| Summary: | The need for the research project is driven by the Crossrail project in London for which new 7 m diameter tunnels are to be constructed close to numerous existing operational tunnels of the London Underground (LU) network. The main aim of this research is to investigate the impact of new tunnel excavations on existing tunnels. This research component is based on field instrumentation and experimental work conducted on half-scale grey cast iron (GCI) tunnel lining segments with chemical composition similar to the Victorian age GCI segments in the LU network. Currently, there is great uncertainty about the behaviour of segmental linings. General belief is that the behaviour of the lining is influenced by the behaviour of the joints, but there has been little experimental work to investigate this relationship. The laboratory experiments aim to find out the deformation behaviour of the bolted segmental lining and the influence of parameters such as overburden pressure, bolt preload and presence of grommets at small distortions. The measured behaviour of the segmental lining is compared against the theoretical behaviour of a continuous lining based on the assumption of linear elasticity. The laboratory results are used to assess the validity of the tunnel assessment methods used by the industry. The results from the parametric tests will form the basis for future experimental investigations taking the half-scale test ring to large deformations and ultimately to failure. The field component involved taking measurements of existing bolted segmental grey cast iron tunnels. Small sections of tunnels constructed at the LU Acton Depot, at Tottenham Court Road Station and in the Central Line running tunnel were monitored to gain an understanding of the deformation of tunnels from construction and self-weight, from ground loading and finally from the influence of adjacent tunnelling works. The thesis proposes recommendations for future in-tunnel monitoring based on the findings obtained in this research.
|
|---|
