Evaluating the Effectiveness of Asphalt Layer in Improving Railway Track Stiffness through 3D Numerical Simulations

In the last three decades, railways have gradually increased the weight and speed of trains to improve their capacity, profitability, and efficiency. This approach has provided overall benefits; however, it has also led to increased track and structure maintenance costs. The subgrades of railway tracks now experience higher stress, resulting in significant deformation and, in extreme cases, embankment shear failure. Therefore, ground improvement methods should be introduced to reduce stress and deformation in tracks and ensure that the subgrade can safely withstand the increased axle load. One effective ground improvement method is the use of an asphalt layer, which has been successfully applied in many countries. The thickness of the asphalt layer varies from 10 to 20 cm, depending on the regulations of each country. In this study, the finite element program ABAQUS is utilized to model a three-dimensional railway track and investigate the effectiveness of using an asphalt layer to improve the track modulus. The model is calibrated based on experimental observations and used to determine the effects of different combinations of asphalt and granular layers on the stress and displacement of the subgrade under static load. Considering the importance of track modulus in long-term track behavior, the Winkler theory is employed to estimate the track modulus. The results suggest that increasing the thickness of the asphalt layer from 10 to 18 cm significantly reduces the stress and displacement of the subgrade, resulting in uniform displacement.