THE PROBLEM
The Port of Gisborne Logging Yard has been constructed over reclaimed land. The subgrade for the log yard contained soft areas with a CBR of less than 1%. The client experienced considerable problems with trucks and loaders sinking up to their axles.
THE SOLUTION
The solution was to provide a Tensar mechanically stabilised layer (msl). This enabled a reduction in pavement depth from 700mm to 350mm. Road building materials in the Gisborne area are very expensive and considerable savings were made.
PROJECT DESCRIPTION
The reclamation fill comprises approximately a 4m depth of variable material including organic matter, timber, concrete and hardcore all over a shelf of unconsolidated muddy sandstone, known locally as papa soil. Occasional infilled channels up to 10m deep were encountered.
Loadings on the yard include a 70 tonne axle loading Wagener which unloads approximately seventy to ninety, 14 tonne tandem axle trucks per day. The fully laden trucks are up to 46 tonnes capacity.
Tensar Geogrid was laid on the subgrade and covered with 150mm to 200mm of quarry scalpings. This was topped with 100mm of AP40 basecourse and 50mm of AP20 surfacing.
’’After ten years of heavy duty use, the installation has performed satisfactorily and has proved a cost effective construction.”
