Study on the performance variation and failure mechanism of natural gas pipeline under the action of water failure

Water-induced disasters in long-distance pipelines are prevalent geological hazards, characterized by their frequency and widespread distribution. The complexity of factors contributing to pipeline damage in practical engineering poses a significant challenge for analysis using solely theoretical models. This study systematically reveals the cross-scale failure mechanism of long-distance pipelines under hydrodynamic impact through the combination of multi-scale experimental representation and theoretical modeling. Employing a combination of macroscopic measurements, advanced material testing of residual samples from failed pipelines, and consideration of operational conditions and environmental factors, the failure modes is systematically analyzed. The findings reveal that under the vibrations induced by water impulses, the pipe material exhibits a pronounced ratchet effect, leading to an 8.92% reduction in elongation at break. Furthermore, the Bauschinger effect is observed, resulting in a 2.95% decrease in yield strength. Cyclic hardening significantly diminishes the impact toughness of the weld by 22.2%. Notably, at high vibration frequencies of approximately 18.98 Hz, the stress concentration in the girth weld near the axial midpoint of the pipe section initiates cracking, ultimately leading to failure under the alternating load generated by the oscillation. This study provides valuable insights into the scientific understanding of pipeline failure mechanisms under water impact, contributing to the development of more robust and resilient pipeline systems.