Evaluating fiber-optic cable–soil mechanical coupling using elastoplastic pullout interaction modeling

The mechanical coupling between a fiber-optic cable and surrounding soil is a significant concern in distributed strain sensing-based geotechnical monitoring. In this study, the cable–soil mechanical coupling is quantitatively evaluated using elastoplastic pullout interaction modeling. Data from a laboratory pullout test performed on a 2-mm-diameter tight-buffered cable buried in a sand–gravel–clay mixture are used to validate a documented elastoplastic pullout model. By using cable axial strain profiles and cable–soil relative displacement measurements, two new indices are proposed to quantify the cable–soil mechanical coupling based on this model, in addition to the common interface shear strength proxy. A parametric study is conducted to investigate how the geometrical and mechanical properties of the cable and the cable–soil interface characteristics affect the two indices. Relating the parametric analysis to practical considerations, recommendations are made as to the design of strain-sensing cables for use in field and laboratory scenarios. Furthermore, modification to the elastoplastic pullout model is discussed to better simulate cable–soil pullout interactions. This study demonstrates that the elastoplastic pullout model can be effective in assessing cable–soil interface behavior and mechanical coupling.