Estimation of the soil cyclic resistance by flat dilatometer accounting for the fines content effect

The application of semi-empirical charts based on in-situ tests results represents the first step in the earthquake-induced soil liquefaction assessment. Among them, the CPT-based charts have been largely developed in the last decades, especially after the 2010-2011 Canterbury earthquakes in New Zealand, while the main drawback of the existing approach based on DMT is related to the lack of a correction factor for the fines content. In this regard, this study proposes a new empirical relationship between the Cyclic Resistance Ratio and the horizontal stress index where the effects of the fines content are incorporated. The new method is calibrated on a specific site located in the Emilia- Romagna plain (Italy), where an extensive soil characterization from in-situ and laboratory tests was available for the silty sand and sandy silt deposits affected by liquefaction after the 2012 Emilia earthquake. Even though verified only for Italian natural soils, the new approach allows to reduce substantially the discrepancy between the results obtained when the CPT-based and the DMT-based methods are applied.