Dynamic response of three-dimensional rigid and flexible foundations on layered soils with local inhomogeneities

The dynamic response of rigid and flexible three-dimensional (3D) foundations of arbitrary shape, placed on a homogeneous or layered halfspace, which may contain a finite, longitudinally invariant structure or inhomogeneity, is determined numerically. A 2.5D coupled Integral Transform Method (ITM) - Finite Element Method (FEM) approach is used to compute the dynamic compliance at the surface of the stratified soil with inclusion, whereas 3D ITM fundamental solutions are applied in case of a homogeneous or layered subgrade. The foundation is modelled by 3D finite elements in both cases and coupled to the underlying ground by enforcing the compatibility conditions at the interface. Compliance functions at the soil foundation interface are presented and compared with existing solutions for verification as well as displacement distributions within the underlying ground are illustrated. The influence of the foundation stiffness on the total response as well as on the frequency dependent power transmission into the soil due to different load types is studied. Finally, the method is applied to evaluate the influence of a tunnel and a stiff cylindrical inclusion on the dynamic response of the foundation, thereby demonstrating the importance of taking into account the Structure-Soil-Structure-Interaction (SSSI).