Assessment of Ageing Soil Effects on the Structural Integrity and Life Extension Feasibility of Ageing Offshore Jacket Platform

Abstract The stability and strength of the seabed soils supporting offshore jacket platforms are vital to preserving their long-term performance and structural integrity. As offshore platforms operate exceeding their intended design life, the effect of ageing soils supporting the structure presents significant challenges in determining the feasibility of platform life extension. However, extensive studies on assessing the ageing of offshore jacket platforms and their life extension in relation to ageing soil conditions are still limited. This study evaluates the effect of soil ageing on pile-soil interaction and its implications for the structural integrity of an ageing offshore jacket platform, which is critical for evaluating platform life extension. In the evaluation of Reserve Strength Ratio (RSR) and Probability of Failure (PoF) of the observed structure, ageing effect is considered by applying upper and lower soil capacities covering as sensitivity study. Through numerical modelling and probabilistic analysis, this study demonstrates that increasements in soil stiffness and strength impacted from soil ageing, can affect the platform’s structural integrity by raising the collapse base shear an average of approximately 5%, as reflected in the RSR and might be the benefit in reducing the risk of structural failure. The findings emphasize the importance of incorporating the effect of ageing soil into structural assessments to define global performance of the structure and support recommendations for enhanced platform inspection and monitoring strategy, updated soil reports, risk-based inspection strategies to inform life extension decisions.