Soft Ground, Hard Decisions

Navigating Known and Unknown Geotechnical Risks and Challenges for Boorloo Bridges

Su Kwong Tan

The Boorloo Bridge project, comprising two cable-stayed bridges, represents a culturally significant crossing over Perth’s Swan River (Derbal Yerrigan), symbolizing both historical heritage and modern infrastructure advancement. The bridges aim to provide safer, segregated access across the river, linking East Perth and Victoria Park via Heirisson Island. Challenging foundation conditions at the site include soft Swan River Alluvium (SRA) underlain by layered alluvial sand, clay (Perth Formation), and Kings Park Formation (KPF), with fill materials above the SRA. These conditions required a combination of various ground improvement and piling techniques to ensure compliance with design requirements.

This presentation delves into the geotechnical risks and challenges encountered during the design and construction phases, emphasizing the mitigation measures and decisions in response to variable ground conditions to ensure safety and compliant foundation performance. It explores strategies for addressing construction-phase changes due to unforeseen geotechnical conditions and design adjustments, which were critical to the project’s success. By showcasing adaptive real-time problem-solving, meticulous planning, and effective stakeholder communication, the presentation demonstrates how the construction schedules were maintained despite significant challenges. This presentation aims to offer valuable lessons and practical insights for tackling complex geotechnical issues in similar future infrastructure projects.

Su Kwong Tan Technical Executive, WSP

Su Kwong Tan is a Technical Executive with over 22 years’ experience in soil and site investigation works, design of temporary earth retaining systems, design of shallow and pile foundations, design of reinforced earth walls, ground improvement design and the assessment of slope stability.  Su Kwong has expertise in the interpretation of high strain dynamic pile test data and low strain test data following from his MEng Science (Research) at Monash University.  His recent experiences mainly focus on the foundation design of major infrastructures within Perth, which are primarily Alliance projects. His extensive experience in the geotechnical life cycle, managing variable and complex ground conditions, enables him to adeptly identify, mitigate, and promptly respond to both known and unforeseen geotechnical risks.

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