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 accelerotion and vehicles travelling at constant speed on damaged or bumpy .surfaces. In the case of damaged or bumpy surfaces, excitation of axle-hop reson(tnces is taken into account, whereas an accelerating or braking vehicle is modelled as a point horizontal tractionforce applied to the ground and moving along with the vehicle. Frequency spectra of the vertical component of the groundvibrationvelociQ are investigatedfor dffirentfunctions of road surface roughness, acceleration,final (initial) speed ofthe vehicle, ground attenuation, Poisson's ratio, and radiation angle relative to the direction of the vehicle moveruent. It is shown that damaged or bumpy road surfaces normally generate vibrcttions 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.