Swelling pressures and size effect correlations of expansive soils

This study investigates procedures for estimating the empirical relations necessary for predicting swell pressures from natural deposits of high-, medium- and low-expansive soil samples, which were obtained from three locations in Erbil City. These soils are denoted as Soil-1, Soil-2, and Soil-3. Bentonite clay minerals of 5%, 10%, 15%, 20%, and 25% were mixed with Soil-2 to obtain an extensive swell index. The experimental information necessary to obtain the prediction formula could be acquired from small-size oedometer tests in the proposed methodology. Then, a relatively large-size model simulated to be equivalent to the small-size standard test methods was established and used to study the size effect on the swell pressures of reconstituted soil samples. This approach allowed for obtaining physical-based predictions of swell pressures. The empirical correlations of multiple regression were determined for analysis models. Results suggested that the swell pressures could be estimated on the basis of physical soil properties. Overall, the oedometer technique overestimated the Constant Volume (CV), whereas for the Consolidation Swell (CS), the swell pressure magnitude over large-size models was significantly underestimated.