Geogrids have been found to effectively improve the performance of unbound aggregate layers in transportation applications by providing confinement and arresting movement through interlock between individual aggregate particles and their apertures. Geogrid reinforcement offers an effective remedial measure when railroad track structures are susceptible to track geometry defects resulting from excessive movement and particle reorientation within the ballast layer. This paper presents an ongoing research study at the University of Illinois aimed at quantifying the effects of geogrid reinforcement on the shear strength and permanent deformation behavior of railroad ballast. Geogrids with triangular, rectangular, and square apertures were tested in the laboratory experiments. Cylindrical ballast specimens were prepared and tested with geogrids placed at different heights within the specimen using a large-scale triaxial apparatus. An imaging based Discrete Element Method (DEM) modeling approach was developed to model triaxial test results and investigate geogrid reinforcement mechanisms. With the capability to create actual ballast aggregate particles as three-dimensional polyhedron elements having the same particle size distributions and imaging quantified average shapes and angularities, the DEM simulations were able to capture the ballast behavior with and without geogrid reinforcement reasonably accurately.
This is an author-produced, peer-reviewed version of this article. The final, definitive version of this document can be found online at Proceedings of the Institution of Civil Engineers: Ground Improvement, published by the Institution of Civil Engineers. Copyright restrictions may apply. doi: 10.1680/jgrim.17.00068
Qian, Yu; Tutumluer, Erol; Mishra, Debakanta; and Kazmee, Hasan. (2018). "Effect of Geogrid Reinforcement on Railroad Ballast Performance Evaluated Through Triaxial Testing and Discrete Element Modeling". Proceedings of the Institution of Civil Engineers: Ground Improvement, 171(4), 223-231.