Investigating the performance of geosynthetic-reinforced asphaltic pavement under various axle loads using finite-element method

One of the major factors influencing the performance of highway pavements is traffic loading, which is continuously increasing in number, magnitude and contact pressure. Geosynthetic reinforcement of asphalt pavements is a method for improving the bearing capacity of pavements against heavy traffic loads. This study aims to investigate the effectiveness of geosynthetic on the reduction of critical strains of flexible pavements under various axle load levels. Three types of geogrid have been placed in different positions in a typical asphalt pavement structure, and the critical strains, including the compressive vertical strain on top of subgrade, the maximum tensile strain at the bottom and the maximum shear strain of asphaltic layer have been evaluated under different axle loads of 5, 8.2 and 15 ton. The finite-element method has been utilised for modelling and analysis of pavement structure, in which, the asphaltic layer has been characterised as a viscoelastic material using Prony series. Results show that placing the geosynthetic beneath the asphaltic layer results in the reduction of the longitudinal tensile strain of asphaltic layer, while it is not effective on the vertical compressive strain on the subgrade. Furthermore, results show that, in spite of increasing the critical strains with increasing axle load, the effectiveness of geosynthetic reinforcement under different axle loads varied. At higher levels of axle load, the geosynthetic on the subgrade is more effective in reducing the compressive strain on the subgrade. However, the effectiveness of the geosynthetic beneath the asphaltic surface layer decreases with increasing axle load. In addition, the highest improvement in the effectiveness of geosynthetic for reducing the critical strains at higher axle load levels is achieved when it is placed at the position of the desired critical strain. It is also found that the effectiveness of geosynthetic in reducing the critical strains at higher axle loads increases with an increase in the modulus of geosynthetic.