The Lee Tunnel in Beckton, London is the first tunnel to be nominated and to win the prestigious UK Concrete Society Award. Built as part of the Thames Tideway CSO project, the tunnel is lined with an innovative Dramix 5D steel fibre reinforced concrete.
The 7m i.d. tunnel is the deepest tunnel currently in London and has five shafts supported by diaphragm walls of up to 90m deep. The steel fibre reinforced SFRC self-compacting in-situ concrete lining of both the tunnel and its shafts took 18 months for design teams to develop. In construction, the SFRC lining system was faster and safer and saved substantially on the amount of steel used.
The steel fibres in the mix provided superior bending hardening properties due to the high ductility and high tensile strength of the wire and the specifically shaped hooks. In replacing traditional reinforcement with steel fibres, designer UnPS replaced about 17,000 tonne of rebar with 2,000 tonne of Dramix 5D steel fibres. During construction, the Morgan Sindall/Vinci Grand Projets and Bachy Soletanche joint-venture (MVBJV) crews were spared the logistical challenge of installing rebar reinforcement.
This is the 48th year of the award and the 50th anniversary of the Concrete Society. The panel of judges for the 2016 series of the Awards said: “The Lee Tunnel was the most outstanding structure and therefore the outright winner for its technical achievements in the use of concrete, its demanding placement conditions and the innovative structural solutions applied. The statistics for concrete volume placed are impressive and the innovation and execution is exemplary. This project pushed the technical boundaries of what is possible with concrete.”
Peter Remory, General Manager of Bekaert Maccaferri Underground Solutions, said “We are grateful we were a contributor to this award winning project. The fibre solution we offered brought added value to the project and for its stakeholders. The newest Dramix 5D steel fibre allows higher productivity, is also more cost effective and offers enhanced durability.”
Richard Kershaw of CEMEX UK Materials, concrete supplier to the project, said: “We are honoured to receive such acclaim. Concrete was the only realistic material choice for this structure and CEMEX is proud to be part of the scheme and its legacy for London.”