Fall 2009

Testing Apparatus for the Future of the Nation's Railways

University of Wisconsin, Madison Geological Engineering
Project: Reconstruction of Railways with In-situ Reclaimed Materials


A prototype large-scale triaxial testing apparatus has been developed at the University of Wisconsin-Madison with potential of testing the specimen up to 457-mm diameter. The triaxial test is used to investigate the mechanical behavior and the stability of railroad substructure under heavy freight haul or high speed trains.  Railway substructure, particularly the large grained size stones called ballast, deteriorates under repetitive traffic loading, which reduces the track safety.  Ballast, in-situ reclaimed ballast, and degraded ballast are tested in the large-scale triaxial testing to determine the shear strength, modulus, breakage characteristics, and permanent deformation. The characterization of substructure materials allows developing a method to enhance the life expectancy of the rail track.

This equipment is accommodated to perform the monotonic and cyclic test in different confining pressures, rates of deformation and loading, frequencies, pulse shapes, and saturation conditions, similar to the field condition.  In this equipment, air pressure produces the confining pressure varying between 1 and 300 kPa as a typical confining pressure experienced in the railway substructure.  The specimen is instrumented to measure the deformation and loads during monotonic and cyclic testing.

The project is funded by The National Center for Freight and Infrastructure Research and Education (CFIRE).

The results of this project will be used for the future design and maintenance of railways under heavier freight loads and higher speed trains throughout the nation.  This project is motivated by increasingly environmental and economical benefits of using railroads as a reliable transportation system, and desire for reducing the maintenance cost to meet the sustainability criteria of railroad tracks.

Thank you to: Research Assistant Ali Ebrahimi for the contribution of this article.


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