Upprustningsmetoder för en bankropp : En jämförelse ur ett LCC-perspektiv

Sammanfattning: In recent years, the Swedish railway track system has been neglected in terms of capacity and maintenance. To adapt the existing system to current traffic load there is a great need for extensive improvement and maintenance. Shortcomings are especially occurring on older embankments running over soft subgrades. To select the most suitable method for reinforcement of the embankment, it is important to evaluate different solutions from a life cycle cost perspective. In long-term perspective, it is often shown that a method with low investment cost causes a higher maintenance cost and a shorter technical lifetime. Today, most of the decisions regarding reinforcement and maintenance are based on existing experience and budgetary constraints. This can often limit the ability to think long term and make sustainable cost efficiencies. Currently the most common reinforcement method is ballast cleaning with frost insulation. A method that should be seen as relatively short-term and in most cases does not increase the capacity to a desired level. An alternative to this method is to reinforce the embankment with geogrid and shift the ballast in the top ballast layers. The method is practical more comprehensive but from a theoretical perspective it is more beneficial. The purpose of this study is therefore to investigate whether reinforcement of track bed using geogrids and shift ballast in the overlaying ballast layer is more beneficial from a life-cycle cost perspective, than ballast cleaning and new frost insulation. This study is based on a simplified life cycle cost analysis that includes investment costs, maintenance costs and energy costs. System boundaries and model specifications will be based on a literature review, reference projects and interviews with suppliers of used products and technical solutions. The established model should be seen as a simplification of reality but seeks to illustrate a realistic case where an older railway embankment over soft subgrade is in need of reinforcement. The life-cycle cost analysis showed that reinforce the track bed with geogrid and shifting ballast in the overlaying ballast layer was the most favorable option from both a cost and environmental standpoint. This is mainly due to the long lifetime and extended maintenance intervals. In the model, there is some uncertainty and it seems to be that an area that is in need of more research. If resources are spent on expanding the use of life-cycle cost analysis in the transport sector there can be economically, socially and ecologically sustainable development.