Abstract: The dynamic response characteristics and long-term cumulative deformation development law of silty sand stratum under the metro train load are important engineering topics. In order to study them, the following works are carried out. At first, we analyze the long-term settlement monitoring data of Nanjing Metro Line 2 in typical silty sand stratum. Then, based on two- and -a-half-dimensional(2.5D)numerical method, we analyze the vibration characteristics of silty sand stratum under the train vibration load. Finally, we sum up the cumulative deformation formula of silty sand under vibration load, and use the stratified summation method to study the long-term cumulative deformation development law of silty sand. We have the following results. (1)With the increase of the depth, the dynamic deviator stress of the silty sand layer under the tunnel increases at first and then decreases. Its maximum value usually appears at 1 m below the bottom of the tunnel and is about 3.5 kPa. (2)The long-term deformation of the silty sand stratum induced by the train vibration load develops rapidly at the initial stage of the metro operation. However, it can reach a stable stage in about one year, then the deformation increases slowly. The total deformation value after stabilization is about 15.1 mm. (3)After 7 years of metro operation, the settlement value of the tunnel silty sand foundation induced by the long-term metro vibration loads takes up about 26% of its total settlement value.