NATM tunnel collapse at Heathrow Airport

Abstract On 21 October 1994, a collapse occurred in the Central Terminal Area (CTA) Tunnels of the Heathrow Express Project. The New Austrian Tunnelling Method (NATM) ‒ new in the UK ‒ was used in London Clay. The New Engineering Contract (NEC) and a self‐certification system were chosen by the client British Airport Authority (BAA). This contractual setup was a major contributing factor to the incident. The article describes the circumstances and events which lead to the collapse, the trial in the Criminal Court and the lessons learned.