Shear Modulus and Cyclic Undrained Behavior of Sands

Abstract

The results of laboratory experiments performed to investigate the effects that factors such as fabric, anisotropic consolidation and stress-strain history have on the shear modulus at very small strains (G0), on the drained modulus degradation curve, and on the cyclic undrained shear strength of sands are summarized. The results presented show that G0 is relatively insensitive to sand fabric, initial stress ratio, monotonic prestressing, and cyclic strain history. Thus, specimens with the same G0 can exhibit very different behaviors in cyclic undrained shear, depending upon their initial fabric, initial stress ratio, or stress-strain history. To a lesser degree, this is also true for the shear modulus (G) at larger strains, as interpreted in the conventional manner from drained cyclic shear tests (unload/reload modulus). Based on these findings, the limitations involved in the use of G0 and G to interpret behavior in cyclic undrained shear are discussed.