Tubelines Ltd (now London Underground) contracted ITM Monitoring to undertake work on three sections of the network; the first was a section of tunnel between Embankment to Waterloo running South on the Northern Line, and two ‘comparison sites’ were named as Golders Green to Hampstead also on the Northern Line, and Aldwych, a disused Underground Station.
With the objective of understanding the effects of transport function on a tunnel in comparison to a similar structure in disuse, the project studied the tunnel movement, the cause and then the most effective solution, in order to better predict these occurrences in the future.
Summary of the works
Client: Tubelines/London Underground
Duration: 2011 – Present
Monitoring System: Golders Green – Joint meters and Tilt sensors – ARGUS software – Deep level Cross passage monitoring to measure any deformation of Cross passages/openings and surrounding cast tunnel pans on the Northern Line.
Monitoring System: Aldwych Disused Station – Joint meters and Tilt sensors – ARGUS software – Deep level Cross passage monitoring to measure any deformation of Cross passages/openings along with surrounding cast tunnel pans, spiral staircase and disused lift shaft which are now used for filming such as the James Bond films.
Monitoring System: Embankment –Waterloo (Northern Line) – Tilt sensors & Tape Extensometers arrays – ARGUS software – The section of Northern Line running south between Embankment and Waterloo consists of two tunnels suffering the effects of ‘river scour’, causing the top of the tunnels to become exposed. There is a risk here of tunnel deformation so in order to monitor this section of works chains of electrolevels and tiltmeters were installed along with back-up monitoring from tape extensometers.