Thames Tideway Tunnel: TBM Performance in the London Clay Formation and Overcoming Man-made Obstructions
This case study examines the performance of the earth pressure balance tunnel boring machine (TBM) used to construct Main Tunnel A of the Thames Tideway Tunnel through the London Clay Formation (LCF). The TBM operated effectively across LCF subdivisions A2, A3, and B, with minimal impact from geological faults or stratigraphic variations. A robust preconstruction ground model, supported by detailed geological logging and seismic surveys, helped anticipate conditions and reduce risk during tunnelling.
Operational data confirmed that subtle lithological changes within the LCF had limited influence on TBM performance, with only minor deviations observed during the initial 1 km, likely attributable to team familiarisation. The most significant challenges arose from intersecting two man-made obstructions: a project GI borehole and a historical abstraction well. Both events required activation of emergency contingency procedures, including adjustments to TBM operating parameters and enhanced settlement monitoring. These responses successfully mitigated potential structural and environmental impacts.
The study underscores the importance of precise ground modelling, contingency planning, and adaptive TBM operation in urban tunnelling. It recommends detailed geological training and risk registers as best practice for future infrastructure projects involving complex subsurface conditions.
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This paper appeared in the Proceedings of the Institution of Civil Engineers – Civil Engineering, the flagship journal of the Institution of Civil Engineers, published by Emerald Publishing Limited.
Image credit: Tideway