Simplified approach for ground reinforcement design to enhance critical speed

Abstract

In recent years, there have been significant advances in the railway sector, with a substantial increase in train speed, resulting in new challenges for the technical community in terms of infrastructure performance. When the supporting soil of the railway track is soft, the train speed can approach the speed of wave propagation in the track-ground system, giving rise to the so-called critical speed effect. This effect is characterized by the great amplification of the track response with dramatic consequences in terms of safety, ground-borne vibrations and maintenance costs. This well-known issue can be mitigated in several ways, one of them based on the reinforcement of the soil with columns. Bearing that in mind, the present paper aims to study the enhancement in the critical speed of the railway system achieved by a soil reinforcement with jet grouting columns, for a homogeneous and layered ground. Despite the inefficiency verified for the homogeneous scenario, the reinforcement of layered grounds produces a considerable improvement in the critical speed of the system. It has been proved that deepening the reinforced columns in the stiffer layer does not lead to a continuous improvement in the critical speed of the system. Furthermore, a simplified methodology capable of accurately predicting the critical speed for reinforced grounds is proposed. A validation study showed the high accuracy of the simplified methodology in predicting critical speed, proving to be an interesting tool for engineering purposes.