CPT-Based Liquefaction Case History from the 2012 Emilia Earthquake in Italy: Fid-Bau Portal

CPT-Based Liquefaction Case History from the 2012 Emilia Earthquake in Italy

Vannucchi, Giovanni

AbstractSignificant and widespread liquefaction phenomena were observed after the main shock of the Emilia earthquake (Italy) on May 20, 2012. A considerable number of surveys were subsequently performed to accurately test the susceptibility to liquefaction of soil deposits affected by the most severe liquefaction-induced effects and damage. Ground surface morphology was defined in detail by means of LIDAR survey results; subsoil stratigraphy and water table level were inferred from CPT tests and soundings; physical properties and mechanical parameters of soils were obtained from laboratory tests or indirectly inferred from the results of a large number of CPT tests carried out in the area. Two main sandy layers susceptible to liquefaction were identified and appropriately characterized. Seismic loading induced by the main shocks of the sequence was carefully estimated from the peak ground acceleration map produced by the National Institute of Geophysics and Volcanology. More than 90 sites were examined in the area of interest where the most significant cases of liquefaction occurred. A number of statistically independent CPT-based liquefaction field case histories were selected, the critical layer towards liquefaction was identified, and the liquefaction resistance parameter and loading parameter were assessed. Key parameters for each site and critical layer were provided to be added to a select larger and worldwide liquefaction case history database proposed by other authors for estimating CPT-based liquefaction-triggering resistance curves. Finally, applicability to the case study of some more widely used CPT-based simplified approaches was tested. A systematic underestimation of liquefaction potential was found and is discussed, possible reasons are explored, and suggestions are proposed.