Behavior of unsaturated weathered residual granite soil with initial water contents

There is a significant difference between the SWCCs response for drying and wetting curves in unsaturated state. In other words, the initial water content condition can influence the behavior of unsaturated soils. To find this out, a series of triaxial compression tests was performed on samples of compacted granite soils in a modified triaxial cell that can separately control pore air pressure (ua) and pore water pressure (uw). Unsaturated granite soil samples were prepared with different initial water contents (dry, wet, and optimum moisture) by compaction in a mould. These samples were tested at different suction and confining stresses. The volume change of an unsaturated soil during shearing is more sensitive to the confining pressure compared to the initial water content and the matric suction. The volume expands during shearing, and the volumetric strain is much larger at the smaller confining pressure and at the higher matric suction. The variation of the internal frictional angle with the initial water content and the matric suction is negligible, but the effective cohesion increases with matric suction.