Sensing solutions for assessing the stability of levees, sinkholes and landslides

Abstract: Monitoring large-scale structures such as dams and levees has always presented significant challenges, in particular when localized damage needs to be detected and mapped. Traditionally, the only monitoring procedure allowing the detection and localization of damage such as leakages, settlements, cracks, or abnormal joint movements was periodic visual inspection. However, inspecting large structures regularly is a tedious and subjective procedure, which reveals issues only visible to the eye. The interval between inspections can be large and it is difficult to obtain rapid feedback on the conditions of a structure during or immediately after an event such as an earthquake or a large storm. Permanent monitoring systems based on distributed optical fiber sensing technology, laser distance meters, and synthetic aperture radar (SAR), have opened new possibilities to address these needs. They allow integrity monitoring with direct detection, localization, characterization, and immediate reporting of new local conditions. These systems are therefore not only able to measure strain and temperature (answering the ‘how much’ question) but also to localize possible damage areas (answering the ‘where’ question). This makes them ideal for monitoring structures where the location of a possible instability or failure is unknown. For example, the sensors can detect and localize a seepage zone in a levee, the onset of a sinkhole, or the formation of a crack in a concrete wall. This also allows a more targeted approach to inspection, since it is now possible to concentrate the interventions on specific areas showing abnormal behavior. These technologies and several field application examples will be presented in this chapter.