Stochastic heterogeneous approach for wave propagation in ballasted railway track
Lucio de Abreu Correa1; Regis Cottereau1; Baldrik Faure2; Sofia Costa d'Aguiar2; Charles Voivret2; Estelle Bongini2
1 CentraleSupelec; 2 SNCF - Innovation & Research
doi:10.20906/CPS/CILAMCE2015-0401
Resumo
Stronger competition with other means of transportation has increased the demand for performance in the railway industry. In this study, we focus on a numerical model that represents the dynamical response of a ballasted railway track. Two classes of numerical models can be used: (1) a discrete model; and (2) a continuum model. The discrete approach (using molecular dynamics or non-smooth contact dynamics algorithms) was effectively used for ballast modeling, but two issues remain: the coupling with the underlying layers of soil, and an efficient scheme for parallelization over large clusters of computers. The later issue unfortunately means that the largest systems that can be solved today represent only a few meters-long of ballasted railway track. On the other hand, the methods based on continuum mechanics model (like the Finite Element Method) can solve very large models due the efficient parallelization scheme. However, a homogeneous continuum cannot represent the non-affine field of stress and strain present in the actual mechanical system. The objective of this continuous model is to represent the heterogeneity of the stress field in a continuum model as well as in a discrete granular model. To do this, the mechanical properties are represented using random fields. The present study can be divided into two parts: (1) the statistical identification of the parameters of the continuum material, and (2) the wave propagation in a ballasted railway track. A finite element model was first constructed to identify the first-order marginal density, mean and variance of the continuum stochastic properties. The correlation model and correlation length are chosen based on theoretical grounds. The parameters found in the identification step are then used to generate the stochastic field of mechanical properties for a dynamical analysis (solved with the Spectral Element method). As a result, the dispersion curves for this structure are obtained. Results are obtained for different combination of soil-ballast properties
Palavras-chave: ballasted railway track; Stochastic heterogeneous media