Eyre Hover, Sotiris Psomas and Colin Eddie, UNPS. This paper was first published in GE’s December 2015 edition.
In a forever changing world, urban environments are becoming gradually more congested – both by increasing populations and increasing infrastructure. The underground space is no exception, with basements, foundations, pipes, utilities and tunnels among the structures competing for room. While the effect of any new construction on its vicinity can be reasonably predicted in the short-term, methods for doing so for the long-term are less well defined.
This paper presents an investigation into the tunnellinginduced short- and long-term settlements measured over the Whitechapel Station sprayed concrete lining (SCL) tunnelling works between 2012 and 2014, and a tentative prediction of the future ground behaviour. A novel approach to analysis has been used owing to the long-term interaction between the two parallel station tunnels and this method is proposed for predicting such behaviour at similar sites in the future.
It was found that settlements and slopes increase over time at a logarithmically decreasing rate, and rapidly can no longer be described by a Gaussian curve. The long-term effects are dependent on the number of tunnels and their spacing, the permeability of the lining, and the material surrounding the excavation.