Jian-Hua YIN* and Hong-Hu ZHU
The Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
* Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it , Yin’s group website: www.cse.polyu.edu.hk/~cejhyin

Wei JIN
The Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong

Albert T. YEUNG
The Department of Civil Engineering, The University of Hong Kong, Hong Kong, China

LM MAK
LMM Consulting Engineers Ltd, Hong Kong, China

Abstract:  The pullout resistance of soil nails installed in slopes is affected by a number of factors.  The measurement of the pullout resistance and the shear resistance on the soil nail cement grout is required. The existing technique of using electrical strain gauges monitoring pullout tests has limitations. This paper introduces two types of optical fibre sensors and associated devices for measuring strain distribution in soil nails. The two types of sensors were calibrated first in the lab. Typical calibration results are presented.  Afterwards, the two types of optical fibre sensors were used to monitor strains of two Fibre Reinforced Polymer (FRP) soil nails in Hong Kong together with electrical resistance-type strain gauges. The field test data were collected and analysed.  In particular, the strains measured by the two types of optical fibre sensors are compared to those by electrical strain gauges and are found to be in good agreement. The advantages of optical fibre sensors are presented.

Yin, J. H., Zhu, H. H., Jin, W., Yeung, A. T., and Mak, L. M. (2007). "Performance evaluation of electrical strain gauges and optical fiber sensors in field soil nail pullout tests." Geotechnical Advancements in Hong Kong since 1970s, The HKIE Geotechnical Division 27th Annual Seminar, Hong Kong, China, 249-254.