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Details of Grant 

EPSRC Reference: EP/G063486/1
Title: Assessing ground interaction effects and potential damage on existing tunnels before and after new excavation works
Principal Investigator: Standing, Dr JR
Other Investigators:
Potts, Professor DM Burland, Professor J Vollum, Professor R
Researcher Co-Investigators:
Project Partners:
Crossrail Limited London Underground Ltd Morgan Est plc
Department: Civil & Environmental Engineering
Organisation: Imperial College London
Scheme: Standard Research
Starts: 13 March 2010 Ends: 12 September 2014 Value (£): 1,111,545
EPSRC Research Topic Classifications:
Ground Engineering
EPSRC Industrial Sector Classifications:
Construction
Related Grants:
Panel History:
Panel DatePanel NameOutcome
15 Apr 2009 Engineering Systems Panel Announced
Summary on Grant Application Form
Tunnels and underground railway systems are a popular solution to the increasing need to provide fast efficient transport systems in urban environments. Because in many cases the ground contains dense networks of existing tunnels for transportation and services and also deep foundations, new tunnels have to be constructed deeper to pass beneath these obstacles. New tunnel construction results in stress changes and consequent deformations in the ground and these are transmitted to and affect other existing structures. Services and particularly operational metro tunnels are very sensitive to such movements. Railways operate within narrow 'kinematic envelopes' and if a tunnel deforms so as to restrict this envelope the running of trains is severely restricted, requiring reduced speed limits or shutdown of the network and, in the extreme case, their stability might be compromised. At any of these levels, efficient running of the train network is severely hindered. If it is necessary to halt operation of a train line, even for a short period, there are astronomical daily costs from loss of ticket revenue and from loss of time to the commuting workforce. The societal impact is also enormous with inconvenience to thousands of people, frustration and unrest.Many existing tunnel networks were constructed over a century ago when traditionally linings were made mostly from grey cast iron segments. Little is known about the detailed response of segmental tunnel linings made from this material, e.g. how much deformation they can sustain and when and how they will fail. Grey cast iron is a very brittle material and its response depends on a number of factors such as the force in the bolts, nature of the gaskets/grommets used, and whether the 'pan' is infilled with concrete.Royal Assent for Crossrail, a new transport link across London, was granted this year. Construction is due to start in 2010. The tunnels for Crossrail are larger and deeper than most existing tunnels and they will pass beneath more than forty such tunnels. Many of these are aged and constructed from cast iron segments and transport thousands of commuters hourly.This research project sets out to gain a full understanding of the limits of deformation of existing cast iron tunnels when deformed by underground excavation such as tunnelling. Because of the nature of these linings (connections etc) it is necessary to consider their response at an appropriate scale. A three-path approach is to be adopted with laboratory testing of large-scale rings formed from cast iron segments, field monitoring of existing tunnels during Crossrail tunnel construction and numerical analysis of both laboratory and field conditions. The laboratory study will enable limits of deformation to be established, e.g. yield and failure, under different conditions such as bolt forces, gaskets types. The rings will be instrumented to monitor changes in stresses, bolt force etc as the ring is deformed to simulate typical shapes observed and predicted in situ. This is relevant to understanding conditions both before and after new tunnel construction. Numerical analysis will be used to model the laboratory set-up and refined prior to making predictions of a field situation at Hyde Park where the Crossrail tunnels will pass beneath the Central line tunnels. Comprehensive instrumentation will be installed in the ground and existing tunnels at this location to monitor in detail and understand their response during new tunnelling. The numerical analysis can then be further refined to achieve more accurate predictions for future projects.Bringing together these three research components will allow guidelines to be drawn up on expected and allowable tunnel lining deformations and the effectiveness of mitigation measures for future projects involving tunnelling beneath existing tunnels, such that safe and efficient operation of underground railway networks is not compromised.
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