A liquefaction potential integral index based on pore pressure build-up

Abstract

The increased attention paid to the effects of liquefaction on the built environment has led over time to the introduction of vulnerability integral parameters that somehow quantify for a given site and a given seismic shaking the severity of the potential liquefaction damage induced at ground level. If the vulnerability parameter is properly calibrated and effective, it should somehow correlate to the observed damage datasets, increasing as the severity of liquefaction effects increase.In some cases, as for instance for the Canterbury earthquakes (New Zealand, 2010–2011) and for the 2012 Emilia Romagna seismic sequence, the existing vulnerability parameters for the assessment of liquefaction potential were not able to capture the observed damages induced by liquefaction, highlighting that further progress remains to be made in the current state-of-practice. The potentiality of a new index (Induced dAmage paraMeter- IAM), strictly related to the free-field post-volumetric consolidation settlement and therefore based on the estimate of liquefaction induced excess pore pressure, has been verified for a reference site located in the area struck by the 2012 Emilia seismic sequence by means of simplified and 1D effective stress dynamic analyses. The results were compared with those obtained by using one of the most convincing parameters existing in literature (Liquefaction Severity Number, LSN), showing the robustness of IAM, as well as the possibility to calculate it at different levels of complexity (via either coupled, simplified or super simplified and conservative analyses). The outcomes of the analyses allowed to define a simplified procedure for defining liquefaction microzonation maps, then representing a step forward towards the definition of a sound but easy-to-implement procedure to assess the resilience to liquefaction of urban centres.