DYNAMIC CHARACTERIZATION OF VERTICALLY LOADED FOUNDATIONS ON GRANULARSOILS

By means of scaled modeling on a geotechnical centrifuge, a systematic experimental investigation was conducted to examine the vertical dyna mic response of surface foundations on granular soils. From the result s of more than 100 tests, it was found that the dynamic characteristic s of such foundations can be well represented in the frequency domain by the homogeneous half-space analytical solution despite the gravity- and load-induced spatial variations of the soil's modulus. However, i t was also revealed that the foundation response has a significant non linear dependence on the soil bearing pressure and footing dimension. To capture such aspects, a set of equivalent-homogeneous elastic param eters was determined from the physical measurements for a wide range o f soil-foundation configurations. Through an analytical synthesis, it was found that the equivalent-homogeneous Poisson's ratio of the soil can be taken as 0.25 while the equivalent-homogeneous shear modulus of the soil can be related through a power law to the soil's void ratio, footing radius, and average foundation bearing pressure. The practica l relevance and potential applications of the resulting semiempirical formula for the dynamic foundation compliance are discussed.