Estimation of Swelling Pressure Using Simple Soil Indices

In arid to semiarid regions, damage from expansive soils to light structures in the long term may be as costly as damage by major natural hazards. Swell characteristics, including swell pressure, of expansive soils have been the subject of numerous studies. Studies examining this property employ almost exclusively the conventional oedometer apparatus, which indirectly measures swell pressure. The results of such studies are often speculative. This investigation covers 1000 swell tests on 124 soil samples, using constant swell and free swell tests. Identical specimens at different initial water contents and dry densities were constituted through static compaction for each soil sample. Atterberg limits were incorporated into regression analyses along with the water content and dry density data. The resulting empirical relationship reasonably predicts the swell pressure. The correlation between the data from constant volume and free swell tests was even more conclusive. Comparing the empirical form obtained from this investigation and the previously published two equations reveals that the other relationships dramatically underestimated the swell pressure, which was attributed to the use of indirect methods.