Performance during construction of a cut-and-cover tunnel founded in London Clay at Edmonton. Prepared for the Highways Agency, Quality Services (Civil Engineering).

Field instrumentation was installed to investigate the performance of the diaphragm walls of Fore Street Tunnel at Edmonton. The tunnel was founded in over-consolidated clay and constructed top down with an integral roof and carriageway prop slab. Field observations of wall movements and bending moments, loads and moments in the props, and vertical streses in the clay beneath the carriageway prop slab were taken at the various construction stages. The measured values were compared with those predicted from finite element analysis using a soil model based on the Mohr-Coulomb yield criterion. The measured and predicted loads and moments in the structural members were also compared with those which would be determined using current design procedures. (A)