Seepage Anomaly Detection via Fiber Optic Distributed Temperature Sensing: Insights from Physical and Numerical Modeling

Abstract

The principle of detecting seepage anomalies in water-retaining earthen structures through temperature monitoring has yet to gain extensive acceptance in modern field applications. As such, this study demonstrated the practical detection of seepage anomaly from fiber optic distributed temperature sensing (DTS) through physical and numerical modeling. A high-resolution DTS, capturing temperature at a sub-cm interval, was embedded in a laboratory-scale earth dam featuring normal and anomalous seepage conditions (induced by artificial defect). Then, a fluctuating reservoir thermal load was applied, and the internal temperature of the dam was monitored. Evaluation of the temperature lag time showed a quicker detection of temperature changes on the DTS sensing locations traversed by the anomalous seepage flow. The disparity in temperature lag times across the DTS increased significantly when a severe seepage anomaly was induced by systematically channeling the reservoir water directly into the artificial defect through a small tube tapping into the reservoir. Further insight into the heat-seepage interaction was achieved through coupled hydrothermal numerical modeling using COMSOL Multiphysics. Numerous dam and levee failures worldwide linked to poor conditions and erosion have caused much damage and loss of life. This study practically demonstrated temperature analysis as a robust indicator for identifying potential issues related to seepage in earthen water infrastructures, such as dams and levees. This methodology facilitates efficient early detection, allowing for proactive intervention to avert potential failures and improve public safety. Moreover, the research findings are expected to lay the groundwork for a proof of concept, cultivating an improved understanding and appreciation of the technique among practicing engineers. Building on the success of this study, future laboratory investigations are planned to explore deeper into seepage-heat interactions and optimize the technique for enhanced practical applications, including determining factors such as the ideal location and embedment depth for the distributed temperature sensing system.