Spanning Multi-Storey Building Foundations Over Tube Lines

Gravity consulting engineers was appointed in 2013 to provide planning designs and advice relating to the construction of 515 units on a site in the 9 Elms area of London, below which the new Northern Line extension is due to be constructed. The Northern line extension will cut diagonally through the site, imposing exclusion zones in which foundations cannot be constructed. The early Gravity design concepts started with an agreement with the architects to follow a list of seven structural principles that would help us to develop an economic design for all buildings on site, along with a practical design for buildings over the top of the tube line whereby we were able to span the buildings on a grillage of 17.5m long transfer beams. The project involved consultations with Network Rail and Transport for London in order to help establish the design parameters and restrictions, and in order to agree the principles of the design such that our client could progress with the purchase of the site in the knowledge that the scheme was technically viable. Our involvement in October 2013 saw us placed in a position whereby we had to generate a full scheme design with drawings, pile numbers and loads, and reinforcement estimates for substructure and superstructure with less than 2 weeks notice, ready for presentation to our client’s technical team and a concrete frame contractor. We achieved the deadline with the delivery of a package that even surprised our client.