Excavation, Structural Stabilisation And Groundwater Management By Jet Grouting On Sydney Harbour Foreshore

A former town gasworks site on Sydney Harbour’s foreshore has been the subject of site remediation to address residual industrial contamination. Jet Grouting was undertaken under a Design & Construct contract to form a temporary retaining structure behind and under the full length of a 19th Century seawall, thereby facilitating the excavation and exsitu remediation of contaminated materials at the site and ensuring long-term stability of the seawall. In addition, existing heritage buildings were underpinned with Jet Grouting to ensure the structural stability and integrity of these structures during the excavation phase. The excavation was up to 7m deep and 6m below sea level. Jet Grouting was undertaken under strict settlement and deflection controls, with a target permeability no greater than 1×10-7 m/s. The works were performed by installing over 300 Jet Grout Columns ranging from 1.2m to 2.5m in diameter. Jetting was partially carried out from within the confines of existing heritage structures, while the bulk of the external works was carried out from within an environmental odour control enclosure. The confined nature of the site and its access limitations required the effective co-ordination of Jet Grouting with other site works.