Heathrow's hidden gems

The tunnelling associated with the construction of Heathrow Airport Terminal 5, UK includes two rail tunnels: the extension to London Underground's Piccadilly Line and BAA's Heathrow Express. The rail tunnels are due to carry their first passengers in March 2008. To reduce the risks associated with tunnelling, the same companies have been responsible for the construction of all tunnels. Signalling is the only activity carried out by different contractors. London Underground PPP contractor Tube Lines has carried out signalling on the Piccadilly Line extension and Westinghouse has installed signalling on the Heathrow Express extension. When the Heathrow Express was built, T5 was planned, and stub tunnels were constructed, enabling tunnel boring machines (TBMs) to drive straight off. To construct the new twin Piccadilly Line bores, Morgan Vinci had to construct a box from which to launch its TBMs. A new junction box had to be constructed to connect the new tunnels with the existing Piccadilly Line at Terminals 1, 2 and 3. A new form of New Austrian Tunnelling Method, known as Laser Shell, developed by Mott MacDonald and Morgan Vinci, was used for the cross passages and connections on the two rail extension projects.