Abstracts

Abstract

This chapter addresses the hydraulic properties of soils, which are primarily expressed through the concept of the hydraulic conductivity parameter in Darcy's law. In that respect, it is a companion to Chapter 5 of this book, which provides the background for the material discussed here. Initially, different models to estimate the hydraulic conductivity are presented, followed by laboratory methods of its estimation. The scale effect is particularly emphasized, the discrepancy that has been observed between laboratory and field estimates of hydraulic conductivity, which may range over several orders of magnitude. Field tests, through the pumping of wells in aquifers, are extensively presented. Steady-state solutions are initially discussed, followed subsequently by methods to assess the hydraulic parameters when the test, as is in most cases, has not reached equilibrium flow conditions. Transient radial flow to a well in a confined aquifer is presented through the Theis and the Cooper-Jacob methods. In addition, the Hantush-Jacob method for leaky aquifers, and the Neuman method for pumping tests in unconfined aquifers are described. The chapter also discusses the physical and chemical factors that affect the hydraulic properties of clay mixtures that are used as engineered barriers such as the heterogeneity, soil structure and composition, fracturing, and adsorption capacity, among others. It concludes with the effect that inorganic and organic contaminants may have on the hydraulic properties of soil-based engineered barriers.