The current understanding of geotechnical engineering and the development of underground structural health monitoring (SHM) methodology are still far behind the pace of the underground infrastructure development. The detection and estimation of time dependent displacement in tunnels and caverns have always been in the top iii reference for future development in underground engineering. CONTENT iv CONTENT ACKNOWLEDGMENTS i ABSTRACT ii CONTENT iv LIST OF TABLES ix LIST OF FIGURES x LIST OF SYMBOLS xiv CONTENT v 2.5.2-Traditional SHM System 2.5.3-Moving Forward into the New Era of SHM 2.5.4-Present SHM System 2.5.5-The Long Term SHM for Underground Construction 2.6 The Fiber Optic Sensor (FOS) 2.6.1-Fiber Optic Sensor (FOS) and Technology 2.6.2-Fiber Optic Sensor (FOS) Available for Civil Engineering Application 2.6.3-Selection of Monitoring System 2.6.4-Fiber Optic Deformation Sensors for Underground Engineering 2.6.5-Shortcomings and Problems of Fiber Optic Sensing 2.7 The Spatial Fiber Optic Sensor-Brillouin Optical Time Domain Reflectometry (BOTDR) 2.7.1-Distributed Brillouin Optical Time Domain Reflectometry (BOTDR) 2.7.2-Fiber Optic Strain and Temperature Measurement 2.7.3-BOTDR Principle and Method of Measurement 2.7.4-BOTDR Measurement Process 2.7.5-Distributed BOTDR Sensing Cables 2.7.6-Issues in Long Term SHM Using BOTDR System 2.7.7-BOTDR in Civil Structural Health Monitoring (SHM) Application CHAPTER 3-THE NEW LONGITUDINAL DISPLACEMENT PROFILE WITH EXCAVATION ADVANCEMENT RATE 3.1 3.4 Deformation Analysis with Excavation Face Dimension Relationship 3.4.1-The ARLDP Relation to Tunnel Excavation Advancement Rate Effect 3.5 Conclusion CHAPTER

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Recent developments in fiber optic sensors for monitoring civil structures have been of great help for engineers dealing with these structures. After literature survey it is observed that while using fiber optic sensor system for health monitoring of civil structures not much attention is given to the core quality of the fiber, types of coating on fiber, implementing methodologies, handling of fiber optic sensors and their long term effect on reliability of the performance of the monitoring system. These issues are important because the structural conditions, stress level and environment in which fiber optic sensors are placed are different from telecommunication industry. In this paper issues related to long term structural health monitoring of civil structures are investigated. The issue of the fatigue property of optic fiber is discussed since reversal bending of the fiber may cause adverse effect on the light carrying capacity of the fiber. Other long term structural health monitoring (SHM) issues such as life of fiber, strain transfer process from fiber core to coating, calibration of fiber and selection of fiber are also discussed based on the experiments carried out for successful implementation of long term health monitoring of civil structures. The main objective of these experiments is to come up with comprehensive long term structural health monitoring system for strain measurement.

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