THE BLACKWALL Tunnel in east London is being closely monitored during construction of a new block of flats straddling one end of the 100year-old Thames crossing.
Excavation of the basement and installation of piles for St James' Homes' multi-storey Lighthouse development will alter the vertical stresses acting on the tunnel. There must be no risk of damage to the important transport artery.
Card Geotechnics worked with main contractor Laing O'Rourke and structural engineer Walsh Associates to ensure design of the basement excavation and temporary support for the foundations met the approval of Transport for London, which operates the tunnel.
Finite element analyses of the interaction between the new structure, the ground and the tunnel have been undertaken to assess the impact of the development.
Distortions are being monitored by Card Geotechnics using strain gauges attached to the tunnel lining. These are read remotely using wireless technology to provide real-time data.
Card says that with construction well under way, measured deflections have been well within the targets agreed with TfL based on computer predictions.