Post-liquefaction analysis and shear wave assessment by means of instrumented DCP: application to Cephalonia island (Greece) and Petrinja region (Croatia)
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Soil liquefaction causes damage to soil and structures, which can result in a significant risk to people, as well as material damage and major economic impacts. Consequently, and due to the difficulty of obtaining representative soil samples in the field, the assessment of liquefaction potential based on in-situ tests becomes an important issue in the study of a seismic site susceptibility. Moreover, seismic events often take place in areas that are difficult to access, especially once the earthquake has occurred. It is therefore necessary to develop new techniques, alternatives to conventional methods (CPT, SPT), based on light, quick and cost-effective equipment. The French instrumented DCPs (Panda 3® & Grizzly 3®) allows an estimation of soil stress-strain properties almost continuously with depth. Theses lightweight tools also has the advantage of being able to be rapidly deployed on sites with difficult access. This work presents both an example and a summary of its implementation at two post-seismic sites: the island of Cephalonia (Greece), and the Petrinja region (Croatia) along the Kupa river. In the first case, the main objective is to characterize the surface formations of the Koutavos plio-quaternary sedimentary basin to propose a 1D model of the surface soil column and assess the influence of the variability of these surface formations on the amplification of seismic motion. The second experimental campaign, at Petrinja, was aimed at identifying the soil layers that had been liquefied following the events of 2020, as well as highlighting the different soil models obtained by geophysics or constructed from instrumented DCP. For each investigated site, geophysical and geotechnical additional test were carried out. The data collected with this new technology will be compared with those obtained previously with other methods (boreholes, SPT, electrical tomography, MASW...), in particular to assess the shear wave velocity obtained.