Optical fibre sensors for remote monitoring of tunnel displacements – Prototype tests in the laboratory

Abstract

This paper discusses three experimental arrangements designed to explore the challenges of installing the monitoring system and interpreting the results. The first experiment uses an I-section beam to simulate a longitudinal arrangement of the sensors in the tunnel. The second experiment involves a purpose built rig to simulate the movements of one complete ring of tunnel segments at a scale of approximately 1:5. The third experiment concentrates on a bench test, which has been designed to calibrate the new system and determine its accuracy and resolution. Results from all of these experiments are encouraging with the bench test showing that the Smart Rod is sensitive enough to measure small rotations and translations. Furthermore, methods of interpreting the strain measurements and hence determining the displacement of the structure are presented. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. Reprinted with permission from Elsevier.