Shear wave velocity as function of cone penetration test measurements in sand and silt mixtures

A database of research-quality piezocone test (CPTU) results and shear wave velocity Vs measurements, assembled in the context of an ambitious research project carried out at the Treporti test site (Venice, Italy), has been interpreted in order to study the seismic response of the predominantly silty sediments forming the Venetian lagoon basin as well as to explore potential correlations for such intermediate soils. The experience gained so far with the Treporti database and other field data collected in the lagoon area has shown that the mechanical behavior of Venetian soils cannot be easily interpreted using the existing and well-established CPTU-based approaches, hence the interest in examining whether or not the seismic response of these sediments, expressed in terms of shear wave velocity, follows the framework published for other soils. The applicability to the available data of a number of existing correlations, originally developed either for sands or fine sediments, has been first investigated and updated relationships have been then suggested. Furthermore, the small-strain stiffness calculated from Vs measurements has been compared with the field stiffness derived from the observed performance of a full-scale test embankment built in the Treporti site, so as to verify common design assumptions. The verification and calibration of existing approaches are likely to constitute a useful contribution to the practice of geotechnics not only in the Venetian lagoon area, but also in the silty deposits usually present in the surrounding alluvial plain and other similar depositional environments, allowing rapid estimates of seismic soil classification as well as small-strain stiffness properties for preliminary design or at sites where only cone penetration data are available.