Review of shear-wave velocity prediction equations based on piezocone penetration test data; example from Yangtze River floodplain deposits at Nanjing, Jiangsu province, China

Small-strain parameters of soils play an important role in modern engineering geology. A research database of seismic piezocone test (SCPTu) results has been collected to develop empirical correlations for shear-wave velocity (Vs) prediction of recent floodplain deposits at Nanjing in the lower reaches of the Yangtze River. First, several existing cone penetration test (CPT)-Vs or CPTu-Vs correlations for general soils have been investigated. Four indices were used in the assessment, including the ratio of the estimated to measured Vs values, the root mean square error, the ranking index and the ranking distance. It is observed that all the selected correlations are biased towards overestimation or underestimation of Vs values for such floodplain deposits, demonstrating the need for a site-specific Vs prediction model. Then, new correlations for Yangtze floodplain deposits were developed through multiple linear regression, the performance of which has been assessed through comparisons of predicted and observed Vs values. The recommended correlation is entirely based directly on CPT data (qc, fs and z). The verification and calibration of this newly developed correlation for floodplain deposits constitute a useful contribution to the practice of geologists and engineers not only in the Yangtze delta region, but also in other similar depositional environments worldwide.