Unsaturated characteristics of undisturbed expansive shale from Saudi Arabia

The aim of this paper is to evaluate the soil water characteristic curves (SWCC) of undisturbed expansive shale identified at different locations of Kingdom of Saudi Arabia. The SWCCs were evaluated for suction ranging from 0.5 to 400 MPa. Based on test results, all SWCCs reveal a bimodal curve indicating the presence of two distinct pore size distributions referred to as small and large micropores. Volume change measurements were performed to evaluate void ratio–suction relationships which confirmed the expansive nature of shale. Similarities between measured SWCCs and void ratio–suction relations developed for expansive shale originating from same geological formation suggests the impact of geological and environmental conditions on the unsaturated behavior of shale samples. Finally, a modified approach based on Mckeen’s classification methodology was proposed to assess the swelling potential using bimodal SWCCs. The modified approach was used to assess the relative contribution of different micropores on the swelling potential of shale.