Vibration isolation by wave barriers.

摘要

The transmission of vibratory energy through propagating waves generated by machine foundations, traffic or blasting may adversely affect nearby structures and vibration-sensitive installations. It may be possible to reduce this type of high-frequency ground vibrations significantly by providing a suitable wave barrier in the ground between the source and the area to be protected. The concept of isolation by wave barriers is based on reflection, scattering and diffraction of the incident wave energy. This dissertation deals with the isolation of ground vibration through the use of open and in-filled trenches as wave barriers.; An advanced direct boundary element method (BEM) incorporating higher order isoparametric elements and a sophisticated self-adaptive numerical integration scheme is used for this study. The BEM algorithm is able to handle both boundary value problems as well as incident wave (wave scattering) problems.; An extensive numerical investigation of the influence of various geometrical and material parameters on the screening efficiency of rectangular open and in-filled trench barriers is conducted. The soil is modelled as a homogeneous isotropic viscoelastic half-space. Both active (near field) and passive (far field) isolation by such barriers have been studied. Based on the analytical study, important dimensionless parameters are identified and simple models involving algebraic expressions and/or design graphs are developed for the design of wave barrier based vibration screening systems. Through comparisons with results from rigorous numerical analyses and available experimental data, the applicability of these models are demonstrated. In addition, studies with layered soil profile are performed to identify important layering effects on vibration screening. Simple physical models for the wave phenomena have been presented for some cases to provide additional explanation for the analytical results.