Development and calibration of interaction diagrams to predict the geotechnical failure of subsea pipelines in normally consolidated clay

Subsea pipelines are used for the transport of hydrocarbons from offshore oil platforms, where they are, to onshore processing facilities, where they are prepared to be distributed to the market. Pipelines from production site to shore, is one of the most efficient and economic mean to transport. They are also very versatile, as they are also used to pump soil during dredging/land reclamation projects when nearshore. In addition to transportation, they are used in other subsea operations such as subsea cabling, feeders to subsea wells, casing to subsea umbilical. Therefore, it is essential to have a clear understanding on its stability in its environment. Due to global warming and the transition towards renewable forms of energy, pipeline sector has expanded in various market, it can play a crucial role in casing subsea electrical cables to transport electricity from offshore renewable fields, like wind farms or floating solar panels, to shore or to transport hydrogen fuel. The thesis investigate the geotechnical aspects of pipeline beahviour and develops new failure envelopes clayey deposit was based on the Finite Element Limit Analysis (FELA) method with OPTUM G2. Calibration of failure envelope equation parameters was performed using the Non-Linear Least-Square approach. Finally, the failure envelope is applied to determine a preliminary design of a pipeline on a soft clay deposit, casing electrical cables, in the Central Adriatic Sea.