Field Monitoring and Laboratory Testing for an Integrated Modeling of River Embankments under Transient Conditions

The need for a reliable estimate of the actual failure probability of existing river embankments under changing boundary conditions represents an ever-demanding task for researchers and designers, and those involved in their maintenance and management. Uncertainty and variability of soil suction and water content spatial and temporal distributions, together with the definition of a suitable soil model that accounts for the partially saturated state of embankment materials, are among the most critical aspects to be possibly included in the advanced analysis and design of such linear earthen infrastructures. The use of specialist integrated monitoring can be here functional to enable calibration and to enhance reliability and consistency of predictive analyses. Site measurements of the main variables at relevant depths are typically rarely available, whereas an accurate soil characterization under partially saturated conditions is only performed in research applications, thus producing limited confidence on stability conditions. To provide a useful and innovative tool to evaluate realistic stability conditions of levees under transient flow conditions, a full-scale monitoring system has been implemented on an existing section of the River Secchia (northern Italy) 11-m-high flood defenses. The complementary use of specific laboratory tests, innovative field measurements and numerical analyses presented in the paper aims at providing a suitable methodological approach to the performance assessment of these vital geotechnical systems throughout their entire lifetime and highlighting possible limitations of typically used methods of analysis.