The pressure to achieve a higher speed of train operation has increased in the last few years due to the development of high-speed railway lines. In the presence of soft soils, this speed increase is not possible without undertaking soil improvement measures, since the critical speed is lower than the desired speed of train operation. One of the most widely used soil improvement techniques is that of stone columns. In relation to these is the concept of critical length which, up to now, has only been studied for static cases. This research focuses, for the first time, on the enhancement of the critical speed in high-speed railways with stone columns and with special reference to critical length. Moreover, others parameters such as: maximum rail displacement and Dynamic Amplification Factor (DAF) are also studied. Analysing three profiles of ground representative of soft soils, it can be observed how the effect of the stone columns on critical speed is relevant, showing that critical length is different with respect to the three parameters above, the most restrictive one being that which corresponds to the critical speed. The influence of other parameters on the critical length and on the effectiveness of stone columns, such as the area replacement ratio, the dynamic pressure bulb and the existing soil stiffness is analysed and discussed.

由于高速铁路线的发展，过去几年实现更高列车运行速度的压力越来越大。在存在软土的情况下，如果不采取土壤改良措施，这种速度增加是不可能的，因为临界速度低于列车运行的所需速度。最广泛使用的土壤改良技术之一是石柱。与这些相关的是临界长度的概念，到目前为止，它只针对静态情况进行了研究。本研究首次重点研究了石柱高速铁路临界速度的提高，并特别参考了临界长度。此外，还研究了其他参数，例如：最大轨道位移和动态放大系数 (DAF)。分析三个代表软土的地面剖面，可以观察到石柱对临界速度的影响是如何相关的，表明临界长度相对于上述三个参数是不同的，最严格的是对应于临界速度。分析讨论了其他参数对临界长度和石柱有效性的影响，如面积置换率、动压球和现有土刚度。