The generation and propagation of vibrations in railway field is a complex problem that involves many factors. Ground-borne vibrations can annoy the people and damage the surrounding buildings, its reducing in urban areas is a very challenging task in railway transportation. Many mitigation measures can be considered and applied; among these the open trenches have showed a great effectiveness. This paper deals with the study of the effect, in terms of reduction of vertical and horizontal displacements and velocities, of the open trenches regarding railway ground borne vibrations. 2-D FEM simulations have been performed and several open trench configurations have been analysed varying the main geometric features such as: width (w), depth (d), distance of the rail (l), thickness of the bank (h), type of the terrain (vs, ζ), depth of the trench over thickness of the bank (d/h). A great number of simulations have been carried out and vertical and horizontal displacements and velocities have been calculated. To the aim of evaluating the influence of the quoted parameters in reducing ground-borne vibrations a sensitivity analysis using artificial neural networks (ANNs) has been carried out. Many feed-forwards ANNs, having different architectures, have been trained and tested with samples patterns created by FEM simulation data. It has been noted that the choice of the correct geometric configuration, in function of the type of the terrain strata, is crucial to obtain a reduction of ground borne vibration, otherwise can be obtained also an amplification. The sensitivity analysis showed that among the geometric parameters, the weight of the depth of the trench is very significant; however the influence of the depth must be also evaluated in relation to the thickness of the bank.
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