Swell- Shrinkage Paths of a Swelling Soil in Wetting and Drying Cycles with Saline Water

Expansive soils swell or shrink when subjected to water content changes. These volume changes can give rise to ground uplift which may cause damages to the on site structures. In this research the behavior of an expansive soil was investigated through a number of wetting and drying cycles. Laboratory tests were carried out on statically compacted samples in a modified odometer under surcharge pressures of 10 and 20 kPa. The vertical deformation of the soil sample and EC (electrical conductivity) of the water of the consolidation cell were measured during cycles of wetting and drying. The void ratio and water content of the soil samples were determined at different stages. The results showed that swelling and shrinkage were reversible after the fifth cycle while soil deformation reached the equilibrium condition. The value of EC increased during each cycle and attained to a constant value but it decreased with increasing the number of cycles. Wetting and drying paths were as S shaped curves. These curves consisted of a linear and two curved portions، and in equilibrium condition these paths coincided. The majority of the soil deformations occurred in the middle part of the curves between the degrees of saturation 50% and 90%.