| Silt widely distributed in Chinese northern region. It's one of the major filler resources of the sub grade. Finding out the dynamic characteristics of the silt has important significance for construction quality of sub grade. This paper bases on the dynamic properties of compacted silt. Consider compaction, water content, frequency and confining pressure, and other factors. With a mass of related information and existing achievements, through the saturated and non-saturated silt dynamic triaxial test, This paper carries out a study on compaction, dynamic modulus, dynamic strength and the pore pressure developing mode of silt, the conclusions are as followings:(1) Take the air volume ratio of silt as the support of the compaction control standards, and the reasonableness is analyzed.(2) Dynamic modulus of silt samples decrease with the strain grows. In the same level of dynamic strain, it increases with confining pressure and dry density increase. It reduces with the initial water content increases. The paper has finds out the Ed～εcurve under the large strain. Damping ratio changes with shear strain under different confining pressure .The paper puts forward the curves.(3) The dynamic strength of the saturated silt is greater when consolidation is bigger. The silt dynamic strength decreases with the destruction of vibration increased. At the same time-under consolidation the dynamic strength of the silt increase as consolidation grows. The dynamic strength of the silt increases with confining pressure increasing. (4)Driven out the curve of Uf /3 and Kc which is nearly the linear relationship. Put forward the pore pressure index model of growth U/Uf =α-bcN/Nf and fits better with the test data.
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