Influence of sand content on the flow characteristics of soft soil under cyclic and high-frequency vibration

The flow characteristics of foundation soils subjected to train loads can present engineering hazards in high-speed railways. In order to verify the feasibility of blending coarse sand in modifying soft subsoil, undrained pulling sphere tests were carried out and the train loads were simulated through localized and cyclic vibration at various frequencies. Laboratory testing results indicate that the flow characteristics of soft soil can be significantly enhanced by high-frequency vibration; meanwhile the continuous increase in flow characteristics caused by cyclic vibration may be an important reason for the long-term settlement of soft subsoil. The influence of sand content on flow characteristics is also studied in detail, and it is shown that the addition of coarse sand can weaken the flow characteristics of soft soil induced by sudden vibration at lower than 50 Hz. Under the condition of cyclic vibration, the growth of the flow characteristics of sand-clay mixtures is mainly caused by the first-time vibration in the cycle, and the increase in sand content can make the flow characteristics present a faster convergent tendency.