Assessing the dynamic stiffness of piled-raft foundations by means of a multiphase model

The problem of evaluating the dynamic impedance of a vertically loaded piled raft foundation is investigated in this paper, based on the macroscopic description of the pile-strengthened soil as a two-phase linear elastic continuum. Conceived as an extension of the classical homogenization approach, this multiphase model incorporates elastic interaction laws between the soil and the reinforcing piles, which can easily be identified from the solution to a specific auxiliary problem. The equations of elastodynamics associated with this model can then be implemented into a dedicated finite element numerical code, the use of which makes it possible to produce reliable and accurate predictions for vertical impedance of large pile groups in a much easier and quicker way than with direct numerical simulations.