Pore water salinity effect on the intrinsic compression behaviour of artificial soft soils

The framework of the intrinsic compression behaviour of normally consolidated soft clay proposed by Burland (1990) is widely adopted in engineering practices. However, further investigations should be conducted on its validity in the coastal and offshore environments to verify the effect of pore water salinity. In the present work, oedometer tests were performed on remoulded artificial soft clays (mixtures of kaolin and bentonite with 0%, 5%, 10%, and 20% of bentonite by mass). The artificial clays were salinized with sodium chloride solutions at concentrations 0 mol/L (distilled water), 0.17 mol/L, 0.51 mol/L, 0.86 mol/L, and 1.70 mol/L at water contents equal to 1.0-1.5 times of the liquid limits. The results showed that the 'intrinsic' properties of clays, including the compression index C-c*(100-1000 kPa), void ratio e(100)*, and compression line based on the void index I-v, changed with the pore water salinity. Following the empirical correlation proposed by previous researchers, the decrease in C-c* caused by pore water salinity could be generally characterised by the liquid limit and void ratio at the liquid limit (e(L)). The dispersed correlation between the predicted e(100)* and the experimental results in this study were caused by the significant changes in e(0)/e(L), controlled by pore water salinity. The relationships between void index I-v and vertical stress sigma(v)' deviated from the intrinsic compression line (ICL) under the saline environment. For the artificial clay rich in smectite, the slopes of I-v-log sigma(v)' before yielding increased with pore water salinity at the initial water content. Pore water salinity affected the intrinsic compression behaviour of soft clays primarily composed of kaolinite to a lesser extent.