Model for Coupled Large Strain Consolidation and Solute Transport in Layered Soils

A numerical model, called CST3 (Consolidation and Solute Transport 3), is presented for coupled one-dimensional large strain consolidation and solute transport in layered soils. The consolidation algorithm accounts for vertical strain, soil self-weight, general constitutive relationships, relative velocity of fluid and solid phases, changing compressibility and hydraulic conductivity during consolidation, unload/reload, time-dependent loading and boundary conditions, external hydraulic gradient, variable preconsolidation stress profiles, and multiple soil layers with different material properties. The solute transport algorithm accounts for advection, diffusion, mechanical dispersion, linear and nonlinear sorption, equilibrium and nonequilibrium sorption, porosity-dependent effective diffusion coefficient, and first-order decay reactions. CST3 is based on a dual-Lagrangian framework that separately tracks the motions of fluid and solid phases. The development of CST3 is first described, followed by verification checks. Numerical simulations indicate that layered soil heterogeneity and preconsolidation stress can have important effects on consolidation-induced solute transport behavior. Failure to correctly account for soil heterogeneity or preconsolidation stress profile can lead to significant errors in the analysis of consolidation and solute transport in layered soils.