Abstract: The equal-size 3D asphalt mixtures were reconstructed using laser scanning equipment and image processing techniques. Three-dimensional asphalt mixture models with identical gradation and size were then developed via the discrete element method (DEM) to simulate the compaction processes of Marshall impact compaction and gyratory compaction. A novel intelligent granular sensor is embedded to capture mechanical response data and validate the DEM simulations. The contact force Gini index, the probability of force chain distribution for different strengths P(f), the characteristics of force chain direction distribution, and the constitutive anisotropy of asphalt mixtures were analysed under different loading methods. The results showed that the Gini index G of contact force between aggregate-aggregate, aggregate-mortar, and mortar-mortar are 0.178, 0.129, and 0.107, respectively, for the specimens moulded by percussive action. The distribution probability P(f) of the strong force chain (f≥1) reaches 32.4%, and is predominantly concentrated near the angle of 0° of the force chain, leading to a higher anisotropy of the group structure. In contrast, under kneading-dominant compaction, the contact force between particles tends to be uniform, weakening the formation of highly resistant strong-compaction regions. The distribution probabilities P(f) of strong force chain, sub-strong force chain (0.5<f<1), and weak force chain (f≤0.5) are 26.1%, 30.7%, and 43.2%, respectively, and the distribution orientation of the force chain develops toward anisotropic uniformity.

Key words: loading mode, smart particles, discrete element method, homogeneity, isotropy