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In this study, the combined effect of temperature (T) and pore water salinity on electrical surface conduction parameters was investigated. Two new electrical surface conduction parameters, namely, electrical conductivity of effective solid (σs) and size of diffuse double layer (DDL) water per unit volume of soil (χ), were considered in this study. The tested samples included two commercially available clays and four natural clay soils with diverse physico-chemical properties. The two surface conduction parameters were also used to assess the influence of temperature (T) and pore water salinity, as well as the electrical conductivity of free water (σFW), on the evolution of the free swelling index (FSI) of clays/clay soils through experimental methods. The findings suggested that elevated temperature and σFW increased σs but reduced χ, as well as the FSI of clays/clay soils. Furthermore, the rate of reduction for both χ and FSI augmented under the influence of increased free water salinity, particularly for clays/clay soils with high swelling capacity. The combined reductions of χ and FSI provided substantial evidence that clay DDL thickness decreases as T and σFW increase concurrently. [ABSTRACT FROM AUTHOR]

Semarang-Demak and other cities along the coast of North Java are vulnerable to land subsidence. The presence of saline groundwater in the coastal region is thought to affect the high subsidence rate, in this case the compressibility of the aquitard layer. We aimed to analyze the effects of groundwater salinity on the compression characteristics of the Semarang-Demak clay using physical analysis. Methods included the determination of groundwater salinity, clay mineralogy and fabrics, and consolidation tests under various salinity conditions. The Semarang-Demak clay is dominated by smectite of high activity, and saline clay exists at the depth of 10 to 35 m. Consolidation tests revealed that the increase insalinity increases the average consolidation rate and hydraulic conductivity up to 42% and 37.5%, respectively. Clay fabric analysis showed that the groundwater salinity modified the interconnectivity of pores by changing the fabric into parallel alignments, facilitating faster porewater dissipation, hence the clay is more readily compressed. These findings are useful for explaining the mechanism of the fast-subsiding coastal plains of North Java. [ABSTRACT FROM AUTHOR]