Interpretation of vibration-induced compaction deformation of sand-gravel mixtures: Perspective of multi-scaled dynamic responses

Sand-gravel mixture, a common subgrade filler, is subjected to vibration loads in the subgrade compaction stage, the vibration loads of which differ from the dynamic loads in the subgrade service stage. Sand content, affecting the mesoscopic particle motions and inter-particle contacts, determines the macroscopic compaction deformation of sand-gravel mixtures. However, the interpretation of vibration-induced deformation remains unclear due to the insufficient understanding of mesoscopic responses. To break through this deficiency, a series of sand-gravel mixtures with varying sand contents were established to obtain multi-scale dynamic responses via DEM simulations, and the reliability of DEM models was verified through dynamic triaxial tests with corresponding stress conditions. Based on the simulated dynamic information, the differences in strength and stiffness caused by sand contents were systematically explored, and the reasons for these macro-mechanical differences were analyzed from the perspectives of mesoscopic particle motions and inter-particle contacts. This study aims to provide a theoretical basis for the subgrade compaction with geotechnical granular fillers.