London Heathrow is one of the busiest airports in the world. The "Heathrow Airside Road Tunnel" was intended to connect the western airport area logistically to the terminal. Two tunnel tubes, each measuring 1,273 meters, were to be excavated, crossing under the airport taxiway as well as the existing Heathrow Express Tunnel. This called for surgical precision while constructing a tunnel with a diameter of nine meters.
The EPB Shield (S-185) was designed to operate in compressed-air mode as well as in classical EPB mode with mechanical support of the tunnel face in order to drive through heterogeneous geology with optimal performance. With success, because both tunnels were completed in June 2003 after just ten months' tunnelling without even coming close to the defined limits for heave or settlment.