Mudmat Foundation Design: Evaluating Non-Seismic and Seismic Conditions Across API, ISO and DNV Standards

Abstract This paper presents a comparative study of mudmat foundation design standards to evaluate their effectiveness for undrained conditions. The evaluations are performed for both non-seismic and seismic loading conditions. This study considers widely adopted geotechnical standards – API RP 2GEO, ISO 19901-4, and DNV-RP-C212. API RP 2GEO primarily uses the Working Stress Design (WSD) methodology but can also be applied using the Load and Resistance Factor Design (LRFD) methodology, as outlined in API RP 2A-LRFD. In contrast, ISO 19901-4 and DNV-RP-C212 are inherently based on the LRFD method. The WSD method applies global safety factors for bearing and sliding failure, while LRFD uses partial load and material/resistant factors, which are defined based on design situation/limit states. To facilitate comparison, design calculation templates were developed for both loading conditions, based on the methodologies outlined in respective standards. Five distinct subsea structures with varying mudmat sizes were assessed under different field conditions characterized by different soil properties, ensuring clarity in comparison. The findings offer valuable insights into the relative performance of WSD and LRFD methods, as well as variations among multiple standards under both loading conditions. Furthermore, the study highlights the standards’ adaptability to complex scenarios, enabling engineers to achieve robust, optimized, and cost-effective mudmat foundation design for subsea applications.