Ductile failure analysis and crack behavior of X65 buried pipes using extended finite element method

• Fracture history of buried pipe including crack onset and growth is demonstrated.
• Mechanical property of surrounding soil is employed by D–P hardening model.
• Limit load-bearing ability of buried pipes during landslide process is predicted.
• Limit strain on buried pipes due to deflection is compared with related standards.

This paper aims to study the ductile fracture mechanism of API X65 buried pipes including crack initiation and propagation using the extended finite element method (XFEM). First, the crack evolution histories of X65 specimens with initial crack-like flaws during tensile and three-point bending tests are illustrated, and the numerical results are compared with experimental data. In addition, effects of different crack configurations, damage initiation and evolution criteria are investigated. Second, the burst processes of straight pipes with initial gouge flaws are presented, and the FE results are compared with assessment in related standards and experiments. Finally, the crack onset and growth of buried pipes due to deflection arising from landslide movements are predicted, and the numerical results are compared with previous study. Particularly, the internal pressure, wall thickness, and soil properties on crack behavior and limit load-bearing ability are investigated. This paper provides a fundamental support for the integrity assessment and safety evaluation of buried pipes.