Geotechnical analysis and optical fiber based monitoring of an existing river levee affected by piping

The study examines a 350 m long section of the Adige river levee, located in the Province of Bolzano (Italy) close to the village of Salorno, that has been affected in the recent past by moderate piping phenomena and subjected to subsequent interventions for the risk mitigation. Extensive geophysical and geotechnical investigations were performed to characterize the levee and its foundation soil. This careful investigation provided a multi-dimensional description of the levee and of the close soil water-meadows, which are possible preferential paths for piping. To measure preferential seepage paths, the foundation soil was instrumented using both piezometers and an advanced monitoring technique, the latter based on a fiber optic system installed in a shallow trench at the bank base on the landside. In the last ten days of October 2018, the Adige river was subjected to a relevant double flooding event that likely induced a significant seepage flow in the levee foundation soil. The paper presents some results of the geotechnical site monitoring together with a preliminary discussion of the data provided by the piezometers and optical fiber system.