Effects of natural abrasion on railroad ballast strength and deformation properties Andrew K. Rohrman a,⇑ , Hamed F. Kashani b , Carlton L. Ho c a University of Massachusetts Amherst, Department of Civil and Environmental Engineering, 28 Marston Hall, 130 Natural Resources Way, Amherst, MA 01003, United States b Hyground/LORAM Maintenance of Way, Inc., P.O. Box 324, Williamsburg, MA 01096, United States c University of Massachusetts Amherst, Department of Civil and Environmental Engineering, 28 Marston Hall, 130 Natural Resources Way, Amherst, MA 01003, United States article info Article history: Received 6 March 2019 Accepted 29 January 2020 Keywords: Ballast Abrasion Fouling Triaxial test Box test Performance abstract Railway ballast is an important component of the track substructure that provides vertical, lateral, and longitudinal support, increases track resiliency, reduces stress applied to the subgrade, and facilitates the drainage of water away from the track. Ballast is typically composed of highly angular, uniformly graded crushed stone that provides high shear strength. However, the properties of ballast are continu- ally changing under repeated loading from train traffic. Abrasion between ballast pieces often results in more rounded particles as corners are broken off. This process also contributes to fouling, or the introduc- tion of finer grained particles into the ballast. Abraded material accounts for the majority of fouling, but it can also be introduced via other processes, such as infiltration from the subgrade or infiltration by wind- blown particles. While laboratory testing of ballast has been performed extensively over the past several decades, much of the testing is performed on fresh ballast with manufactured fouling materials. This study performs laboratory tests on naturally abraded ballast, taken from real track, and the naturally occurring fouling material which includes abraded and windblown material. This study builds on tests previously performed at the University of Massachusetts, Amherst which used fresh, highly angular bal- last and fouling which originates from the same parent rock. Triaxial and box tests are performed on specimens, which are prepared to the same fouling and water contents as the previous testing so that the material properties and behaviors can be directly compared. The triaxial tests reveal similar strength properties, but significantly different volumetric strain behaviors. The box tests show similar results, with higher overall settlements from the abraded ballast, particularly under initial loading. This testing has also resulted in the first known basal failure of ballast in a box test. The results show that abraded ballast exhibits distinct behavioral differences, as well as reductions in performance when compared to highly angular ballast in the same conditions. Ó 2020 Elsevier Ltd. All rights reserved. 1. Introduction Railway ballast is primarily responsible for draining water away from the track. However, it also plays very important roles in resisting loading forces, reducing stress on the subgrade by dis- tributing load, maintaining track geometry, and providing large voids for the storage and movement of fouling material [12,19]. Fouling is the introduction of finer particles less than 3/8 inch (9.5 mm) into the ballast void space [19]. Fouling can be intro- duced by fluvial or aeolian processes, or by infiltration from the subballast and subgrade, but the primary source of fouling is from ballast breakdown [19]. The breakdown of ballast occurs under repeated loading, during which the particles abrade with one another, resulting in the breakage of particle corners or in the cre- ation of fine stone dust. Thus, over the life of the ballast, its phys- ical properties, and therefore its mechanical performance, are changing in a way that is generally not favorable. Studies have shown that the introduction of fines into the ballast results in increased settlements and decreased strength, particularly at high water contents [4,13]. As ballast particles abrade under repeated traffic loading, the angularity of the particles changes through mechanisms such as attrition, grinding, and impact [16]. Several studies have shown that particle shape and angularity have influence over the perfor- mance of granular materials. Work by Indraratna and colleagues [10] [12] have shown that angular rock had much higher shear https://doi.org/10.1016/j.conbuildmat.2020.118315 0950-0618/Ó 2020 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: arohrman@umass.edu (A.K. Rohrman), hamed@hyground.com (H.F. Kashani), ho@ecs.umass.edu (C.L. Ho). Construction and Building Materials 247 (2020) 118315 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat