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Ground disturbance due to waves generated by a machine foundation can be detrimental to adjacent structures or sensitive equipment operating nearby. Most of the vibratory energy that affects structures nearby is carried by surface (Rayleigh) waves that propagate in a zone close to the ground surface. Therefore, for machine foundations vibrating from moderate to high frequencies, the amplitude of ground motion can be reduced significantly by installing a wave barrier around the source. A three-dimensional boundary element algorithm incorporating quadratic elements has been used to perform an extensive parametric study on the effectiveness of open trenches as wave barriers. The key geometrical and material parameters that govern the performance of an open trench wave barrier have been identified, and a design formula in the form of an algebraic expression has been developed for estimating the vibration screening effectiveness of such barriers. Furthermore, through comparisons with published field test data and rigorous boundary element solutions, the validity of the design formula has been established.

Vibratory energy transmitted through propagating waves generated by machine foundations can be detrimental to adjacent structures or sensitive equipment operating nearby. Most of the vibratory energy affecting structures nearby is carried by surface waves that propagate in a zone close to the ground surface. Thus, for machine foundations vibrating at moderate to high frequencies, vibration amplitudes in the vicinity of the foundation can be reduced significantly by installing an annular in-filled trench wall around it. An in-filled trench wave barrier reduces the ground motion by interception, scattering, and diffraction of the surface waves. This approach of isolating a vibrating machine foundation from its surroundings is known as active isolation. This paper presents a numerical investigation on active isolation of machine foundation by in-filled trench wave barriers in a three-dimensional viscoelastic half-space. A rigorous boundary element method (BEM) algorithm for dynamic analysis of three-dimensional solids has been used to study the effects of various geometric and material parameters on the performance of the in-filled trench barriers. Important dimensionless parameters have been identified and design guidelines are presented.