Design And Construction Of A Resilient Motorway On Difficult Ground

Resilience is the ability of assets, networks and systems to anticipate, absorb, adapt to and / or rapidly recover from a disruptive event. Where motorways cross floodplains, a major flood poses the greatest risk of a disruptive event. Deep deposits of soft, compressible materials are often encountered in floodplains making construction of resilient infrastructure difficult and potentially expensive.

In order to optimise the balance between time, cost, resilience and risk the Roads and Maritime Authority of New South Wales (RMS), in conjunction with the Ballina Bypass Alliance, developed a low embankment strategy to minimise the whole of life cost of the Ballina Bypass motorway while allowing the motorway to operate during a 1 in 20 year flood. The low embankments traversed very poor ground conditions and the geotechnical challenge was to estimate performance of the embankments at the design stage, monitor the actual performance of the embankments during construction and to take actions to achieve the strategic goals if required.

This paper presents the low embankment strategy, the associated pavement strategy and discusses the geotechnical elements pivotal to its success.