Feasibility Study on the Use of Coaxial Strain-Sensing Cable to Monitor Strains on Buried HDPE Pipelines Crossing a Normal Fault

Monitoring pipeline strain is essential for assessing structural integrity and guiding seismic design. Buried pipelines are prone to large localized strains under fault movement. Due to their limited measurement range, current strain-sensing techniques struggle to capture the entire evolution of pipeline strain during fault displacement. To address this, we propose a coaxial strain-sensing cable for buried pipelines (CSSC-BPs). This innovative cable transplants the fiber optic sensing mechanism onto a high ductility coaxial cable and is manufactured through specialized structural design and integrated packaging. We first detail the CSSC-BP’s working principle, structural design, manufacturing method, and installation process, followed by evaluating its sensing performance through tensile tests. Results indicate that the CSSC-BP can measure strains exceeding 16% with excellent repeatability within a 5% deformation range. Additionally, we conducted a model test involving a high-density polyethylene (HDPE) pipeline subjected to normal fault movement. The results confirm that the CSSC-BP can offer accurate and reliable large-strain measurements for buried pipelines under fault movement. It not only measures the strain response of the pipeline throughout the entire fault displacement process, but also captures bending strain softening and axial strain hardening behaviors during the large-strain deformation stage. The findings of this study will provide an effective tool for monitoring large strains in pipelines crossing faults.