ABSTRACT
The application of the observational method (OM) to the Channel Tunnel cut and cover works was both metaphorically and literally ground breaking. The cut and cover works constituted a major part of the construction in and adjacent to the UK terminal for the Channel Tunnel. In Holywell, the relationship of the vertical alignment of the tunnels and the existing topography created substantial variations of cut and fill. The applications of the OM developed for the Channel Tunnel cut and cover works involved both bottom-up and top-down construction. Bulk excavation and construction of the cut and cover tunnels followed in the same sequence, starting at Castle Hill East in June 1988. The New Austrian tunnelling method tunnels through Castle Hill involved a separate application of the OM. Its implementation for the cut and cover works at the tunnel portals thus involved abutting applications of the method though with different teams.
