Validation of a three-dimensional finite element model for critical velocity

This paper studies the response of soft soils to high-speed trains, using finite element methods. Critical velocity effects occur once the train speed approaches a certain limit and large deflections are observed in the track. Several phenomena are associated with critical velocities, including the generation of ground surface waves and vibrations in the underlying soil layers beneath the track. These effects increase track damage, thus causing safety considerations and increasing maintenance costs. The main concern is soft soils, due to their low stiffness, which results in larger ground amplification response. Being able to predict the critical velocity effects is useful for designers, because it allows them to define strategies to mitigate the damage caused by the amplified response, and, therefore, increase the safety and comfort of passengers. A three-dimensional model of the Alfa-Pendular train track in Portugal is developed and validated. Another model, based upon a site in Ledsgard, Sweden, is also used for validation. The Ledsgard site is characterised by weak soft soils. The simulations are run in the time domain and the results of the ground response are presented in terms of vertical deflections and velocities. Theoutcomes of the simulations are compared against actual field results.