Projekt BVFF - publicerade   BVFF nummer:  2012-080 Projekttitel  Development of mechnics based design procedure for the railway track ballast Projektledare/Kontaktperson  Denis Jelagin Telefon  08-7908698 Utförarorganisation  KTH Medutförare  - Bakgrund  Granular ballast is a major component of the railway track substructure controlling to a great extent the track geometry deterioration. In addition to retaining the railway track position ballast also provides resilience and energy adsorption for the track, ensures adequate drainage and is a major component of bearing capacity. Correct predictions of ballast requirements are crucial, as under dimensioning implies a risk for structural failure and large maintenance costs and over dimensioning implies unnecessary large costs and environmental impact. In order to ensure adequate performance of the ballast, conventional methods for design of granular ballast materials put requirements on ballast gradation, ballast particles shape as well as on its resistance to crushing and wear. These requirements rely however heavily on empirical evidence, and presently there is no mechanistic model relating ballast material parameters to the ballast performance, i.e. ballast resilient modulus, permanent deformation and ballast resistance to fouling. As a result the state-of-practice design methods cannot describe the progress of ballast degradation in the field and are not able to capture the effect of using unconventional materials, such as marginal or recycled materials in the railway ballast. Development of granular mechanics based models for ballast performance will allow for more accurate prediction of ballast performance in the field under realistic load and environmental characteristics and will provide a fundamental tool for designing ballast materials for better performance. Sammanfattning  Granular ballast is a major component of the railway track substructure controlling to a great extent the track geometry deterioration. Correct predictions of ballast requirements are crucial, as under dimensioning implies a risk for structural failure and large maintenance costs and over dimensioning implies unnecessary large costs and environmental impact. Another important aspect of the problem is the need to optimize the material use in the railway ballast layers as natural material resources become scarce and more energy consuming due to increasing transport distances and higher exploitation efforts. Novel methods for increasing the granular material use efficiency in the railway ballast are needed, in which material management in rail infrastructure is considered and which integrates technical innovations with the life cycle costs and environmental impact. In order to achieve this, there is a need to increase the knowledge on granular material characteristics and degradation mechanisms, and to develop efficient and rapid methods for prediction of their long term influence on railway track structures. The primary goal with the project is to develop a granular mechanics-based design framework for railway ballast. The framework developed will include models to predict the impact of gradation, aggregate shape and strength on the performance of the ballast layer in the railway track subjected to traffic and environmental loads. These models will facilitate understanding of the fundamental mechanisms behind the strength, deformation and degradation characteristics of unbound layers in the railway track structure. The developed design tool will provide input parameters to the LCC/LCA design framework developed at KTH. As a result, a better theoretical basis will be formed for implementation of novel materials in railway ballast construction. Förväntat resultat  In addition to the theoretical and experimental insight to the mechanics of the granular ballast layers in the railway tracks, the project’s main outcome will be a tool for mechanics based design of the railway track ballast materials, including: - Predictive models for the resilient modulus and permanent deformation accumulation. - Model describing the progress of aggregate breakage and wear as a function of aggregates strength, shape and gradation. - Design tool finding the optimal gradation and ballast layer thickness for a given aggregate type. As already state above comprehensive models relating ballast gradation, aggregate shape and mechanical properties with the performance of the ballast are not available presently. It is anticipated thus that projects results will help to close this gap and will be used by both practitioners and researchers in the field of railway engineering to optimize the railway ballast materials and ballast layers design for better performance. Plan för resultatspridning och implementering  In order to ensure that the results of the project are communicated to the research community and to the users, the following steps will be taken: - Research progress will be bi-weekly presented at the Highway and Railway Engineering Division seminars, attended both by researchers and industry representatives; - A user reference group will be formed at the start of the project. The reference group will consist of representatives of the following authorities/companies: Trafikverket (Klas Hermelin, Tomas Winnerholt), NCC (Jonas Ekblad), VTI (Sigurdur Erlingsson), Svevia (Fredrick Lekarp). Three times a year, a detailed presentation will be given to this this reference group. - Results of the project will be published in several scientific papers and summarized in a PhD-thesis. - Results will be as well presented in national and international conferences. - Developed performance models and design framework will be transferred into standalone software, which will be distributed to the practitioners. To encourage the use of the results in engineering practice a workshop on the software and models developed will be organized at KTH. Tidsramar  -