Measured short-term ground surface response to EPBM tunnelling in London Clay

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Title: Measured short-term ground surface response to EPBM tunnelling in London Clay
Authors: Wan, MSP
Standing, JR
Potts, DM
Burland, JB
Item Type: Journal Article
Abstract: Earth-pressure-balance machines (EPBMs) were used for the construction of Crossrail tunnels in London, providing opportunities for field investigation of consequent ground response. Analysed results from an instrumented research site in Hyde Park with extensive surface and subsurface monitoring arrays are presented and discussed. The Crossrail tunnels at the site are 34·5 m below ground, deeper than those in most case histories of tunnelling in stiff clay in the UK. This paper characterises the tunnelling-induced ground response, both ‘greenfield’ and in the proximity of the existing Central Line tunnels, dealing with measurements at the ground surface. A companion paper covers the subsurface ground response. Vertical and horizontal ground surface displacements were obtained from manual precise levelling and micrometer stick measurements. Several key findings will benefit future tunnelling projects involving EPBMs. Volume loss values measured at the instrumented site were low, being less than 0·8% and 1·4% for the first and second tunnel drives respectively, higher values being associated with ground softening from the first tunnel construction. Smaller volume losses were recorded in the vicinity of the existing Central Line tunnels, compared with the greenfield location, suggesting that their presence inhibited the development of ground movements. Asymmetric settlement troughs developed due to either the nearby pre-existing tunnels or the construction of the first tunnel. Marginally smaller values of trough width parameter, Ky, were determined for these deeper tunnels compared with previous greenfield ground case histories. Resultant vectors of ground surface displacement were directed to well-defined point-sinks above the tunnel axis level.
Issue Date: 16-Nov-2016
Date of Acceptance: 23-Sep-2016
ISSN: 0016-8505
Publisher: ICE Publishing
Start Page: 420
End Page: 445
Journal / Book Title: Géotechnique
Volume: 67
Issue: 5
Copyright Statement: © ICE Publishing, all rights reserved. Original article available at Permission is granted by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees.
Sponsor/Funder: Geotechnical Consulting Group
Engineering & Physical Science Research Council (EPSRC)
Funder's Grant Number: GCG Chair
Keywords: Science & Technology
Engineering, Geological
field instrumentation
ground movements
tunnels & tunnelling
Geological & Geomatics Engineering
0905 Civil Engineering
Publication Status: Published
Appears in Collections:Faculty of Engineering
Civil and Environmental Engineering

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