Controlled Modulus Columns Ground Improvement for Sydney Gateway Project

The proposed alignment for Sydney Gateway predominantly requires new embankments with a relatively small proportion of cut and at grade pavements. These embankments are founded on compressible soil and municipal landfill, which are expected to undergo consolidation under the increased effective stress imposed by the new embankment loading. Rigid inclusions in the form of Controlled Modulus Columns (CMCs) have been adopted to meet the design criteria settlement requirements. Primarily, CMCs were adopted to support nine embankment bridge approaches with fill heights reaching up to 9.1 m. CMC ground improvement was also adopted to support a box underpass structure and a new road through Tempe Tip mainly consisting of shallow cuttings and embankments on a municipal landfill. This paper presents an overview of the CMC design features for the Sydney Gateway. The aim of the paper is to highlight how upfront support from specialist geotechnical contractor to the main contractor and the designer ensured efficient and practical ground improvement solutions were designed.