Pile Foundation Optimisation for Rail Bridge: A Case Study From Dodson Road, Bunbury, Western Australia-PPT Presentation

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The Dodson Road rail bridge in Western Australia, a four-span timber structure serving the Australind rail line, was replaced during an eight-month shutdown. The project required a cost-effective, low-risk piling solution that limited community and environmental impacts.<br /><br />Ground conditions varied sharply between abutments. Dense sand over soft clay at the east abutment created a risk of pile refusal, while acid sulfate soils (ASS) made excavation and spoil handling undesirable. The original design used large steel tubular piles, but durability concerns and cost led to an optimised solution: 400 mm square precast concrete displacement piles, which disturbed less soil and avoided ASS spoil treatment.<br /><br />Additional construction-stage CPT investigations, drivability modelling and an instrumented trial pile were used to manage uncertainty. Although the analysis identified potential refusal under some ground-strength scenarios, the trial pile was driven successfully to 14.5 m without predrilling. Dynamic testing confirmed adequate capacity and acceptable stresses.<br /><br />All 28 production piles were installed to the required depths without refusal or predrilling. PDA testing on 14 piles confirmed capacity and structural performance, with measured capacities exceeding design requirements. Ground conditions influenced load transfer: east-abutment piles relied more on end-bearing, while west-abutment piles developed more shaft resistance.<br /><br />The project demonstrated the value of integrating design analysis, trial installation, dynamic testing and field monitoring. The change in pile type, efficient installation and avoidance of ASS spoil treatment delivered estimated savings of $800,000–$1 million while reducing construction risk and uncertainty.

Keywords

Dodson Road rail bridge

Western Australia

Australind rail line

timber bridge replacement

precast concrete displacement piles

acid sulfate soils

piling solution

dynamic testing

pile drivability

construction risk reduction