ABSTRACT
Small-scale model tests were performed to evaluate effects of cyclic loading conditions on the contact pressure distribution between on sleepers and ballast and the residual settlement of sleepers. (1) Cyclic concentrated vertical load at a fixed place on the rail; and (2) laterally moving load using a roller with constant vertical load running on the rail at a constant velocity, as actual train loading, were applied. In the fixed-place cyclic loading tests, the distribution of the contact force between the sleepers and the ballast changed with cyclic loading and the residual settlement of the sleeper at the point of loading became largest. In the moving load tests, the distribution of contact force did not change noticeably with cyclic loading, while the distributions when the load was applied to different sleepers were similar. For the same amplitude of cyclic vertical load applied to a sleeper, the residual settlement of sleeper was larger in the moving load test than in the fixed-place loading test due to an extra settlement component caused by cyclic load applied to the adjacent sleepers in the moving load tests. The test results indicate that in some important aspects, the conventional fixed-place loading method could not be representative of actual full-scale train loading conditions.
