Effects of confining‐pressure dependent Lame moduli on the frequency‐dependent amplification of a poro‐viscoelastic soil layer under horizontal cyclic loading

Abstract

In this paper, a series of Biot theory-based analytical solutions are proposed to study the dynamic response of a viscoelastic two-phase porous medium subjected to horizontal cyclic loading. To investigate the effect of material dynamic properties' depth (or confining-pressure) dependency, two types of soil stiffness profiles are adopted, along with the constant Lame elastic and loss moduli with depth: the moduli that are linearly increasing with depth and the moduli that are nonlinearly increasing with depth. The influence of the loading frequency, retardation time (or viscous damping), and a newly introduced model parameter that expresses the effect of soil cohesion on the moduli are numerically examined. When the retardation time is small and the dynamic response is periodic, it is demonstrated that the ground surface displacement versus loading frequency is greatly affected by the Lame moduli's depth-dependency; the peak-to-peak period becomes shorter and the amplitude decay tends to be minimal, considering the depth-dependency, particularly in the linearly increasing condition with depth. In addition, the cohesion-related parameter affects not only the periodic displacement amplitude but also the phase characteristics. Furthermore, the effect of the Lame moduli's depth-dependency is investigated on the amplification factor distribution with depth under horizontal loading.