CPT Cone Factor: Numerical-Analytical Approach

AbstractDoes the overconsolidation ratio have any effect on the cone factor value used for determining the undrained shear strength? In order to find the answer, first the numerical modeling of a cone penetration test (CPT) in clay is performed in this study, and then the obtained results are used to achieve a reliable analytical solution for determining the undrained shear strength. In this regard, the numerical simulation is verified by some existing laboratory tests. Then the observations obtained from the comprehensive numerical analyses are investigated. Based on the numerical simulation results for the region located around the cone tip, the velocity field is formulated and the stress states are studied. According to the analytical solution, the vertical stress distribution is obtained by solving the differential equation of motion for the soil located around the cone tip. Determining the corrected cone tip resistance through integrating the vertical stresses applied to the cone tip surface, two new relationships are subsequently presented for the cone factor in terms of the initial conditions of clay. Based on the proposed solution, the effect of overconsolidation ratio on the cone factor, which was unclear as yet, is specifically determined. Finally, the cone factor relationship developed in this study is compared with the existing relationships in the literature as well as the field measurements.