Three-dimensional modeling of joint kinematic of ductile iron pipelines subjected to normal faulting

Abstract

Buried ductile iron (DI) pipelines are of paramount importance for urban water networks. The joint sealing performance can be seriously affected by fault offset, showing failures of axial pull-out of joint, joint crushing, joint rotation, and circular cracking caused by pipe bending. Analytical or beam-on-spring based numerical models and physical experiments have been done in the past, but the kinematic mechanism of DI pipes subjected to normal fault deserves to be understood using the three-dimensional (3D) finite element method. In this study, an explicit 3D numerical model is calibrated against a full-scale experiment, and is further adopted to analyze the impact of different parameters. It is demonstrated that joint rotation leakage dominates the failure mode, showing leakage at a single joint or two joints closest to the fault trace. The most unsafe fault-pipe crossing position is derived when the fault acts on one quarter of the rotated pipe barrel from the spigot, which can result in highly consistent pipe rotation pattern in the even configuration as proposed in existing theories. When the fault passes through the middle of the pipe barrel perpendicularly, the joints of DN 400 pipeline are more susceptible to leakage.