Deformations and Remedies for Soft Railroad Subgrades Subjected to Heavy Axle Loads

A 213-meter (700-foot) long soft subgrade section was built under a railroad test track at the Federal Railroad Administration's Transportation Technology Center (TTC), Pueblo, Colorado, to characterize soft subgrade deformations and to test various remedies for the heavy axle load environment. The test track is a 4.3-km (2.7-mile) loop and is used to test various track components under heavy axle freight trains (346 kN or 39-ton axle loads). The type of soil placed in the subgrade is Vicksburg "Buckshot" clay and has an average moisture content of 33 percent (10 percent above the optimum moisture content). Each year, approximately 100 MGT (million gross tons) of traffic is operated on the test track. To date, the following remedy techniques have been or are being tested, including increasing the granular layer thickness, geocell reinforcement and asphalt trackbed stabilization.