Bridges

This paper covers the geotechnical design and construction of a temporary retention structure used for the construction of the northern abutment of the Go Between Bridge in Brisbane, Australia in 2009. Due to site constraints along the northern riverbank of the Brisbane River, a steel pipe pile wall retention system was adopted to support a temporary excavation up to approximately 6 m deep. This retention solution was adopted for its ability to be constructed using relatively compact and light-weight equipment. The retention system was approximately 70 m wide and comprised 273.1 mm diameter contiguous pipe piles. A combination of short and long pipe piles were used to resist horizontal and vertical wall loads respectively. Short piles were 12 m in length whilst long piles spaced at approximately 3.5 m c/c extended down to bedrock. Due to the presence of a thick soft/firm clay layer above the bedrock, two rows of pre-stressed ground anchors were required to limit structural forces and displacement with a free length of more than 50 m and an average inclination of 45 degrees. All pipe piles above were structurally integrated through the use of continuous steel waler beams at the location of the anchors. The successful completion of the excavation and consequent bridge abutment construction demonstrates that this innovative pipe pile wall retention system is an effective solution for use in populated urban environments, where spatial site constraints limit the use of conventional retaining systems.