Laboratory Swell Pressure Determination of Expansive Clays

Abstract

Swell pressure is an essential phenomenon in the case of expansive clays to know the overall behavior and performance of the clay. Expansive clays are being used as a buffer material in the deep geological repository or as geosynthetic clay liners for the landfills. Such expansive clays are intentionally used, because of the high swelling capacity by coming in contact with the moisture and serve the purpose of barrier successfully by swelling. Therefore, the determination of swelling characteristics and swelling pressure for the expansive clays are considered as an important factor in selecting the expansive clay for the purposes mentioned above. The present work examines the critical aspects of laboratory swell pressure determination, and various phases of swelling of expansive clays are discussed in detail. Bentonite was used as expansive clay for the experimental purpose, and samples were compacted at three different densities, i.e., 1.5 Mg/m3, 1.75 Mg/m3, 2 Mg/m3. It was observed that the time of saturation for the expansive clay depends upon the density at which the samples were compacted. According to literature, several other factors such as percentage of montmorillonite, cation exchange capacity, specific surface area, dry density of the sample, saturating liquid, and temperature are also responsible for the swelling of expansive clays. In this particular work, the laboratory swell pressure determination of bentonite and the factors on which the swell pressure depends are discussed, and the data is compared with the work of past researchers. The overall swelling mechanism is affected by the repulsion forces between different particles as well as the osmotic pressure in the micro-pores due to the differences in concentrations of the pore solutions.