GNGTS 2014 - Atti del 33° Convegno Nazionale

432 GNGTS 2014 S essione 2.3 of many embankment works and land reclamation, in order to impede further disastrous flooding events near Sant’Agostino (Franceschini, 1983), which led to the almost straight trend of the paleo Reno. Despite all the efforts, at the end of the XVIII century the river was definitely diverted southeastwards, in a preexisting channel of the Po River (Po Primaro) (Cremonini, 1988). The old course was thus gradually dried up, while still maintaining its morphological evidence, only locally obliterated by human activities. Therefore, the morphologically elevated areas corresponding to the levee bodies mostly accumulated during the Middle Ages (Caputo et al. , 2012). Since the beginning, these areas have shown obvious advantages in terms of urbanization and simultaneous development of the road network. Indeed, these sand bodies are characterized by excellent geotechnical properties (in static conditions) for the construction of buildings and are raised with respect to the surrounding flat countryside, thus avoiding flooding due to overflowing of the rivers or heavy rainfalls. On the other hand, as was evident in concomitance with the earthquake of May 20, saturated sand bodies are prone to liquefaction. Moreover, since the crests of the paleo levees are up to 5 m higher than the surrounding interfluvial areas, high topographic gradients exist and, in case of widespread liquefaction, this setting may play a key role in the lateral spreading phenomena. Data collection and analysis. The first phase of this work consisted in the collection, georeferencing and archiving of all the geognostic and geophysical data that can provide Fig. 2 – Examples of secondary effects due to liquefaction phenomena occurred in occasion of the May 20, 2012 earthquake. a) fractures with gravitational movements and ejection of sand; b) eruption of sand from a floor inside a garage built in correspondence of an old water well; c) broken pipes; d) differential settlement of foundations and consequent damage to the building.