Development and assessment of a numerical model for non-linear coupled analysis on seismic response of liquefiable soils

Abstract

Widespread liquefaction evidences characterized the most recent earthquakes in Italy (Emilia, 2011) and in the world (Canterbury, New Zealand, 2010-2011), resulting in a renewed interest on the characterisation and modelling of pore pressure build-up during seismic events. In particular, it has been highlighted the roughness of some traditional tools for assessing the liquefaction susceptibility as well as the overall complexity of the available numerical models. Therefore, it seems necessary to develop reliable analysis method that comprehensively take into account for the complexity of the mechanical behaviour of soils, even though remaining accessible for professional practice. In this work, a simplified constitutive model, incorporated in a one-dimensional code, is proposed. It allows to pursuing a simplified dynamic analysis: it is easy to be applied as the semi-empirical methods and reliable as an advanced numerical approach. The proposed model is based on the results of laboratory undrained cyclic tests. lt is easy to calibrate and reasonably approximates the main features of soil behaviour. The numerical formulation of the model has been incorporated in a one-dimensional computer program for seismic soil response, in order to develop a useful tool for engineering practice. In the same code it has been also implemented a numerical routine modelling the pore pressure dissipation thus allowing to simulate both the pore pressure build-up during the seismic event as well as its dissipation. The upgraded code has been validated using test sites data in order to provide an extensive documentation of the capabilities and limitations of the implemented model in prediction the seismic site response under strong ground motions. Finally, the developed code has been used to perform specific analyses on a dyke, severely damaged by the 2012 Emilia earthquake sequence. Taking into account the aftershocks that followed the main seismic event, effective stress analyses have been allowed a better understanding of the damage source detected along the embankment.