Il campo prova di San Carlo (FE): sperimentazione di una tecnica di mitigazione per il rischio da liquefazione

The seismic sequence that struck the Emilia-Romagna Region (Northern Italy) in May 2012 caused extensive liquefaction phenomena in the villages of San Carlo, Sant'Agostino, and Mirabello (Province of Ferrara ). Such phenomena mostly affected the sandy soils deposited along the ancient path of the Reno River, causing extensive damages to houses and infrastructure. The Emilia-Romagna authority immediately activated to assess, investigate and analyze the areas that experienced liquefaction. A few months after the earthquake, the Emilia-Romagna Council issued a regional law (N.12418, October 2, 2012) where several ground improvements techniques are suggested to mitigate the liquefaction hazard. In this paper we present the results of a field test carried out at San Carlo (FE) in the summer of 2012 to test the compaction-grouting mitigation technique. The test consisted in the execution of 16 injections of cement mortar through holes of diameter 0.5 m, driven to a depth of 12 m and with a distance of 2 m. The site was characterized before and after the soil treatment by means of geotechnical surveys and laboratory tests. The results show that the compaction grouting, possibly combined with drainage gravel columns, is an effective technique to reduce the liquefaction hazard in the considered case.