Upper-bound solutions for undrained uniaxial capacities of foldable mudmats

Subsea foldable mudmats can effectively resolve the challenges and the high expense arising from the deployment of the excessively large isolated mudmats. During service, the undrained bearing capacity and failure mechanism of the foldable mudmats depend significantly on the foundation spacing and the soil strength profiles. The numerical simulation and theoretical analysis are conducted to reveal the bearing behavior of the foldable mudmats, and a method for calculating the bearing capacity is established. The undrained failure mechanisms are illustrated for the foldable mudmats under vertical V, horizontal H and moment M, and their dependency on the foundation spacing and the soil strength heterogeneity is also revealed. Based on the revealed failure mechanisms, the corresponding kinematically admissible velocity field is built. The formulations of the upper-bound solutions are then derived for the uniaxial capacities of the foldable mudmats by using the virtual work equation and the internal energy loss rate function. A computer program is implemented for optimization. In comparison with the numerical results, the upper-bound solutions are within 9.0% higher than the numerical counterparts, which indicates the accuracy is highly credible. The outcomes have solved the insufficiency of the conventional bearing capacity theory of isolated mudmats, which is not feasible for design of the foldable mudmats.