January 2009
A new third berth is being built at Vancouver's Deltaport to meet an expected threefold increase in container traffic on the west coast of North America by 2020.
The berth is being created using ten large pre-cast concrete caissons. Before the caissons could be sunk into position however the seabed first had to be densified in order to provide an earthquake proof founding layer.
In order to do this a million cubic metres of seabed were dredged to form a trench, which was then filled with a million tons of crushed rock. This crushed rock then had to be densified to a strict specification, for which Pennine was awarded the $6.5M subcontract.
Commencing in October 2007, Pennine employed the wet top feed marine vibro stone column technique to provide the required densification and mitigate against seismic risk.
The materials had an average thickness of 13.35m within the seaward apron, with an additional overbuild layer of granular feed stock placed above the filled trench to provide a sufficient supply of material for producing the stone columns.
In total Pennine has densified some 377,000m³ of granular materials within the trench, providing a team of 15 engineers operating ten BD400 vibroflots and four HD150 vibroflots to complete the work on schedule and meet the required densification prior to loading the caissons.
