关键词: 饱和粉土, 波浪荷载, 孔压比, 广义剪应变, 等效循环应力比

Abstract: To ensure the dynamic stability of seabed site is the prerequisite for the safe operation of offshore engineering. However, limited test data on the dynamic properties of saturated silt subjected to cyclic loading with complex stress path in marine environment are available. Using the GDS hollow cylinder apparatus, a series of undrained tests is performed on the remolded saturated silt under combined axial-torsional cyclic loading for simulating changes in the amplitude of the wave and the depth of seabed. To take the generalized shear strain ?g = 5% as the liquefaction triggering criteria, the influences of cyclic stress paths (cyclic stress ratio CSR and cyclic loading amplitude ratio ? ) on the undrained behavior of saturated silt under isotropic consolidation conditions are studied. The test results show that the effects of CSR and ? on the development patterns of excess pore pressure and deformation of saturated silt are significant. The saturated silt under the cyclic loading with circular stress path (? = 1) is the most susceptible to liquefaction. The liquefaction of saturated silt is not triggered when CSR≤ 0.050, but when CSR≥ 0.065 and ? = 1, the liquefaction of saturated silt can be triggered, and the saturated silt is more susceptible to liquefaction when CSR > 0.150. The correlation between ?g and excess pore pressure ratio (ru) is less influenced by CSR and ?, and the ?g can be characterized by the tangent function of ru. When the equivalent cyclic stress ratio ESR is uesd as the index of the amplitude of cyclic stress with complex stress paths, the liquefaction number of cycles (NL) required to cause ?g = 5% may be uniquely correlated to the applied ESR, and the ESR decreases with the increase of NL.

Key words: saturated silt, wave loading, excess pore pressure ratio, generalized shear strain, equivalent cyclic stress ratio