ABSTRACT
True determination of soil parameters for thin clay layers in sand or silts from CPTU measurements is challenging. Cone resistance in thin layers is influenced by the surrounding layers resulting in unrepresentative measurements. Measurements should be corrected for this effect prior to interpretation of parameters. Such correction requires accurate information about the thickness of the thin layer. Previous studies have shown that the pore pressure parameter of the CPTU may not properly identify the layer interfaces for thin clay layers in sand. In this study a “cone resistance rate of change” parameter is suggested for thin-layer interface detection. Results from recently performed physical experiments at NTNU as well as from prior studies are used to evaluate the ability of this parameter to detect thin layers of clay in sand. The parameter appears to detect layer interfaces with good accuracy, even for layers with thickness as thin as the cone diameter. The results suggest that the approach may estimate layer thickness quite well and aid towards efficient correction of cone resistance to achieve more realistic soil parameters for thin clay layers in sand.
