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Generation of Low-Frequency Rayleigh Waves by Heavy Lorries

Generation of low-frequency ground vibrations by heavy lorries is considered theoretically for both vehicles accelerating (decelerating) with a constant acceleration and vehicles travelling at constant speed on damaged or bumpy surfaces. In the case of damaged or bumpy surfaces, excitation of axle-hop resonances is taken into account, whereas an accelerating or braking vehicle is modelled as a point horizontal traction force applied to the ground and moving along with the vehicle. Frequency spectra of the vertical component of the ground vibration velocity are investigated for different functions of road surface roughness, acceleration, final (initial) speed of the vehicle, ground attenuation, Poisson's ratio, and radiation angle relative to the direction of the vehicle movement. It is shown that damaged or bumpy road surfaces normally generate vibrations of higher amplitudes, in comparison with accelerating and braking lorries. In contrast to vehicles travelling along bumpy or uneven roads and generating vibrations propagating at all directions, the ground vibrations generated by accelerating and braking vehicles are characterised by the directivity function showing that there is no radiation in the direction perpendicular to the vehicle movement.