Ground improvement works for Brunswick Heads to Yelgun Freeway

Jeff Hsi, Anthony James Jones and Viet Nguyen

Brunswick Heads to Yelgun Upgrade of the Pacific Highway, which was awarded as a design, construct and maintain for 10 years project, involved duplicating and reconstructing the existing two lane carriageway to provide four lane carriageways over a length of about 9 km. It also involved conversion of the existing Pacific Highway over part of this length into a service road running parallel to the through-carriageways. The project alignment included cuttings to 30 m depth and embankments reaching up to 10 m over soft ground. There were 13 sets of bridges including the major Brunswick River bridges which had a 10 m high southern approach founded on soft ground. There were two sets of three bridges at Marshall’s Creek and its overflow where soft ground extended to significant depths. The project included 20 retaining walls, several of which were in soft ground areas requiring foundation treatment. Concrete Injected Columns (CICs), which were installed using the Soil Displacement Pile technique (Bauer BG-System), had been adopted at several bridge approaches and retaining walls in order to support the embankments and limit differential settlements to acceptable amounts. This method had significant cost, environmental and programme benefits. This paper will outline the project, the design and construction methodology and performance of the CICs.