Porewater salinity effect on flocculation and desiccation cracking behaviour of kaolin and bentonite considering working condition

Cracking behaviour of clays at a local working climate and soils' evolution under seepage boundary is very important for the geological engineering. In coastal regions, pore water salinity is incorporated into above processes. In this study, the properties of typical clays (kaolin and bentonite) in saline environments, including the consistency limits, particle sedimentation and crack pattern, were investigated. The consistency limits of kaolin remain constant regardless of the pore water salinity, while the liquid limits of bentonite noticeably decrease with increasing salinity. Flocculation of kaolin occurs in both distilled water and NaCl solution, whereas the fine particles in bentonite disperse in distilled water but aggregate in saline water. At the end of the evaporation process, the total crack area of bentonite is obviously decreased, and the total crack length increases with pore water salinity, whilst that of kaolin is not influenced. In the subsequent wetting process, the bentonite clods disperse easily in saline environment, but the collapse of kaolin clods is not significantly influenced by the water salinity. The above observations are explained by the initial aggregation of clay platelets for the interactive forces between particles.