Toshiro Okamoto - Senior Research Engineer, Dept. of Geotechnical Earthquake Engineering, Central Research Institute of Electric Power Industry, JAPAN

Seismic analysis of rockfill dam in Japan has often applied Sawada’s formula as dynamic property at very low strain level, which is empirical basing on measured elastic wave velocity for 5 dams. Then many velocities have been measured by PS logging, so in this study these data of Vs (secondary or shear velocity) and Vp (primarily velocity) are evaluated by regression analysis and its result is compared with Sawada’s formula. The statistical average value and dispersion of Vs and ν（Poisson ratio）are derived for unsaturated and saturated upstream side rock zone, unsaturated and saturated core zone and unsaturated downstream side rock zone.