Vertical Dynamic Response of Foundation Resting on a Soil Layer over Rigid Rock using Cone Model

摘要

In this paper, the impedance functions for a rigid massless circular foundation resting on a viscoelastic soil layer underlain by rigid rock under vertical harmonic excitation are found using one-dimensional wave propagation in cones taking into consideration the reflections at layer-rigid base interface and free surface, based on the theory of strength of materials. Linear hysteretic material damping independent of frequency is introduced by using correspondence principle. The frequency-amplitude response of a massive foundation is then found using impedance functions in the dynamic equations of equilibrium. Both static and dynamic response of the foundation predicted by the model compare well with the published results. Finally, for experimental verification of the model, the predicted resonant frequencies are compared with reported experimental results arrived from a total of 84 model footing vibration tests, which shows a good engineering accuracy (deviation of± 15%) with a vast variation of influencing parameters. Thus, the novel method is accurate and compared to rigorous procedures based on three-dimensional elastodyamics, it is easier to apply, provides conceptual clarity and physical insight in the wave propagation mechanism and offers a cost effective tool in the design offoundations under dynamic loads.