Soft soil work
Soft soils are an important design consideration for the project as there are deep soft soils in floodplain areas along the upgrade.
Key features of soft soils include high water content, low capacity for allowing water to pass through and low strength. Without soft soil treatment there is the potential for highway foundations and main alignment to sink and crack. This is because the bearing capacity of the soil is not strong enough to support the highway.
Treating soft soil before building the main alignment takes time but saves money. The aim is to consolidate the soil so it can be built on. Consolidation involves squeezing the water from the soil to make it denser.
It will take about two and a half years for the soil to consolidate once the water is removed. This is the reason soft soil treatments are starting early.
Soft soil work will occur in four waves:
- Wave 1 Farlows Lane to Chatsworth Road
Work between Farlows Lane, Maclean, and Chatsworth Road, Chatsworth Island, is well advanced. Heavy machinery was used to remove earth from a hillside at Tyndale. This was eventually used for fill along the alignment. Similar work is being carried out at Green Hill, Gulmarrad, where fill is being collected for the foundation at Chatsworth Island.
- Wave 2 Whytes Lane to Pimlico Road
Work between Whytes Lane and Pimlico Road, Pimlico, is also progressing well.
- Wave 3 Shark Creek to Maclean
Roads and Maritime Services has contracted FKG Group to carry out soft soil treatment work and early work activities on the Woolgoolga to Ballina upgrade between Tyndale and Maclean.
- Wave 4 Tuckombil Canal
Work includes a 1.7km section of soft soil work between Trustums Hill Road and Woodburn-Evans Head Road.