A FIBER BRAGG GRATING SENSING NETWORK FOR STRUCTURAL INTEGRITY MONITORING OF UNDERGROUND WATER PIPES: ANALYSIS OF MONITORING DATA

摘要

A fiber Bragg grating (FBG) sensing network for monitoring the structural integrity of the Dongjiang water mains (DJWM) was developed by The Hong Kong Polytechnic University in conjunction with the Water Supplies Department of Hong Kong SAR Government.The structural integrity of a 200-meter-long segment of the glass-reinforced-plastic (GRP) underground water pipes has been monitored in terms of strain, temperature, and flow pressure for about one year.In this long-term monitoring system, all the sensors and signal transmission lines were specially designed to be waterproof, anticorrosive and suitable in contact with potable water.A database has been established for statistically analyzing the structural performance of the GRP pipes under different conditions.This paper is devoted to the statistical analysis of the monitoring data with the expectation to recognize the performance patterns of the GRP pipes.Firstly, the correlations of the data acquired by sensors deployed at different locations along the GRP pipeline are investigated for two purposes: (i) to examine the spatial relationship between different measurement cross-sections, and (ii) to recognize critical cross-sections along the GRP pipeline.Secondly, the time histories of the measured strain, temperature and pressure at critical cross-sections are evaluated for the analysis of irregularities.Finally, the correlations between the measured parameters acquired at the critical cross-sections are analyzed over a long period to obtain temporal performance patterns.After excluding environmental influential factors, these formulated patterns can be used to qualitatively and quantitatively evaluate anomalies incurred in either sensors or structural integrity of the GRP pipeline.