Swelling behavior of expansive soils

Abstract

Volumetric changes (usually swell) of expansive soils in presence of water are undesirable from stability reasons. Swell and Swelling pressure of an expansive soil is primarily dependent on the initial dry unit weight or void ratio and also on the moisture content. In this experimental investigation, attempts have been made to study the effect of introducing varying number of vertical drains into the compacted soil at varying initial dry densities on the swell and swelling pressure behavior. Both percent swell and the swelling pressure are significantly influenced by the presence of vertical drains (facility of water availability). The percent swell versus time relationship could be identified as a rectangular hyperbola, facilitating the prediction of ultimate percent swell. This is advantageous to predict the swell from the data obtained from the initial stages of the swell test and the experiment could be terminated without continuing till equilibrium conditions are reached. This concept was also extended to predict swelling pressure determined by constant volume method. Irrespective of the presence or absence of drains, the density effect on rate of secondary swelling and consolidation behavior of swollen sample was found to be almost the same for all testing conditions used in this study.