Experimental Study On Dynamic Characteristics Of Saturated Fine Silt With Different Fine Content Under Long-term Cyclic Loading

In this paper,the saturated silt in the Xiasha section along the Hangzhou Metro is taken as the research object.The effects of the content of clay,drainage conditions and loading levels on the dynamic characteristics of saturated silt under long-term cyclic loading were investigated.The content of this study was as follows:(1)Under the condition of long cyclic loading,the influence of clay content and dynamic stress amplitude on cumulative dynamic strain of silt samples was investigated by indoor dynamic triaxial test.And the influence of the clay content and the amplitude of dynamic stress on the cumulative dynamic pore pressure and critical dynamic stress under the undrained condition was also investigated.(2)Two variables of dynamic stress amplitude and clay content were also controlled,and the influence of drainage conditions on dynamic characteristics of silt soil was investigated.Through indoor dynamic triaxial test,we get the following research results:(1)The study found that,the cumulative dynamic strain curve and dynamic pore pressure curve has accumulated similar rules under undrained condition.It could be classified as two basic types:stable profile,and destructive profile.The curve increases with the increase of the vibration,and the larger the dynamic stress amplitude,the larger the cumulative dynamic strain and the cumulative dynamic pore pressure.At the same time,the changes of silt clay content affect the critical dynamic stress,when the clay content is between 7%?14%,with the increase of clay content,saturation powder increases critical dynamic stress of soil specimen.At the same time,the changes of silt clay content affect the critical dynamic stress,when the clay content is between 7%?14%,with the increase of clay content,saturation powder increases critical dynamic stress of soil specimen decreases and then increases.It is also found that the drainage process has an enhanced effect on normally consolidated silt,and the cumulative dynamic strain under drainage under the same dynamic stress amplitude is smaller than under undrained condition.(2)The cumulative dynamic strain and the cumulative dynamic pore pressure development curve of the silt specimen under the long-term cyclic loading are fitted and analyzed.In view of the large difference in the curve development of R ? R' and R<R,the cumulative dynamic strain and the cumulative dynamic pore pressure development curve are need to be processed in segment.According to the critical dynamic stress R,curves under R ? R condition used the improved zhang Jianmin B model to fit while curve under R<R condition used improved semilog model to fit.Through the consolidation of the model parameters,the relation formula between the clay content and the critical dynamic stress is obtained,and the relation formula between the clay particle content,the dynamic stress ratio and the model parameters is obtained.