The opening of the new runway at Brisbane Airport in Queensland marks the successful culmination of one of Australia’s largest aviation construction projects, and leading global engineering and consulting firm Golder is proud to have been involved throughout the journey.
The runway, which opened on 12 July 2020, doubles the capacity of Brisbane Airport, enabling the airport to meet increased demand as the city and region continue to grow.
Golder has supported this extensive project with geotechnical and environmental services since its inception, as part of Golder’s long-term relationship with Brisbane Airport of more than 35 years.
“Over our lengthy involvement with Brisbane Airport, we’ve been able to build a deep knowledge of the complexities of the airport site and the intricacies of our client’s business and industry, so that we can deliver solutions that match their priorities,” said Scott Fidler, Golder’s Regional Manager in Australia and New Zealand. “We are proud that our multi-disciplinary expertise has supported our client to safely and successfully complete the runway despite complex and challenging ground conditions.”
The runway project posed unique challenges. To protect against flooding and storm surges, the site level needed to be raised by approximately 3 m. However, the new runway site overlies the compressible clay soils of the Brisbane River Delta, which can be up to 35 m deep and 25 m thick. The weight of the sand fill used to raise the site level caused consolidation and settlement of the compressible clay soils as water ‘squeezes out’.
Golder’s specialists undertook extensive site investigations to understand how the ground conditions varied across the 360 hectare site and to design the appropriate ground treatments to create a stable, solid and reliable foundation for the runway and related infrastructure (such as roads).
In areas with very thick, deep clay deposits, Golder applied a surcharging technique to accelerate settlement and minimize the risk of ground movement after construction. This involved placing large loads of sand on areas of the site to squeeze out water and compress the soil, creating a firm foundation for the runway.
To create the temporary and permanent ‘load’, 11 million m3 of sand was dredged from Moreton Bay and pumped onto the site, staying in place for up to 3 years. More than 330 000 prefabricated vertical wick drains were installed across the site, allowing water to escape, and speeding up settlement by 30–40% compared with gravity alone.
Golder’s team monitored the performance of the ground improvement works against predictive modelling. The ground improvement works were successful, and construction was able to begin in 2017 on the 3.3 km long, 60 m wide runway and the parallel and linking taxiways.
Over the past 15 years, Golder has also provided environmental impact assessments, acid sulfate soil assessments, groundwater monitoring and modelling.
“The investigations, design and monitoring that our teams have undertaken at the site have been essential for reducing risks and have provided our client with a high level of confidence of achieving their goals,” said Fidler.
“Our guiding principles throughout the project have been to deliver not only value for our client but also the lasting, reliable infrastructure that will serve the community for generations.”