Influence of Soil Moisture on Interfacial Behavior of Soil-Embedded Fiber Optic Sensor


H.H. Zhu 1, 2, J.K. She 1 and C.C. Zhang 1

1 School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China

2 Nanjing University High-Tech Institute at Suzhou, Suzhou 215123, China

Geotechnical Engineering Journal of the SEAGS & AGSSEA

ABSTRACT: Fiber optic sensor-based distributed geotechnical monitoring is being used in an increasingly wide variety of applications in geotechnical engineering all over the world. The fiber optic sensors have been directly embedded in slopes and embankments for monitoring the deformation and stability of geotechnical structures. The mechanical behavior of the interface between the distributed strain sensing fibers and the surrounding soil is a key factor governing the reliability of fiber optic measurements. To evaluate the influence of soil moisture on the fiber–soil interfacial behavior, a series of fiber pullout tests were performed under different overburden pressures. The test results show that soil moisture has a significant effect on the pullout performance of the test fiber. The shear stress–pullout displacement relationship can be described by a tri-linear bond-slip model. The peak and residual shear strengths decrease linearly with the increase of soil moisture content, while the overburden pressure plays a critical role in enhancing the fiber–soil bond strength. A reliable sensor fixing system should be provided for long-term geotechnical monitoring, especially for water-rich soil strata.

KEYWORDS: Distributed fiber optic sensing, Fiber–soil interface, Pullout test, Soil moisture, Overburden pressure


Abu-Farsakh, M., Coronel, J., and Tao, M. (2007) “Effect of soil moisture content and dry density on cohesive soil–geosynthetic interactions using large direct shear tests”. Journal of Materials in Civil Engineering, 19, Issue 7, pp 540-549.

Fan, C., and Su, C. (2008) “Role of roots in the shear strength of root-reinforced soils with high moisture content”. Ecological Engineering, 33, pp157-166.

Gao, L., Ji, B., Kong, G., Huang, X., Li, M., and Mahfouz, A.H. (2015) “Distributed measurement of temperature for PCC energy pile using BOFDA”. Journal of Sensors, 2015, p610473.

Huntley, D., Bobrowsky, P., Zhang, Q., Sladen, W., Bunce, C., Edwards, T., Hendry, M., Martin, D., and Choi, E. (2014) “Fiber optic strain monitoring and evaluation of a slow-moving landslide near Ashcroft, British Columbia, Canada”, Landslide Science for a Safer Geoenvironment: Vol.1, pp415-421.

Iten, M. (2011) Novel Application of Distributed Fiber-Optic Sensing in Geotechnical Engineering, PhD Thesis, EPFL, Switzerland.

Klar, A., Dromy, I., and Linker, R. (2014) “Monitoring tunneling induced ground displacements using distributed fiber-optic sensing”. Tunnelling and Underground Space Technology, 40, pp141-150.

Lanticq, V., Bourgeois, E., Magnien, P., Dieleman, L., Vinceslas, G., Sang, A., and Delepine-Lesoille, S. (2009) “Soil-embedded optical fiber sensing cable interrogated by Brillouin optical time-domain reflectometry (B-OTDR) and optical frequency-domain reflectometry (OFDR) for embedded cavity detection and sinkhole warning system”. Measurement Science and Technology, 20, Issue 3, p34018.

Linker, R., and Klar, A. (2017) “Detection of sinkhole formation by strain profile measurements using BOTDR: Simulation study”. Journal of Engineering Mechanics, 143, Issue 3, pB4015002.

Mohamad, H., Bennett, P.J., Soga, K., Mair, R.J., Bowers, K. (2010) “Behaviour of an old masonry tunnel due to tunnelling-induced ground settlement”. Geotechnique, 60, pp927–938.

Olivares, L., Damiano, E., Greco, R., Zeni, L., Picarelli, L., Minardo, A., Guida, A., and Bernini, R. (2009) “An instrumented flume to investigate the mechanics of rainfall-induced landslides in unsaturated granular soils”. Geotechnical Testing Journal, 32, Issue 2, pp788-796.

Piao, C., Yuan, J., Shi, B., Lu, H., Wei, G., and Gu, C. (2015) “Application of distributed optical fiber sensing technology in the anomaly detection of shaft lining in grouting”. Journal of Sensors, 2015, p678634.

