GEOTECHNICAL AND GEOPHYSICAL TESTS FOLLOWING THE 2020 EARTHQUAKE-INDUCED LIQUEFACTION PHENOMENA

Abstract

Earthquakes and related coseismic effects at the surface, such as liquefaction and lateral spreading, can impact humans due to the resulting economic or social disruptions (e.g. slope and foundation failures, flotation of buried structures, etc.). In this respect, the 2020 Petrinja Mw6.4 earthquake (Croatia) provided many examples of liquefaction and lateral spreading, as identified by the post-earthquake field reconnaissance campaigns. The observed liquefaction cases occurred in the alluvial plains of the Kupa, Sava and Glina Rivers or along faults, with ejecta composed of sands and/or gravels of different grain size and mineralogy. The lateral spreading phenomena were observed along river embankments and roads. In this context interest in studying these different features arose, and an international research team from Italy, the United States and Croatia recently performed an intensive geological, geotechnical and geophysical campaign to assess the liquefaction susceptibility at selected sites located throughout the epicentral area (from Glina to Petrinja to Sisak). Innovative in-situ test equipment, such as the dynamic cone penetration test (DPT) for liquefied gravels and the Medusa flat dilatometer test (Medusa DMT) for liquefied sands, were employed in combination with standard in-situ tests,such as the standard penetration test (SPT), the piezocone test (CPTU), and shear wave velocity (Vs) measurements. These techniques were employed to verify their advantages relative to the existing iquefaction triggering charts and to characterize the soil properties of the buried liquefied layers and the non-liquefied crust. This paper presents preliminary results and comparisons at some of the investigated liquefaction sites.