Performance of shallow foundations on municipal waste landfills

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There are tens of thousands of closed municipal landfills in Canada, primarily in and near urban communities, and these lands, for the most part, remain unused or used only for very low-value purposes. There is an opportunity to explore the use of these lands for industrial or municipal infrastructure, thus freeing up other land for high value activities. It is therefore necessary to consider the properties of landfilled waste when evaluating the possibility that infrastructure may be constructed on closed landfills. At present, technical and regulatory barriers to higher-value uses of closed landfill sites are associated with two categories of risk, which may be termed: i) "Environmental Risk"; and ii) "Geotechnical Risk". There is evident environmental risk associated with explosion hazard as well as contaminants in landfill gas. Without dismissing concerns regarding Environmental Risks, the intent of this proposal is to consider that -assuming modern engineered barriers can be used to mitigate environmental risk - the limitations to higher-value after-uses would increasingly switch toward the risk associated with the geotechnical or mechanical properties of the waste fill material and the consequent performance of facilities constructed on waste. There are several examples of significant infrastructure supported by shallow foundations on waste. For example, 3 wind turbines supported by large ring footings on a landfill in Karlsruhe Germany have undergone significant vertical settlement with only minimal problems with differential settlement or tilting, although the degree to which the designs might have been made more efficient is not known. A number of researchers have studied the overall settlement of landfills, however studies to date have not addressed the scale and patterns of differential settlement and the consequent effect on shallow foundations. The research will incorporate field and laboratory tests intended to provide engineering designers with an enhanced basis upon which to design facilities on landfilled waste, with the view to reducing the level of uncertainty and associated overdesign.