Blocking Masses Applied to Surface Propagating Waves

Ground vibration generated by rail and road traffic is a major source of environmental noise and vibration pollution in the low-frequency range. A promising and cost-effective mitigation method could be the use of heavy masses placed as an array on the ground surface near the road or track, these could be concrete or stone blocks, or specially designed brick walls, for example. This work concerns the effectiveness of such “blocking” masses. We consider propagating waves in a finite depth elastic layer assuming plane strain conditions. Given that the masses are considered solid objects we may place these on the surface, embedded or submerged in the elastic medium where a finite element method is considered as a computational solution technique. Next, we may assume the masses are aligned as a periodic infinite array and enforce periodic boundary conditions around a “unit-cell”. By consideration of propagating waves via Floquet-Bloch theory we shall investigate the existence or lack thereof of propagating surface and body waves. This analysis supports a semi-analytical lumped-parameter method assuming the blocking masses are point masses situated on an elastic waveuide. The work is enhanced by an example highlighting advantages and disadvantages of multiple-mass scatterers in terms of possible stopband intervals related to propagating surface waves.