A 1D Simplified Approach for Liquefaction Potential Evaluation of Soil Deposits

Build-up of seismic-induced pore water pressures in saturated sandy soils and the resulting reduction of effective stresses may lead to dramatic consequences. Indeed, as observed during several seismic events occurred over the last decade (Tohoku, Japan and Christchurch, New Zealand 2011; Emilia, Italy 2012; Palu, Indonesia 2018), severe damage due to liquefaction has caused both economic and environment-wise adverse impacts. Therefore, the development of a reliable although simplified tool for the assessment of liquefaction risk may be favorably perceived both in the Academia and in the current practice. In this framework, the paper presents an improvement of the uncoupled method originally proposed by Seed et al. [1], where the excess pore water pressures induced by seismic loading under partially-drained conditions were evaluated. In their work, the Authors modified the well-known Terzaghi onedimensional consolidation equation by adding a source term, which represents the rate of excess pore pressures generated under fully-undrained conditions. The governing equation is hereby solved using the Finite Difference Method implemented in a homemade Matlab script, taking into account the drainage conditions related to soil layering and possible filtering of the input motion caused by soil stiffness degradation, which in turn is induced by the excess pore pressure build-up. The proposed implementation is validated against the results of fully-coupled 1D FE analyses carried out with the Finite Element code Plaxis 2D, where the response of liquefiable sandy layers is reproduced through the advanced constitutive model SANISAND [2].