NUMERICAL ANALYSIS OF UPHEAVAL BUCKLING OF PIPELINE ON THE UNEVEN SEABED USING FINITE ELEMENT METHOD

In recent years, application of offshore pipelines has been increased due to increase in energy demand in the industries, and need to explore new oil and gas fields. This issue leads to transfer explorations of new hydrocarbon sources to the deep waters. Production and discovery of oil and gas in the deep waters needs to long pipelines. More importantly, design of these pipelines have generated many challenges for big corporations and engineers. Pipelines play an important role in the offshore transportation system. For the time being, it is the cheapest and the best transportation way of hydrocarbons from deep waters to the shore and refineries. In accordance with DNV-RP-F110 (2007) [1], in deep water and on the uneven seabed, there are two types of buckling possibility; lateral buckling and upheaval buckling. These two modes of buckling are kind of global buckling. Also upheaval buckling can be occurred in buried situation or in the trench. In deep water, by imposing the initial imperfection, increasing the temperature and internal pressure; compression axial tensions develops on the pipeline wall thickness and shape of pipeline is changed when compression load is more than soil resistance. Subsequently, this issue will be led to release of inner accumulated tension that it has been made by interaction between pipeline and seabed. Many researchers have studied on this topic and they have obtained good results, but all of them have neglected one or some parameters for simulating and analyzing due to easier analysis [2, 3, 4, 5, 6, 7]. In this research, an attempt has been made to verify the upheaval buckling of pipeline on the uneven seabed using ABAQUS software. Several parameters including pipeline length, pipeline weight, external and internal pressure, initial imperfection and operating temperature more have been considered.