Using fully-coupled constitutive models in the assessment of seismic soil liquefaction

In current day practice, conventional assessment of liquefaction triggering is carried out through de-coupled approach based on the assessment of cyclic shear strength using a method without considering the effect of excess pore water pressure and using a cyclic resistance ratio of the deposit as a proxy obtained from in-situ tests. For the consequences, engineer attmepts to find free-field ground deformations (lateral or volumetric) again from emprical approaches calibrated based on the factor of safety values obtained from the decoupled approach. An alternative to empirical method discused in previous paragraph is the use of advanced fully-coupled constitutive models which consider shear – volumetric coupling of the soil matrix in a relatively reliable manner. In this thesis, an effort is made to utilize two of those advanced constitutive models by calibrating their parameters using (i) triaxial cyclic compression test (Giretti and Fioravante, 2016) carried out on Ticino sand; (ii) Cyclic resistance ratio curve of Cavezzo Sand (Giretti and Fioravante, 2017). Former step serves for increasing the practical knowledge on the use of the models and latter one serves for attempting to calibrate a model for Cavezzo sand under framework of H2020 European research LIQUEFACT project, considering the microzonation study undergoing in the Italian Municipality of Cavezzo (Emilia-Romagna). The results of the calibrated model is tested for one of the well investigated sites, through the comparisons of the liquefation triggering obtained from numerical and emprical methods. Finally, a parametric analysis is also made (by considering a hypothetical slope angle as the considered site is flat) to compare the lateral deformations obtained from numerical models with the ones obtained from emprical approaches.