An optical fibre monitoring system for evaluating the performance of a soil nailed slope

Hong-Hu Zhu*1 , Albert N. L. Ho2 , Jian-Hua Yin3 , H. W. Sun4 , Hua-Fu Pei3  and Cheng-Yu Hong3
1. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China
2. Ove Arup & Partners Hong Kong Limited, Hong Kong, China
3. Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
4. Geotechnical Engineering Office, Civil Engineering and Development Department, Government of the Hong Kong Special Administrative Region, Hong Kong, China 

SOURCE Smart Structures and Systems, Volume 9, Number 5, May 2012
Link: http://technopress.kaist.ac.kr/content/?page=article&journal=sss&volume=9&num=5&ordernum=1

Abstract
Conventional geotechnical instrumentation techniques available for monitoring of slopes, especially soil-nailed slopes have limitations such as electromagnetic interference, low accuracy, poor longterm reliability and difficulty in mounting a series of strain sensors on a soil nail bar with a small-diameter. This paper presents a slope monitoring system based on fibre Bragg grating (FBG) sensing technology. This monitoring system is designed to perform long-term monitoring of slope movements, strains along soil nails, and other slope reinforcement elements. All these FBG sensors are fabricated and calibrated in laboratory and a trial of this monitoring system has been successfully conducted on a roadside slope in Hong Kong. As part of the slope stability improvement works, soil nails and a toe support soldier-pile wall were constructed. During the slope works, more than 100 FBG sensors were installed on a soil nail, a soldier pile, and an in- place inclinometer. The paper presents the layout and arrangement of the instruments as well as the installation procedures adopted. Monitoring data have been collected since March 2008. This trial has demonstrated the great potential of the optical fibre monitoring system for long-term monitoring of slope performance. The advantages of the slope monitoring system and experience gained in the field implementation are also discussed in the paper.


Key Words
optical fibre sensing; soil nailing; slope monitoring system; fibre Bragg grating (FBG); geotechnical instrumentation

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