GCG’s initial role was to analyse the results of the trial tunnel and advise Charles Haswell & Partners and London Underground Ltd (LUL) on the effects of tunnel construction on the existing LUL Piccadilly Line tunnels. Eight and a half metre diameter station tunnels were to be constructed directly beneath the Piccadilly Line and finite element modelling was used to predict the potential tunnel settlements and distortions.
The station tunnels in the Central Terminal Area collapsed in October 1994 causing much uncertainty over the reliability of the SCL technique in London’s ground conditions. After an investigation, the project was restarted the following year and successfully completed in 1998. GCG was asked to provide expert witness advice to Balfour Beatty on the detailed cause of the collapse. State-of-the-art numerical analysis was used to model the construction sequence and examine soil behaviour. This evidence played a key role in the resolution of the associated legal proceedings.
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