Experimental Study on the Ballast Pick-Up Problem in High Speed Trains

A new theoretical approach on the determination of the conditions for the initiation of the motion of the ballast stones due to the wind gust created under the high-speed trains has been recently developed (Sanz-Andres & Navarro-Medina, 2009). This determination is critical to predict the starting of ballast pick-up, because once the motion is initiated a saltation-like chain reaction could take place. Sometimes the flying stones reach an height which is larger than the lowest parts of the train, striking them (and the track surroundings) producing considerable damage that are to be avoided e.g. by limiting the maximum allowed operational train speed. The aim of this contribution is to present the experimental results that have been obtained to check the validity of the proposed model. The experimental facility is a wind tunnel, with a gust generator, with a maximum wind speed of some 20 m/s (65.6 ft/s) and 10 Hz gust frequency. The test section is 0.39 m × 0.54 m (15.4 in × 21.3 in), which is suitable to perform experiments with stone models. It is shown that in the range of parameters explored, the experimental results are in good agreement with the theoretical model predictions. In this contribution the theoretical model is summarized, the experimental facility is described, showing some of its typical performances, the experimental procedure is outlined, and the experimental results are compared with the theoretical predictions.