Abstract

Offshore/onshore oil and gas pipelines are commonly buried in soil to protect the pipeline from external damage (in offshore due to trawlers or anchors), for better thermal insulation provided by the soil and to prevent the upward bending of the pipeline, known as upheaval buckling (UHB) caused by pipe expansion. In order to avoid upheaval buckling, the pipeline has to be buried deep enough such that the soil cover is sufficiently robust to resist the pipe upward movement. Failure to provide sufficient cover soil can lead to upheaval buckling failure of the pipeline. Repair and loss in revenue costs can run into millions of pounds, not to mention the environmental damage caused by the pipe leak.

The talk will present the design methodology used in UHB design and highlight the uncertainties faced by the design engineers when calculating the uplift resistance of a buried pipeline. Research results over the last two decades have provided better understanding and insight into the failure mechanisms associated with upheaval behaviour of pipelines. However, the majority of the results have been from either small scale lab testing or centrifuge testing. Hence, one of the key design parameters, the mobilisation distance, has not been fully understood. Gap in knowledge with regard to mobilisation distance will be highlighted and results from full scale testing will be compared with centrifuge test results and literature data.