Abstract
Earthen levee embankments are critical flood defense infrastructures subject to progressive destabilization caused by transient seepage, matrix suction degradation, and pore water pressure buildup during extreme hydrological events. Conventional geotechnical monitoring using discrete point sensors often fails to capture localized preferential flow paths and spatial variability within heterogeneous embankment fills. This study presents a novel real-time monitoring and slope stability assessment framework using Distributed Fiber Optic Sensing (DFOS) based on Actively Heated Fiber Optics (AHFO) combined with distributed strain-temperature optical cables embedded across a scaled experimental levee embankment. By applying controlled thermal pulses and recording transient temperature decay curves, spatial distributions of volumetric water content and phreatic surface trajectories were resolved at a 0.2 m spatial resolution along the cross-section. The continuously measured moisture and derived pore water pressure distributions were seamlessly coupled into a transient unsaturated-saturated limit equilibrium and finite element slope stability workflow. The experimental findings reveal that the integrated AHFO-DFOS system reliably tracks the advancement of the unsaturated wetting front and detects early-stage internal seepage localization up to 4.5 hours before surface manifestation. Continuous updates of the Factor of Safety (FoS) demonstrated a sharp drop from 1.84 to 1.06 as the phreatic surface intersected the landside slope toe. This distributed sensing framework offers a transformative, continuous monitoring tool for real-time asset management and early warning against geotechnical levee failure.
