An experimental investigation of factors affecting drained CPT resistance in normally consolidated granular materials

The cone penetration test (CPT) is commonly used to assess the relative density of sands and fine gravels because of the difficulties and expense associated with obtaining undisturbed samples of these materials. Relationships between normalised cone resistance and relative density developed in calibration chambers are currently used in practice but these have not evolved or improved from proposals made over 30 years ago. The experimental study presented in this paper examines results from a large number of CPTs conducted specifically to investigate the effects of particle mineralogy, shape, and friction angle. Results from 12 different granular materials show that the estimation of relative density from cone resistance can be improved significantly if a reasonable assessment of the soils constant volume friction angle can be made. Additional test results demonstrate the effects of the ratio of the cone diameter to particle size (relevant to interpretation in gravels) as well as the importance of stress history (or overconsolidation ratio) on cone resistance. The results provide a useful database for ongoing development of numerical approaches modelling cone penetration.