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

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