FEASIBILITY STUDY ON APPLICATION OF BOTDR TO HEALTH MONITORING FOR LARGE INFRASTRUCTURE ENGINEERING

Shi Bin, Xu Hongzhong, Zhang Dan, Ding Yong, Cui Heliang, Chen Bin, Gao Junqi

ACEI, Department of Earth Sciences, Nanjing University,  Nanjing 210093 China

Chinese Journal of Rock Mechanics and Engineering, 2004, 23(3): 493-499.

Abstract The characters of large infrastructure engineering and its requirements for the health monitoring are large scale, such as tens or hundreds of kilometers of tunnels and dikes, big diversity of engineering environment, such as oil pipes sometimes transiting the various geographic areas and time domain with quite complex engineering environment, high requirements of real-time and long-distance monitoring for some engineerings, such as dike monitoring during the flood,and high accuracy of monitoring,such as large-span gymnasium buildings and underground facilities requiring the order of micron or millimeter measuring accuracy. Hence the conventional measurement and monitoring methods and techniques are more and more not to meet the monitoring demands of health monitoring for large infrastructure engineering.

The Brilliouin optical time domain reflectometer (BOTDR) is a newly developed innovative measureing technique,which utilizes Brilliouin spectroscopy and optical time domain reflectometry to measure strain generated in optical fibers as distributed in the longitudinal direction. Because of the BOTDR’s distinctive characters,it has been paid more and more attention to and begun to be applied to monitoring system of various infrastructure engineerings, such as tunnels, river embankments and landslide prediction. In this paper,the operation principle and merits of BOTDR are introduced. Its application feasibility to the health monitoring for large infrastructure engineering are analysed based on authors’ research achievements and application cases. The relative topics about application of BOTDR are discussed in detail, which include installation methods of optic fiber, distance resolution impact for measuring results, temperature and humidity impact, fatigue effect of optic fiber, deformation conversion from strain and establishment of intelligent monitoring system. The research results show that the BOTDR is quite applicable to the health monitoring for large infrastructure engineering.

Key words geo-engineering,engineering health monitoring,BOTDR,infrastructure engineering,distributed monitoring