| Over the last few years, covers with capillary barrier effects (CCBE) have been proposed as a possible alternative to low saturated hydraulic conductivity covers, made of natural or synthetic materials, for isolating different contamination sources (domestic, industrial, hazardous or mining wastes). In that regard, CCBE can be used to restrict the ingress of both water and gas into the disposal facilities, hence limiting the exchanges between wastes and the environment.; The unidimensional hydraulic behavior of CCBE is pretty well known, and it has served as a design basis for covers installed on reactive mine wastes. So far however, little attention has been paid to geometrical (slope inclination and length) effects. The effects of cover geometry for gas barriers have been neglected even when systems were placed on the side of stacks which can have slope angles up to 20°. This has lead to misleading conclusions, and sometimes unsafe design. The main objective of the work presented in this thesis was to investigate the influence of different parameters on the humidity distribution and to relate these parameters to the efficiency of CCBE used to restrict water and gas transport, with an emphasis on the effects of cover geometry.; Laboratory and in situ tests were conducted with various layered cover systems at different scales to evaluate their hydraulic behavior under well controlled conditions, making successful comparisons between 1D, 2D and 3D calculations and actual observations. The influence of cover geometry was further investigated with a new and original experimental set up, called the laboratory inclined box, which allowed direct measurements of critical parameters.; This study also made use of results obtained from an instrumented CCBE built on a real large scale site. The in situ measurements confirmed that the position in the slope greatly affects the response of the cover. A parametric study was then performed based on various numerical analyses of unsaturated water flow through a portion of the cover placed on the side of the LTA stack. The detailed results were used to establish empirical relationships for assessing, based on simple system properties, the performance of the CCBE. (Abstract shortened by UMI.)... |
