Investigation into the Evolution of Main Force Chains and Skeleton Composition in Asphalt Mixture Using the Discrete Element Method

To clarify the load transfer mechanism of the asphalt mixture skeleton, the discrete element method simulation analysis was conducted to investigate the evolution of the morphological characteristics of the main force chain (MFC) and the mechanical composition of the skeleton. Results indicate that AC-type asphalt mixtures form a greater number of force chains compared with SMA- and OGFC-type asphalt mixtures. Although AC-type asphalt mixtures exhibit more MFC, both SMA and OGFC have a higher proportion of MFC (PMFC) throughout the loading process, which is beneficial to transfer external loading effectively. In AC-type asphalt mixtures, the skeleton undergoes reorganization during the initial loading stage, especially in the case of small NMAS. This makes it easy to form MFC with a longer length, some of which exhibit a relatively low alignment coefficient. Consequently, the MFC network of AC is more complex and less efficient for transferring external loading compared with SMA and OGFC. For all asphalt mixtures, the MFC structure evolves in a manner that facilitates load transfer. For skeleton mechanical composition, aggregate within 1.18~2.36 mm is mainly used to fill the void space of the skeleton and has a small amount of participation in the formation of the skeleton. Aggregates within 2.36~9.5 mm mainly participate in the skeleton composition and make a small contribution to filling the void of the skeleton. Aggregates larger than 9.5 mm are fully incorporated into the skeleton composition.