Frequency‐dependent dynamic behavior of a poroviscoelastic soil layer under cyclic loading

Abstract

In this study, a linear poroviscoelastic model based on the Biot theory is proposed to analyze the dynamic response of partially saturated soil. Both the flow-dependent and flow-independent poroviscoelastic behaviors are described in the proposed model. The compressibilities of both the constituents, including the skeleton material and porefluid, are considered, and the effective skeleton stress is determined using the linear viscoelasticity law based on the generalized spring-dashpot model. The soil surface is subjected to two types of harmonic loading, namely, vertical compressive loading and lateral shear loading. The influences of the relaxation time, saturation degree, and soil permeability on the surface and interior dynamic responses of the soil layer are investigated. It is revealed that the amplification factor, effective stress, and pore pressure decrease as the viscous damping increases, indicating that neglecting the viscoelastic property of solid skeleton could overestimate the induced dynamic responses. Furthermore, in comparison with the viscous damping of the solid skeleton, the viscous coupling involving the viscous resisting forces between the solid skeleton and pore fluid has limited effect on the dynamic behavior of the soil layer.

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

“…However, this paper sheds light on introducing the confining-pressure dependency of material dynamic properties into the viscous type Kelvin-Voigt model, leaving the non-viscous type Kelvin-Voigt model for future work. Following Chen et al, 22 the constitutive equation for the compressible pore fluid is formulated by…”

“…As described in the following section, the parameters and in Equation ( 8) do not affect the governing equations for horizontal loading (e.g., Equations ( 21) and ( 22)) but do affect the governing equations for vertical loading as studied by Chen et al, 22 in which the Lame elastic moduli were assumed to be constant (i.e., depth-independent). This paper focuses only on the horizontal vibration response of soils with depth-dependent elastic moduli, but the depth-dependency effect on the vertical vibration should be studied in the future.…”

“…Researchers [19][20][21] applied the linear viscoelastic theory to a Biot model to investigate the viscous damping effect. In particular, a recent study by Chen et al 22 presented a linear poro-viscoelastic model to analyze the one-dimensional dynamic response of a partially saturated soil layer subjected to horizontal and vertical harmonic loadings.…”

“…The above previous studies [19][20][21][22] considered the effects of viscoelastic properties (i.e., viscous damping) but did not take into account an essential feature of the soil, confining-pressure dependency; material dynamic properties were assumed to be constant with depth. However, several investigators [23][24][25][26] have shown that dynamic properties (e.g., shear modulus) of both sandy and clayey soils are strongly affected by the confining-pressure, even at the same void ratio (or relative density).…”

“…This study proposes analytical solutions based on Biot theory [8][9][10][11] to investigate the dynamic response of a viscoelastic two-phase porous medium, of which material dynamic properties are depth (or confining-pressure) dependent. To differentiate between the condition of the constant Lame elastic and loss moduli with depth, 22 two types of soil stiffness profiles are adopted in this study: the moduli are assumed to increase linearly and nonlinearly with depth. Furthermore, the dynamic response of a viscoelastic soil layer subjected to horizontal cyclic loading is numerically discussed in detail, focusing on the influence of loading frequency, retardation time (or viscous damping), and a newly introduced model parameter that expresses the effect of soil cohesion on the moduli.…”