Dynamic amplification of rail tracks in high-speed lines: Exploring train effects and impact of ground treatment

When the train circulation speed is much lower than the critical speed of the track-ground system, problems with dynamic amplification effects are purely theoretical. However, the situation can change if a new high-speed line, with a higher operation speed, is planned for a site with soft soils. In such cases, it may be necessary to assess the importance and consequences of the critical speed phenomenon on safety and operational costs of the railway track. A practical measure involving the ground treatment may contribute to an improvement of the system behaviour. This measure is based on replacing a portion of the natural soil with stiffer materials or by employing grouting. The current paper provides numerical evidence as the soil reinforcement significantly improves the dynamic behaviour of the ground-track system. It is also possible to conclude that localized ground reinforcement below the track yields a response similar to extending the reinforcement over a larger area. This conclusion is particularly interesting for engineering practice and for numerical/semi-analytical analysis. The study of the effect of the train geometry on the critical speeds of the train-track system is also carried out. However, the main conclusion is that the definition of the critical speed as the value that induces larger amplification due to the passage of a single load is a conservative approach. Finally, it was observed that an approach based on the calculation of the dispersion curves enhances an adequate estimation of the system's critical speed.