Dynamic Behavior of Machine Foundation on Two-Layer Soil System

Abstract

In this paper, a dynamic analysis of strip machine foundation is placed at the middle of the top surface of two-layer saturated sand with different states (i.e. loose, medium and dense), and vertical harmonic excitation is carried out with assessment of liquefaction potential and building up of the excess pore water pressure. The dynamic analysis is performed numerically by using finite element software, PLAXIS 2D. The soil is assumed as elastic perfectly plastic material obeys Mohr-Coulomb yield criterion. A harmonic load is applied at the foundation with amplitude of 25 kPa at a frequency of 5 Hz.A parametric study is carried out to evaluate the dependency of machine foundation on the modular ratio of soil layers. It was concluded that the displacement decreases remarkably when E1 (elastic modulus of the top soil layer) is duplicated 2-4 times E2 (elastic modulus of the underlying soil layer), then the effect decreases. The pore water pressure increases remarkably when E1 is increased to about 5 times E2, then the effect decreases. Liquefaction potential zone (when the effective stress approximately equals to zero) forms first near the end of the loading adjacency to the surface at shallow depth of the soil and extended to few meters for all frequencies.

Keywords

• Dynamic
• soil
• machine foundation
• two layers
• Liquefaction