| Reflective cracking is one of the most serious problems in AC overlays. The application of geosynthetics in pavement rehabilitation has been considered to strengthen pavement and extend its service life, with one of the effects being the mitigation of reflective cracking. There is a major gap in the understanding of the contributing mechanisms of geosynthetics in overlays under applied loading conditions. To quantify the benefits of geosynthetics in pavement overlay for reducing or retarding reflective cracking, a better understanding of the contributing mechanisms is needed. The discrete element method (DEM) is the most suitable for capturing the particle-level behavior of complex systems such as reinforced overlays with geosynthetics.;A DEM fracture model based on field scale is used for model calibration, and reflective cracking is analyzed and compared with field data with respect to both overlay thickness and geosynthetic properties, with and without reinforcement. Based on model calibration, the current research uses the discrete element method to quantify the mechanisms that govern the response of reinforced overlays with geosynthetics under different loading conditions (e.g., constant loading, constant loading rate, and dynamic wheel loading). The DEM pavement model is developed and analysis is conducted under constant loading. Analyses of displacement of overlay on top of asphalt concrete, as well as strain and stress distributions, are performed both with and without reinforcement. In addition, the stress and porosity contours of the overlay are displayed in order to enable visual evaluation. To evaluate the effects of geosynthetics, the following factors are investigated without and with reinforcement: i) effect of an initial crack on overlay (including geosynthetic properties, geosynthetic locations and aggregate distribution), ii) effect of existing pavement conditions (PCC properties, PCC crack widths), and iii) effect of overlay thickness. In addition, DEM pavement modeling is conducted under a constant loading rate of y-velocity equals 0.7 mm/s. This study includes the comparisons of maximum stress and maximum strain observed from 5 different measurement circles at a local level, and macro and micro cracks are displayed in order to enable visual comparison of reflective cracking. Finally, moving wheel load tests, as one of the different loading conditions for unreinforced and reinforced overlays, are conducted by using a DEM model. The effect of wheel movement from the left to the right side of the overlay is examined only once because of the issue of computational time. Stress and strain are monitored from measurement circles at 5 different positions along the moving wheel.;The results obtained under different loading conditions clearly indicate that geosynthetic reinforcement provides significant benefit in reducing/retarding reflective cracking by reducing stress and strain. Reinforcement at one-third of depth is most effective, and increasing overlay thickness also has a strong effect on decreasing stress and strain. |
