Coomera Connector Stage 1 – South (Smith Street Motorway to Nerang-Broadbeach Road)

The project involved the delivery of a 4.4-kilometre section of new road corridor designed to improve connectivity between Logan City and the Gold Coast by providing a vital alternative to the M1 Pacific Motorway. The project scope of works included bulk earthworks, hard rock excavation for major cuttings, ground improvement activities, and the construction of three new bridge structures including a 300m long bridge over the Nerang River.

FSG’s scope comprised the detailed design of all geotechnical elements including piled foundations to bridges and ancillary structures, soft soil treatments, embankments and culverts, earthworks, cuts and batters, and reinforced earth structures. A key highlight of the design included the early development of geotechnical models in the soft ground areas using an extensive CPT, CPTu and Geophysical (MASW) investigation to redirect the horizontal and vertical alignment of the road to areas that required significantly less ground improvement and interaction with the adjacent QR rail line resulting in significant time and cost savings.

Initial site investigation (SI) data was limited with no detailed soft soil design data. FSG scoped and managed the supplementary SI (executed by TMR). FSG initially commissioned MASW to identify paleo channels and high risk/high reward areas. High quality nested testing was then performed in key soft soil areas with side-by-side CPTu, DMT, shear vane and undisturbed sampling for odometer testing. This high quality testing facilitated the development of reliable soft soil correlations which could then be applied to more rapid standard CPT testing across the project thereby increasing confidence in the soft soil design and accelerating the design program.

At the request of TMR, the geotechnical design was then fast tracked in order to facilitate an early works contract which was tendered and awarded ahead of program to mitigate overall program risk. FSG’s ability to work closely with TMR in order to accelerate the SI program and geotechnical design resulted in significant time savings and risk mitigations to the project.