CPT data interpretation for an improved characterization of the paleosol stratigraphy in the Po River valley, Italy

Post-depositional phenomena can produce significant changes in the geotechnical properties of soils. Although the identification of the effect of such phenomena on the soil structure may contribute significantly to the interpretation of the soil mechanical behaviour, their characterization is not routinely carried out in practice. In this context, the novel application of paleosol features in the definition of geotechnical stratigraphic models can result in improved characterization of soil deposits in alluvial sites. Sedimentology uses paleosols (i.e. fossil soils with peculiar geologic properties) as markers for stratigraphic correlations in alluvial areas at large scale. This paper outlines the main properties of these geological objects and investigates the strategies for their identification in cone penetration tests (CPT). The analyses are discussed with reference to boreholes and CPTs data in 3 well documented sites in the Po River Valley (Italy). First, sedimentological identification of paleosols from borehole corings is introduced; then, geotechnical interpretation of CPT is carried out on such a basis, showing how poorly developed paleosols (Inceptisols) found in the investigated sites, are difficult to be identified through CPT logs and how they plot in the well-established Robertson’s classification charts.