IMPACT OF WEIGHT FALLING ONTO THE GROUND

The application of some nondestructive testing procedures for soils and pavements, such as the spectral analysis of surface waves method, requires the use of dynamic sources at some point on the surface of the ground to create vibrations that can be recorded and related to the material characteristics of the medium. These sources are typically accomplished by means of falling weights of various sizes. This paper applies a simple mass-spring-dashpot model to assess the characteristics of the forces transmitted to the ground by the falling weight so as to be able to rationally decide on its size, mass, and dropping height. It is found that if inelastic effects are disregarded, a falling weight always rebounds; that the drop height affects only the impact velocity and amplitude of the contact force-not the duration of contact; and that increases in the drop weight lead to reductions in damping, increases in contact time, increases in contact force, and enhancement of the low-frequency components in the Fourier spectrum of the contact force.