A UNIQUE NATM SOLUTION FOR THE LONDON UNDERGROUND

This paper describes the unique NATM primary lining solution that was developed for the construction of one of the large diameter, multi-tunnel London Underground stations that forms part of the new Jubilee Line Extension Project. The successful NATM approach was developed for all lower level tunnels due to the numerous difficulties associated with constructing a complex tunnel structure in soft ground, beneath a high value urban environment. These difficulties were compounded by the impact of compensation grouting to control surface settlement, and additionally by the consequences of the Heathrow Express collapse in October 1994 which led to significant programme delays. This paper presents an overview of the effective management system required to control the work, and the shotcrete technology adopted on the project which highlighted the benefits of the wet mix system. (A) For the covering abstract see IRRD 896729.