INNOVATION AND economy in design and construction of Ramsgate Harbour approach road won the project the South Eastern Association's annual award for engineering excellence.
ICE president Sir Joe Dwyer presented the award to the winning project team of client Kent County Council, consultants Babtie, Halcrow and Halliburton Brown & Root, and contractor Taylor Woodrow/Perforex joint venture (TWPJV), at the Association's annual dinner this week.
The 2.2km road links Ramsgate Harbour with the A253 Canterbury Road, running along the sea wall on a piled raft before cutting through the chalk cliffs via an 820m long tunnel.
As originally designed, the tunnel was to be constructed partly by cut and cover and partly by full face excavation, using the New Austrian Tunnelling Method (NATM). Full face excavation was not feasible along the whole length due to limited soil cover. Cut and cover, however, would have required demolition of 11 houses.
TWPJV proposed an alternative excavation technique, never before used in the UK, that eliminated any need for demolition and delivered environmental and financial savings to KCC.
A giant 'chainsaw' was used to cut a 200mm wide slot 5m into the chalk around the tunnel's circumference. This slot was filled with sprayed concrete to form a primary lining, or prevault, allowing excavation by traditional methods.
The operation was repeated every 0.5-4.0m, depending on ground conditions, and a 300mm thick secondary lining installed using a travelling shutter and pumped concrete.
The judges described the scheme as quite simply 'an outstanding example of a civil engineering project'.
Four other projects were commended and received their awards at the annual dinner.