Mitigating ground vibration by periodic inclusions and surface structures

Ground vibration from traffic is a source of nuisance in urbanized areas. Trenches and wave barriers can provide mitigation of vibrations, but single barriers need to have a large depth to be effective-especially in the low-frequency range relevant to traffic-induced vibration. Alternatively, periodic repetitions of mass, stiffness or both in an infinite structure lead to so-called stop bands in the frequency domain. Harmonic loads applied within these stop bands will not induce propagation of energy through the structure, i.e. the energy stays within a nearfield surrounding the source. Less well-defined behavior can be expected for transient loads and finite structures. However, some mitigation may occur. The paper aims at quantifying the mitigation effect of nearly periodic masses placed on the ground surface using two approaches: a small-scale laboratory model and a three-dimensional finite-element model. The laboratory model employs soaked mattress foam placed within a box to mimic a finite volume of soil. The dynamic properties of the soaked foam ensure wavelengths representative of ground vibration in small scale. Comparison of the results from the two models leads to an assessment of the mitigation that can be expected in a real project compared to the mitigation predicted by a numerical model.