Laboratory and field studies of dynamic sil properties for geotechnical earthquake engineering analyses are presented. The dynamic properties are expressed in terms of shear wave velocity, V_s, shear modulus, G, and material damping ratio, D. The effects of various parameters ont hese properties are studied int he laboratory using combined resonant clumn and torsional shear equipment. Intact specimens were tested over shearing strains, gamma, where the soil response ranged from lienar (gamma < 0.001 percent) to highly nonlinear (gamma > 0.1 percent). The results are compared with generic nonlinear modulus and damping curves, and strong correlations with plasticity index and effective confining pressure are shown. Recent developments in correlating field measurements of V_S with the liquefaction resistance of granular soils are presented. Field studies involving surface wave measurements to evaluate profiles of V_S and small-strain material damping ratio are also discussed. Results from a study in which V_S profiles evaluated independently by downhole, surface wave, and suspension-logging tests are compared.
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