The Use of Fibre Optic Sensors to Monitor Pipeline Response to Tunnelling

ASCE Conf. Proc. doi:10.1061/40803(187)33

GeoCongress 2006: Geotechnical Engineering in the Information Technology Age
Proceedings of GeoCongress 2006
T. E. B. Vorster1, K. Soga2, R. J. Mair2, P. J. Bennett2, A. Klar2, and C. K. Choy2
1 Africon Engineering International (Pty) Ltd, P O Box 905, Pretoria, 0001, South Africa (formerly Cambridge University, UK)
2 University of Cambridge, Department of Engineering, Trumpington Street, Cambridge CB2 1PZ, UK

This paper describes the use of fibre optic sensing with Brillouin Optical Time‐Domain Reflectometry (BOTDR) for near‐continuous (distributed) strain monitoring of a large diameter pipeline, buried in predominantly granular material, subjected to a pipe jack tunnelling operation in London Clay. The pipeline, buried at shallow depth, comprises 4.6 m long sections connected with standard bell and spigot type joints, which connect to a continuous steel pipeline. In this paper the suitability of fibre optic sensing with BOTDR for monitoring pipeline behaviour is illustrated. The ability of the fibre optic sensor to detect local strain changes at joints and the subsequent impact on the overall strain profile is shown. The BOTDR strain profile was also used to infer pipe settlement through a process of double‐integration and was compared to pipe settlement measurements. The close approximation of the measured pipe settlement provides further confidence in fibre optic strain sensing with BOTDR to investigate the intricacies ......