EXPERIMENT STUDY ON MECHANICAL PROPERTIES OF INTERFACE BETWEEN SENSING OPTICAL FIBER AND SAND

In recent years, the application of distributed optical fiber sensing(DOFS)technologies to geo-engineering monitoring has been a research focus. But in engineering practices, the deformation compatibility between the embedded sensing optical fibers and the soil and rock masses can significantly affect the monitoring results, which is the main barrier for the DFOS based engineering monitoring. This paper is based on a series of laboratory pullout tests on the three types of the single-mode optical fibers embedded in sand. The comparisons between the pullout force-pullout displacement curves of these fibers under different overburden pressures are conducted. A tri-linear pullout model is established to describe the fiber-sand interfacial mechanical characteristics. Using this model, the variations of the four model parameters, i.e.peak pullout force, residual pullout force, effective pullout displacement and residual pullout displacement, are analyzed considering the influence of overburden pressure. The analysis results indicate the mechanical properties of fiber-sand interface and stress-transfer mechanism, which provides valuable references for the application of the distributed optical fiber optic sensing to soil deformation monitoring, especially in terms of selection criterion of the deformation sensing fiber.