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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.

In order to better explain the influence of induced anisotropy on the strength and deformation characteristics of loess, a complex stress path experiment of induced anisotropy of the remolded loess was carried out by using a hollow cylinder apparatus. Under the same condition of the intermediate principal stress coefficient b, the test carried out directional shear tests in the case of drainage. The effects and regularities of induced anisotropy on the strength and deformation properties of remolded loess were revealed. The results show that the remolded loess has obvious induced anisotropy, which cannot neglect the stress-strain relationship, strength and deformation of soil. The maximum difference in fail strength is 25% under different principal stress direction. Induced anisotropy has great influence on the stress-strain relationship of soil, which is the essence of soil properties. In some engineering practices, the result of stress-strain analysis of soil has great influence. Approximately isotropic remolded loess substantially eliminates inherent anisotropy. Therefore, this experiment will provide a good reference for the further study of soil anisotropy under complicated stress paths such as principal stress axis rotation.

In order to research the effect of different moisture content of intact loess in Qinghai on its strength and deformation characteristics, undrained triaxial compression are performed using the British GDS Standard Stress Path Test System. The results show that under the same moisture content, the failure strength of samples increases with the increase of cell pressure. Under the same cell pressure, the failure strength decreases with the increase of moisture content. The cohesive decreases with the increase of moisture content, but the change of internal friction angle is very small. By fitting the cohesion and internal friction angle with the change of moisture content curve, the formula of Coulomb shear strength cooperating moisture content is obtained. The formula has certain reference value for the design of foundations and ground treatment to practical projects in the Qinghai area.