As part of the redevelopment of London Bridge Station, the 28 storey Southwark Tower block was demolished, the core foundation removed, a new secant wall installed, and a three level basement formed.
The tower sits immediately adjacent to and partly over the very busy Network Rail London Bridge Station. Major pedestrian flows pass through the station each rush hour and all works had to allow sufficient space for these pedestrians. The basement excavation was adjacent to the existing railway arches which had already suffered movement at some period in their history.
Wentworth House Partnership developed the temporary works and solutions to maintain stability of the existing tower during demolition to allow the Shard to be constructed. These included design of scaffold including cantilevers, assessment of floor for demolition plant, assessment of slab openings for drop zones, back propping of ground floor over basements for demolition plant, assessment of basement wall stability and propping.
Wentworth House Partnership was also engaged as independent CAT III checker, undertaking parallel designs for temporary works (hoardings, piling mats, dead shoring and many others), and verifying existing retaining walls to sustain construction plant loads (mobile cranes). All work was undertaken in accordance with LUL design standards. This work was all carried out immediately adjacent to the live station and with passengers from platform 13 going under part of the works.
Sections of the building had to be stabilised with shoring to allow faster demolition progress on the key elements and a protection deck over the exit to platform 13 was designed to maintain the safety of pedestrians passing below. This had to be fitted into an extremely confined space to allow sufficient space for the passenger flows. A 7m high screen was designed to separate the works from the station.
For the section of basement which was not constructed top down, three levels of propping frame to the secant piled wall were designed to limit movements of the adjacent railway arches.
An ancillary part of the works required the retention of the 9m high facing wall to the arches whilst the arches behind were demolished to make way for a ramp. At this location, Wentworth House Partnership chose scaffold as the most economic solution to suit the site constraints.