REVIEW OF THE INTERNATIONAL USE OF ASPHALT FOR RAIL TRACK SUPPORT SYSTEMS

Engineers have over 100 years of experience with the use of asphalt under rail and some 30 years with its use on major rail corridors in both Europe and North America. In Australia its use has been much more limited, due primarily to the logistics of supplying asphalt over extended lines of construction and the ready access to lower cost ballast material, coupled with "low" performance requirements in the past which could be satisfied by traditional ballast track construction methods. In view of the recent revival of interest in the Very Fast Train (VFT) project for the Sydney-Canberra-Melbourne corridor and the rail connection to Darwin, it is appropriate to re-examine whether the traditional performance requirements and practices still provide the optimal solution for rail trackbeds. These new rail developments will require tracks that provide long term smooth and quiet wheel motion with minimal maintenance, when subjected to higher speed traffic and heavier axle loads. The track structures must also be sufficiently rigid to maintain their geometry and not deflect excessively. They should also be sufficiently flexible not to fatigue under continuous repetitive loading. Asphalt in heavy-duty road pavements has been shown to meet these performance criteria, and can provide a significant reduction in the cost of future maintenance and operation and represents such an economic alternative. The paper discusses the design, specification and construction aspects governing the economic use of asphalt in rail trackbeds. (a) For the covering entry of this conference, please see IRRD abstract no. 492019.