Estimation of SWCC for unsaturated soils and its application to design of shallow foundations

Abstract

The importance of unsaturated soil mechanics stems from the fact that the majority of geotechnical engineering projects are taking place in unsaturated soil zones. Soil suction, especially matric suction, is controlling the unsaturated soil behavior. However, measurements and determination of the soil suction is still a concern for geotechnical engineers and researchers regarding its accuracy, practicality, cost, and reliability. In this study, the filter paper method (FPM) has been adopted as a secondary indirect measurement of the suction. Both total and matric suction were measured for three different mixtures of coarse soil (sand) and fine soil (industrial Bentonite/Montmorillonite) at two different saturation levels for each mixture. An extensive characterization has been conducted for the soil samples and, thereafter, samples were prepared at 95% of the maximum dry density (MDD) on wet and dry sides of optimum for suction measurements. The soil-water-characteristic/retention curve (SWCC/SWRC) was then completed for each sample using an estimation method reported in the literature. A new prediction model has been developed, in this study to determine a fitting parameter for estimating SWCC. Also, a review on the application of SWCC to design of shallow foundations has been presented in a simplified manner. Finally, recommendations for future work and conclusions were reported.