Dr. Sauer & Partners Ltd. continue to supervise complex tunnelling in the highly congested ground beneath Bank Station (see Figure 1).
The pilot tunnel through the new Southbound platform has now been enlarged to the final geometry. The new platform tunnel with a springline width of 10.5m and height 9.6m was safely excavated 5.3m below Thames Water’s Low Level Sewer No.2.
Cross Passage No.4 has been excavated to a temporary headwall 3.0m from the extrados of the existing Southbound platform tunnel lining. From this headwall a temporary ramped tunnel and construction canopy have been excavated over and between the existing platforms. This inventive use of sprayed concrete for temporary works will facilitate construction of a new passenger adit (see Figure 2). Safety benefits include a significant reduction in the amount of hand mining required.
Running tunnel excavation continues North from the platform tunnel. Piles under the highly sensitive New Court Rothschild Bank have been encountered and removed. During the design phase a thorough desktop study coupled with 3D modelling meant the building piles were accurately located. This detailed work supported collaborative discussions with the building owner and their engineering representation.
The next major tunnel to be excavated is the upper machine chamber for the new escalator down to DLR level.
Fig 1: Construction progress to date. Excavated tunnels in cyan.
Fig 2: Sprayed concrete lining temporary works to facilitate adit construction. New tunnels in cyan.