THE PROJECT
Airportlink Brisbane is a 6.7 km toll road and the longest tunnel in Australia at the time of construction. A total of 15 km of tunnelling includes twin 5.25 km running tunnels, a 3 km busway tunnel and various exit and entry ramps, interconnecting emergency access ways, and cross passages. It connects the CLEM7 Tunnel, Inner City Bypass and local road network at Bowen Hills, to the northern arterials at Kedron; Sandgate Road, and the East West Arterial Road leading to Brisbane airport.
PSM was engaged to provide expertise in investigation interpretation, ground characterisation and excavation support design as part of the JV design team.
OPPORTUNITIES
This high-profile project had an exacting delivery timeframe and attracted a high level of public concern about the impact of excavation and construction. A joint venture with multiple partners, effective communication was critical.
Engineering and technical opportunities included:
- Up to 25 m span caverns excavated below residential areas
- Difficult ground conditions including interactions between shales and volcanic tuffs, with a significant extent of ‘bad ground’
- Tunnelling beneath heritage structures
- Presence of artesian ground water
- High traffic flow and haulage of spoil through residential areas.
APPROACH AND INNOVATION
Following rigorous assessment and modelling, PSM’s tailored approach included:
- Design of initial support structures including large span caverns, decline structures and mainline running tunnels
- Development of project-wide tunnelling design parameters
- Creation of a tunnel design manual
- Provision of training in data interpretation
- Development of a project-wide, 3D geological and geotechnical ground model.
OUTCOMES
As part of a multi-partner design team, PSM’s models contributed to the understanding and visualisation of the ground conditions. This resulted in innovative and efficient design by minimising unforeseen bad ground. More precise prediction of conditions also enabled the client to improve resources and deliverables scheduling.
Services: #Airportlink #Geological #Geotechnical #Tunnelling
