Effect of Wetting and Drying Cycles on the Behavior of Compacted Expansive Soils

In the United States alone, the cost to repair structures damaged by expansive soils has been estimated to be twice the combined damages of natural disasters. Despite the widespread occurrence of these soils, the damage caused by the presence of expansive soils is regularly overlooked because it might take years of distress exposure before extensive damage to infrastructure can be observed. To predict the heave and swelling pressure an expansive soil will experience in the field, it is standard practice to subject a remolded specimen to a wetting process at a particular net normal stress. This practice does not capture the behavior of expansive soils in the field and therefore, it is necessary to assess the long-term environmental effects on their behavior. In this study, an assessment of the effect of multiple wetting/drying cycles on the volume change behavior of two naturally occurring expansive soils was performed. The soils were remolded at different initial compacted conditions, loaded to different net normal stresses, wetted to nearly 100% saturation and then subjected to full drying. In general, it was observed that after four cycles, the swelling or collapse strain and the swell pressure reached equilibrium. When the applied stress exceeded 25% of the swell pressure, both soils exhibited an increase in collapse potential from the previous wetting cycle. However, when the applied stress was less than 25% of the swell pressure, both soils exhibited an increase in swell potential from the previous cycle.