Moisture effects on degraded ballast shear strength behavior

Yu Qian, Debakanta Mishra, Erol Tutumluer, Youssef M.A. Hashash, Jamshid Ghaboussi

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Ballast consisting of large sized aggregate particles with uniform size distribution is an essential component of the track substructure, to facilitate load distribution and drainage. As freight tonnage accumulates with traffic, ballast will accumulate an increasing percentage of fines due to either aggregate breakdown or outside contamination such as subgrade soil intrusion and coal dust collection. According to the classical text by Selig and Waters [1], ballast degradation from traffic involves up to 76% of all fouling cases; voids will be occupied by fines from the bottom of ballast layer gradually causing ballast clogging and losing its drainage ability. When moisture is trapped within ballast, especially fouled ballast, ballast layer stability is compromised. In the recent studies at the University of Illinois, the focus has been to evaluate behavior of fouled ballast due to aggregate degradation using large scale triaxial testing. To investigate the effects of moisture on degraded ballast, fouled ballast was generated in the laboratory through controlled Los Angeles (LA) abrasion tests intended to mimic aggregate abrasion and breakdown and generate fouled ballast at compositions similar to those observed in the field due to repeated train loadings. Triaxial shear strength tests were performed on the fouled ballast at different moisture contents. Important findings of this preliminary study on characterizing wet fouled ballast are presented in this paper. Moisture was found to have a significant effect on the fouled ballast strength behavior. Adding a small amount of 3% moisture (by weight of particles smaller than 3/8 in. size or smaller than 9.5 mm) caused test specimens to indicate approximately 50% decrease in shear strength of the dry fouled ballast. Wet fouled ballast samples peaked at significantly lower maximum deviator stress values at relatively smaller axial strains and remained at these low levels as the axial strain was increased.

Original languageEnglish (US)
Title of host publication2016 Joint Rail Conference, JRC 2016
PublisherAmerican Society of Mechanical Engineers
ISBN (Electronic)9780791849675
StatePublished - 2016
Event2016 Joint Rail Conference, JRC 2016 - Columbia, United States
Duration: Apr 12 2016Apr 15 2016

Publication series

Name2016 Joint Rail Conference, JRC 2016


Other2016 Joint Rail Conference, JRC 2016
Country/TerritoryUnited States

ASJC Scopus subject areas

  • Transportation


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