Compaction of Sands by Repeated Shear Straining

Fundamental considerations and published data show that shear strain is the primary factor causing compaction of granular materials. New and published data from laboratory simple shear tests demonstrate the compaction behavior of uniformly graded sands in response to repeated cycles of shear strain. The data from this investigation confirm previous conclusions that the rate of compaction increases with shear strain amplitude but is not significantly affected by the normal stress applied. In addition, it is shown that compression followed by dilation occurs during each moderate- to large-size shear strain excursion; however, the net result of each excursion is a finite density increase until a limiting maximum density is reached. Laboratory simple shear and in situ shear strain data provide a basis for predicting density changes during compaction. Predicted density changes are consistent with published data from field studies of static, vibratory and seismic compaction.