Laboratory study on pore pressure generation and liquefaction of low Plasticity silty sandy soils during the 2012 earthquake in Italy

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