Experimental study on thermal effect of deep-sea cohesive sediment under monotonic and cyclic loads

In this study, a series of monotonic and cyclic triaxial tests were conducted to investigate the thermal effect on the mechanical behaviors of sediment from the South China Sea (SCS). The excess pore water pressure (including temperature-induced and shear-induced), shear strength, accumulative plastic strain, and stiffness degradation index were measured and analyzed. Two modified empirical models were proposed to predict the evolution of the accumulative plastic strain and stiffness degradation index with the cyclic number (N) at different temperatures. A unified index of normalized cyclic shear ratio (CSR¯) taking the cyclic stress and temperature into account was proved to be suitable to describe the model parameters. Compared with the constant temperature condition (4 °C), both the monotonic and cyclic shear strength of the samples decreased as the temperature increased. Moreover, a temperature-independent correlation between cyclic and monotonic shear strengths was derived. A more markedly cyclic softening behavior could be observed under high-temperature conditions in which the undrained shear behavior showeds somewhat quasi-overconsolidated (QOC) characteristics.