Title

COST COMPARISONS OF REMEDIAL METHODS TO CORRECT TRACK SUBSTRUCTURE INSTABILITY

Document Type

Journal Article

Publication Date

2000

Subject Area

operations - traffic, infrastructure - track, planning - methods, mode - rail

Keywords

Train traffic, Tracks, Trackbeds, Tonnage, Thickness, Test facilities, Tamping, Subgrade (Railroads), Soil strengthening, Soil stabilization, Soil stabilisation, Soft clays, Railroad traffic, Railroad tracks, Ground treatment, Granular materials, Geoweb, Geosynthetics, Economic analysis, Cost effectiveness, Accelerated tests

Abstract

The effectiveness and costs of various remedies for stabilizing track over a soft clay subgrade were tested and compared. To date, the techniques of repeated tamping, increasing granular layer thickness, and placing a geoweb layer have been tested under 39-kip (170-kN) wheel-load traffic. Using typical industry cost figures, economic analysis shows that the most cost-effective selection depends on traffic volume. For the heavy-axle load conditions studied at the Facility for Accelerated Service Testing (located at the Federal Railroad Administration's Transportation Technology Center, Inc., near Pueblo, Colorado), analysis indicates that continued tamping of the ballast can be the best choice when the annual tonnage is less than about 40 million gross tons (MGT; 360 GN). For annual tonnage levels greater than 50 MGT (450 GN), fixing the problem by use of a remedial technique is less costly. Of the two remedies tested, increasing the granular layer thickness appears to be the lower cost option, mainly because of the lower material cost compared with geoweb. The intent of this analysis is to help railroads decide whether to make temporary repairs with low initial costs or more permanent remediation with higher initial costs.