Liquefaction Resistance of Sandy Soil in South-Eastern Sicily from Cyclic Direct Simple Shear Testing

Port and waterfront facilities can suffer extensive damage due to liquefaction during an earthquake as evidenced by recent events (e.g. 1995 Kobe earthquake, 2005 Fukuoka-ken Seiho-oki earthquake). In these cases, it is necessary to consider not only the human casualties but also the direct and indirect economic impact on the commercial sector. In light of this, the evaluation of the excess pore pressure build-up induced by seismic action is crucial to ensure waterfront facility safety. In this paper, laboratory and in-situ investigations were conducted to evaluate the liquefaction resistance of a sandy soil in the port of Pozzallo, located in south-eastern Sicily (Italy), which is considered as one of the highest seismic risk areas in Italy. The physical properties and results obtained from in-situ and laboratory tests for the “Pozzallo sand” are discussed. In particular, cyclic direct simple shear (CDSS) tests were conducted to evaluate the liquefaction resistance using the CDSS apparatus at the Laboratory of Soil Dynamics and Geotechnical Engineering of the "Kore" University of Enna (Italy). The CDSS testing procedure was described in detail and the Liquefaction Resistance Curve was defined according to the pore pressure ratio criterion. Moreover, the results provided by the CDSS tests were compared with those obtained by the simplified stress-based procedure to evaluate the susceptibility of a site to seismic-induced liquefaction. Results showed that the simplified procedure for evaluating soil liquefaction is conservative compared to the laboratory results. This demonstrated the importance of performing advanced laboratory tests for soil improvement techniques to mitigate liquefaction risks.