Numerical Investigation of Transition Mechanism between the Two Kinds of Compressional Waves in Saturated Geotechnical Media

Abstract

The hydromechanical coupling effect between soil skeleton and pore fluid phases, that is, dissipation of dynamically induced excess pore water pressure, can be a critical factor in determining the dynamic response of geotechnical structures in a certain permeability range. A theoretical study for investigating this certain permeability range is the propagation mechanism of compressional waves in geotechnical media, which has not been thoroughly investigated, especially for its dual behavior (i.e., the fast wave and slow wave) in the concerned frequency range for geotechnical engineering problems (0.1–20 Hz). Therefore, this paper numerically studies the propagation mechanism of compressional waves in saturated geotechnical media under soil dynamics loads. Investigations reveal the transition mechanism between the two kinds of compressional waves considering the effects of loading frequency, soil stiffness, and permeability. More importantly, based on the numerical results, this paper proposes empirical transition lines between the fast wave and slow wave, specified by loading frequency and material permeability. Practically, the proposed empirical lines can be used as the boundaries defining the applicable ranges of one-phase and two-phase coupled analysis for predicting the dynamic response of saturated geotechnical structures.