Abstract
This study aims to predict the unsaturated shear strength of highly expansive clay locally available in Saudi Arabia. The Soil Water Characteristic Curve (SWCC) for the expansive soil was determined using the combined techniques of axis translation and filter paper and fitted using Fredlund & Xing (1994) equation to obtain the SWCC over a wide range of suction. The SWCC combined with saturated shear strength parameters were used to predict the Unsaturated Shear Strength Function (USSF) using the prediction model proposed by Vanapalli et al. (1996). To validate the predicted USSF, a series of unconfined compression strength tests were performed on expansive clay samples at different suction levels. Finally, a discussion on the impact of volume change experienced by expansive clay samples due suction application on the SWCC, and consequently USSF prediction, was provided.