Experimental investigation of volume change behavior of swelling soil

The present paper examines the effect of rate of wetting, type of wetting, surcharge pressure and lateral confinement on the swelling deformation of expansive soil using laboratory experiments. The experimental program consisted of two main parts. In Part I, the deformation under free swelling is measured, where the specimens are subjected to different rate and type of wetting. In Part II, series of constant volume oedometer test (CVOT), one-dimensional swelling test (1DST) and submergence tests are conducted. It is observed that significant swelling occurs when the degree of saturation is more than 80%. When the degree of saturation is lower than 80%, the deformation during swelling is significantly small and this small deformation is attributed to the volumetric expansion associated with suction decrease. It is shown that the swelling rate of expansive soil decreases as the surcharge pressure increases. Experimental results are analysed based on several constitutive relationships such as void ratio - moisture content, void ratio - swelling pressure and moisture content-soil suction. Relationship of parameters such as coefficient of compressibility, coefficient of permeability and hydraulic diffusivity with equilibrium swelling pressure is examined. It is observed here that coefficient of permeability of swelling soils depend up on the degree of saturation in addition to the void ratio.