Picarelli, L., Damiano, E., Greco, R., Minardo, A., Olivares, L., and Zeni, L. (2015) “Performance of slope behavior indicators in unsaturated pyroclastic soils”. Journal of Mountain Science, 12, Issue 6, pp1434-1447.

Schenato, L. (2017) “A review of distributed fibre optic sensors for geo-hydrological applications”. Applied Sciences, 7, p896.

Shi, B., Xu, H., Chen, B., Zhang, D., Ding, Y., Liang, H., and Gao, J. (2003) “A feasibility study on the application of fiber-optic distributed sensors for strain measurement in the Taiwan strait tunnel project”. Marine Georesources and Geotechnology, 21, Issue 3–4, pp333-343.

Su, L.-J., Chan, T. C. F., Shiu, Y. K., Cheung, T., and Yin, J.-H. (2007) “Influence of degree of saturation on soil nail pull-out resistance in compacted completely decomposed granite fill”. Cananidan Geotechnical Journal, 44, Issue 11, pp1314-1328.

Su, L.-J., Chan, T. C. F., Yin, J.-H., Shiu, Y. K., and Chiu, S. L. (2008) “Influence of overburden pressure on soil–nail pullout resistance in a compacted fill”. Journal of Geotechnical and Geoenvironmental Engineering, 134, Issue 9, pp1339-1347.

Su, L.-J., Yin, J.-H., and Zhou, W.-H. (2010) “Influences of overburden pressure and soil dilation on soil nail pull-out resistance”. Computers and Geotechnics, 37, Issue 4, pp555-564.

Sun, Y., Zhang, D., Shi, B., Tong, H., Wei, G., and Wang, X. (2014) “Distributed acquisition, characterization and process analysis of multi-field information in slopes”. Engineering Geology, 182, pp49-62.

Tang, C.-S., Shi, B., and Zhao, L.-Z. (2010) “Interfacial shear strength of fiber reinforced soil”. Geotextiles and Geomembranes, 28, Issue 1, pp54-62.

Wang, B., Li, K., Shi, B., and Wei, G. (2009) “Test on application of distributed fiber optic sensing technique into soil slope monitoring”. Landslides, 6, Issue 1, pp61-68.

Wang, X., Shi, B., Wei, G., Chen, S.-E., Zhu, H., and Wang, T. (2018) “Monitoring the behavior of segment joints in a shield tunnel using distributed fiber optic sensors”. Structural Control and Health Monitoring, 25, Issue 1, 26, pp1-15.

Wu, J.-H., Shi, B., Cao, D.-F., Jiang, H.-T., Wang, X.-F. and Gu, K. (2017) “Model test of soil deformation response to draining-recharging conditions based on DFOS”. Engineering Geology, 226, pp107-121.

Xu, D.-S., Yin, J.-H., Cao, Z.-Z., Wang, Y.-L., Zhu, H.-H., and Pei, H.-F. (2013) “A new flexible FBG sensing beam for measuring dynamic lateral displacements of soil in a shaking table test”. Measurement, 46, Issue 1, pp200-209.

Zhang, C.-C., Zhu, H.-H., Liu, S.-P., Shi, B., and Zhang, D. (2018) “A kinematic framework for calculating shear displacement of slope mass using distributed fiber optic strain measurements: application to the Majiagou landslide”. Engineering Geology, 234, pp83–96.

Zhang, C.-C., Zhu, H.-H., Shi, B., and She, J.-K. (2014) “Interfacial characterization of soil-embedded optical fiber for ground deformation measurement”. Smart Materials and Structures, 23, Issue 9, p95022.

Zhu, H.-H., She, J.-K., Zhang, C.-C., and Shi, B. (2015) “Experimental study on pullout performance of sensing optical fibers in compacted sand”. Measurement, 73, pp284-294.

Zhu, H.-H., Shi, B., and Zhang, C.-C. (2017) “FBG-based monitoring of geohazards: current status and trends”. Sensors, 17, Issue 3, 452.

Zhu, H.-H., Wang, Z.-Y., Shi, B., and Wong, J.K.-W. (2016) “Feasibility study of strain based stability evaluation of locally loaded slopes: Insights from physical and numerical modeling”. Engineering Geology, 208, pp39-50.