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Rock and Soil Mechanics

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.

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