Undrained horizontal-torsional resistance of subsea foldable mudmats

• Published in: Ocean engineering Vol. 338; p. 121867
• Main Authors: Li, Xiaolong, Feng, Xiaowei, Sun, Liqiang, Han, Congcong
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2025
• Subjects: Failure mechanisms; Foundations; Offshore engineering; Spacing; Torsion; Upper-bound solutions; Foundations; Spacing; Offshore engineering; Upper-bound solutions; Torsion; Failure mechanisms
• ISSN: 0029-8018
• DOI: 10.1016/j.oceaneng.2025.121867

For deepwater oil and gas developments, the constraints by the installation vessels over the size of the single mudmats can be avoided by the foldable design. The plastic limit analyses (PLA) are performed to calculate the undrained horizontal-torsional sliding resistance of the foldable mudmats which often represents the governing load case. The results of PLA and finite-element analyses (FEA) are presented as a function of foundation spacing, embedment depths and soil shear strength profiles. The maximum discrepancy of the predicted capacities between the two methods falls within 16.5 %. For a given foundation spacing, the difference becomes more pronounced for foundations with deeper embedment in uniform soil. The failure mechanisms of the PLA compare well with the soil displacement contours of the FEA. The interaction of the two mudmats at close spacing results in an increase in the uniaxial and biaxial horizontal sliding resistance due to the arch-shaped mechanism, while at wide spacing, the interference effects vanish. For combined horizontal-torsional sliding, the enhancement in the capacity at close spacing is attributed to the coupling effects of arch-shaped mechanism and increased lever arm due to the rigid connections, whereas only the influence of increased lever arm is critical at wide spacing. •A general failure mechanism of the foldable mudmats subject to combined horizontal load and torsion.•Calculation of the undrained horizontal-torsional sliding resistance.•Coupling effects of foundation spacing, embedment depths and degree of soil heterogeneity.•Principal failure mechanisms that govern the capacity of the representative loading paths.•Comparisons of the analytical solutions with the results of finite-element analysis.