How do you expedite building a road across a swamp?
ARRB – your National Transport Research Organisation - was lucky enough to be involved in a construction site visit as part of a recent national road Asset Management Task Force meeting in Darwin to see how it’s done.
The process adopted by the NT Department involves deep soil stabilisation to provide a supporting foundation for road construction over the saturated soft silt deposits.
Using a 45 tonne excavator with a grout injection and mixing attachment, the soft soil was stabilised with a GP cement slurry mixed to depths of up to 4 m.
Using one such excavator working inwards from each end of the alignment, the soft soil stabilisation will cross the swamp in a matter of weeks as opposed to traditional consolidation methods which can take years.
The cemented slurry sets up within 3 hours to meet the QA strength requirements with detailed records of the volume of slurry injected at each grid location and the resultant strength recorded with a cone penetrometer and shear vane.
The stabilised material is covered with a geotextile then a capping layer prior to the normal earthworks and pavement construction.