Matric suction, swelling and collapsible characteristics of unsaturated expansive soils

Unsaturated expansive soils are recognized as one of the most problematic soils owing to its swelling-shrinkage characteristics. The presence of such soils in highway/railway embankments, slopes and earthen dam sites manifests various critical issues during and after the construction of structures. The current research aims on the evaluation of the suction, swelling and collapsible characteristics of four expansive soils possessing different expansiveness and mineralogical composition. A series of constant volume swell pressure, double-oedometer and incontact filter paper tests were performed on four different expansive soils to acquire swelling pressure, collapse potential and matric suction at different degree of saturation. Swelling pressure, collapse potential and matric suction of all expansive soils degraded substantially with increment in the degree of saturation. The results revealed significant impact of magnitude of matric suction on volumetric deformation (swell and collapse) behavior of expansive soils. Swelling and collapse potential were observed to be higher for the expansive soils with larger matric suction. Higher matric suction governed the water intake within interlayer spacing of the Montmorillonite mineral present in expansive soil, which contributed to higher crystalline swelling response. Larger collapse potential indicated development of larger localized deformations within the soil mass owing to higher matric suction.by Saloni Pandya and Ajanta Sacha