Response of an Uncased, Buried Steel Pipeline Crossing Railway Embankments at Various Crossing Angles

The growth of railways and highways has increased the number of intersections with buried pipelines, which must withstand both soil weight and live loads from passing traffic. The incidents of fire breakout and fluid leakage from carrier pipes have been witnessed at some railway embankment crossings. Although API 1102 provides design recommendations, there are still many bounding limitations in terms of the angle of crossing, burial depth, soil type, pipe diameter to thickness ratio, among others. To address some of these limitations, a numerical investigation of the behavior of uncased buried pipelines has been conducted. The results indicate that the maximum Von Mises stress in the pipeline occurs at a 90° crossing angle (at crown position). While the circumferential stress has less variation, the longitudinal stress increases as the crossing angle decrease from 90° to 0°. The observed longitudinal stiffness factor is higher for the 0° crossing angle. The study also infers that the ovalization, which could lead to ring buckling of the pipe cross-section, increases with a decrease in burial depth and an increase in embankment height.