Silt Response To Different Cyclic Stress Path

Dynamic hollow cylinder apparatus (HCA) can be used to simulate earthquake load or wave load. The dynamics of sands under different cyclic loading stress path is intensively studied, but that of silts was not paid enough attention to.In this paper, the development of HCA and study on this kind of machine are reviewed and the configuration of ZJU's HCA was introduced. And then, a new compacting tool for HCA was developed to do reconstituted samples. After that, the same experiments with Fujian sand were carried out on HCA and HX-100(A kind of dynamic triaxial apparatus) respectively to validate the stability of HCA.On the HCA, four series of silt samples with the same density were consolidated isotropic under the same effective confining pressure (100kPa) and were subject to four kinds of undrained cyclic loading stress (Circular cyclic load, elliptical cyclic load, cyclic triaxial and cyclic pure shear).The accumulation of pore pressure is independent of cyclic stress path. In this paper, the critical point is defined. Normalized with the number of cycles and excess pore pressure at the critical point, the pore pressure accumulation curves of all four series were well fitted with Finn's equation。Under different cyclic stress path, the generalized strain increased significantly after reaching the inflection point (0.1%～0.3%) on each strain curve. There is a little lag in the appearance of critical point than the strain inflection.Compared with results on saturated sand, the cyclic resistance of silt under different stress path also varied. The cyclic resistance of silt under circular cyclic load is lower than that under cyclic pure shear by around 40%, which is a little bit higher than Ishihara's result but quite close to Guo's. The loading efficiency was defined, and the cyclic resistance difference was well explained.