Abstract:To investigate the dynamic characteristics and cumulative deformation behavior of saturated soft clay under multi-level cyclic loading, a multi-level staged cyclic dynamic triaxial test was used to simulate the Foreshock-Mainshock-Aftershock sequential seismic loading. The effects of intermittent combined cyclic stress ratio, loading frequency, and the number of cycles to failure on the deformation and strength characteristics of saturated soft clay were studied and analyzed. On this basis, a mathematical model describing the development of cumulative plastic strain of soft clay under multi-level staged dynamic loading, incorporating multiple influencing factors, was proposed. The research results indicated that the dynamic strength of soft clay increased during the initial stage of dynamic loading due to vibration-induced compaction, while the structural damage during failure was intensified, leading to a reduction in residual strength. Under the influence of the mainshock-aftershock type cyclic stress ratio, the cumulative deformation of soft clay under multi-level staged dynamic loading exhibited three different patterns: stable, progressive, and failure types. Under the foreshock-mainshock type dynamic loading, the dynamic strength of soft clay decreased with increasing loading frequency, whereas under aftershock loading, it was jointly affected by both loading frequency and the number of cycles to failure. A deformation prediction model for soft clay, using the number of cycles to failure as the main fitting parameter, was established in this study. The model provides an engineering reference for evaluating the development of cumulative deformation and the stability of geomaterials under sequential seismic dynamic loading.
