Vibration isolation using open or filled trenches
ABSTRACT The problem of structural isolation from ground transmitted vibrations by open or infilled trenches under conditions of plane strain is numerically studied. The soil medium is assumed to be linear elastic or viscoelastic, homogeneous and isotropic. Horizontally propagating Rayleigh waves or waves generated by the motion of a rigid foundation or by surface blasting are considered in this work. The formulation and solution of the problem is accomplished by the boundary element method in the frequency domain for harmonic disturbances or in conjunction with Laplace transform for transient disturbances. The proposed method, which requires a discretisation of only the trench perimeter, the soil-foundation interface and some portion of the free soil surface on either side of the trench appears to be better than either finite element or finite difference techniques. Some parametric studies are also conducted to assess the importance of the various geometrical, material and dynamic input parameters and provide useful guidelines to the design engineer.
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ABSTRACT: This study investigates a prediction model for free-field response in the vicinity of a vibrating foundation. The model is based on a mathematical description of physical phenomena that occur when the massless machine foundation system is excited by a harmonic vertical force. The foundation has a square and rigid shape and is assumed to be placed on the surface of visco-elastic soil overlying the bedrock. Vertical displacements of both the foundation and the surrounding soil are obtained by solving the wave's equation, while considering the conditions of the dynamic soil-foundation interaction. The solution of this equation is formulated in the frequency-domain Boundary Element Method (BEM). In this paper the Thin Layer Method (TLM) is used to calculate the Green's functions for each element. By this approach, the amplitudes of the soil in the vicinity of a vibrating foundation may be obtained under the effect of various parameters.
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ABSTRACT: The establishment of wave impeding barriers (WIBs) beneath the railway track or below the protected residential buildings resting on soft soil can be commonly used to reduce the ground borne vibrations caused by high-speed train traffic. This paper deals with the non-linear 2D finite element modeling for the prediction of shielding performance of WIB on the dynamic response of vibrating coupled soil–structure system. Energy absorbing boundaries along the truncated interfaces of the unbounded nature of the underlying soil media are implemented in the time domain along with Newmark’s integration. This numerical model and its computational work were adapted with simulation of the passing train load completely account for plastic deformations of the underlying soil medium under Mohr–Coulomb failure criterion and directly predicting the reduction effect on the structural response. Extensive parametric investigations for both passive and active isolation cases under different train speeds have been performed to reveal the influence of its wave impedance ratio on the shielding efficiency. The important findings based on obtained numerical results are presented.Construction and Building Materials 11/2012; 36:1–13. · 2.27 Impact Factor
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ABSTRACT: Field vibration tests were carried out at a proposed site for the vibration testing room, and 2D numerical analysis using finite difference tool FLAC 5.0 was performed to suggest effective vibration isolation systems. In the analysis, the numerical model is first calibrated with respect to material properties, damping value, and boundary conditions to obtain the output comparable to the field test results. The calibrated model was further used to perform a parametric study by (1) providing vibrating input motions from vibrating machines to be operated; (2) using two depths of cutoff trench; and (3) providing gravel bed, gravel bed with rubber pad, and gravel bed with rubber pad and cutoff trench to study the isolation effects. Comparing the results from the parametric studies with the human perception level of vibration, a decision on the isolation system was determined.International Journal of Geomechanics 10/2010; 11:364-369. · 1.20 Impact Factor