Three dimensional dynamic interaction of adjacent foundations on a halfspace with local inhomogenity applying a coupled itm-fem approach

The dynamic subsoil coupling for a finite number of adjacent foundations has a sig-nificant effect on the dynamic behaviour of the foundations involved and the structures basedon them. As the mutual influence of the foundations on each other is decisively influenced bythe properties and the composition of the subsoil, buried structures or inhomogeneities have tobe included, in order to model the real soil conditions as exact as possible and to enable anaccurate prediction of the interaction phenomena of adjacent foundations. In this contributionan efficient 2.5D coupled Integral Transform Method (ITM) – Finite Element Method (FEM)approach is used in conjunction with a conventional 3D FEM to compute the dynamic stiff-ness of foundations resting on the surface of a halfspace including a longitudinally invariantstructure or inhomogeneity. Herein, the analytical ITM solutions of the dynamic wave equationallow to account for the infinite extension of the soil by satisfying the radiation condition. The2.5D FEM formulation enables to model complex, spatially limited structures and a part ofthe surrounding soil within a cylindrical outer boundary, on which both methods are coupled.The finite foundations on the halfspace surface are modelled using 3D finite elements and arecoupled to the soil substructure enforcing the compatibility conditions (full coupling or relaxedboundary conditions) at the common interface. The influence of the embedment depth, size andstiffness of the inclusion on the dynamic response of the foundations, taking into account thethrough soil coupling, is investigated for different configurations of the surface foundations (dis-tance, width). Frequency dependent compliance functions at the soil-foundation interface arecalculated for the different parameter settings and compared with existing solutions to verifythe method as well as with the results for the homogeneous halfspace to illustrate the influenceof an inclusion. Furthermore the displacement distribution over the total surface of a halfspacewith a stiff inclusion due to a dynamic excitation of either one or both of the two consideredadjacent rigid surface foundations obtained by a post-processing procedure is presented.     «

The dynamic subsoil coupling for a finite number of adjacent foundations has a sig-nificant effect on the dynamic behaviour of the foundations involved and the structures basedon them. As the mutual influence of the foundations on each other is decisively influenced bythe properties and the composition of the subsoil, buried structures or inhomogeneities have tobe included, in order to model the real soil conditions as exact as possible and to enable anaccurate prediction of the interaction phe...     »