Abstract:
The Fitzroy River Bridge replacement in Fitzroy Crossing, Western Australia, was a critical and urgent project led by Main Roads Western Australia following the destruction of the original bridge during flooding caused by ex-Tropical Cyclone Ellie in January 2023. The bridge is located on the Great Northern Highway, the sole sealed road linking Western Australia and the Northern Territory, making its replacement vital to regional freight and community connectivity.
Due to the emergency nature of the project, detailed geotechnical investigations could not be completed prior to the commencement of detailed design. To address this, historical pile penetration data from 1972 was re-purposed using pile driveability back-analysis (GRLWEAP 14) to estimate shaft friction and end bearing capacity. Although these pile penetration tests are now considered obsolete, they provided a valuable basis for parameter estimation in the absence of contemporary subsurface data.
The replacement structure is supported by open-ended steel tubular piles driven 30 to 40 metres into the riverbed to withstand scour up to 15 metres below pile cutoff level. Pile Design and Construction methods needed to consider a strict timeframe and particular extreme load cases. Construction support included pile installation monitoring, soil and rock logging, and verification of pile capacities via PDA testing and CAPWAP analysis.
This paper outlines the adaptive geotechnical strategies that enabled successful delivery of a resilient foundation under rigorous time and information constraints.
This project went on to win the national Engineers Australia’ s “ Project of the Year” award in 2024.