Ballast State of Good Repair
(Room Sagamore 7)
19 Sep 17
2:00 PM
-
2:30 PM
Tracks:
AREMA Technical Sessions- Maintenance
Settlement within the ballast layer is most often the largest contributor to track geometry roughness and poor ride quality. Excessive ballast layer deformation also causes higher-than-normal rates of tie, fastener and rail deterioration. Prediction of ballast behavior over time, by defining present ballast condition and future traffic-induced deterioration from fouling and water retention, is the key input for developing accurate life-cycle costs of the ballast. Once the life-cycle costs are defined, then decisions regarding the type and timing of ballast maintenance and renewal can be made with confidence and the status of the ballast State of Good Repair (SGR) backlog can be quantified. This paper presents an approach for defining the State of Good Repair of the ballast component of the track. This new approach is founded on soil mechanics principles, previous laboratory and field studies, and mechanics-based models that have been developed over the past half-century. This new approach, however, incorporates actual track settlement and fouling condition for over 200 revenue-service locations, including both mixed passenger and freight lines as well as freight only track. The approach uses precisely-aligned track geometry records over a history of up to 8 years and ballast fouling and moisture information as measured by ground penetrating radar (GPR). The paper shows the relationship between track geometry roughness (vertical surface data) and track settlement, and then presents the relationship between the ballast fouling condition and future settlement. The influence of water is also examined and correlations shown between track settlement and track internal and external drainage conditions.