Static stability of Po river banks on a wide area

The Po is the longest river in Italy. Over half its length is controlled by embankments as protection measure against heavy flooding. Recently, the Italian Government has funded a number of activities aimed at seismic hazard control in the territory, including evaluation of the seismic stability of about 90 km of embankments of the Po river. Hundreds of geotechnical investigations within the study area were performed and the water level variations in the embankments and their subsoil investigated. This paper describes some of the results for the whole project: the global stability analyses of the river banks under static conditions. The river stretch was modelled by 99 cross-sections. Following a criterion of representativeness and uniform distribution along the river, 43 of them were selected to perform limit equilibrium stability analyses. Detailed stratigraphic soil profiling as well as careful geotechnical characterization of the riverbank sediments and the surrounding subsoil have been carried out, mainly on the basis of in-situ tests. All geotechnical and geometrical parameters relevant to the outcome of the analyses were modelled as random variables and stability analyses performed in terms of probability of failure. The probability turned out to be negligible for all the sections investigated, but the detailed geotechnical models here allowed for the identification of possible piping phenomena in a number of significant sections. The results of the analysis provide a useful tool for the local Authority towards flooding risk assessment.