The effect of varied stiffness of soil layers on interpretation of CPTU penetration characteristics

This article presents results of studies conducted in a calibration chamber and concerning the effect of stiffness of a layer of sand and silty clay on recorded values of cone resistance and sleeve friction in the process of static penetration. Results of analyses made it possible to determine the qualitative and quantitative effects of stiffness in both layers on the fluctuations in penetration characteristics. Analyses also showed that in the evaluation of soil layer stiffness the thickness of the layer with a lower stiffness needs to be taken into consideration. This article presents an analytical proposal for a correction of cone resistance in the layer of lower stiffness. This article contains examples for the incorporation of diverse layer stiffness on the evaluation on undrained shear strength, constrained deformation modulus and liquidity index of clay layer.