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Title: Numerical investigation of tunnelling beneath existing tunnels
Author: Avgerinos, Vasileios
ISNI:       0000 0004 5989 5099
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2014
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Tunnels under large metropolitan cities have been constructed for almost two centuries. As the cities expand their surface and subsurface space become congested. The construction of the new Crossrail tunnels under central London, which has been on-going during the preparation of this thesis, has more than 30 interfaces with existing London underground tunnels. In this thesis the effects of excavating the Crossrail tunnels under the existing Central line tunnels below Bayswater road are explored and various aspects of tunnelling in London clay are investigated using the finite element code ICFEP (Imperial College Finite Element Program). The first part of this thesis focuses on the short and long-term behaviour of grey cast iron tunnel linings by modelling the cross-section of the Central line tunnels under Bayswater Road. The effect of the lining permeability on the lining response in terms of deformation and internal forces is highlighted. Simulations of a large-scale experimental set-up (that studies the lining behaviour) are made and ways to overcome some of the experimental limitations are presented. In the second part of the thesis the use of a sophisticated two surface kinematic hardening model for modelling tunnelling in stiff London clay is explored by analysing the Jubilee Line Extension under St. James's Park and the Crossrail tunnels under Hyde Park. The calibration of the model parameters against laboratory tests on intact samples and the modelling of previous stress history improve the predicted soil displacements due to tunnelling. In the last part of this thesis, a three-dimensional numerical model is used in order to qualitatively estimate the response of the Central line tunnels due to the excavation of the new Crossrail tunnels. Despite the simplifications made, the numerical predictions show that finite element analysis is a useful and reliable tool to analyse such complicated problems.
Supervisor: Potts, David ; Standing, Jamie Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral