Long-term cyclic behavior of soft clay under different variable confining pressures and partially drained conditions

Traffic loading is one of the essential causes of the excess settlement of soft subgrade. The stress path induced by traffic loading is more complex than a single dimensional path and coupling of both vertical and horizontal stresses. Also, under long-term cyclic loading, the pore water pressure (PWP) generated in soft clay eventually dissipates. Therefore, to study the cyclic behavior of soft clay under a long-term traffic loading, a series of longterm (50,000 cycles) cyclic triaxial tests involving variable confining pressure (VCP) on saturated remolded clay were conducted under partially drained conditions in this study. The result shows both the cyclic vertical stress and VCP have detrimental effects on the soft clay. Thus, a new index (CSR eta) is proposed to synthesize these two factors. The peak PWP and final volumetric strain are all linearly related to CSR eta. An empirical model involving CSR eta is proposed to predict the final permanent axial strain. Compare to the empirical models in previous studies in which both the constant confining pressure (CCP) and VCP tests are necessary, only three CCP tests are needed to obtain the parameters in this model.

Automated summary

Traffic loading is a significant cause of the excess settlement of soft subgrade. This study conducted long-term cyclic triaxial tests to investigate the effects of cyclic vertical stress and variable confining pressure on soft clay. A new index called CSR eta was proposed to synthesize these two factors. An empirical model based on CSR eta was suggested to predict the final permanent axial strain.