Structural and drainage designer for new station building and underpass, assessment of on an existing viaduct structure for the effects of displacements induced
Transport for London
Tony Gee provided the structural and drainage design at the new White Hart Lane London Overground Station.
Originally constructed in 1872 with only minor upgrades since, the project to build new station buildings and interconnecting underpasses presented significant technical challenges.
To predict the effects of construction-induced displacements on the historical railway masonry arched structure, we made extensive use of 2D geotechnical finite element modelling. 3D modelling of existing and new structures was also required, and there was extensive interaction between our structural and geotechnical teams, to ensure the predicted displacements and induced strains could be taken safely by the structure.
Two independent brick arch viaducts support each of the existing platforms, and retain the earth embankment which sits between them, supporting the tracks. Ground lowering for the works required the existing brick piers to be underpinned, and the carefully staged installation of temporary kingpost retaining walls at the rear of the viaduct.
The precast concrete box underpasses were designed to be jacked into position during a weekend possession. With tight clearances all round, two hand dug headings were constructed under each box, containing reinforced concrete and steel slide beams which interface with steel shoes, cast into the boxes.
We also developed steel shields attached to the front of the box assemblies, incorporating a drag reducing system which allowed lubricated elastomer membranes to slide over one another.
The jacking was staggered between the box assemblies, advancing at a rate of ~1mm per second per stroke. Simultaneously, two mini excavators, straddling conveyors in each box, removed the soil.