Extreme passenger congestion in two interconnected London Underground Stations, the Victoria Line and Circle / District Line Stations (both underground), required an extensive upgrade program.
Engineering and Design Services for Ground Improvement, Building Protection, and Tunnel Construction:
Gall Zeidler Consultants provided engineering and design services for the ground improvement, building protection, and construction of passenger connection tunnels, tunnel junctions and ventilation and egress shafts for this project. Mined tunneling primarily used sequential methods and Sprayed Concrete Lining (SCL) / New Austrian Tunnel Method (NATM). Various methods including jet grouting and ground freezing were considered for ground improvement. Also included in this project were two new escalator tunnels constructed by SCL / NATM methods, and two ticket halls constructed using cut-and-cover methods. All structural elements were built under confined space conditions and at shallow depths. Tunneling using SCL / NATM occurred mainly in the London Clay and sandy gravels.