ANALYSIS OF FOUNDATIONS ON FLUID-FILLED POROELASTIC STRATUM

A spatially semidiscrete finite-element technique is developed for the linear analysis of wave propagation in layered, fluid-filled poroelastic media. The wave motion is expressed as a combination of modes that are discrete in the vertical direction but continuous in any horizontal direction. Algebraic eigenvalue problems are derived for the wave numbers and shapes of these modes. Plane-strain and antiplane-shear motions are considered, while arbitrary motions in axisymmetric regions are expanded in Fourier series with respect to the azimuthal coordinate. Consistent transmitting boundaries are constructed for both plane and axisymmetric regions. In problems of dynamics of foundations, these boundaries provide an accurate and convenient representation of the far field and can be coupled directly with conventional finite elements modeling the near field. In the companion paper, results of an application of the present technique to the calculation of the dynamic stiffness of rigid strip and circular foundations are reported and analyzed.