Subsurface Multi‐Physical Monitoring of a Reservoir Landslide With the Fiber‐Optic Nerve System

• Published in: Geophysical research letters Vol. 49; no. 11
• Main Authors: Ye, Xiao, Zhu, Hong‐Hu, Wang, Jia, Zhang, Qin, Shi, Bin, Schenato, Luca, Pasuto, Alessandro
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.06.2022
• Subjects: Boreholes; Bragg gratings; Canyons; Deformation; Design; Design analysis; Evaluation; extreme climate impacts; Extreme weather; fiber optic sensing; Geological hazards; Landslides; Landslides & mudslides; main driver; Mechanical properties; Mechanical stimuli; Moisture; Moisture effects; Monitoring; Monitoring systems; multi‐physical evolution processes; Nerves; Optic nerve; Rain; Rainfall; Remote sensing; reservoir landslide; Reservoirs; Slopes; Strain; Synergism; Temperature; thermo‐hydro‐mechanical interactions; China
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2022GL098211

Reservoir landslides are typical geohazards with sophisticated thermo‐hydro‐mechanical interactions. However, direct observations of subsurface multi‐physical processes in bank slopes remain rare. Herein we present the design, implementation and evaluation of an innovative fiber‐optic nerve system based on weak‐reflection fiber Bragg grating to monitor a giant landslide located in the Three Gorges Reservoir region, China. The system is capable of measuring and imaging spatiotemporal distributions of temperature, moisture and strain along boreholes in near real‐time. Such visual profiles offer unique insights into the subsurface thermo‐hydro‐mechanical link between external conditions and geotechnical deformation, making it possible to decipher the substantial trigger of accelerated movements. Multi‐physical responses at depths of interest also enable us to better understand the evolution mechanism of reservoir landslides. Fiber‐optic nerve sensing can synergize with remote sensing and surface‐based technologies to build a space‐sky‐ground‐subsurface integrated monitoring system for landslides. Plain Language Summary Field monitoring of multi‐physical processes of reservoir landslides in the context of extreme weather events has remained challenging. Here we present the design, implementation and evaluation of a novel fiber‐optic nerve system (FONS) and the results and interpretation of recent FONS monitoring at the Outang landslide in the Three Gorges Reservoir region, China. The spatiotemporal profiles of subsurface temperature, moisture and strain are obtained, which enable us to understand the subsurface thermo‐hydro‐mechanical interactions. The deep‐seated slip surface has been successfully identified, together with a shallower one newly generated in the rear section of the landslide. We further verify that precipitation was the substantial trigger of accelerated deformation in the rear slope, and argue that short‐duration high‐intensity extreme rainfall was most likely to drive an abrupt movement. The monitoring system allows us to investigate the characteristics and mechanism of specific deformation acceleration events from daily to annual time series and relate the thermo‐hydro‐mechanical behaviors of sliding masses to creeping motion and progressive failure. Key Points The fiber‐optic nerve system with weak‐reflection fiber Bragg gratings produces multi‐physical spatiotemporal profiles at high resolutions Thermo‐hydro‐mechanical responses at the slip surface uncover subsurface‐scale landslide kinematics, hydrological transport and retention Short‐duration high‐intensity rainfalls promote landslide dynamics relative to uniform‐intensity rainfalls of similar amount and duration