IMPACT OF WEIGHT FALLING ONTO THE GROUND

The application of some nondestructive testing procedures for soils an d pavements, such as the spectral analysis of surface waves method, re quires 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 ma terial characteristics of the medium. These sources are typically acco mplished by means of falling weights of various sizes. This paper appl ies a simple mass-spring-dashpot model to assess the characteristics o f 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. I t is found that if inelastic effects are disregarded, a falling weight always rebounds; that the drop height affects only the impact velocit y and amplitude of the contact force-not the duration of contact; and that increases in the drop weight lead to reductions in damping, incre ases in contact time, increases in contact force, and enhancement of t he low-frequency components in the Fourier spectrum of the contact for ce.