Abstract: The foldable mudmat rigidly connected by two adjacent foundations is a new type of infrastructure used in subsea production systems. During service, the stress state is a multi-degree of freedom-combined loading mode, and the bearing characteristics are affected by the foundation spacing and soil strength heterogeneity of the seabed. The undrained capacity of the foldable mudmats is investigated in three-dimensional numerical analysis by means of the finite element software ABAQUS, the results are presented in terms of the ultimate limit states under pure vertical or moment loading, and the failure envelopes under combined V-M loading, and the influence of the foundation spacing and soil strength heterogeneity of the foundation soil are systematically analyzed. Based on the finite element calculated results combined with failure mode analysis, the formulas for the vertical bearing capacity, moment capacity and V-M failure envelope of the foldable mudmats are proposed to provide evidence for stability analysis of the foldable mudmats.