The 3rd Badong International Geohazards Symposium (BIGS2021)

20 / 2021-10-20 19:05:48

Surface and subsurface multi-physical field monitoring of reactivated reservoir landslide using quasi-distributed fiber optic

Surface and subsurface monitoring,Reservoir landslide,Fiber Bragg grating (FBG),Ultra-weak fiber Bragg gratings (UWFBG),Evolution process

Achieving real-time monitoring of detailed surface and subsurface information in a landslide is not an easy task due to the unique geoenvironmental conditions in the Three Gorges Reservoir (TGR) area, China. The quasi-distributed fiber optic sensor (i.e., fiber Bragg grating (FBG) and ultra-weak fiber Bragg grating (UWFBG)) offers the possibility of continuous measurement at high spatial resolution, overcoming the defects of point-wise measurement for traditional monitoring techniques. Herein, we propose a novel quasi-distributed fiber-optic monitoring system using FBG and UWFBG technology for multiple surface and subsurface parameters contributing to the landslide stability in terms of temperature, moisture and deformation. The proposed system is further applied to the Outang landslide located in the TGR area as a case study. Surface monitoring here is mainly focused within the depth of 1.0 m, whereas subsurface observations adopt the specialist sensing cables installed in a borehole down to the bedrock. The results show that the monitoring system is competent in real-time measuring both surface and subsurface temperature, moisture and strain in the studied landslide and helps to elucidate the deformation mechanism better. FBG-based temperature and moisture results show a good agreement at a shallow level. UWFBG-based subsurface temperature and moisture evolution processes can be captured and reasonably related to the external ambient events. Intriguingly, the deep-seated sliding surface of the studied landslide was successfully confirmed, and another shallow sliding surface at a depth of about 10 m was also recognized.