Studies on wave propagation in granular media

Abstract

Experimental studies relating to the propagation and attenuation of disturbances in unconsolidated materials encouraged a theoretical investigation suggesting a mechanism governing propagation in such materials. From these physical considerations it is inferred that a disturbance imparted to a granular material is propagated in two principal parts. One consists of a wave of small amplitude which anticipates a wave of much higher amplitude propagating at a lower velocity. The first wave is called here a precursor and is identified with the visco‐elastic deformation of the grains of the unconsolidated material. The second component propagating at a lower velocity and carrying most of the energy imparted by the disturbance is identified with consolidation, accomplished by filling the voids between the grains. It is thus inferred that there would be appreciable dissipation of energy associated with the second wave and little attenuation of the precursor wave. Further experiments were conducted to check these conclusions. The results of these experiments show the composite wave structure predicted from theoretical considerations.