Keywords: ballast reinforcement, polyurethane foam, ballast settlement, lateral confinement.

Problem areas on ballasted track are known for non-homogeneous track support, excessive settlement, poor track geometry and track component fatigue and failure. Ballast reinforcement using rigid polyurethane foam (RPF) was utilised in this study to strengthen the ballast, thereby reducing settlement and improving the long-term performance of the ballast. Full ballast layer as well as ballast shoulder reinforcement were investigated by carrying out cyclic loading tests in a laboratory using both a single sleeper and a half sleeper in a large ballast box. Unreinforced, reinforced, 50% reinforced and shoulder reinforced ballast with a thickness of 300 mm depth were tested at accelerated frequencies to a total of nearly 5 million load cycles. The results indicated that RPF reinforced ballast settled 60% less than an unreinforced layer and in the test where only the lower half of the ballast layer was reinforced, 42% less settlement was recorded compared to the unreinforced ballast layer. In tests where only the shoulder of the ballast was reinforced, a 30% reduction in settlement was obtained when compared to that of unreinforced ballast. By implementing ballast shoulder reinforcement, the resilient modulus of the ballast layer was not altered significantly. The use of RPF to reinforce ballast is beneficial to track performance and could result in improved track geometry and reduced maintenance, resulting in lower life cycle costs at specifically track problem areas.

download the full-text of this paper (PDF, 9 pages, 758 Kb)

go to the previous paper
go to the next paper
return to the table of contents
return to the volume description