UC San Diego

The phenomenon of coupled consolidation and contaminant transport occurs for a variety of practical applications in the area of geotechnical and geoenvironmental engineering. These applications, among others, include mechanical dewatering of contaminated soil or slurry, and contaminant transport through a landfill compacted clay liner during waste placement operations. In these applications, soil consolidation and contaminant transport occur simultaneously and the coupled effects must be accounted for in order to accurately simulate the transport process. First, an enhanced version of the CS2 model (Fox and Berles 1997) is presented for one- dimensional large strain soil consolidation. A variety of numeric examples indicate that the new capabilities describe important considerations for consolidation analysis. Based on the enhanced CS2 model, a numerical model, called CCRS1, is developed for one-dimensional large strain consolidation under constant rate of strain (CRS) loading conditions. Results indicate that analytical solutions obtained using small strain theory can be in significant error for large strain conditions with changing coefficient of consolidation. Based on an existing CST2 model (Fox and Lee 2008) and the newly developed CCRS1 model, a numerical model, called CSTCRS1, is developed for coupled one-dimensional large strain consolidation and solute transport under CRS loading conditions. Numerical investigations are presented to illustrate the effects of initial concentration distribution, transport conditions, applied strain rate, initial specimen height, and drainage and concentration boundary conditions on consolidation-induced solute transport for CRS loading conditions. Using the CST2 model and CSTCRS1 model, numerical investigation is conducted to compare the solute transport for increment loading (IL) and CRS consolidation conditions. Using the CST2 model, the results of a numerical investigation are presented to assess the significance of compacted clay liner (CCL) consolidation on contaminant transport through single CCL and composite geomembrane/CCL landfill bottom liner systems. Simulation results indicate that consolidation can have an important effect on contaminant transport through CCL, not only during the course of the consolidation process but also long after consolidation has ended. Analysis based on traditional advective- diffusive transport fails to consider the transient advection and properties changes of CCL caused by consolidation and thus can lead to significant errors