Experimental Study of Dynamic Shear Module and Damping Ratio of Intact Loess from Xining, China

Abstract

There is no common understanding on the influences of loess anisotropy on dynamic modulus and damping ratio. A series of laboratory tests were carried out on Xining intact loess using the GDS bidirectional dynamic triaxial test system. This study aimed to investigate the dynamic shear modulus and damping ratio of the Xining intact loess at different angles associated with the index plane. In addition, the difference between loess in Xining and other regions was also discussed. The following conclusions could be drawn based on the test results. Firstly, the anisotropy of the loess had a significant influence on the development of dynamic shear deformation and the dynamic shear modulus, indicating that it is necessary to keep the deposition direction of intact soil unchanged during sampling. Secondly, the increase of consolidation pressure reduced the effect of the anisotropy of loess. Higher confining pressure and a closer sampling angle to the natural deposition direction of soil resulted in higher dynamic shear modulus and slower rate of the development of soil dynamic shear deformation. In other words, the ability of soil to resist dynamic shear deformation became stronger. Finally, the damping ratio of Xining loess increased with the increase of dynamic shear strain. The increase rate of damping ratio of Xining loess was much quickly than that in other western regions, which could provide reference for the research on seismic zoning.