The main cause of failure for the most transmission pipelines is mechanical damage due to third party activities [1]. Usually, the damage takes form of a dent with an associated gouge. When this type of defect is detected, repair procedures of pipelines operators necessarily implies the removal of the gouge by grinding. This type of defect is considered as critical for the pipeline integrity; however, the importance of the various characteristics of the dent (depth, length, width) regarding pipeline integrity is not well known. To achieve a better understanding of this kind of mechanical damage, Gaz de France has been working on the numerical modelling of realistic defects for several years. This study presents the comparison between the results of experimental and realistic dent creation tests, and the predictions of the associated numerical model. Tests were carried out using different pipelines. All the parameters of the study were chosen in the range of gas transmission pipelines. Dents with gouges were created with Gaz de France Research and Development Division full-scale external damage testing facility: the pipe aggression rig. The tests were simulated with the general-purpose finite element (FE) package Abaqus/Standard 6.4. A good correlation was found between the FE calculation results and experimental data, in term of residual dent depth, load and strain levels measured during the creation of the dent. This study shows that a better knowledge of the mechanical damage induced by third party activity can be achieved with the development of numerical models.

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