Abstract: Groundwater table might significantly fluctuate due to seasonal rainfall. In order to investigate the effect of the moving water table on the screening performance of multiple open trench barriers, a finite element model is developed to describe wave propagation in a layered ground, which is modeled as a dry layer resting on a saturated substratum. The effect of infiltrated water in trenches is considered in this model, and the vibration isolation efficiencies of multi-trench barriers with equal and unequal trench depth, multi-trench barriers with inclined trench wall and continuous undulating terrain barriers at different water levels are analyzed as comparable cases. Comparing with the corresponding single-phase elastic foundation, the numerical results show that a low permeability coefficient of the saturated substratum might have a significantly adverse effect on the vibration isolation efficiency for most of water tables. A triple trench barrier with a depth of 0.3LR (LR is Rayleigh wavelength) usually can achieve a satisfactory screening efficiency (i.e. 75% reduction), while the depth should be at least 0.6LR at the critical water table, where the worst isolation efficiency occurs. A multiple trench barrier with decremental depth can effectively reduce the adverse effect of the resonance. The larger sloping sides are, the better isolation effect of a barrier is for the shallow trenches, while it is not important for deep ones. Moreover, a rolling terrain landscape can be an environment-friendly isolation measure, which would achieve a great vibration isolation efficiency.

Key words: groundwater table, saturated soil, multiple open trench barriers, isolation effectiveness, COMSOL software