Sediment shear waves: a comparison of in situ and laboratory measurements
Surficial sediment shear wave velocity measurements were made at eight sites (water depths 7-22 m)in the vicinity of La Spezia, Italy. Values of shear wave velocity measured in situ ranged from 16 m/sin flocculent clays to 90 m/s in hard-packed sands. Values of laboratory measured shear wavevelocity were 6-22 m/s lower from the same sites. Low variability of measured shear wave velocitiesallowed laboratory measurements to be corrected to in situ conditions using the following empiricalrelationship: Vs, (in situ) = 10.46+1.17 Vs, (lab) The most likely causes for the lower laboratory shearwave velocities were sediment disturbance during collection, transportation, storage andmeasurement both by mechanical manipulations and by changes in confining pressure. Sedimentporosity, void ratio or wet density can be used to predict in situ shear wave velocity. Further studiesare required to refine and extend these empirical relationships, and to accurately define the highgradients in shear wave velocity predicted for the upper few meters or sediment.
Richardson, Michael D.;