FIRST ROUND WINNER

This article describes the construction of the twin road tunnels, now being carved through Round Hill for the A20 at Folkestone, Kent, England, using the New Austrian Tunnelling Method (NATM). The advantages of the NATM were shown well, when a major inflow of rock into the tunnel was rapidly stopped and controlled. The tunnel's contractor and consultant both consider the NATM to be ideal for relatively short bores and also for the complex caverns that will be needed for some future engineering works in the UK. At Round Hill, some key staff, who worked on the Channel Tunnel, are again working together driving two 380m long road tunnels, which will carry part of the dual carriageway realignment of the A20 from near the Tunnel's Cheriton terminal to Dover's Western docks. The most outstanding feature of the construction of these tunnels is the remarkably productive use of both labour and machinery there. A Voest Alpine roadheader from the Channel Tunnel is excavating chalk marl from the face in 1.5m bites. The exposed chalk arch is stabilised with shotcrete sprayed on from each side of a twin pot pump; the precise mix of the shotcrete is critical, and the shotcrete has to be available 24 hours a day. A minimum of labour is used.