Modern sanitary disposal sites, in contrast with old garbage dumps, are based on the concept of assuring minimum environmental impact. Clay is a material nearly unavoidable in the design of landfill bottom liners. However, if mechanical behaviour of clay in contact with water is rather well known, we have little knowledge about properties of clay permeated with leachate. The influence of leachate on geomechanical properties of clay is examined. Various tests are performed with and without leachate to see clay evolution when in contact with pollutant. Leachates vary from one landfill to another and also evolve with time according to the age of deposits. For this reason, a composed leachate as representative as possible of landfills in general is used. The first tests concern the changes in intrinsic properties of the clay: structure, suction, Atterberg limits, compacity. Mechanical properties of clay are examined too. Geotechnical tests, in saturated conditions, have been performed in laboratory for two temperature (20° and 60° C) and four combinations: clay prepared with water and water used during testing (reference); clay prepared with water and leachate used during testing (real case in landfill); clay prepared with leachate and leachate used during testing (particularly unfavourable case); and, clay prepared with leachate and water used during testing (unreal case to show influence of osmotic phenomena). The paper will overview the first results gained.
The time of garbage dump seen as a pile of wastes is over. Our concern is to improve the environmental quality of these sites. The aim of the investigation described here is to compare the behaviour of clay - the mechanical properties of which as landfill bottom liner have long been proved - wet by water with that wet by municipal solid waste leachate.
