Abstract: By constructing the confined disposal facilities for contaminated dredged sediments from lakes in China the thick clay layer is usually chosen as a natural barrier. Because the clay layer will undergo a large-deformation consolidation due to the overburden of dredged material, the soil deformation should be considered by investigating the transport and transformation of contaminant in clay barrier. Based on the Gibson’s one-dimensional consolidation theory and the dispersion-advection equation of contaminant in saturated porous media, a theoretical model for coupled large strain consolidation and solute transport is herein presented, in which soil weight and biodegradation effect are first taken into account. Using numerical solutions of the derived model the transport and transformation of contaminant in a deforming soil layer are first studied thoroughly; the effects of different parts and parameters of the model are then analyzed respectively. It is shown that the large deformation of soil has complex effects on the transport of contaminants in clay layer. On one hand, soil deformation can accelerate the transport speed of contaminant, and on the other hand, decrease of coefficient of permeability due to soil consolidation is able to increase the breakthrough time of contaminant. These two different effects rely on many factors, such as the thickness of soil layer, adsorption ability of soil, etc. The obtained results from this study are meaningful by assessing the separating capacity of natural clay barrier for contaminant transportation.

Key words: contaminant, clay barrier, large-deformation consolidation, solute transport model, biodegradation