NUMERICAL ANALYSIS OF ESSENTIAL FACTORS AFFECTING PIEZOCONE PENETRATION TEST IN CLAYS BY APPLYING FINITE ELEMENT METHOD

Due to its repeatability and reliability, the piezocone penetration test (PCPT or CPTu) is widely used in geotechnical site characterization. This paper presents a numerical technique for the analysis of the PCPT in cohesive soil. The Mohr-Coulomb yield criterion with the associated flow rule is assumed to model the elasto-plastic behavior of clays under undrained condition. A volumetric weighting algorithm adjusts the relative positions of nodes after each loading increment. The variation of the cone resistance is examined in relation to various parameters such as the in situ stress state, cone apex angle and penetration rate. For different penetration rates and cone sizes, the cone tip resistance profile and excess pore pressure profile are provided. A full parametric study was undertaken, quantifying the influences of the rigidity index, in situ stress anisotropy and the cone roughness. The trends of these variations are highlighted and compared with those found by other researchers. This technique can be extended to analyze the plastic behavior of elastoplastic sands often modelled using either the Drucker-Prager yield criterion or a critical state model. The results show this study would provide some useful insights into the factors affecting the data interpretation of PCPT in clays.