Effective soil density for small-strain shear waves in saturated granular materials

This paper presents an experimental investigation of the concept of effective density for the propagation of small-strain shear waves through saturated granular materials. Bender element tests and resonant column tests were conducted on various granular materials in dry and saturated conditions. Values of small-strain shear modulus for the dry condition are compared with corresponding values for the saturated condition, which are calculated using saturated density and effective density. For bender element tests, the use of saturated density produced errors as high as 28% in the shear modulus, whereas the use of effective density resulted in errors generally less than 5%. For resonant column tests, errors in the shear modulus that were obtained using saturated density were smaller than those for bender element tests because of the lower range of excitation frequency and effect of mass polar moment of inertia of the loading system. A quick chart is provided to help users determine if effective density should be considered for a given application. Effective density is expected to be important for fine and medium sands at high-frequency excitations, such as bender element tests, coarse clean sands at lower frequencies, such as for resonant column tests, and clean gravels at essentially all frequencies of geotechnical interest