Assessment of Effect of Cyclic Frequency and Soil Modulus on Liquefaction Using Coupled FEA

Abstract

The present paper describes briefly the establishment of an adequate mathematical framework to describe the liquefaction phenomenon which uses the Biot’s basic theory for dynamics of saturated porous media. The variational principle is applied to the field equations of fluid flow in a fully saturated porous elastic continuum, and the finite element method is used to numerically solve the resulting continuity equation and equilibrium equation. In-situ stresses are computed from static analysis prior to dynamic analysis. Pastor–Zienkiewicz Mark III constitutive model is used to describe the inelastic behavior of soils in the dynamic simulations. Kelvin elements are attached to transmitting boundary to absorb the wave energy and prevent back propagation of wave into the soil domain. The response of fluid-saturated porous media which are subjected to time dependent loads has been simulated numerically to predict the liquefaction of a loose sandy soil layer. It is noticed that liquefaction occurs throughout all the depth of sand layer at frequency 1 Hz of the cyclic loading. This model is compared with centrifuge experimental results and shows good predictive capacity. Effect of frequency is more significant. With increase in frequency, substantial increase in displacement and EPP is observed.