Particle motion and stress response interacted with machine activity: Railroad tamping strategy

Tamping is a vital maintenance activity to correct railroad track geometry by lifting, aligning, and levelling the track. Traditional tamping practices are often rather empirical and rely heavily on operator's experience. Railroads have learned that improper tamping parameters impact ballast stability and cause quick track geometry deterioration. The purpose of this study is to investigate the effect of tamping parameters on ballast performance at the particle level, expecting to figure out the optimized tamping parameters to improve track quality. To achieve this objective, field tamping tests were conducted on Norfolk Southern Railway's mainline. In the tests, four tamping parameter combinations of squeeze time (0.6 s, 1.0 s) and number of squeezes (1 insertion, 2 insertions) were executed by Plasser's tamper. In addition, “SmartRocks” sensors were preinstalled under the ties to record ballast and contact stresses caused during and after tamping. It was found that 1.0 s squeeze time results in a more compact and stable ballast status than 0.6 s squeeze time, with a more stable rearrangement of particles and stable bulk stress after tamping. employing two insertions appeared to neutralize the impact of squeeze time duration, given a small lifting value of 25 mm. These findings provide insights into optimizing tamping strategies to improve the stability and durability of railroad tracks.