A fully coupled dynamic poroelastic analysis for partially saturated soils incorporating inertial effects under transient stress loading

Abstract

An accurate characterization of transient interactions between interstitial fluid flow and solid matrix deformation under dynamic stress loading is essential for understanding the poroelastic response of unconsolidated, fluid‐bearing sedimentary deposits. This paper develops a rigorously derived, fully coupled system of poroelastic governing equations that systematically incorporates the momentum balance equations for each constituent phase, explicitly accounting for both intraphase material inertia and interphase coupling inertia within a continuum‐mixture approach. The resulting analytical framework utilizes excess pore water pressure, excess pore air pressure, and solid phase displacement as the primary dependent variables, thereby establishing an integrated basis for evaluating dynamic fluid‐stress processes in partially saturated poroelastic media. Through the proposed model, we demonstrate that inertial effects are significantly influenced by soil texture, excitation frequency, spatial position within the medium, and degree of water saturation. Specifically, inertial contributions generally weaken with increasing water saturation and strengthen with increasing excitation frequency. The results further indicate that inertial effects are substantially more consequential for the dissipation of excess pore water pressure while exerting comparatively limited influence on soil deformation or the rate of settlement. Owing to the symmetric spatial distribution of excess pore water pressure along the soil‐column height, the maximum inertial influence occurs in the vicinity of the mid‐height region. Moreover, the effects exhibit marked textural sensitivity, being substantially more pronounced in clayey soils than in sandy soils. Finally, intraphase material inertia dominates the overall inertial response, whereas interphase coupling inertia contributes comparatively little.