In-situ experimental investigation of intelligent pneumatic vibration probe compaction method for reinforcing soil–rock mixture foundations based on the "BNE"

• Applied the BNE to improve uneven foundations. • Developed intelligent pneumatic vibration probe for compaction of foundations. • Demonstrated gas–vibration–induced particle migration in theory and field. • Achieved 60% cost reduction in SRM foundation treatment. Soil–rock mixtures (SRM) are highly heterogeneous materials characterized by inherent structural weakness, pronounced particle-size disparity, and significant water-induced collapsibility. These features often render SRM foundations problematic in civil engineering practice, and conventional reinforcement methods struggle to handle, leading to long-term underutilization of SRM-dominated ground. This research, based on a large-scale quarry foundation treatment project, proposes a new in-situ reinforcement approach that exploits the "Brazil Nut Effect" (BNE) through gas–vibration coupling. The coupling generates a quasi-fluidized environment that amplifies particle-size segregation and accelerates fabric reorganization. The main contributions of this study are: (i) a particle-scale dynamic model to establish the critical conditions, serving to intuitively reveal the dependency of particle migration on specific vibration indicators; (ii) the development of intelligent pneumatic vibration probe compaction (PVPC) system with intelligent construction capabilities; and (iii) full-scale field trials to elucidate the reinforcement mechanism and its influence on engineering performance. Field observations demonstrate that gas–vibration coupling induces a depth-oriented stratification, with enriched coarse-particle enrichment above and accumulated fines in below. This reconfigured structure markedly increases bearing capacity, suppresses water-induced collapsibility, and improves uniformity of the SRM. The findings extend the application of granular physics to heterogeneous materials and provide a theoretical and practical framework for efficient treatment of SRM foundations.