Laboratory Study on Pore Pressure Generation and Liquefaction of Low-Plasticity Silty Sandy Soils during the 2012 Earthquake in Italy

AbstractThis paper describes the results of a laboratory investigation performed on clean sand and low-plasticity silty sands, recovered at different locations of the bank stretch at Scortichino, which was affected by serious damages following the 2012 Emilia Romagna earthquake in Italy. A comprehensive cyclic simple shear (CSS) testing program was undertaken to evaluate the liquefaction potential and pore pressure response of silty sand layers, which form the subsoil at the site. A series of undrained CSS tests were carried out on undisturbed samples by applying an initial static driving shear stress before cyclic loading (nonsymmetrical tests), with the aim of gaining a better understanding of the role played by a static preshearing on the observed liquefaction phenomena. The results obtained prove that, in nonsymmetrical cyclic loading tests, low-plasticity silty sands tend to be more susceptible to liquefaction than in symmetrical cyclic loading tests. The onset of liquefaction occurs by large shear strains, and not by complete loss of effective stress resulting from the pore pressure buildup.