Temporary works specialist Groundforce Shorco has supplied what are believed to be the largest-ever proprietary hydraulic shoring struts for use on a mixed-use development in North London.
Five custom-built MP250 hydraulic struts, measuring 1.2m in diameter and up to 43m long, are being used to support a massive basement excavation on the site of developer Sager’s new multi-million mixed use scheme at Fortune Green Road, Hampstead comprising 72 apartments, a gymnasium and retail units over two levels of car parking.
Occupying a roughly triangular excavation measuring 93m in length and up to 59m wide, the sloping nature of the ground across the length of the site meant that two of the project’s storeys are below ground. Asked to tender for the supply of ground support equipment, Groundforce Shorco specified a combination of its MP125 and MP250 heavy duty hydraulic struts to support the 7m steel sheet piles that line the excavation.
“The longest, single span is 43m and for this we originally specified 250 tonne capacity MP250 struts with standard 600mm tubular extensions” says Groundforce Shorco design office manager Neil Bleakley.
“However, these struts would have required central, vertical supports to maintain sufficient axial capacity over their length and the client wanted a clear span to aid the development programme”, he says.
In response to this challenging demand for a clear span, Groundforce Shorco designed and produced five custom-built MP250 struts incorporating 1.2m diameter tubular extensions. The largest struts of their type in the UK – they offer superior rigidity and strength, capable of withstanding the full 250 tonne load at spans up to 45m without additional support.
The £4.5 million groundworks package of this multi-million pound project commenced November 2006 with the installation of sheet piling using a Giken silent piling machine. Sager then started excavating the basement before installing a steel waler beam around the piled perimeter. Groundforce Shorco worked closely with Sager and Structural Engineers Michael Baigent Orla Kelly Ltd to coordinate delivery and installation of the large diameter struts, each being supplied in modular format, built in-situ and lifted into place.
Groundforce Shorco’s involvement is due to finish in May, when the struts will be de-mounted and lifted out of the excavation. However, Mr Bleakley says the specially developed 1.2m diameter MP250’s will not lie idle for long.
Sager’s Managing Director commented,
“The whole experience with Groundforce Shorco on this project has gone incredibly smoothly, considering complexities with the span of the excavation and the obstacles that we had to overcome to use the struts without a central support to prevent them from sagging. It was important to us not to have a central support system which would require king posts being installed and thus pose practical difficulties to our programme.
From the intricate design and decision stage through to the on-site installation, Groundforce Shorco has been extremely professional and innovative throughout.
