Laboratory assessment of swelling pressure of expansive soils

Several methods have been suggested for the determination of swelling pressure of expansive soils. The two most commonly used methods are the zero swell test and the swell-consolidation test. This paper introduces two relatively new techniques termed the “restrained swell test” and “doubleoedometer swell test”. By using ten different soils obtained from northern and central Jordan, the effect of initial water contents, initial dry unit weight and soil type on the results of these methods is investigated. The experimental data obtained are used to develop mathematical models for predicting the swell pressure as determined by the aforementioned techniques. Furthermore, equations relating the swell pressure obtained by the restrained swell test to the other techniques were produced. Based on the experimental data it was observed that the swell pressure obtained from all four techniques increases with the dry unit weight and clay content of the soils and decreases with increasing initial water content. Additionally, the results indicate that the zero swell test and the swell-consolidation test produce the lowest and highest values of swell pressure, respectively. The restrained swell test, on the other hand, is believed to give more reasonable results for swell pressure determination and thus is considered to more closely resemble field conditions.