Keywords: high speed rail, reduced models, wave propagation, soil-sleeper interaction, vibration analysis, B-spline impulse response function.

High speed rail (HSR) transportation has become a popular form of mass transit throughout the world. Plans are being made in the United States for several high speed rail systems to be constructed in different areas of the country over the coming decades. As the HSR speeds continue to increase, potential problems arise when the HSR travels over soft soils with inherently lower shear wave velocities. In such cases, the wave field generated by the HSR propagates at speeds lower than the speed of the trains that generated them, creating a phenomenon equivalent to the sonic boom and supersonic travel, as described for example in [1]. Such phenomena induce vibrations that are potentially damaging to both the trains and the infrastructure facilities and cause annoyance to passengers and residents impacting negatively on the public perception of the benefits of HSR. The development of numerical methods to accurately and efficiently estimate HST induced vibrations, is required. In such a scheme, the models of the physical system consider the dynamic interaction among the wave propagation in the soils, the deformable rail and track structure, and the train vehicle. In the present paper, the soil-track interaction problem is investigated, focusing on the development and validation of a model reduction technique to increase the efficiency of the computational approach reported in [1]. The real rail-sleeper system consisting of a large number of sleepers loaded in an asynchronous pattern due to the moving train load is simplified to a two-sleeper system with the one being the source and the other the receiver. The boundary element method (BEM) is used for the modelling of the soil region and considers the kinematic interaction with the sleepers, in order to account for the travelling wave and the soil interaction effects. Model reduction pertains to the development of B-spline impulse response function (BIRF) by taking advantage of the scalability of these functions. These BIRF functions are established by appropriate scaling operations of time and amplitude of a reference BIRF function while retaining all input information of the full model. The derivation of the closed form solutions for the reduced models is discussed. The models are validated through comparisons with other BEM solutions, and the accuracy and efficiency are established.

1

J. O'Brien, D.C. Rizos, "A 3D BEM-FEM methodology for simulation of high speed train induced vibrations", Soil Dynamics and Earthquake Engineering, 25, 289-301, 2005.

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