Effects of fouling containing plastic fines on abraded ballast strength and deformation properties

Abstract

Abstract The introduction of fouling, or finer grained material into the voids of railroad ballast is one of the main issues effecting ballast performance. Fouling reduces the ability of ballast to serve it’s main functions, including providing drainage of water away from the track, resisting loads in the vertical, lateral, and longitudinal directions, and maintaining track position. Dynamic loading in the track causes ballast particles to abrade together. This is the most common source of fouling, and results in a progressive change in ballast particle shape over time. Fouling can also enter the track through windblown processes as well as infiltration of the subgrade from the bottom of the track. Many studies have been done to better understand the influence of fouling on ballast strength properties, deformation characteristics, and overall performance. These studies usually use fresh ballast and fouling made from the stone dust of the same parent rock. There are few studies which use ballast taken from track, and fewer that investigate fouling by clay particles. This study aims to better understand the influence of fouling containing clays by comparing two sets of laboratory tests. The first set of tests uses abraded ballast taken from a track and the natural fouling found at that location. The second set of tests uses the same ballast but mixes the natural fouling with Prestige clay in a ratio of 55:45. Unlike tests with purely clay fouling, this mixture should be more realistic to what might be found in the field. By directly comparing the results of these two sets of tests, the effects of fouling containing plastic fines on ballast properties becomes more apparent. The results of these tests show that the fouling containing clay reduces strength and increases the variability in deformation behavior of the ballast.