Fiber Bragg grating-based performance monitoring of a slope model subjected to seepage

In the past few years, fiber optic sensing technologies have played an increasingly important role in the health monitoring of civil infrastructures. These innovative sensing technologies have recently been successfully applied to the performance monitoring of a series of geotechnical structures. Fiber optic sensors have shown many unique advantages in comparison with conventional sensors, including immunity to electrical noise, higher precision and improved durability and embedding capabilities; fiber optic sensors are also smaller in size and lighter in weight. In order to explore the mechanism of seepage-induced slope instability, a small-scale 1 g model test of the soil slope has been performed in the laboratory. During the model’s construction, specially fabricated sensing fibers containing nine fiber Bragg grating (FBG) strain sensors connected in a series were horizontally and vertically embedded into the soil mass. The surcharge load was applied on the slope crest, and the groundwater level inside of the slope was subsequently varied using two water chambers installed besides the slope model. The fiber optic sensing data of the vertical and horizontal strains within the slope model were automatically recorded by an FBG interrogator and a computer during the test. The test results are presented and interpreted in detail. It is found that the gradually accumulated deformation of the slope model subjected to seepage can be accurately captured by the quasi-distributed FBG strain sensors. The test results also demonstrate that the slope stability is significantly affected by ground water seepage, which fits well with the results that were calculated using finite element and limit equilibrium methods. The relationship between the strain measurements and the safety factors is further analyzed, together with a discussion on the residual strains. The performance evaluation of a soil slope using fiber optic strain sensors is proved to be a potentially effective approach.

[1]  Nicholas Ioannides,et al.  Approaches to mitigate polymer-core loss in plastic optical fibers: a review , 2014 .

[2]  Zhang Jie,et al.  Distributed Fiber Optic Monitoring and Stability Analysis of a Model Slope under Surcharge Loading , 2014 .

[3]  An-Bin Huang,et al.  Stability monitoring of rainfall-induced deep landslides through pore pressure profile measurements , 2012 .

[4]  Jian-Hua Yin,et al.  An optical fibre monitoring system for evaluating the performance of a soil nailed slope , 2012 .

[5]  D. Fredlund,et al.  Equations for the soil-water characteristic curve , 1994 .

[6]  Dong-Mei Zhang,et al.  Impact of overhead excavation on an existing shield tunnel : field monitoring and a full 3D finite element analysis , 2013 .

[7]  Qi Tao,et al.  Q mechanism analysis of landslide of a layered slope induced by drawdown of water level , 2005 .

[8]  K. Hill,et al.  Photosensitivity in optical fiber waveguides: Application to reflection filter fabrication , 1978 .

[9]  Bin Shi,et al.  The BOTDR-based distributed monitoring system for slope engineering , 2006 .

[10]  Antonio Quintela Incera,et al.  Fiber Optic Sensors in Structural Health Monitoring , 2011, Journal of Lightwave Technology.

[11]  Hongde Wang,et al.  Real-time monitoring and early warning of landslides at relocated Wushan Town, the Three Gorges Reservoir, China , 2010 .

[12]  Tony L. T. Zhan,et al.  Performance of a large-scale slope model subjected to rising and lowering water levels , 2009 .

[13]  Yun-min Chen,et al.  Influence of Reservoir Level Change on Slope Stability of a Silty Soil Bank , 2006 .

[14]  John Dunnicliff,et al.  Geotechnical Instrumentation for Monitoring Field Performance , 1988 .

[15]  Xiaoqian Zhang,et al.  Some key technics of drop tower experiment device of National Microgravity Laboratory (China) (NMLC) , 2005 .

[16]  An-Bin Huang,et al.  Development of a fibre Bragg grating sensored ground movement monitoring system , 2006 .

[17]  Gerald Meltz,et al.  Fiber Optic Bragg Grating Sensors , 1990, Other Conferences.

[18]  Bin Shi,et al.  Application of a distributed optical fiber sensing technique in monitoring the stress of precast piles , 2012 .

[19]  P. Cui,et al.  Monitoring and warning of landslides and debris flows using an optical fiber sensor technology , 2011 .

[20]  Ching-Jer Huang,et al.  Calibration and Deployment of a Fiber-Optic Sensing System for Monitoring Debris Flows , 2012, Sensors.

[21]  Joachim Rohn,et al.  Numerical simulation of Qiaotou Landslide deformation caused by drawdown of the Three Gorges Reservoir, China , 2011 .

[22]  Chin Jian Leo,et al.  Analysis of Baishuihe landslide influenced by the effects of reservoir water and rainfall , 2010 .

[23]  Eiji Murakami,et al.  Development of the monitoring system for slope deformations with fiber Bragg grating arrays , 2002, SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring.

[24]  Ke Li,et al.  Test on application of distributed fiber optic sensing technique into soil slope monitoring , 2009 .

[25]  A. Othonos.  Fiber Bragg gratings , 1999 .

[26]  Keiichi Ota,et al.  Evaluation of slope stability by finite element method using observed displacement of landslide , 2012, Landslides.

[27]  BOTDA road-embedded strain sensing system for landslide boundary localization , 2009, Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring.

[28]  Gangbing Song,et al.  Design and application of a fiber Bragg grating strain sensor with enhanced sensitivity in the small-scale dam model , 2009 .

[29]  A. Bishop.  The use of the Slip Circle in the Stability Analysis of Slopes , 1955 .

[30]  B. V. S. Viswanadham,et al.  Centrifuge model tests on soil-nailed slopes subjected to seepage , 2009 .

[31]  Chuan Li,et al.  Monitoring pressure and thermal strain in the second lining of a tunnel with a Brillouin OTDR , 2006 .

[32]  Hong-hu Zhu,et al.  Monitoring of lateral displacements of a slope using a series of special fibre Bragg grating-based in-place inclinometers , 2012 .