Model uncertainty in uplift resistance calculations for sandy backfills

摘要

Trenching and backfilling is one of the most practical and cost-effective methods for protection and stabilization of offshore pipelines. Defining the geotechnical properties of backfill material resulting from mechanical backfilling or jet trenching is an area of substantial uncertainty and the resistance against pipeline uplift provided by these backfills needs to be characterized accounting for these uncertainties. This paper compares the properties of sandy backfill material and the available calculation models for uplift resistance against a database of more than 300 controlled pipeline uplift tests. The model uncertainty for uplift resistance calculations is derived from a back-analysis of the uplift tests. The uncertainties on uplift resistance and mobilization distance are correlated and characterized using a joint probability distribution. The selected distributions are applied to an example uplift resistance problem. When compared against this probabilistic formulation, the factors applied to uplift resistance in pipeline analysis can be refined to lead to a more cost-effective solution.