Enhanced mixed boundary for modeling infinite domain in 2.5D soil vibration analysis

Abstract

In this paper, an enhanced mixed 2.5D boundary for treating the infinite domains of the half-space is proposed. Unlike the perfectly matched layer (PML) that has a fixed outer boundary, the proposed method replaces the fixed outer boundary by infinite elements (IFE) to allow waves to propagate uninterruptedly to infinity. Such an approach not only improves the absorption capacity of the PML, but reduces its dependence on the attenuation function. The proposed boundary in the stretched coordinates is formulated in detail, for which the criteria for selecting the reference wavenumbers for multi types of waves are deliberately analyzed. A comprehensive parametric study for assessing the accuracy of the proposed boundary is presented, where the superiority of the proposed boundary relative to the pure PML and IFE is demonstrated. Particularly, the optimal ranges of parameters of the proposed boundary are identified. For illustration, the proposed boundary is applied to analyzing the frequency and time domain responses of a surface train moving at sub- and super-critical speeds. The results indicate that the proposed method can accurately predict the wave propagation characteristics, including the Mach cone at super-critical speeds.