Asphalt trackbeds: selection, design, installation practices, long-term performances & material properties

The recent history of the freight railway industry in the USA is described. Controlling maintenance costs and reducing associated traffic interference are primary objectives if the railroad industry is to remain productive and competitive in the expanding transportation marketplace. It is realized that maintenance of railroads with conventional all-granular ballast systems may no longer be economically feasible, the use of hot mix asphalt (HMA) in railroad trackbeds becomes a practical and most effective answer. The following information on the use of HMA in trackbeds, including details of both in-service and experimental structures, has been primarily developed during the past two decades. The advantages of HMA underlayments are described and practices and designs given. Typical HMA underlayment projects in the USA are described, including a tunnel application. The primary benefits of the HMA layer are to improve load distribution to the subgrade, waterproof and confine the subgrade, and to confine the ballast providing consistent load-carrying capability even on subgrades of marginal quality. The waterproofing effects are particularly important since the impermeable HMA mat essentially eliminates subgrade moisture fluctuations, which effectively improve and maintain the underlying support. Additionally, the resilient HMA mat provides a positive separation of ballast from the subgrade, thereby eliminating subgrade pumping without substantially increasing the stiffness of the trackbed. The resulting stable trackbed has the potential to provide increased operating efficiency and decreased maintenance costs that should result in long-term economic benefits for the railroad and rail transit industries. For the covering abstract see ITRD E125214.

Language

  • English

Media Info

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Filing Info

  • Accession Number: 01011764
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • ISBN: 0-947644-43-1
  • Files: ITRD
  • Created Date: Dec 19 2005 3:30PM