Computation of ground vibrations generated by accelerating and braking road vehicles

The problem of ground vibration generation by accelerating and braking road vehicles is considered theoretically for vehicles accelerating (decelerating) with a constant acceleration a from rest to a constant speed, or braking to a stop from a constant speed. According to the low-frequency approximation considered, an accelerating or braking vehicle of mass M is modelled as a point horizontal traction force Fx = aM applied to the ground and moving along with the vehicle. Frequency spectra of the vertical component of the ground vibration velocity are investigated as functions of acceleration, final (initial) speed of the vehicle, ground attenuation, Poisson ratio, and radiation angle Θ relative to the direction of the vehicle movement. It is shown that, in contrast to vehicles travelling on uneven roads, the ground vibrations generated by accelerating and braking vehicles are characterised by directivity patterns V(Θ) which show, in particular, that there is no radiation in the directions perpendicular to the direction of vehicle movement.