Prediction model of shear wave velocity by using SPT blow counts based on the conditional probability framework

Prediction models of shear wave velocity (V_s) based on standard penetration test (SPT) blow counts (N) are widely used in design practice. Recently, a V_s prediction model that uses multiple predictor variables (e.g., N and effective overburden stress) was suggested by several researchers to improve prediction capability. However, the application of these models to design practice is limited because calibrating the regression parameters for a site-specific condition is difficult because of multicollinearity in the model. This study describes the problem of this recently suggested V_s prediction model and proposes a calibration procedure to develop a site-specific model. The framework is based on conditional probability theory and can be applied to any site. Two application examples are presented to develop the site-specific model depending on data availabilities. The first application considers a site where only N are available from several borings, and the second application considers a site where both N and V_s are available from several locations. The examples show that the conditional probability approach is useful to obtain the site-specific V_s prediction model.