Energy-based analysis of the effect of fastener failure on ballast bed under train load

This study investigates the impact of fastener failure on the mechanical characteristics and energy distribution of a railway ballast bed under dynamic train loading. A high-fidelity model was developed based on the Discrete Element Method (DEM), which meticulously incorporates the real shapes of ballast particles to accurately simulate the granular behavior of the ballast track. The research specifically evaluates how varying degrees (partial and complete) and quantities (single and multiple) of fastener failures alter the kinetic energy, strain energy, and slip energy within the system. The findings demonstrate that fastener failure triggers a significant redistribution of energy. This redistribution is attributed to an alteration in load transfer paths and a reconstruction of force chains within the ballast assembly due to the local stiffness loss at the failure site. The ballast box directly beneath the failed fastener experiences a substantial reduction in kinetic energy, strain energy, and slip energy, concomitant with a decrease in the number of high-energy particles and high-energy contacts. Conversely, the adjacent ballast boxes exhibit a marked increase in all three energy forms. Critically, the strain energy and slip energy in these neighboring boxes can escalate to 1.5–2 times the normal values, a surge that significantly accelerates the degradation processes of particle breakage and abrasion. The results also demonstrate that the presence of three consecutive fastener failures leads to more detrimental consequences compared to an individual failure, and total failure produces a more marked influence than partial failure. Moreover, the spatial extent of the disturbance and energy redistribution is notably wider for multiple failures. These results underscore the critical importance of timely maintenance and repair of fastener systems to mitigate accelerated track deterioration and ensure operational safety.