José João Pires De Oliveira Filho
Due to the accumulation of traffic, the railway components are affected by the induced stresses. As a result, the geometry of the railways is degraded over time. The degradation occurs either through the partial loss of the track's geometry or through the development of a specific damage on the track component. The degradation of the vertical geometry is due to the permanent deformation of the granular materials that results from the progressive rearrangement of the granular particles from the ballast and subgrade layers. In order to reduce the impact of degradation, different methods of maintenance are used. Tamping is a common procedure to restore the track position of ballasted tracks. For the rails, a grinding process is used to eliminate partially rail roughness, while ballast renewal is employed when ballast material attains a certain level of deterioration. The different maintenance types are performed under different strategies. In the active approach, maintenances are executed according to pre-determined values of accumulated transported materials, while in the reactive strategy, a value of a structural or geometric parameter is used to determine the moment a maintenance must be executed. Therefore, the problem related to the degradation of railway tracks subjected to high loads, typically larger than 22.5tons/axle, is a particular case. These loads attain values of approximately 40 tons/axle, as in the case of railways for transportation of commodities. In a heavy haul scenario, the higher values of loads lead to extra amount of efforts on the track elements that may cause excessive damage in a component level, hence causing faster general track deterioration. The aim of this research is to provide answers related to the structural and geometric conditions under load increase and its consequence on maintenance, including a cost analysis. These results are useful for rail managers, so as to have a preview of certain potential structural and geometric consequences at the railway components. Moreover, the knowledge about the impact of maintenances on tracks' structure is useful for maintenance strategy selection. The maintenance costs, in a certain time period under different loads, assists to decide the strategy to follow in the case of load increasing planning. In this research, an accumulative track degradation model is developed and used to determine the struc-tural and geometric responses, and consequently the needs for maintenances over time. The model con-siders the evolution of the parameters in function of traffic accumulation and material degradation. Different types of maintenance are considered in this model, including their specific consequences to the track structure. For a certain scenario defined by initial operational, structural and geometric conditions, the structural and geometric parameters are calculated over time. Therefore, the number of maintenances is determined taking into account the different maintenance strategies. The costs are calculated from the executed maintenances. The results are presented considering a case study of a heavy haul railway, and in particular for transportation of iron ore material. In the simulation, representative data from a heavy haul scenario for operational and structural conditions are used, in order to determine the impact of load increase on track behavior under two different maintenance strategies. Furthermore, these strategies are evaluated based on their cost and the general impacts on the track structure. A cost analysis is also conducted in a scenario of load increase considering different maintenance strategies and different number of simultaneously working maintenance teams. This analysis with structural and geometric data aims to provide an indication about a maintenance strategy decision and/or procedures to optimize the track performance subjected to high loads.
EPFL2016
