Whole Life Design: Theory and Applications of This New Approach to Offshore Geotechnics

Abstract

Geotechnical properties can evolve throughout the design life of a structure due to actions imposed during installation, the operational life or late and end of life management of an asset. Whole life geotechnical design seeks to predict soil-structure responses across the design life by considering the whole life of imposed actions coupled with geotechnical properties that evolve with each action. In contrast, traditional geotechnical design considers the ‘worst case’ single value of minimum resistance or stiffness coupled with the ‘worst case’ single value of maximum action over the design life. The emerging philosophy of whole life geotechnical design checks limit states at different stages of the ‘whole life’ against ‘current’ geotechnical properties, updated based on the processes that have occurred and the responses that have accumulated earlier in the design life. Consideration of whole life geotechnical response provides greater insight, enabling forecasting of the response of a supported structure through and beyond its design life. Insights can be applied at the initial design stage for optimal sizing; through life for assessing or predicting cumulative displacements or changes in resistance, and assumptions in the initial design against observed performance. By extension, these insights can be used to predict actual remaining design life; for re-lifing or re-purposing; and decommissioning. This paper presents the overarching philosophy of whole life geotechnical design, theory underpinning the evolution of geotechnical properties, derivation of the appropriate parameters, and some applications. This paper demonstrates the potential of whole life design, particularly to the emerging opportunities of offshore renewable energy infrastructure.

UK perspective research landscape for offshore renewable energy and its role in delivering Net Zero

“…For some limit states, such as the geotechnical capacity, the reliability can improve through the operating life, rather than decay, as gains in capacity accumulate (e.g. 'set-up' of pile capacity or consolidation hardening in soft clays, Jardine and Chow 2006, Gourvenec 2020, Laham et al 2021.…”

Offshore Decommissioning Horizon Scan: Research Priorities to Support Decision-Making Activities for Oil and Gas Infrastructure

“…• how different materials, substances and structures decompose/degrade in large or small parts over decades or centuries beyond their initial design life (Melchers, 2006;Paik and Melchers, 2014;Rosen et al, 2015); • how different seabed sediments evolve over time frames relevant to offshore infrastructure decommissioned in situ, and how loading imposed on the seabed from the decommissioned infrastructure may affect the seabed profile and properties − in turn influencing the stability and integrity of the structure (Gourvenec and White, 2017;Gourvenec, 2022b); • how the marine environment, epibenthic communities (marine growth) and other fauna impact (positively or negatively) the stability or integrity of decommissioned offshore infrastructure (Leckie et al, 2016); • how augmentation structures can be engineered to contribute the most benefit to the ecosystem in which it resides; • the technology required to assess and clean (or contain) hazardous substances for offshore decommissioning; • the technology required to monitor the impact of our interventions on the ocean environment for the long term; • the technology required to pursue recycle, re-purpose and re-use opportunities for infrastructure that is recovered to shore; and • the testing and validation required in order to achieve confidence of the sector and inclusion in industry standards (Table 1).…”

Centrifuge modelling of whole-life pipe–soil interaction in clay with different overconsolidation ratios

“…In contrast, the pipe may undergo large displacement amplitude motions during storm events, causing water entrainment in the seabed soils (Cathie et al, 2005;Gaudin & White, 2009a;Sahdi et al, 2020). Understanding the whole-life evolution of pipe-soil interaction, notably with regards to stiffness changes associated with remoulding and reconsolidation from combined effects of alternating fatigue motions and storm motions, has become a critical aspect of the improvement of pipeline design (Gourvenec, 2018(Gourvenec, , 2020Laham et al, 2021).…”