Physico-Chemical Effects on Shrinkage Behavior of Compacted Expansive Clay

摘要

Physico-chemical effects have a significant impact on the behavior of clay barriers due to the interactions between the pore fluid and clay particles, and they pose a great challenge because the efficiency of clay barriers and cover systems may be altered. Therefore, this paper highlights the effect of physico-chemical factors on shrinkage behavior of compacted expansive clay. To achieve this, the compacted clay specimens were inundated with distilled water, NaCl, and CaCl2 salt solutions in separate oedometer cells at a vertical pressure of 6.25kPa and allowed to swell. The swollen specimens were gradually shrunk until the specimens attained constant mass, and the changes in void ratio and water content were monitored during drying. The experimental results showed that magnitude of induced osmotic suction and type of pore fluid had a significant impact on shrinkage behavior of compacted clay specimens due to the changes in soil structure. The average pore size of compacted specimens significantly decreased with the induced osmotic suction due to the reduction in size of micropores owing to the suppression of double layers. The discussions are supported by scanning electron microscopy images. Also, the experimental shrinkage data were fitted using modified van Genuchten and Fermi mathematical models, and the results showed that these models fit well with an adjusted R-2 higher than 0.9962.