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Smart Structures and Systems
  Volume 30, Number 1, July 2022 , pages 63-74

Characterizing the strain transfer on the sensing cable-soil interface based on triaxial testing
Guan-Zhong Wu, Dan Zhang, Tai-Song Shan, Bin Shi, Yuan-Jiang Fang and Kang Ren

    The deformation coordination between a rock/soil mass and an optical sensing cable is an important issue for accurate deformation monitoring. A stress-controlled triaxial apparatus was retrofitted by introducing an optical fiber into the soil specimen. High spatial resolution optical frequency domain reflectometry (OFDR) was used for monitoring the strain distribution along the axial direction of the specimen. The results were compared with those measured by a displacement meter. The strain measured by the optical sensing cable has a good linear relationship with the strain calculated by the displacement meter for different confining pressures, which indicates that distributed optical fiber sensing technology is feasible for soil deformation monitoring. The performance of deformation coordination between the sensing cable and the soil during unloading is higher than that during loading based on the strain transfer coefficients. Three hypothetical strain distributions of the triaxial specimen are proposed, based on which theoretical models of the strain transfer coefficients are established. It appears that the parabolic distribution of specimen strain should be more reasonable by comparison. Nevertheless, the strain transfer coefficients obtained by the theoretical models are higher than the measured coefficients. On this basis, a strain transfer model considering slippage at the interface of the sensing cable and the soil is discussed.
Key Words
    cable-soil interface; deformation coordination; distributed optical fiber sensing (DOFS); strain transfer; triaxial testing
(1) Guan-Zhong Wu, Dan Zhang, Tai-Song Shan, Bin Shi, Yuan-Jiang Fang, Kang Ren:
School of Earth Sciences and Engineering, Nanjing University, Nanjing, Jiangsu 210093, China;
(2) Dan Zhang:
Key Laboratory of Earth Fissures Geological Disaster of Ministry of Land and Resources, Geological Survey of Jiangsu Province, Nanjing 210018, China.

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