratio on stress-strain curves, resilient modulus and permanent strain. Results show that cyclic stress ratio significantly influences the shape of stress-strain curve and its development. Accordingly, with the increase of cyclic stress ratio, both the decreasing degree of resilient modulus and the cycle number reached steady value increase. By analyzing the resilient modulus and permanent strain after 50000 cycles, the new cyclic stress ratio (in the range of 0.60-0.70) is suggested as a critical stress level. When the cyclic stress ratio is larger than this level, the resilient modulus reaches a constant value called asymptotic stiffness" while the permanent strain increases rapidly."