GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 3.2 ___ GNGTS 2023 Fig. 2 – Geological map of the Sulmona Quaternary basin, after Galli et al. (2015), draped on DTM (Regione Abruzzo) (1) Upper Pleistocene - Holocene alluvial deposit; (2) Middle - Upper Pleistocene alluvial and colluvial deposit; (3) Upper Pleistocene fluvial-alluvial, slope fan and landslide deposit; (4) Lower-early Upper Pleistocene lacustrine deposit; (5) alluvial fan; (6) landslide; (7) active normal fault, inferred (8) (Salvatore et al., 2022). The borehole stratigraphic log of Santa Rufina test site highlighted the variability in sediments within the first few meters of the Holocene alluvial plain, showing, under the present topsoil, an alternance of sandy-gravelly and silty (plastic) thin layers until 7 m depth. The groundwater table (GWT) was intercepted at a depth of 1 m below the ground surface (Salvatore et al., 2022). Fig. 3 summarizes the simplified borehole log obtained using the USCS classification (Unified Soil Classification System) together with the fine content (FC) profile provided by the laboratory testing. To evaluate the CSR7.5 profile according to the “simplified procedure”, the peak ground acceleration at the ground surface ( ) has been determined starting from (1) the = 0. 296 value at outcropping rock conditions equal to 0.255 g, as proposed by Valentini et al. (2019) in the Sulmona area for a return period of 475 years based on a fault based PSHA study, and (2) the stratigraphic amplification factor Ss = 1.16 for the B subsoil class of the Italian building code (NTC, 2018). To evaluate the liquefaction safety factor (FSliq) and therefore the liquefaction potential index (LPI) through the cyclic resistance ratio (Fig. 3) we used the corrected values ( 7.5 1 ) according to Cao et al. (2011) and Rollins et al. (2022). Fig. 3 –Liquefaction assessment results based on methods by Cao et al. (2011) and Rollins et al. (2022) at Santa Rufina test site. We also compared the results from – based methods to those from DPT and SPT already estimated by Salvatore et al. (2022), recalculating also the values according to the laboratory screening criteria (Tab. 1).