Abstract：Through the dynamic triaxial tests of silt soils around the tunnel of Sang-Shang-Jie station，Nanjing subway，the dynamic strain analysis is made on the silt soils under subway train loading，and the influence of consolidation status of soils，consolidation ratio，axial cyclic stress，vibration frequency are taken into account. The variation rule are obtained of the critical dynamic stress ratio of the silt soils and dynamic strain with vibration times，vibration frequency，confining stress and axial stress. Some conclusions could be made from the research as following. (1) There is a critical dynamic stress ratio under train vibrating loading，which depends on soil property，loading characteristic，and consolidation pressure. Soil deformation increases with cyclic times when applied loading is less than the dynamic critical stress. But the increasing rate slows down until it trends to a constant value. On the contrary，the deformation increases quickly with cyclic times until soil is destroyed. (2) In the same vibration condition，the higher the frequency is applied，the less the deformation is induced. The critical dynamic stress ratio decreases gradually with growing of frequency and there is an asymptote. (3) With the same axial consolidation pressure and dynamic stress，the larger consolidation ratio is，the larger ultimate deformation is and the easier it is to make sample destroyed.
