3D Engineering Geological Modeling to Investigate a Liquefaction Site: An Example in Alluvial Holocene Sediments in the Po Plain, Italy

Liquefaction-induced surface manifestations are the result of a complex geological–geotechnical phenomenon, driven by several controlling factors. We propose a multidisciplinary methodological approach, involving engineering geologists, geomorphologists, sedimentologists, and geotechnical engineers, to build a 3D engineering geological model for liquefaction assessment studies. The study area is Cavezzo (Po Plain, Italy), which is a municipality hit by superficial liquefaction manifestations during the Emilia seismic crisis of May–June 2012. The site is characterized by a Holocene alluvial sequence of the floodplain, fluvial channel, and crevasse splay deposits prone to liquefaction. The integration of different geotechnical investigations, such as boreholes, CPTm, CPTu, and laboratory tests, allowed us to recognize potentially liquefiable lithological units, crucial for hazard assessment studies. The resulting 3D engineering geological model reveals a strict correlation of co-seismic surface manifestations with buried silty sands and sandy silts within the shallow 10 m in fluvial channel setting, which is capped and laterally confined by clayey and silty deposits.