Modelling non-isothermal volume change and solute transport behaviours of a semi-permeable clay soil under the combined influence of mechanical loading, chemical-osmosis, and thermo-osmosis

Abstract

Clays are widely used in geotechnical and geoenvironmental engineering applications and it is crucial to understand its behaviour for the dynamic field conditions. The presence of a temperature gradient across clayey soils that exhibit semi-permeable membrane (or osmotic) behaviour may promote a number of complex processes, including thermal expansion or consolidation, thermally induced osmosis, thermal diffusion, along with other flow and deformation processes. Chemical-osmosis and chemico-osmotic consolidation that are significant in isothermal conditions are also affected by temperature. Publications on chemical-osmosis, and to some extent thermo-osmosis behaviour of semi-permeable clays under coupled conditions are widely available. However, studies that include the influence of both thermo-osmosis and chemical-osmosis together are rare. In this paper, a fully coupled numerical model is presented to study the effects of both osmotic processes on thermo-hydro-mechanical-chemical behaviour of semi-permeable clays. Solute spread in a landfill clay liner is investigated under the combined influence of mechanical, thermal, and chemical loading. Model results show that the clay deformation is sensitive to thermo-osmosis; and the effects of thermo-osmotic consolidation, excess pore water dissipation, and the overall settlement increases with temperature. Variation of the source temperature from 40 °C to 80 °C yielded an increase of 11.3% of the peak soil settlement. Significant contribution of thermo-osmosis on solute transport is noticed in this study and ignoring the process substantially deviate from the realism. Up to 80% overprediction of cadmium spread is observed in the clay liner when the thermo-osmotic processes are neglected.