CPT correlations for sands from calibration chambers

* The CPT is a robust test which provides reliable and repeatable measurements. However, estimating mechanical properties of soils based on empirical correlations is problematic in the case of sands? the common use of relative density to characterize sand behaviour exacerbates this situation. * Soil behaviour can be conveniently normalized in terms of the state of the material which is quantified in terms of the distance between current state and a reference state on a void ratio - stress plot. For clays, OCR is commonly used to define the current state of the material while for sands, state parameter ( y ) provides a similar function. Consistent relationships have been developed relating the results of laboratory tests on sands and clays, and their respective state descriptions. * Interpretation of the available calibration chamber test results for sands in terms of state parameter provides a comprehensive and accurate approach in determining the state of sands from CPT data. * The compressibility of the sand is an important factor in the relationship between Qc and ¥. This effect can be quantified using the slope of the SSL to represent compressibility. * It is estimated that the accuracy of the Qc - y relationships for sands is within +/- 0.03 in terms of void ratio. This is a significant improvement over conventional interpretations and is sufficiently precise for most engineering purposes.