An elasto-viscoplastic numerical analysis of the swelling process of unsaturatedbentonite

Abstract

A numerical analysis of the swelling behavior of bentonite is presented using anelasto-viscoplastic theory. It is an extension of an elasto-viscoplastic model for unsaturated soil, which can describe the behavior of macrostructures, such aschange of suction, pore pressure and degree of saturation. The volume increase of montmorillonite minerals due to water absorption into the interlayers, is assumed to be a part of viscoplastic volumetric strain. An internal variable H whichcontrols an increase in water absorption into clay interlayers is adopted to describe the swelling behavior of microstructure. In addition, the internal compaction effect caused by swelling of clay unit is described by the expansion of the overconsolidation boundary surface and the static yield surface. Based on the proposed model, a fully coupled soil-water-air finite element analysis is conducted to study the development of swelling pressure. Comparing the experimental results and the simulated results, it is found that the proposed model can reproducethe effects of dry density and the initial water content on the swelling behavior.