Design Criteria for Upheaval Creep of Buried Sub-Sea Pipelines

Abstract

A new criterion is presented for the design against upheaval creep of buried hot marine pipelines. Observations have substantiated that the gradual upheaval of an “imperfect” buried pipe can take place when subjected to variable temperature and pressure loading. The imperfection amplitudes can thus grow until at a certain stage the overburden is insufficient to prevent upheaval (snap) buckling of the pipe. This paper shows that the “classical” upheaval buckling analysis is not applicable when designing against upheaval creep failure of an “imperfect” pipe. A new design procedure is established which determines the uplift resistance required to keep the upward movement of the “imperfect” pipe below critical values, thus preventing a progressive upheaval failure. The various aspects to be considered during the design and installation of a pipeline are highlighted, resulting in requirements for acceptable out-of-straightness of the pipe.