The Bank Station Capacity Upgrade (BSCU) aimed to relieve heavy passenger congestion during peak hours for boarding, alighting and interchange. The capacity upgrade comprised the construction of a new southbound platform tunnel and associated length of running tunnel for the Northern line, connecting passageways to the existing station tunnels, and the provision of step-free access from King William Street.
GCG was retained by the Contractor to undertake detailed assessments of the effects of construction along the length of the Bank Station Capacity Upgrade scheme for London Underground Ltd. This work involved assessing how a number of structures would be impacted by the scheme and developing methods of construction that would be acceptable to the various stakeholders including the City of London in relation to Mansion House.
It also involved developing methods of construction to support existing historic structures when tunnelling through their foundations. This involved highly complex analysis and close liaison with London Underground when discussing the issues with third parties. GCG also worked as a sub-consultant to the contractor’s designer for the Station Box. This involved the development of construction sequences and over site development interfaces for the new Cannon Street station entrance (top-down deep basement). There were highly constrained work sites with onerous ground movement limits which had to be considered along with the presence of numerous existing underground assets imposing significant constraints on pile design and construction. GCG worked closely with the station designer to develop analytical models and techniques that allowed all these interactions to be consider and to develop the structural design.
This project was the inspiration for the CIRIA publication “Assessing the impacts of construction-induced ground movement on framed buildings” (C796). During the course of the project the impact on a number of framed structures has to be assessed but there was little guidance on the critical factors. GCG suggested to CIRIA that such guidance was needed and a member of GCG chaired the Steering Group for the publication.
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