Examination of Cone Penetration in Non-Plastic Silt with a Direct Cone Penetration Model

The cone penetration test (CPT) is widely used to characterize the behavior and properties of soils ranging from clays to sands. Although the CPT is often used to characterize silts, there exist few methods to interpret CPT data that were specifically developed for silts. This is partly attributed to a limited number of numerical and experimental cone penetration studies that specifically focus on silts. Past studies generally examined either undrained penetration in near-normally consolidated clay or drained penetration in clean sand, whereas cone penetration in silty soils (at the standard penetration rate of 2 cm/s) may be drained, partially drained, or undrained, depending on the soil’s permeability and compressibility. Consequently, uncertainty is introduced into CPT data interpretation for intermediate soils since geotechnical engineering practice lacks an established theoretical basis for evaluating cone penetration data in silts and other intermediate soils such as silty or clayey sands. This study takes a step towards establishing a theoretical basis by examining cone penetration in a non-plastic silt with a direct axisymmetric penetration model and the MIT-S1 constitutive model, calibrated against laboratory element testing and geotechnical centrifuge model tests. The objectives of this study are to (1) validate the numerical model for non-plastic silt with existing experimental cone penetration data from centrifuge tests and (2) use the numerical model to examine how simulated CPT data are affected by drained or undrained conditions during penetration, state-dilatancy relationships, and initial soil state.