Effects of changing geology on the performance of a tunnel boring machine for the Thames Tideway Tunnel, London, UK

An earth pressure balance tunnel boring machine (TBM), 8.8 m in diameter, was used to construct a 7.6 km long section of the Thames Tideway Tunnel through central London, UK, between Battersea and Bermondsey. Two major geological structures – the Lambeth Anticline and the London Bridge fault zone – have imposed significant changes in the tunnel face geology. The TBM was continually monitored for operating parameters such as cutterhead torque, thrust and injection of spoil-conditioning additives. This led to recognition of the structures, in addition to a high frequency of sand channels within the Upper Lambeth Group strata. The monitoring led to validation of the pre-construction geological model and, in conjunction with inspection of the tunnel face during scheduled interventions and geological logging of several interception shafts, provided valuable assurances for the predicted ground ahead of tunnelling operations.