Time-dependent analysis of buried high-density polyethylene (PE100) pipelines with a scratch defect subjected to touchdown impact loading of blasting collapsed body

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The collapsed body generated by the blasting demolition of buildings or structures is likely to impact the buried high-density polyethylene (PE) gas pipelines, which would severely affect the pipeline safety and integrity. In this work, the dynamic response of buried PE100 gas pipelines containing a scratch defect under the touchdown impact was investigated. The tensile tests of scratched PE100 specimens were conducted. A strict 3D finite element (FE) model was then established to simulate the impact process on the scratched PE pipeline. The verified model was employed to investigate the time-dependent response and ultimate bearing capacity of the pipeline under the touchdown load. Parameter effects including the scratch dimensions, defect location, internal pressure and touchdown velocity were examined. The results show that a critical scratch depth equal to 20% of the wall thickness existed, above which the scratch significantly reduces the yield strength and ductility of PE100 material. At the moment when the collapsed body impacts the soil, the maximum von Mises stress, cross-sectional change rate and vibration velocity of the scratched pipeline increases rapidly to the peak value. The maximum von Mises stress and displacement of the pipeline are highly dependent on the scratch depth, defect location, internal pressure and touchdown velocity. A critical internal pressure of 0.6 MPa was determined, exceeding which the ultimate bearing capacity of the scratched PE pipeline is significantly reduced. The significance order of the parameters is: touchdown velocity > scratch depth > internal pressure > scratch width > scratch length.