Some laboratory experiments on shear wave propagation in unconsolidated sands

Abstract

Abstract With the recent development of a method to transmit shear wave energy through laboratory unconsolidated sediments, an important new era of research on the dynamic properties of sediments has just begun. This, in time, will complement the vast amount of compressional wave data existent in the literature and provide the researcher with a very important tool to aid in the classification of sediments by correlating geophysical with geo‐technical parameters. A description is given of laboratory experiments in a specially designed sedimentation chamber to propagate shear waves in saturated sand sediments, using a method which employs a pair of novel design piezoelectric ceramic transducers. For comparison, similar measurements of wave velocity and amplitude were made on the sands using a pair of compressional wave transducers. Results are presented of compressional wave and shear wave velocity and amplitude versus porosity for these sands. A complete laboratory electronics testing facility necessary for acoustic measurements using both types of transducers is detailed. The performance of the shear wave transducers is also demonstrated in preliminary experiments using a plexiglass rod and then a container full of dry sand. Finally, the behavior of a transiently‐stressed saturated sand in the sedimentation cell is monitored geophysically by the continuous propagation of shear waves. It is shown that the duration of the liquefaction event in the sediment can be recognized by the temporary disappearance of shear waves from the record.