An absorbing boundary condition for wave propagation in saturated poroelastic media — Part I: Formulation and efficiency evaluation

In a finite element formulation for dynamic soil-structure interaction, an absorbing boundary condition is needed to model wave propagation in an unbounded problem domain. When the soil is saturated, its dynamic behaviour can be modelled by means of Biot's poroelastic theory. Based on an analytical study of wave propagation in a saturated poroelastic medium, a frequency-dependent local absorbing boundary condition can be obtained at the expense of spurious reflections for oblique incident waves. Reflection curves are presented for all types of incident wave and varying dimensionless frequencies. Alternatively, the effective energy ratio allows the definition of a measure for the overall efficiency of the absorbing boundary condition. Based on these analytical investigations, good wave-absorbing capabilities of the absorbing boundary condition have been revealed. Encouraged by these results, the absorbing boundary condition is implemented in an irreducible finite element formulation for a compressible pore fluid, as discussed in Part II (Degrande, G. & De Roeck, G., Soil Dynamics & Earthquake Eng., 1993, 12(7), 423-32).