Micro-mechanical behavior of stone-blowing in ballast maintenance using DEM-CFD coupling method

Abstract

Stone-blowing restores the track geometry by blowing small crushed stones into the bottom of the sleeper, extending the maintenance period. In this study, ballast and filling stones were modelled using discrete element method (DEM), while the air blowing was simulated using computational fluid dynamics (CFD). The DEM-CFD coupled model has been used to simulate the stone-blowing process and investigate the optimal operation parameters from a micro view.The disturbance of ballast bed during stone-blowing process was analyzed. Meanwhile, the effect of air velocity and tube layouts on the stone-blowing, as well as the sleeper settlement after stone-blowing were discussed. The results show that the maximum disturbance occurs in the inserting area between sleepers, and the disturbance increased with faster insertion speed. It was suggested that the inserting speed of the tube is 0.4 m/s. When the air velocity of stone-blowing was not less than 20 m/s, the blowing quality meets the requirement. Furthermore, the four-tubed stone-blowing approach distributed filling stones more evenly under the sleeper, and reduced the risk of tube blockage. After stone-blowing, the contact number between the bottom of the sleeper and the ballast is greatly increased, reaching 217.9 % after double cross tubes, and 245 % after four tubes stone-blowing. The crushed stone blown in greatly improves the stress distribution of the ballast bed and makes the load transfer more uniform. Overall, this study provides valuable insights into the stone-blowing process and can help optimize the stone-blowing parameters for efficient and effective track maintenance.