Excess Pore Water Pressure along the Friction Sleeve of a Piezocone Penetrating in Clay: Numerical Study

Abstract

Excess pore water pressure (EPWP) measurements taken at different positions on a penetrating piezocone into a clayey soil are believed to play an important role in correlating to its characteristics. On this subject, many correlations were proposed by several researchers, mainly empirically and mostly with EPWPs measured at the cone shoulder (u2). The use of EPWP measurements at other positions, for example, behind the friction sleeve (u3) has not been evaluated, possibly because of the lack of u3 measuring elements for most penetrometers on the market. In this study, the piezocone penetration test in saturated intact clays was numerically modeled using finite element formulation. The EPWP distribution generated along the friction sleeve was investigated and it was found that the previously mentioned distribution closely followed an exponential trend which was mainly affected by the overconsolidation ratio (OCR) and the rigidity index (Ir) of the soil. Further investigations led this study to propose an innovative relationship to estimate u3 values from measurements of common piezocone tests on the market (u2-type) and pertinent soil characteristics. The well-predicting capability of numerical modeling procedures and the proposed relationship was compared with and validated with available experimental and field piezocone test measurements.