Investigation and commissioning of Large Tank, Shell Compound, Lyttleton

Shell (NZ) Limited is constructing three large fuel tanks at their Naval Point compound, Lyttleton. The area is underlain by a very deep deposit of soft soil and the area has a history of problems with tank foundations. Stone columns were installed beneath each tank to stiffen the subsoils and to provide more rapid dissipation of piezometric pressures during tank commissioning. Extensive monitoring was carried out during commissioning including piezometric pressures and settlements. Settlements in the order of 600mm to 700mm were predicted during hydrotesting compared with measured settlement in the order of 550mm.