CUED Publications database

Monitoring tunnel deformation induced by close-proximity bored tunneling using distributed optical fiber strain measurements

Mohamad, H and Bennett, PJ and Soga, K and Mair, RJ and Lim, C-S and Knight-Hassell, CK and Ow, CN (2007) Monitoring tunnel deformation induced by close-proximity bored tunneling using distributed optical fiber strain measurements. In: UNSPECIFIED p. 84..

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Abstract

The paper describes the use of optical fiber Brillouin Optical Time Domain Reflectometry (BOTDR) to monitor the strain distribution in an existing tunnel while a twin tunnel was bored at close-proximity. The twin circular bored tunnels between Serangoon and Bartley stations on the new Circle Line Stage 3 subway in Singapore were constructed at close-proximity to avoid underpinning the foundations of adjacent buildings. The minimum clear separation of the two tunnels is 2.3m (0.4 times the tunnel diameter). The Outer Tunnel was constructed first, followed by the Inner Tunnel, with the earth-pressure balance tunnel boring machines maintained at a minimum of 100m apart. In this trial application of BOTDR, the strain distribution along the Outer Tunnel was measured, in order to monitor its deformation due to the boring of the Inner Tunnel at close-proximity. The aim of the trial application was to determine the practicality of this monitoring method for future use in 'live' tunnels. This paper compares the measurements obtained from optical fiber BOTDR with conventional methods of tunnel monitoring and describes preliminary installation and workmanship guidelines derived from lessons learnt during this trial. © 2007 ASCE.

Item Type: Conference or Workshop Item (UNSPECIFIED)
Subjects: UNSPECIFIED
Divisions: Div D > Geotechnical and Environmental
Depositing User: Cron Job
Date Deposited: 07 Mar 2014 12:14
Last Modified: 30 Nov 2014 21:46
DOI: 10.1061/40940(307)84