Construction is progressing at Bank Station Capacity Upgrade (Fig. 1) and Dr. Sauer & Partners is proud to be an integral part of this ambitious project. Our site team is providing design support services 24/7 and is excited about the excellent progress made so far in tunnel construction.
Fig 1: BSCU SCL Tunnelling
The Arthur Street shaft is now complete and tunnelling is progressing ahead of schedule along the future Northern line running tunnel. The 33 metre deep sprayed concrete lined shaft, which was constructed through the disused King William Street Station, is the centrepiece of the construction site. This shaft will service the tunnelling works from the tight worksite at Arthur Street. The breakouts from the shaft have also been carried out, with the completion of the temporary and permanent tunnels that will be used to ease underground logistics throughout the project: the plant chamber, logistics chamber and muck chamber.
The muck chamber was particularly challenging, requiring excavation right up to the back of the cast iron rings of the live Northern line running tunnel (Fig. 2). Through a combination of careful excavation and detailed monitoring this was successfully completed with no impact to the operational railway.
Fig 2: Exposure of existing Northern line cast iron rings
The initial tunnelling works have seen the employment of the Option A Joint (Fig. 3). It has been designed by Dr. Sauer & Partners to completely eliminate the requirement for entry into the sealed tunnel face at any time. While there was a learning curve for the team during the initial advances, it has been concluded by the entire team that this joint is an innovation that will have a significant impact on the safety of everyone within the tunnel.
Fig 3: Option A Joint Design
After the completion of the logistic support tunnels, works began to extend the new southbound Northern line running tunnel towards the north west of the project area (Fig. 4). Full-face excavation on this tunnel, which employs 1.2m advances, has resulted in efficient progress and works have already begun on the section of tunnel that acts as the platform pilot. The use of a pilot tunnel is a mitigation measure to minimise the surface settlement as a result of the tunnelling works.
Fig 4 - New Southbound Northern line Running Tunnel
Over the upcoming weeks the tunnelling teams will complete the platform pilot tunnel and return to enlarge the full platform tunnel cross section: an impressive 8.8m x 9.9m. The large tunnel will require specialist plant to be brought to site and presents an exciting challenge for the construction team. During the ongoing excavation of this tunnel it is expected that several redundant piles will be encountered and removed.
Finally, the Bank team has bid farewell to its esteemed colleague and Senior SCL Engineer Andreas Spiegl (Fig. 5). He has returned to work in his native Austria. Andreas spent six years with Dr. Sauer & Partners working on projects across the UK and North America. He will be greatly missed by all who had the pleasure of working with him.
Fig 5: Andreas Spiegl