Simplified analytical method for bell-spigot jointed pipeline response to normal faults using two-layer Winkler foundation model

Abstract

Normal faults can severely affect the performance of jointed pipelines. Previous analytical methods based on the finite difference approach generally assume that the pipeline is placed on homogeneous soil springs, failing to account for the complex soil resistance issues under normal faults. This study proposes an analytical method for predicting the response of bell-spigot jointed pipelines subjected to a 90° normal fault with orthogonal pipeline-fault crossing that incorporates distinct bearing and uplift soil springs; axial extension of bell-spigot joints is neglected. The method calculates the pipeline bending strain and joint rotation angle, which are assessed against the results using two sets of large-scale experimental data. It is found that the design standard recommended soil spring calculation methods overestimate the soil resistance, and correction factors for both bearing and uplift soil springs are required to achieve satisfactory prediction. Using the calibrated analytical method, the failure modes of jointed ductile iron pipelines with different segment lengths under three types of sandy soils are predicted. The results show that the maximum rotation angle and bending strain of the pipeline increase linearly with the fault displacement. Short-segment pipelines are more prone to angular failure, while long-segment pipelines are more likely to experience bending failure. Additionally, reducing the friction angle of sandy soil can effectively prevent pipeline bending failure.