Test on application of distributed fiber optic sensing technique into soil slope monitoring

Authors: Bao-jun Wang, Ke Li, Bin Shi and Guang-qing Wei

Abstract: Brillouin optical time-domain reflectometer (BOTDR), a newly developed distributed fiber optic sensing technique, has been proved to be a very suitable and useful technique for monitoring and early warning of structural engineering by laboratory tests and practical projects due to its unique functions, such as distributing, long distance, anti-electromagnetic interference, waterproof, etc. However, its application to geotechnical engineering, especially soil-slope engineering, has been less carried out due to the complexity of the characteristics of geotechnical materials in the field. In this paper, BOTDR technique is applied to monitor the deformation of a laboratory soil-slope model in small scale in order to test the feasibility and early-warning characteristics of this technique with monitoring the deformation of soil slope. Different types of optical fibers are planted directly in the soil-slope model or bonded to geotextiles and geogrids that are planted in the fillings of the test model. Strain measurements of the model slope under various loads are obtained by BOTDR. By data processing and analysis, the abnormal strains can be obtained distributively, and the position of the abnormal strains can be located as well. The results show much valuable information for applications of BOTDR technique into soil-slope engineering. The test proves that the BOTDR technique can be used to ensure the stability of artificial soil slope and is useful for monitoring and early warning of the artificial soil-slope engineering.

Keywords:  Slope deformation - BOTDR - Distributed fiber optic monitoring - Slope reinforcement

Source: Landslides Volume 6, Number 1, 61-68

DOI: 10.1007/s10346-008-0139-y

1.Bao XY, Zhang CS, Li WH, Ozkan F, Mohareb M (2007) Using distribution Brillouin sensor to predict pipe deformation with carbon coated fibers. The Second International Workshop on Opto-electronic Sensor-based Monitoring in Geo-engineering. Nanjing, China, Oct.18–19 pp 9–19.
2.Bastianini F (2005) A Brillouin smart FRP material and a strain data post processing software for structural health monitoring through laboratory testing and field application on a highway bridge. SPIE 5765:600–611
3.Blatz JA, Bathurst RJ (2001) Behaviour of full-scale reinforced emankments loaded to failure by a strip footing near the crest. 54th Canadian geotechnical conference [C], Calgary, Alberta, 16–18 September, pp 481–489
4.Chang KT, Kim KT (2002) A study of slope movements using fibre optic distributed deformation sensor, KGS Fall National Conference pp 475–482
5.Christopher KYL, Niell E, Noah O (2000) A novel distributed optical crack sensor for concrete structures. Eng Fract Mech 65(2):133–148
6.Ding Y, Shi B, Cui HL, Gao JQ, Chen B (2003) The stability of optical fiber as strain sensor under invariable stress, proceedings of Structural Health Monitoring and Intelligent Infrastructure, Tokyo, Japan, November 13–15, pp 267–270.
7.Horiguchi T, Kurashima T, Tateda M (1989) Tensile strain dependence of Brillouin frequency shift in silica optical fibers. IEEE Photonics Technol, Lett 1(5):107–108
8.Lee KM, Manjunath VR (2000) Experimental and numerical studies of geosynthetic-reinforced sand slopes loaded with a footing. Can Geotech J 37(4):828–842
9.Li AG, Yue ZQ, Tan GH (2003) Design and installation of comprehensive instrumentation system for slope in Hong Kong. Chinese J Geotechnical Eng 22(5):790–796 (in Chinese)
10.Ohno H, Naruse H, Kurashima T, Nobiki A, Uchiyama Y, Kusakabe Y (2002) Application of brillouin scattering-based distributed optical fiber strain sensor to actual concrete piles. IEICE Trans Electron E85-C(4):945–951
11.Shi B, Sui HB, Zhang D (2007) Distributed monitoring of slope engineering. Second International Workshop on Opto-electronic Sensor-Based Monitoring In Geo-engineering, Nanjing, China, Oct.18–19, 81–86
12.Yin JH, Ding XL, Yang YW (2004) Intergration of conventional instruments and GPS for remote automatic monitoring of slopes. Chinese J Geotechnical Eng 23(3):357–364 (in Chinese)
13.Yoo C (2001) Laboratory investigation of bearing capacity behaviour of strip footing on geogrid-reinforced sand slope. Geotext Geomembr 19:279–298
14.Zhang D, Shi B, Xu HZ (2004) Experimental study on the deformation monitoring of reinforced concrete T-beam using BOTDR. J Southeast University, (Natural Science Edition) 34(4):480–484