Abstract: Based on the U-W formula of governing equations of Biot’s theory for the saturated porous medium, the corresponding 2.5D finite element method (FEM) equations and the viscoelastic absorbing boundary are deduced by introducing Galerkin method and Fourier transform. The solution in wave-number domain can be obtained firstly from the built model for open trenches in the saturated ground; then the fast Fourier transform (FFT) is applied to gain the results in 3D space domain. For the moving loads, the vibration-isolation effects of open trenches in three saturated grounds (homogeneous saturated ground, layered saturated ground and saturated ground with upper layer being single-phase elastic medium) are investigated. It’s found that not only is the vibration-isolation efficiency of open trenches related to the trench depth, but also it’s affected by the interface properties and parameters varying of the layered soil media. The transmission and reflection of waves in different soil interfaces have great influences on the vibration-isolation effects of open trenches. Besides, the thickness of the upper single-phase elastic layer can greatly affect the vibration-isolation efficiency of open trenches in the saturated ground; as the thickness of the upper single-phase elastic layer becomes larger, the vibration-isolation efficiency of open trenches in the saturated ground gets improved.

Key words: moving load, 2.5D finite elements, saturated soils, open trenches, vibration-isolation effect