Effects of pore-water salinity on soil identification using in situ cone penetration tests

Abstract

In geological surveys of coastal regions, data interpretation and site identification are usually affected by underground water (including salinity). This study aimed to investigate the effect of pore-water salinity on soil identification via in situ CPTs. Combinations of triaxial shearing, cone penetration, and vane shear tests were also performed at a laboratory scale on Lianyungang marine clay with different pore-water salinities. The results suggested that the effective friction angles and shear strength increased with the pore-water salinity. The in situ CPTs showed that the normalized tip resistances increased with an increase in pore-water salinity, whereas no significant correlation between the normalized sleeve fraction and salinities was found. The use of the conventional soil identification method (soil-behavior-type chart, i.e., SBT chart) may be effective in very low-salinity conditions despite that it does not take into account the pore-water salinity effect. The salinity investigation of Lianyungang marine clay suggests that an inhomogeneous salinity distribution significantly influences soil identification when with rich clay mineral of montmorillonite and high pore-water salinity. From the theoretical and practical analyses, an improved soil identification method considering pore-water salinity modification was proposed to avoid the misclassification of in situ soil.