Role of matric suction on wetting-induced collapse settlement of silty sand

Collapsible soils are typically sandy soils that are susceptible to a significant and sudden reduction in volume upon wetting. This phenomenon is associated with loosely deposited, metastable soil structures, which can withstand a considerable stress in the unsaturated state, but they exhibit an excessive settlement when saturated. Soil collapse depends on the initial dry density, initial moisture content and pressure at wetting. Matric suction is also a key factor, which is related to moisture content through the Soil Water Characteristic Curve (SWCC). This study investigated the role of matric suction on the collapse behavior of three silty glacial sands collected from South Australia. The drying SWCC of each sand was determined by the bubbling column and pressure plate methods, between matric suctions of 1 to 1000 kPa. The one-dimensional collapse potentials of the three different sands were determined at different densities and moisture contents, and applied pressures before inundation, termed wetting pressures. It is shown that the collapse potential for a particular density and wetting pressure increases generally with increase in initial matric suction. The effect of initial matric suction on collapse potential was found to be influenced by the dry density ratio, the nature of cementation and wetting pressure.