Two-level quantitative risk analysis of submarine pipelines from dropped objects considering pipe–soil interaction

Pipeline damage from platform dropped objects is a significant risk for offshore installations. Pipelines are usually buried to reduce the risk. Previous methodologies and standards haven't addressed the nonlinearity and pipe–soil interaction in risk analysis. Moreover, the appropriate burial depth remains undetermined, causing unnecessary investment or potential risk. To provide a comprehensive evaluation, this study presents a two-level quantitative risk analysis for pipeline failure. Finite element analysis and probabilistic approaches are coupled to quantify the effects of nonlinearity and pipe–soil interactions and the underlying uncertainties of related factors. At the macro-level, a frequency-consequence procedure is developed to assess the spatial distributions of pipeline failure probabilities, which are then utilised in the preselection of pipeline routes and post-design risk assessment. At the micro-level, based on a secondary development technology, a reliability-based framework is proposed and verified, providing insights into the failure mechanisms of each collision event and investigate the variabilities of related parameters. These methodologies can be used as guidelines for pipeline risk analysis and protection, avoiding excessive conservatism by considering pipe–soil interactions (seabed flexibility and burial depth). The relationships between protection measures and failure probabilities are established to provide clues for the selection of optimal burial depth. •A quantitative analysis framework on pipeline collision risk is proposed.•The pipe-soil interaction and nonlinearity in risk analysis are introduced.•The proposed framework removes the conservatism existing in previous methods.•The relationship between burial depth and failure risk is quantified.•Secondary development technology of FEM-probabilistic method coupling is provided.