In the past decade decade significant advances have been made in the analysis of problems involving the dynamic loading of soils, notably in the areas of foundation vibrations (10,12,12,14,23), earthquake effects (15,16, 17, 18, 19) and protective construction (21,22). For the most part the development of the analytical techniques for the analysis of such problems has advanced ahead of the development of methods for evaluating the pertinent soil properties. Richart, Hall and Woods (13) in their 1970 textbook on Vibrations of Soils and Foundations, state, ‘The process of obtaining representative values for the critical soil properties is probably the most difficult part of the design study. This difficulty arises because the critical soil properties are dependent on so many different parameters. For a given problem these properties may vary by a factor of 10 in a soil deposit that appears to be relatively homogeneous, because of their dependence on such parameters as strain amplitude, state of effective stress, and number of cycles of loading. The response predicted by the analyses that have been developed will change proportionately to, an is no more accurate that, the values uses for the soil properties.
