Geotechnical Challenges of Brownfield Sites for Use as Landfill

This paper looks at the geotechnical challenges associated with siting a landfill at a brownfield site in south east Queensland. In particular, the geotechnical issues encountered at former quarry and mine voids and underground coal workings, when endeavouring to ascertain the maximum airspace at a proposed landfill site, will be considered. Geotechnical features will include highwall stability, managing the risk of subsidence of underground mine workings, dealing with residual waste materials such as carbonaceous material, tailings, spoil etc. and the management of spontaneous combustion of former coal workings and coal rejects. 3D conceptual models of underground workings and photogrammetry surveys of highwalls used to assist in the assessment of geotechnical risks are presented. Key emphasis will be given to the assessment of the stability of selected landfill lining systems for both basal lining and final closure, as innovation in this area can be key to maximising airspace and enhancing asset value. Critical factors affecting the performance of landfill lining/capping systems will also be discussed.