Parametric study of buried steel and high density polyethylene gas pipelines due to oblique-reverse faulting

Abstract

A numerical study is carried out on buried steel and high density polyethylene (HDPE) pipelines subjected to oblique-reverse faulting. The components of the oblique-reverse offset along the horizontal and normal directions in the fault plane are determined using well-known empirical equations. The numerical model is validated using the experimental results and detailed finite element model of a 114.3 mm (4″) steel gas pipe subjected to a reverse fault offset up to 0.6 m along the faulting direction. Different parameters such as the pipe material, the burial depth to the pipe diameter ratio (H/D), the pipe diameter to wall thickness ratio (D/t), and the fault–pipe crossing angle are considered and their effects on the response parameters are discussed. The maximum and minimum compressive strains are observed at crossing angles of 30° and 90°, respectively. It is found that the dimensionless parameters alone are not sufficient for comparison purposes. Comparing steel and HDPE pipes, it is observed that HDPE pipes show larger compressive strains due to their lower strength and stiffness. For both steel and HDPE pipes, peak strains increase with increasing D/t and H/D ratio for a constant pipe diameter and fault offset. For a given H/D ratio, compressive strains increase with increasing D/t ratio in HDPE pipes, while in steel pipes considered in this study, this effect is negligible. Finally, the peak strains of the pipes are compared to those suggested by Canadian Standard Association for Oil and Gas Pipeline System, CSA Z662.