Deformation and fabric of soft marine clay at various cyclic load stages

Abstract

Soft marine clay is susceptible to deformation under cyclic loading, controlled by microstructure variations. To investigate the microscopic characteristics of soft clay with the progression of deformation under cyclic loading, a detailed study has been conducted using consolidated undrained cyclic triaxial tests, as well as mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). The relationships between the micro parameters and accumulated plastic strain of soft marine clay are discussed. Cyclic triaxial test results show that low cyclic stress ratio (CSR) induces stable deformation, while for greater CSR the deformation of soft marine clay presents a closely linear or exponential increase, which leads to the destructuration of the soil structure. The microanalysis shows that with vibration cycles under 0.15 CSR, the content of pore obtained by SEM decreases from 37% to 25%, and large aggregates are visibly crushed into smaller ones, leading to a 24% increase in the pore numbers, which shows the slow increase of the deformation. When the CSR is greater than 0.25, large diameter pores generate resulting in divergent development of accumulated plastic strain. An empirical model of accumulated plastic strain involving micro parameter is proposed for assessing the deformation of soft marine clay.