Dynamic response and energy dissipation characteristics of sand-tire composite cushion under impact loading

To address the challenges of excessive thickness and high costs associated with conventional rock shed cushion layers, this study proposes a cost-effective and highly efficient sand-tire composite cushion structure designed to enhance rockfall impact protection. A numerical finite element model of the composite cushion was developed using LS-DYNA and validated through field impact tests. Subsequently, the deformation behavior and energy dissipation mechanisms of the composite cushion under impact loading were systematically investigated, with a particular focus on the influence of the number of tire layers. The results demonstrate that the sand-tire composite cushion exhibits a four-stage dynamic response consisting of compaction, diffusion, enhancement, and rebound. The primary energy dissipation mechanisms include sand compaction and frictional sliding at the sand-tire interfaces, while the tire layers significantly restrict sand deformation and provide additional energy absorption. Increasing the number of tire layers markedly enhances specific energy absorption; notably, the energy absorption per unit displacement for a three-layer tire configuration increases by approximately 50% compared to a pure sand cushion. This study elucidates the efficient energy dissipation mechanisms of the sand-tire composite cushion and proposes a novel cushioning structure that balances economic feasibility with superior performance. These findings provide robust theoretical guidance and practical support for optimized design and engineering applications in rockfall protection.