The Ohio State University 2007. - 270 с.
A Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Jangguen Lee, M.S
Abstract
Classical solutions for solute transport through a porous media are derived for rigid materials in which no deformation occurs during the transport process and advection is steady. There are cases, however, in which consolidation causes volume change during solute transport.
The consolidation process takes on particular significance for fine grained soils at high water content, such as dredged sediments, but has also been shown to be important for compacted clay liners during waste filling operation A numerical model, called CST2, is presented for coupled large strain consolidation and solute transport in saturated porous media. The consolidation and solute transport algorithms include the capabilities of a previous code, CST1, with the addition of a variable effective diffusion coefficient during consolidation and nonlinear nonequilibrium sorption. A parametric study illustrates that, for the test cases considered, variation of effective diffusion coefficient during consolidation has an important effect on solute transport, and nonequilibrium (i.e., kinetic) sorption can have a strong effect on consolidation-induced solute transport and that this effect becomes more important as the rate of consolidation increases.
An experimental investigation was performed to determine the effect of clay consolidation on solute transport parameters. In general, the experimental results suggest that changes in effective diffusion and hydrodynamic dispersion coefficients should be taken into account during clay consolidation whereas the sorption isotherm and dispersivity may be considered as unchanged during the consolidation process.
Solute transport tests were conducted on composite specimens of kaolinite slurry consisting of an upper uncontaminated layer and a lower layer contaminated with potassium bromide. Numerical simulations were performed using the CST2 model. The importance of the consolidation process on solute transport is assessed based on measured and simulated solute breakthrough curves and final contaminant concentration
profiles.
CST2 simulations closely match the experimental data for different initial boundary and loading conditions. Results also indicate that both diffusion and consolidation-induced advection made an important contribution to solute transport and mass outflow, with consolidation having the largest effects for tracer transport. This study suggests that neglecting transient consolidation effects may lead to significant errors in transport analyses involving soft contaminated clays undergoing large volume change.
Dissertation Organization
This dissertation is organized as follows:
Chapter 2 presents a literature review of past work related to the research topic. Chapter 3 presents the development of the CST2 numerical model including verification with existing analytical and numerical solutions, and a parametric study with respect to the significance of variable effective diffusion coefficient and nonlinear nonequiliribrium sorption for consolidation-induced transport. Chapter 4 presents the experimental program used to evaluate the effect of clay consolidation on solute transport parameters and to investigate consolidation-induced solute transport. Chapter 5 presents the experimental results and numerical solutions for consolidation-induced solute transport for a variety of boundary conditions and loading schedules. Finally, Chapter 6 presents conclusions and recommendations for future research.
