Lessons learnt from the installation of field instrumentation to monitor ground response to tunnelling

Research is being undertaken by Imperial College London to investigate the effects of tunnelling on existing tunnels in London Clay. The research opportunity arose with the Crossrail construction of 21km of underground twin-bore railway tunnels through central London where the new tunnels will interface with existing networks of London Underground Limited (LUL) tunnels and other utilities tunnels. The Crossrail western tunnel section involves construction of twin tunnels using 7.2m diameter earth pressure balance tunnel boring machines (TBMs) mostly in London Clay. The tunnel drives below the existing LUL Central Line tunnels near Hyde Park allows a field investigation of the effect of new tunnelling construction on both the “greenfield” ground and the ground in proximity to existing segmental cast iron lined tunnels. The research, involving instrumentation and monitoring (I&M) fieldwork in Hyde Park and Bayswater Road, aims to provide a high quality case study of tunnel construction in London Clay and the mutual interaction of both the new and existing tunnels.