Dynamic fracture analysis of buried steel gas pipeline using cohesive model

Pipeline play an irreplaceable role in long-distance oil and gas transportation. However, the initiation and propagation of cracks associated with defects may lead to pipeline fracture or explosion. In this paper, the numerical model of dynamic fracture in full-size natural gas buried pipeline are established based on cohesive model. The dynamic crack propagation of X80 pipeline steel is simulated with and without backfill soil. These parameters, like the crack-tip-opening angle (CTOA), are investigated quantitatively in the simulation in this paper. The results show that a threshold value of the crack propagation rate and CTOA does exist. With considering the backfill soil, the crack propagation rate decreases dramatically, and the curve of crack propagation distance will appear many horizontal trend stage against time. The lower the internal pressure, the more obvious the horizontal trend stage will be. The soil layer stress caused by pipeline crack propagation is mainly near the pipeline. Comparing the buried pipeline with penetrating cracks and surface cracks, it is found that surface cracks are more dangerous. The study of the dynamic fracture mechanism of full-scale pipeline provides necessary supplement for experiment.