11 th International Conference on Vibration Problems Z. Dimitrovová et al. (eds.) Lisbon, Portugal, 9-12 September 2013 THE DEVELOPMENT AND MITIGATION OF GROUND MACH CONES FOR HIGH SPEED RAILWAYS Peter K. Woodward*, Omar Laghrouche, Abdellah El-Kacimi Infrastructure & Environment Scotland, Heriot-Watt University, Edinburgh, EH14 4AS, UK {P.K.Woodward, O.Lagrouche, A.Elkacimi}@hw.ac.uk Keywords: Ground Mach Cones, Track Critical Velocity, Rayleigh Waves, High-speed Abstract. In this paper the application of the DART3D (Dynamic Analysis of Railway Track – 3D) finite element program is used to model the development of ground Mach Cones for high-speed trains approaching the ground Rayleigh wave velocity, particularly for both weak and weak-medium stiff subgrades. Multiple train axles and complete train-track interaction are included in the studies. The results show, in a systematic way, how the Mach Cone is formed as the train speed increases incrementally. The geometrical angle of the Mach Cone is compared to analytical solutions and good agreement found. The difference between the Ray- leigh wave velocity and the track resonant velocity is further highlighted through parametric studies and through 3-dimensional graphical representations of the advancing wave front. The effect of the Mach Cone development on the transient response of a sleeper is also shown, as is the development of non-linearity in the stress strain response and the subsequent effect on the track deflections.