Reliability analysis of upheaval buckling of offshore pipelines

Offshore pipelines are commonly buried in seabed for protection against damage, for better insulation and to prevent upheaval buckling induced by thermal and pressure loadings. The uplift resistance provided by the backfill soil is an important design parameter when determining the correct burial depth for a given pipeline. In this paper, the effect of variability in soil backfill stiffness and operation conditions on the performance of the pipeline upheaval behaviour is investigated. Variations in the soil backfill stiffness, pipe properties and the operational factors such as temperature and pressure are considered to assess the safety of the pipeline probabilistically. An optimized Latin Hyper Cube (LHC) sampling technique is used to draw the sample of soil stiffness, pipe properties and operational conditions from preassigned probabilistic distribution for each variable. Pipeline behaviour was simulated using elastic model, and the interaction was modelled using pipe-soil interaction elements using ABAQUS. The response surface method was used to establish approximate functional relationship between the input parameters and the output response. Reliability analysis of pipeline was performed using first order reliability method and simulation method. The results presented are useful to better understand the performance of offshore pipeline and probabilistic upheaval buckling assessment.