Numerical Modeling of Anchored Fiber Optic Cable–Soil Interaction for Distributed Geotechnical Monitoring

The implementation of distributed strain sensing technology in geotechnical monitoring faces a key challenge: achieving high deformation compatibility between embedded fiber optic (FO) cables and the surrounding soil, which significantly affects the accuracy of strain measurements. This study investigates cable–soil interactions through numerical simulations of FO cables equipped with two types of anchors, i.e., circular plate anchors and cylindrical anchors. By analyzing the stress and strain distributions, the enhancing effects of both anchor types on the interfacial behavior were systematically compared. The results demonstrate distinct reinforcement strategies: cylindrical anchors primarily mobilize cable–soil interfacial friction, whereas plate anchors generate localized stress zones that utilize the soil-bearing capacity to achieve greater resistance. Two quantitative indicators, the deformation ratio and coupling ratio, were proposed to evaluate cable–soil deformation compatibility at the scales of an infinitesimal cable segment and the entire cable embedded length, respectively. The plate anchors significantly improve cable–soil coupling, thereby increasing strain-sensing accuracy in low-pressure and long-term deformation monitoring, but they face the risk of material failure in high-stress environments. Cylindrical anchors exhibit minimal soil disturbance and are suitable for small-strain monitoring. Based on these insights, design recommendations for anchor group arrangements of FO cables were provided to ensure effective cable–soil deformation compatibility, preserve cable integrity, and minimize disturbance to the soil stress–strain field. These findings provide important guidelines for geotechnical monitoring using distributed fiber optic sensing.