Dynamic damage evolution mechanism of buried cast iron pipeline under corrosion-blast coupling effects

This study systematically investigated the dynamic response and failure mechanism of aging cast iron pipes affected by blasting operations in urban renewal projects. In response to key challenges such as the vibration safety risks brought by adjacent blasting activities, the lack of targeted control standards in the current "Blasting Safety Regulations", and the insufficient understanding of the corrosion-blast coupling effects in existing research, a case study was conducted using the Beijing Metro Line 16 tunnel. Nine full-scale on-site blasting tests were carried out. The results showed that the vibration and strain propagation patterns were significantly different. When the explosion source was directly aimed at the lower part of the pipe, the blasting hazard was the greatest. The experiment also proved that the blasting exposure side was mainly subjected to axial tensile failure, which challenged the traditional engineering assumption. The study also developed and verified a refined numerical model including bending corrosion defects, quantifying the influence of corrosion depth on the dynamic response. The research results indicated that corrosion defects would cause significant stress concentration, and the peak vibration velocity and effective stress would increase sharply with the increase in corrosion depth. At a corrosion depth of 8 mm, the maximum effective stress during pipe blasting was 253% higher than that without corrosion. The corrosion depth is the core factor affecting the blasting safety threshold of cast iron pipes. The threshold decreased by 85.4% at 8 mm corrosion, and 4 mm is already close to the critical failure point. The current regulations have both overly strict requirements for non-corroded pipes and overly lenient requirements for old and corroded pipes. The arc-shaped defect model constructed in this study is more accurate, overturning the conventional understanding of control on the facing side of the explosion, and the proposed single-section explosive dosage control table can be directly applied, balancing safety and construction efficiency, providing a scientific basis for regulation revision and engineering control.