Critical insights in laboratory shear wave velocity correlations of clays

Shear wave velocity, V-s, is an important mechanical-dynamic parameter allowing the characterization of a soil in the elastic range ( g < 10-3%). Thirty-five existing Gmax or V-s laboratory correlations were examined in this study and are grouped into different general forms based on their geotechnical properties. A database of 11 eastern Canadian clay deposits was selected and used for the critical insights. The effect of the coefficient of earth pressure at rest, K-0, was also examined. A range of variation for each general form of correlation was determined to take the plasticity index and void ratio values of investigated sites into account. The analysis shows a significant scatter in V(s)1 values predicted by existing correlations and raises questions on the applicability of these correlations, especially for eastern Canadian clays. New correlations are proposed for Champlain clays based on laboratory measurement of V-s using the piezoelectric ring-actuator technique, P-RAT, incorporated in consolidation cells. An analysis of P-RAT results reveals the sample disturbance effect and suggests an approach to correct the effect of disturbance on laboratory Vs measurements. The applicability of the proposed correlations, including the disturbance correction, is validated by comparison with in situmeasurements using multi-modal analysis of surface waves (MMASW).