Response of stratified soil deposits to the severity of liquefaction phenomena: the Piniada Valley, Greece, case study

The last decades, successful attempts have been made to quantify the liquefaction potential of a site using liquefaction indices, i.e., LPI and LSN. The accuracy of these indices has been recently questioned due to the mismatch of well-documented cases in stratified soil deposits. We applied these methods at point-bar deposits along the Piniada Valley, Greece, where widespread liquefaction phenomena were triggered by the 2021 Damasi earthquake, considering data derived by six CPTu. The aim of our study was twofold: firstly, examine the vertical and lateral heterogeneity of subsoil profiles within this specific geological-geomorphological feature and secondly investigate the role of the subsoil stratigraphy, on the severity of the ejected material. To address these issues, we additionally applied a geophysical method, i.e., ERT, aiming at testing its capability to detect clay-like and sand-like soil layers and validating the obtained tomographies with in-situ tests data. As a result, we conclude that the stratigraphy of the subsoil layers within a point-bar setting could significantly vary even within a distance of 10-15 m, thus affecting the liquefaction-related behavior and the ejecta potential. The latter seems to be successfully prognosticated by the recently developed approach of LD-CR. At this regard, the partially stratified soil deposits could not generate enough excess pore pressure to create cracks in the crust layer for reaching the surface. In contrast, sites with a thick continuous sand mixture can generate severe liquefaction manifestations even with an overlying crust layer more than 4 m-thick.