Physico-chemical analysis of contaminated clay

While the influence of pore fluid chemistry on engineering behavior of soil has long been ignored in soil mechanics, recent practice in geo-environmental engineering demands an understanding of the interaction between soils and chemical pollutants. For instance, most industrial and municipal wastes are stored in clay-lined landfills. Previous experimental studies indicate that soil properties including stress-strain-strength and permeability might change significantly after being contaminated. Consequently, unless appropriately considered in the design, these changes in soil properties may cause malfunction of the landfill and induce adverse or disastrous effects on the environment.; This study addresses the influence of pore fluid chemistry on soil behavior both theoretically and experimentally. Inter-particle physico-chemical forces including double layer repulsive and Van der Waals attractive forces are considered in characterizing the interaction between soil particles and pollutants. Classical theories are available for computing these forces between two parallel particles of infinite length. However, in a real soil, clay particles are of finite size and generally are inclined to each other. In this study methods have been developed to quantify these physico-chemical forces between two inclined particles of finite size.; To model macroscopic behavior of a contaminated soil, above methods for computing the physico-chemical forces between two particles have been incorporated into a computer simulation of "many particles" interaction. Soil specimen is represented with an assembly of platy particles immersed in a chemical fluid. The physico-chemical inter-particle forces are considered in the simulation. Configuration of soil particles at equilibrium is solved with the technique of "energy minimization". The influence of pore fluid chemistry on certain mechanical behavior has been examined. Laboratory experiments have been conducted on two types of clays in nine organic chemicals and water with different salts to verify the theoretical results. Experimental and theoretical results compare reasonably well.