| dc.description.abstract | Today, Norway has 1259 road tunnels, 1185 are categorized as inland tunnels and 41 are categorized as subsea tunnels. In fact, the number of subsea tunnels has doubled in the last 20 years and entering a more challenging era as deeper and longer underwater tunnels are either already built, in progress, or planned. Keeping such complex assets available at minimal operations and maintenance cost requires effective maintenance engineering analysis to be considered during the early design and project phase. Therefore, the purpose of this thesis is to explore the state of the practice of maintenance engineering for deep underwater tunnels, specifically in Norway. To explore that, a case study method has been applied where the Rogfast tunnel is purposefully selected and analysed. Rogfast will be the deepest and longest underwater tunnel in the whole world and it is currently in the middle of the project phase. The case study has focused on the five main aspects of maintenance engineering: technical hierarchy, consequence classification, failure mode analysis, maintenance data exchange, and reliability and availability analysis. The case study has utilized data from existing tunnels, e.g., Ryfylke tunnel, Mastrafjord tunnel and Karmoy tunnel, to extract failure modes, failure rate, mean time to repair. The findings indicate a lack in the current practice of maintenance engineering at the project phase, due to the domination of safety over other consequences like availability, operating cost, and environmental impact. Considering availability, operating cost, and environmental issues provide a more realistic image of the potential operating expenditures. It will also enable the need to collect specific data categories according to standardized technical hierarchy and data exchange framework and initiate analysis regarding potential failure modes, system reliability and availability, prioritizing maintenance concepts and tasks. Therefore, this thesis proposes and demonstrates a more customised technical hierarchy and consequence classification matrix to enable maintenance engineering analysis and maintenance data exchange. It is found that the Rogfast tunnel has a unique configuration due to the roundabout at Kvitsoy that might be utilized to gain a higher level of tunnel availability. It is also demonstrated how new trends and maintenance programs like condition-based, predictive and perspective maintenance can be explored. The methodology applied in this thesis complies with NORSOK Z-008 and is well known for oil and gas sector. However, it is customised in this thesis to fit the tunnel industry. | |
