Abstract: This study investigated the impact of the direction of cyclic loading on the cyclic behavior of saturated silt under isotropic consolidation condition. GDS hollow cylinder torsional apparatus was employed to perform a series of undrained cyclic shear tests with various principal stress direction angle ?d0 coupling with four dynamic loads, i.e., inner pressure, outer pressure, axial load and torque. The results show that the double normalized pore pressure is independent on the direction angle of cyclic loading, but sensitive to the cyclic stress ratio CSR. The generalized shear strain is independent on the direction angle of cyclic loading during cyclic loading. The direction angle of cyclic loading during cyclic shearing has a considerable influence on undrained cyclic resistance ratio of saturated silt. Cyclic resistance ratio CRR initially decreases then increases as the direction angle of cyclic loading increase, with a minimum value for ?d0=45°. Meanwhile, equations for pore water pressure and deformation to quantify the influence of ?d0 and CSR are established and the corresponding expression for CRR is given.

Key words: silt liquefaction, the direction angle of cyclic loading, cyclic stress ratio, pore water pressure, generalized shear strain, cyclic resistance ratio