The alignment of the proposed Pacific Highway upgrade between Warrell Creek to Nambucca Heads traverses five (5) major floodplain areas underlain by deep soft alluvium sediments. The low bearing capacity and high compressibility of foundation soils were found to attract significant ground settlements, with differential settlements to adversely impact the performance of pavements before the end of their design life.
The paper presents the results of a feasibility study for consideration of a CRCP rigid pavement design at the Warrell Creek floodplain crossing. The study focused on provision of ground treatments suitable to limit the rate of settlement development and magnitude of differential settlements within the limits tolerated by a Mainline Carriageway CRCP pavement design.
A detailed characterisation of the foundation soils is provided based on field test assessments (i.e. to consist of CPTus and boreholes), as well as laboratory investigations (i.e. to consist of Atterberg limits and oedometer tests). On consideration of geotechnical encountered at the bridge abutments, a cost effective ground treatment was considered to consist of fill surcharge assisted by wick drains.
The foundation settlement was assessed using a commercial finite element software, Plaxis 2010. The settlement rate effects were adequately captured during the consolidation phase (i.e. primary and secondary) by adopting advanced soil models (i.e. Modified Cam Clay and Hardening Soil Models).
The settlement profile and the implications on the CRCP pavement design were studied for two (2) types of wick drain installation patterns for an optimum pavement performance.
