Cast-iron tunnels’ tolerance to imposed longitudinal settlement curvature

Displacements imposed upon existing cast-iron tunnel linings attributed to new underground construction often cause changes in their alignment. The rate of change in alignment, or curvature, is a key parameter in assessing the impact of displacement. Owing to the installation limitations and the pre...

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Bibliographic Details
Published in:Géotechnique 2021-11, Vol.71 (11), p.1044-1055
Main Authors: Alhaddad, Mehdi, Wilcock, Mathew J., Gue, Chang Ye, Soga, Kenichi, Devriendt, Michael, Dewhirst, Mark
Format: Article
Language:English
Subjects:
Alignment
Cast iron
Construction
Curvature
Iron
Measurement
Monitoring
Monitoring systems
Photogrammetry
Road construction
Tracking
Tunnel construction
Tunnel linings
Tunnels
Underground construction
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Summary:Displacements imposed upon existing cast-iron tunnel linings attributed to new underground construction often cause changes in their alignment. The rate of change in alignment, or curvature, is a key parameter in assessing the impact of displacement. Owing to the installation limitations and the precision deficiency of conventional monitoring systems, measuring such curvature deformations, especially locally, has been a challenging task. In this paper, the curvature measurement data of the following two case studies are presented: (a) Crossrail's Liverpool Street station construction affecting the Northern Line (NL) tunnels, and (b) the Bond Street station upgrade project affecting the Royal Mail tunnel (RMT). Both new tunnels ran perpendicular to the existing cast-iron tunnels. They experienced substantial longitudinal curvatures, but the damage was limited. The NL tunnels were monitored using conventional electrolevel-beams for minimum chord lengths of 5 m, while the curvature of the RMT was monitored for chords as short as 2 m using a new photogrammetric monitoring system, called Sattar image tracking. The new system offers a high-precision measurement enabling such lengths of local measurements. This paper describes how curvatures are measured and proposes methods that need to be followed to evaluate the accuracy of curvature measurements.
ISSN:0016-8505
1751-7656
DOI:10.1680/jgeot.18.P.182