This paper presents an experimental study to evaluate the effects of moving wheel load on cyclic plastic deformation of ballast of railroad track under train passage. Two types of small scale model tests which differ in the loading method were performed with poorly-graded crushed gravel. One is a fixed-place cyclic loading test, in which a concentrated cyclic load is vertically applied to a sleeper. The other is a moving constant loading test, in which a wheel with a constant vertical load travels cyclically along the rails as actual train loading. As a result, it was revealed that a slight difference in the distribution of ballast grain size noticeably influences the development of residual settlement by cyclic loading. Moreover, it was recognized that the difference in the loading method has a considerable influence on the plastic deformation of railroad ballast.

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