Northern Line Extension

London Underground (Transportation for London)

This project entailed the construction of the expansion of the Northern Line with approx. 3 km of planned bored tunnels (5.2m internal diameter), along with the construction of two new London Underground stations – Nine Elms and Battersea. A Step Plate Junction was constructed using SGI / Timber Heading in order to connect to the Northern Line’s existing loop tunnel at Kennington Station to the new extension. Further the existing Kennington Station was enlarged by 4 additional Cross-Passages with SGI lining and hand mining.

TBM Tunneling Expertise Consulting Services:

Gall Zeidler Consultants provided pre-tender design services to a contractor JV and subsequently independent Category III check design services for all SCL structures, the Step Plate Junction and new Kennington Station cross passages.


London, United Kingdom


2016 - 2018


SCL Shafts, SCL Launch Tunnels, SCL Running Tunnels, SGI / Timber heading for Step Plate Junction and station cross passages


3km Bored Tunnels, 2 x 77m SCL, Launch Tunnels, 2 x 20m SCL Stub, Tunnels and approx. 300m SCL Running Tunnels


SCL up to 40m2, SGI/Timber Headings for step plate junction varying


London Clay, Harwich Formation, Lambeth Group




Laing O’Rourke Ferrovial (FLO) JV


London Underground (Transportation for London)