Abstract: The u-p (representing displacement of soil skeleton u and pore water pressure p) format 2.5D finite element equation of the saturated soil in the frequency domain is used to analyze the effectiveness of different vibration isolation countermeasures in isolating ground vibrations induced by trains moving at sub-and high-speeds. The vibration-isolation countermeasures considered herein include the installation of open trench, in-filled trench (concrete wall), and concrete slab (wave impeding block, WIB). The track and the attached sleepers are simplified as Euler beams resting on a saturated ground; the wave-number transform in the load moving direction is applied to reduce the three-dimensional (3D) dynamic problem to a two-dimensional (2D) problem. The 3D dynamic responses of the track and the ground are obtained from the inverse Fourier transform. For isolating the vibrations induced by trains moving at sub speeds, the isolation effectiveness of open trench and in-fill trench at elastic soil and saturated soil are almost the same; while quite different for WIB. In a word, open trench is not effective, in-filled trench is effective within a certain range; WIB is the best choice. For isolating the vibrations induced by trains moving at high-speeds, open trench can get certain effective at bigger width and depth, in-filled trench and WIB can achieve the desired vibration isolation effects at a smaller size.

Key words: saturated soil, trains moving loads, 2.5D finite element, ground vibration isolation, wave impeding block (WIB)