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 (V-s) prediction of recent floodplain deposits at Nanjing in the lower reaches of the Yangtze River. First, several existing cone penetration test (CPT)-V-s or CPTu-V-s correlations for general soils have been investigated. Four indices were used in the assessment, including the ratio of the estimated to measured V-s 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 V-s values for such floodplain deposits, demonstrating the need for a site-specific V-s 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 V-s values. The recommended correlation is entirely based directly on CPT data (q(c), f(s) 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.