Evaluation of CPT-Based Empirical Characterization Methods for Sands

As a result of the difficulties in obtaining undisturbed samples in cohessionlesss soils, CPT-based empirical correlations often developed from calibration chamber experiments are widely used for determining many soil parameters for geotechnical investigation. This paper describes the application of 19 reduced-scale calibration chamber cone penetration tests for evaluating empirical correlations for predicting relative density, unit weight, and constrained modulus for loose to medium-dense sands. A 6 mm-diameter subtraction cone with an apex angle of 60^o and a net area ratio of 0.75 is used in the laboratory tests. Cone tip resistance, sleeve friction, and pore pressure at the cone shoulder are measured. No excess pore pressure developed in the CPT experiments on the fine sand. Empirical correlations are suggested for predicting the dry and saturated unit weights of silica sands. Existing empirical correlations display a very wide range of estimates for sand relative density and often very different from the experiments of this study. However, the constrained moduli exhibit a better agreement with an empirical correlation.