Coupled thermo/hydro/chemical/mechanical model for unsaturated soils—Numerical algorithm

Abstract

Abstract This paper presents the implementation of a numerical algorithm for a new coupled thermal–hydraulic–chemical–mechanical model for unsaturated soil. A brief treatment of the theoretical development of the coupled model is presented first, with specific attention to the multi‐component chemical transport theory and its cross couplings with other primary variables. The system of coupled equations is based on a mechanistic approach with conservation of mass or energy equations defining the flow behaviour and a stress–strain equilibrium equation defining the mechanical behaviour. The geochemical interactions are incorporated by linking a geochemical model with the system of coupled flow and deformation equations. Two coupling strategies, namely, sequential non‐iterative and sequential iterative approaches are incorporated to link the multi‐component chemical transport equation with geochemical interactions. The model's ability is then demonstrated via a series of 1D examples, which consider complex coupling scenarios involving all the primary variables. Specifically, the effects of multi‐component precipitation/dissolution and ion exchange reactions in a variable thermal–hydraulic–mechanical field are considered. The numerical efficiency of the model is also analysed based on these examples. It is concluded that the model not only provides a stable solution but is able to produce results that are qualitatively consistent with observed behaviour. Copyright © 2006 John Wiley & Sons, Ltd.