Detection of ground-motion-induced pipeline deformation using BOTDR measurements (Conference Presentation)

Abstract

Differential settlement of underground pipelines is one of the major causes responsible for pipeline failures in the U.S. Due to the invisibility of underground pipeline deformation and the requirement for long-range monitoring of underground pipelines, most of the underground pipeline motions are currently undetected. In this paper, a novel long-range sensing technique using fiber optic sensors is proposed for the structural health monitoring (SHM) the deformation and motion of underground pipelines. Two laboratory 304.8x1.7cm HDPE (high-density polyethylene) pipe specimens were manufactured and tested under four-point bending for damage detection. Single mode optical fibers (10.4 ± 0.8 μm) were installed on the surface of these two HDPE pipes for distributed sensing. Four-point bending test was carried out on two HDPE pipes in the range of 445 N to 2670 N at an increment of 445 N. A BOTDR (Brillouin Optical Time Domain Reflectometer) system was applied in collecting distributed strain measurements (spatial resolution =1m, sampling interval =0.5m) from the two HDPE pipes. Fourteen conventional coil-type strain gauges (gauge factor: 2) were also instrumented on each HDPE pipe for validation purpose. From our laboratory results, it was found that the longitudinal BOTDR strain measurements near the neutral axis of the HDPE pipes can be used for detecting pipe rotation. It was also found that the longitudinal BOTDR strains at the bottom of the pipes can be used to detect pipe bending and damage detection.