Insight into Pipeline On-bottom Stability, DNV RP F109 and DNVGL RP 114

Abstract

Abstract On-bottom stability of pipeline is a one of the key factors that affects the design and installation methodology of subsea pipelines. With ever increasing demand for energy, the need for new pipelines in harsher seabed conditions is on the rise and hence accurate on-bottom stability assessment of pipelines plays a vital role in cost effective pipeline design and ensures the long-term integrity pipelines. The recommended guideline DNV RP F109, "On-bottom stability of assessment of submarine pipelines" and American Gas Association/Pipeline Research Council International (AGA/PRCI) stability methodology are the most commonly followed guidelines in the industry for the on-bottom stability assessment. This paper provides insight into on bottom stability assessment, effect of soil classification system on on-bottom stability assessments and compares results from DNV RP F109 and AGA/PRCI methods. It is often assumed that the seabed is stable while undertaking pipeline on-bottom stability of pipelines. However, this may not be case due to seabed mobility and wave induced liquefaction, especially in sandy seabeds. Therefore, insight into how to evaluate the seabed mobility and wave induced seabed liquefaction is provided in this paper. Results from parametric study of on-bottom stability of a typical pipeline are presented to highlight the key influence of seabed classification on the on-bottom stability assessment results. Seabed mobility and wave induced liquefactioin results are presented in graphical form such that they can be assessed quickly for Front End Engineering Designs (FEED). Comparison of soil models from newly released DNVGL RP F114 with that in DNV RP F109 is also presented and discussed. The results presented in this paper are a vital source of information for all pipeline design engineers.