Numerical study on tamping methods to reduce ballast degradation during maintenance work

Abstract

To investigate a tamping method that would reduce ballast degradation during tamping work while ensuring sufficient compaction, the tamping process was simulated using the discrete element method. Six simulation cases were designed, combining Dd (descent depth during the tine descent process), and Ds (the depth during the squeezing process). Indicators such as N_con, the number of contact points with inter-particle contact forces exceeding a threshold, and EneFr, the product of contact force and sliding distance at contact points, were calculated to predict ballast degradation. Additionally, the porosity of the ballast layer under the sleeper and the total volume of ballast particles that moved from the outside to under the sleeper during tamping process (V_bal), were calculated to evaluated compaction. The results demonstrated that N _con and EneFr decreased by at least 8.9% when Dd was shallower than the conventional value; however, porosity remained at the conventional value (38.6) when the Dd + Ds was maintained at the conventional value of 100. These results suggest that ballast degradation can be suppressed by reducing Dd and that the degree of compaction can be ensured by setting Ds appropriately.