A Study on Portable Tamper for Suppressing Railway Ballast Fouling

Abstract

 In ballasted railway tracks, repeated tamping operations and train passages cause crushing and abrasion of ballast particles, leading to fragmentation and the generation of fines—commonly referred to as ballast fouling. This fouling impairs drainage within the ballast layer, and under high moisture conditions, reduces mechanical strength, increasing the risk of track deformation. Suppressing ballast fouling and extending ballast service life are therefore crucial for sustainable railway infrastructure. This study investigates the effect of vibration conditions during tamping using a portable tamper. Based on experimental findings, the vibration force was optimized and its impact on track settlement was evaluated through full-scale testing. A portable tamper was developed that maintains the conventional excitation frequency of 155 Hz while reducing both excitation force and counterweight mass to half of those in the conventional model. This modified condition reduced ballast degradation by approximately 50%, demonstrating its effectiveness in mitigating particle breakage under cyclic loading. Additionally, ballast density increased, and settlement after 300, 000 loading cycles was reduced by 15%, indicating improved compaction performance. Numerical analyses were also conducted to assess the influence of vibration conditions on ballast behavior. The frictional energy (EneFr), defined as the product of inter-particle contact force and slip displacement, was reduced, confirming the suppression of ballast fouling. Moreover, a greater number of contact points and slip occurrences were observed under the reduced excitation condition, suggesting denser compaction compared to the conventional method.