The role of interface force on the deformation compatibility of fiber optic cable and soil: Perspective from 3D discrete element numerical simulation

Abstract

In the application of distributed fiber optic sensing technology to obtain soil deformation, the deformation coordination between the sensing fiber optic (FO) cable and the soil medium is crucial. In this study, a three-dimensional numerical model for pullout test of a sensing cable in sand was constructed utilizing the discrete element method. The results indicate that, with the continuous increase in pullout displacement, the interface forces between the FO cable and soil particles steadily rise. After complete interface failure, these forces rapidly decrease. Throughout the pullout process along the distribution of the FO cable, the magnitude of interface forces undergoes significant changes depending on the contact state of the interface. As the confining pressure increases 0 MPa to 0.4 MPa, the effective contact between the FO cable and soil particles increases by approximately 0.4 times. The micro-anchors installed on the FO cable can generate anchoring forces. The anchoring forces initiate only after interface failure at their respective locations, restricting the development of strain at subsequent positions. We suggest defining the critical strain value, which corresponds to the maximum interface forces during the pullout process, and provides a basis for determining the interface strength between the FO cable and the soil.