ABSTRACT
The base case design for the Airside Road Tunnel (ART) portal structures was undertaken during 2000–2001, with the west portal design being followed by the east – the same order in which they would be constructed. In the long term, the ART forms an integrated transport route between the Heathrow Central Terminal Area and T5. The base case design for the ART was robust and satisfied all of the project criteria of cost and programme. For the ART the key to unlocking the restrictive spatial constraints was the development of using intermediate blinding struts for contingency lateral support. The success of the observational method (OM) at the western tunnel boring machine chamber encouraged the team to extend its application to the other elements of the ART portals. The novel approach of providing contingency support through blinding struts enabled the OM to be applied successively to the wide range of individual elements of the ART portals.
