Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Ballastless railway track transition zones: An embankment to tunnel analysis
Highlights Modelling of a ballastless track over an embankment-tunnel transition zone. Development of a hybrid methodology to simulate the degradation process of a ballastless track. Only 30% of the subgrade is contributing to the permanent deformation. Ballastless track shows satisfactory long-term performance after 1 million loading cycles. Inclusion of a resilient mat under the concrete slab reduces the higher stresses at the transition zone.
Abstract Railway track transition zones are characterised by an abrupt change in track support stiffness, which increases dynamic wheel loads and leads to the acceleration of differential settlement and track degradation. The performance of transition zones is a concern for railway Infrastructure Managers due to the increased maintenance operations and costs typically associated with these short track sections. To date, the majority of transition zone studies are focused on the analysis of ballasted tracks, however, the popularity of ballastless track has been increasing, especially on high-speed lines. Therefore, this work aims to study concrete slab track transition zones, with a focus on embankment/plain line-to-tunnel sections. The analysis uses a hybrid methodology, combining 3D finite element modelling with empirical settlement equations, in an iterative manner. The finite element model is capable of simulating train-track interaction and uses contact elements to simulate the potential detachment (voiding) between the slab’s hydraulically bound layer and frost protection layer. At each iteration, firstly the track-ground stress fields are calculated using a 3D model, before passing them to a calibrated empirical equation capable of computing settlement across the transition. Then, before starting the next iteration, these settlements are used to modify the 3D model geometry, thus account for the effects of the previous settlement, before computing the updated stress fields. The model is used to analyse settlement and stresses for a transition zone case-study, before study the ability of a resilient mat to improve the performance of the track.
Ballastless railway track transition zones: An embankment to tunnel analysis
Highlights Modelling of a ballastless track over an embankment-tunnel transition zone. Development of a hybrid methodology to simulate the degradation process of a ballastless track. Only 30% of the subgrade is contributing to the permanent deformation. Ballastless track shows satisfactory long-term performance after 1 million loading cycles. Inclusion of a resilient mat under the concrete slab reduces the higher stresses at the transition zone.
Abstract Railway track transition zones are characterised by an abrupt change in track support stiffness, which increases dynamic wheel loads and leads to the acceleration of differential settlement and track degradation. The performance of transition zones is a concern for railway Infrastructure Managers due to the increased maintenance operations and costs typically associated with these short track sections. To date, the majority of transition zone studies are focused on the analysis of ballasted tracks, however, the popularity of ballastless track has been increasing, especially on high-speed lines. Therefore, this work aims to study concrete slab track transition zones, with a focus on embankment/plain line-to-tunnel sections. The analysis uses a hybrid methodology, combining 3D finite element modelling with empirical settlement equations, in an iterative manner. The finite element model is capable of simulating train-track interaction and uses contact elements to simulate the potential detachment (voiding) between the slab’s hydraulically bound layer and frost protection layer. At each iteration, firstly the track-ground stress fields are calculated using a 3D model, before passing them to a calibrated empirical equation capable of computing settlement across the transition. Then, before starting the next iteration, these settlements are used to modify the 3D model geometry, thus account for the effects of the previous settlement, before computing the updated stress fields. The model is used to analyse settlement and stresses for a transition zone case-study, before study the ability of a resilient mat to improve the performance of the track.
Ballastless railway track transition zones: An embankment to tunnel analysis
Ramos, A. (Autor:in) / Gomes Correia, A. (Autor:in) / Calçada, R. (Autor:in) / Connolly, D.P. (Autor:in)
17.01.2022
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
Ballastless track , Railway transition zone , Embankment-tunnel transition zone , Railway track settlement , Train-track railway dynamics , FEM , Finite Element Method , LVDT , Linear Variable Differential Transformer , HBL , Hydraulically Bonded Layer , FPL , Frost Protection Layer , EPDM , Ethylene Propylene Diene Monomer , FKN , Normal penalty stiffness factor , <italic>k</italic> , stiffness , <italic>c</italic> , viscous damper , <italic>E</italic> , <italic>Young</italic> modulus , <italic>γ</italic> , dry density , <italic>ρ</italic> , mass density , <italic>ν</italic> , <italic>Poisson</italic>’s ratio , <italic>α<inf>i</inf></italic> , parameter of the damping Rayleigh matrix that corresponds to the material <italic>i</italic> that multiplies the mass’ matrix of the system , <italic>β<inf>i</inf></italic> , parameter of the damping Rayleigh matrix that corresponds to the material <italic>i</italic> that multiplies the global stiffness’s matrix (<italic>K<inf>i</inf></italic>)) , <italic>ξ</italic> , hysteric damping , <italic>f</italic> , frequency , <italic>M<inf>b</inf></italic> , mass of the bogies , <italic>M<inf>e</inf></italic> , mass of the wheelset , <italic>K<inf>p</inf></italic> , stiffness of the primary suspension , <italic>c<inf>p</inf></italic> , damping of the primary suspension , <italic>K<inf>h</inf></italic> , contact stiffness , cohesion , <italic>ϕ</italic> , friction angle , <italic>μ</italic> , friction coefficient , <italic>p</italic> , mean stress , <italic>q</italic> , deviatoric stress , <italic>p<inf>am</inf></italic> , mean stress induced by the passage of the vehicle , <italic>q<inf>am</inf></italic> , deviator stress induced by the passage of the vehicle , <italic>m</italic> , slope of the line of the critical state in the referential <italic>p</italic>-<italic>q</italic> , <italic>s</italic> , ordinate of the line of the critical state in the referential <italic>p-q</italic> when <italic>p</italic> is null , <italic>N</italic> , number of load cycles , <italic>ΔN</italic> , set of cycles , <italic>p<inf>ini</inf></italic> , initial isotropic stress , <italic>q<inf>ini</inf></italic> , initial soil deviator stress , <italic>B,</italic> a <italic>and</italic> ε1po , material constants of the empirical model , <italic>δ</italic> , cumulative permanent displacement
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