Electricity rather than diesel is being used to power a hydrofraise diaphragm wall rig constructing shafts at Tideway’s Chambers Wharf site in Bermondsey in a bid to cut noise levels and improve verticality.
The Costain, Vinci Construction Grands Projets and Bachy Soletanche (CVB) started work using the rig – which is believed to be a world first – at the end of August.
“As well as being more environmentally friendly, it also means the machine will be quieter when it’s in use,” said Tideway geotechnical construction manager Martin Stanley. “This type of Hydrofraise machine is thought to be one of the first of its kind in the world, so we are really proud we’ve been able to launch it and will continue to look at ways of reducing our carbon footprint and minimising any disruption to our neighbours.”
The rig has a Evolution 3/5 Hydrofraise on a Soilmec SC120 powered by a 600kW electro-hydraulic power pack connected to a sub-station on site.
According to Stanley, the challenges of developing the rig centre around cooling and generating sufficient power to run the hydraulic circuits in a compact unit. “The other issue is having sufficient mains power but here that is not a problem as the site is set up for powering the tunnel boring machine (TBM),” he said.
At Chambers Wharf, the rig is being used to construct 36, 1,500mm thick by 2,800mm wide by 73m deep panels to form the launch shaft for the main tunnel drive for CVB. The shaft will also act as a reception chamber for the TBMs being used to drive the tunnel being constructed by Ferrovial Laing O’Rourke from Kirtling Street and a connection tunnel being built by CVB.
Use of a Hydrofraise is essential to achieve the 1:400 verticality specification for the shafts on Tideway and will enable over-cutting for the secondary panels instead of the use of stop ends.
Soletanche Bachy Group developed the rig with input from a number of specialist industry partners and will also be used to construct shafts at Deptford Church Street and King Edward Memorial Park.