Experimental Study on Soil–Water Retention Properties of Compacted Expansive Clay

The soil–water characteristic curve (SWCC) defines the relationship between water content and matric suction in soil, which contains fundamental information needed for the hydromechanical behavior of expansive soil that generally lies within the unsaturated soil mechanics framework. Moreland clay is highly expansive soil abundant in northern Louisiana, part of Arkansas, and Oklahoma. Unsaturated soil properties for shear strength, permeability, and volume change are needed to identify expansive soil-induced stresses on pavement or railroad track due to seasonal variation of moisture content in the subgrade layers. Determination of the two critical variables obtained from the SWCC, i.e., the air-entry value (AEV) and the residual state suction, is essential for the prediction of unsaturated soil deformations. In this research, an experimental testing program was conducted on the expansive Moreland clay to investigate the soil–water retention properties by adopting the axis translation technique to control suction in the range of 0–1500 kPa. A computer program was developed to fit experimental data, and it was compared with predicted SWCC using empirical relationships. The AEV and the residual state suction, two critical variables, were obtained from the SWCC formulation of Fredlund and Xing equation. Finally, the shrinkage curve was determined to interrelate between elastic deformation and SWCC of Moreland clay.