Rigorous test of the performance of shear-wave velocity correlations derived from CPT soundings: A case study for Groningen, the Netherlands

An improved correlation between shear-wave velocity VS and cone penetration test (CPT) parameters was derived for the Groningen region, the Netherlands, using a set of 154 pairs of CPTs and seismic CPTs. An analysis of a high-quality subset showed that the subdivision into Holocene versus Pleistocene intervals or into cohesive
versus non-cohesive intervals did not significantly improve correlation, nor did filtering out of the transition intervals between clay and sand in the non-cohesive dataset. In addition, using qt or qc resulted in similar
regression results. We therefore propose a single new equation and we applied this to all available CPTs in the region. The analysis of the fitting bias showed that there is a trend relative to the measured VS. We therefore recommend performing SCPT measurements when very soft soils (VS < ~100 m/s) are encountered, rather than relying on the empirical correlation based on CPT parameters.
The comparison of the VS30 values from CPTs to the model VS30 of Groningen shows that correlation is excellent: 90% of the calculated VS30 values from the CPTs fall within one standard deviation of the VS30 of the
corresponding geological zone of the model. Although the resulting CPT-VS correlation is specific for the Groningen region, the approach can be applied to other regions with a paired SCPT-CPT dataset.