Salinity effects on the strength and morphological indices of soft marine clay

This study evaluates the strength behaviors and morphological characteristics of Lianyungang marine clay under the effect of porewater salinity. Soil at higher salinity was found to have increased internal friction angle and undrained shear strength. The difference in undrained shear strength enlarges as the confining pressure increases. Different stress paths were exhibited with soil at different salinities. Soil morphology analysis including scanning electron microscopy (SEM) and Image-Pro Plus (IPP) were employed to investigate the underlying mechanism of the enhanced strength behaviors of soft marine clay with increased salinity. Aggregated soil fabric was observed at higher salinity and contributed to enhanced strength. The results demonstrate that the aggregated soil structure is the primary mechanism responding to the enhanced strength behavior of marine clay under relatively high salinity (6%). Quantitative relationships were developed between the strength parameters and morphological characteristics of soil, i.e., area of particles, roundness of particles, area of pores, pore orientation, and fractal dimension of pore distribution, in the forms of empirical equations, and are expected to serve as the references for prediction in undrained behaviors of soft marine clays with known soil index.