Vibration Safety Threshold and Control Technology for Blasting to Prevent Seawater Intrusion in Coastal Tunnel Sections Near Faults

Coastal underground engineering projects are prone to seawater intrusion during blasting operations, posing significant risks to the safety of construction personnel and the structural integrity of the projects. To ensure the safety of blasting operations in areas at risk of seawater intrusion, this study focuses on a section of a coastal tunnel that is at risk of such intrusion. Using fracture mechanics theory and silo theory analysis methods, the minimum safe distance between the workface and the fault to prevent seawater intrusion is determined. Numerical simulations are employed to analyze the dynamic response of the surrounding rock and the attenuation of vibrations as blasting excavation progresses near the fault-controlled zone. This study also explores the impact of dynamic excavation on fault stability. By employing a regression analysis, this study establishes quantitative relationships between the amount of explosive used and the peak particle velocity (PPV) at different distances, as well as between the range of rock damage and PPV at various distances. This analysis allows for the determination of a safe PPV threshold to prevent seawater intrusion in the fault-controlled area. The accuracy of the computational model is validated using field-measured data. Finally, an optimized blasting design and strategy based on electronic detonator initiation are proposed for the control area, ensuring construction safety. This study provides theoretical and technical references for achieving safe and efficient blasting excavation in coastal underground engineering projects.