Push Pull - Case Study
New Basement, Hornsey Street, London
Major UK contractor Kier London, in conjunction with Corus Hydrobarrier, used the Dawson Construction Plant Ltd, Liebherr LRB255 rig and four-cylinder Push-Pull attachment, to install 150No, AU16 sheets. The sheets were between 6.5m and 8.5m long (fully driven into stiff London Clay - cohesion in excess of 150kN/m2) and were used to form the watertight retaining walls of a new rectangular basement. The basement formed part of a new £26m development. This contract was to be the first time that the new “wide” U profile sheets were to be installed using hydraulic pressing.
The sheets had to be installed quietly and without vibration, because of their close proximity to housing and the East Coast Main Railway Line. In the vicinity of the railway line a crane was not permitted, hence the pitching and driving of the sheets had to be done by the rig alone. The basement had to be watertight, so the design required the interlocks to be welded and the sheets also carried significant vertical load from the seven storey building above ground.
Significant cost savings were offered to the client by using “AU” sheets, specifically:
· Efficient use of steel
· Handling and installation savings
· 20% saving in welding of interlocks
The sheets and corners were installed within 10 working days without the use of pre-augering or water jetting. This high productivity was achieved despite the restrictions due to the railway. The productivity was combined with excellent positional accuracy (within ±25mm) and verticality using only a ground beam.
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