A Novel EPB Model Test Equipment For Tunnel Face Stability Analysis: Incorpoarating Dynamic Excavation Process

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4. A Novel EPB Model Test Equipment For Tunnel Face Stability Analysis: Incorpoarating Dynamic Excavation Process

Tunnel construction has become a critical solution to accommodate the rapid urbanization and infrastructure development of modern cities. Face stability is paramount, particularly in earth pressure balance (EPB) shield tunnelling where dynamic soil-cutterhead interactions can induce substantial soil deformations that endanger face stability. Previous studies often overlooked the effect of EPB dynamic excavation process on face stability. We therefore developed an innovative EPB model testing apparatus that simulates the tunnel face instability process, emphasizing the dynamic impacts of the cutterhead excavation. Our investigation into the impacts of cutterhead opening ratio and tunnel cover depth on face stability under dynamic excavation conditions revealed crucial findings. With a lower cutterhead opening ratio of 15%, the dynamic excavation causes less disturbance to the tunnel face than the support effect of the cutterhead panel, enhancing overall face stability. Conversely, at higher opening ratios of 30% or 50%, the excavation-induced soil disturbance surpasses the cutterhead's supportive role, diminishing face stability. This observation suggests traditional method that ignored the cutterhead excavation process may overestimate face stability for large opening ratios and potentially induced face failure and ground collapse. Additionally, the load factor of tunnel face increases with increased cover depths, arising from the cutterhead partially destroying the soil arch ahead of tunnel face. Furthermore, the critical support pressure of tunnel face derived from our model tests offer a valuable reference for anticipating face stability during EPB tunneling. This research provides essential insights for mitigating tunnel face instability and enhances the safety of tunneling projects in challenging geological conditions.

4th Asia-Pacific Conference on Physical Modelling in Geotechnics (ACPMG2024)

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