Structural performance of a steep slope landfill lining system

The stability and integrity of a landfill barrier, in both the short and the long term, are vital to performance as a containment system for leachate and landfill gas, and are a requirement of the UK permitting process. The structural performance of steep, non-self-supporting barrier systems depends in part on the adjacent waste body for lateral support. This paper presents the results of an investigation into structural performance during construction of a typical UK mineral steep slope landfill lining system. Instrument installation, monitoring and results are presented. Measurements and observations have shown shear and overturning modes of clay barrier failure, leading to loss of integrity. Normal stresses measured at the waste/barrier interface demonstrate that waste adjacent to the barrier provides low and variable lateral support. It is concluded that this has led to the observed failure mechanisms. Temporary conditions during phased construction are shown to be critical. This investigation has demonstrated that current UK municipal solid waste, placed using standard practices, cannot by itself provide sufficient support to ensure the integrity of a clay barrier in a steep slope lining system. Waste/barrier interaction must be considered as part of the design process.