Effect of Pore Water Chemistry on Hydro-Mechanical Behavior of Compacted Expansive Clay

ABSTRACT: Pore water chemistry affects properties such as volume changes, including swell-shrinkage and compressibility, water retention capacity, hydraulic conductivity. The soil swell-shrinkage behavior causes deformations both in horizontal and vertical directions, leading to cracking of soils which result in increase in hydraulic conductivity due to formation of preferential flow paths in the location of cracks. The impact of these deformations on volume change behavior of soils still are to be fully understood, hence there is still room for research in this subject. This thesis presents the results of an experimental program studying the effect of pore solution concentration on hydro-mechanical behavior of unsaturated soils. In addition compressive strength and tensile strength properties are also studied. The experimental results are interpreted in relation to the diffuse double layer theory. NaCl and CaCl2 are used in concentrations of 0.5M and 1M to change the pore fluid chemistry, and the behavior is compared to the behavior of soil with distilled water as the pore fluid. The experimental results conform to the results observed in some previous research works, hence contributing to the literature on the effect of pore fluid chemistry on the behavior of unsaturated soils exposed to saline environments. The findings of this study indicated that salts in the pore fluid reduced the swell-shrinkage potential and compressibility, while increasing the strength properties and hydraulic conductivity. Keywords: Desiccation, pore-water chemistry, shrinkage, unsaturated soils. …………………………………………………………………………………………………………………………