Abstract：Research purposes: The maintenance by the ballast blowing car needs to supply the small hard ballast under sleeper bottom to avoid tamping and breaking the ballast and eliminate the ballast memory effect． From the microscopic mechanics，there is a little research on the maintenance mode of blowing ballast and on its applicable effect． In order to research the working principle and the maintenance effect of ballast blowing car from the microscopic mechanics，the DEM was used to produce the ballast － sleeper 3D box model to simulate the ballast blowing． Ballast particles were made of real size irregular clumps to simulate the ballast interactions more precisely，and the research was done on the mechanic effect of the roadbed under monotonic loading on the sleeper before and after the ballast blowing．
Research conclusions: The micro － mechanics simulation results showed that the contact force between sleeper and ballast could be reduced by blowing ballast and the ballast blowing had a little influence on the sleeper － ballast deformation． So the mechanics principle of the ballast blowing car operation was revealed quantitatively from the numerical value principle． Compared with tamping ballast，the ballast blowing is high － efficient，rapid，low － cost and environment protected maintenance way．
2011, Vol. 28 
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