FORMING THE FRENCH CONNECTION - A86

To preserve historic sites such as the chateau de Versailles and scenic parkland, the A86 west, the final link of a ring road around Paris, was built underground. It is comprised of two tunnels, the east tunnel and the west tunnel. The latter will be built later. They are both toll tunnels and are 10 km and 7.5 km long, respectively. The east tunnel will have two decks, each with two lanes of one-way traffic and a hard shoulder with a peak capacity of 4,600-6,400 vehicles an hour. Numerous safety measures are planned, along with an intermediate underground interchange with the A13. It is designed for light traffic only. The west tunnel, which will be a conventional single-deck design will accommodate HGVs and light traffic with a maximum grade of 2%. The project suffered a tunnel fire in 2002, which burned the conveyor belt and the service train fuel. It was caused by a leak in a turbo of the locomotive's propulsion system. Another challenge was tunneling beneath a busy electrified rail line. Describes geology, safety programs and questions from the floor after the presentation before the British Tunneling Society.