Tim Newman and the BGA explain the struggles that have been faced during the Thames Tideway Tunnel excavations.
The Thames Tideway Tunnel is a 25 km long stormwater storage tunnel, up to 65m deep beneath central London and incorporating twenty shafts and ten smaller diameter connection tunnels. It has been constructed through the entire London Basin geological sequence which has had a significant influence on its design.
The large-scale underground structures excavated during construction have facilitated observations of the in-situ geology and revealed sedimentary characteristics that could not be fully evident in disturbed samples from ground investigation boreholes and laboratory tests. These have led to significant improvements in understanding the in-situ groundmass behaviour of several strata within the sequence and their impact on the performance of different construction techniques.