Civil Engineering Association

A Dynamic Response Study on Optimal Piling Depth with respect to Ground Vibrations

Dynamic response of a piled foundation in soil has lately received much attention in research areas such as civil engineering and seismic engineering. The goal of this thesis is to learn more about the dynamic response of a single pile in clay and in particular to study if there is an optimal piling depth. The clay types investigated are an idealized isotropic clay and a case-specific for Gamla Ullevi, Gothenburg, Sweden. The motion and forces are small and the soils are considered as linear elastic materials. A solid finite element model is built in one case-specific and one idealized version. The idealized version is validated by mechanical response theory of a elastic half-space and also by comparison to a semi-analytical wavenumber model published 2013 by Kuo & Hunt. The response results show perfect agreement with half-space response theory and good agreement with the wavenumber model. The point mobility of a vertically loaded pile, and the transfer mobility at surface and in depth, are studied for different pile lengths for frequencies below 20 Hz. The results from both finite element model and the wavenumber model show convergence piling
depth at about 30 meters for both soil types. The transfer function results are reciprocal which allows to consider the foundation as the recipient of ground vibrations.