Ground improvement over soft clay main access road for Port Macquarie Airport NSW Australia Available to Purchase

This paper describes the selection and ground improvement design for a section of Boundary Street Upgrade, the main access road to and from Port Macquarie Airport, New South Wales (NSW), Australia. The existing road is single lane (each direction), constructed over soft clay which extends to a depth of 10 m for a 260 m section and prone to flooding, requires upgrade to support the future growth of the Airport and the future demand. A number of solutions to deal with the soft ground conditions were considered by the Council and Design Consultant, including building a bridge, or ground improvement techniques to reduce post-construction and differential settlement following the road upgrade. Ground improvement options including surcharging with or without wick drains and the use of rigid inclusions were considered. A major constraint was the adjacent wetland and sensitivity of fauna habitat to construction activities. Following an extensive optioneering study, rigid inclusion in the form of concrete injected columns were selected as the preferred solution, balancing cost, performance and ecological preservation. This paper presents the design optioneering process and details of the final design of the ground improvement. The final design featured the concrete injected columns with column caps and a load transfer platform which provide a sustainable and constructible solution for the upgrade.