In recent years, the suction bucket foundations have been widely used in marine engineering. Since methane hydrate bearing sediment (MHBS) is extensively found in outer continental margins, there will be more complex impacts on the installing behavior of suction caissons. In this paper, a coupling method based on “FLAC3D + PFC3D” and “Tough + Hydrate” is proposed to solve the T-H-M-C problem existing in the installation of suction bucket. PFC3D (Particle Flow Code 3D) is used to simulate the large deformation of suction caisson installation, and a part of model is replaced by FLAC3D elements to improve the calculation efficiency. Tough + Hydrate is used to analyze the dissociation of methane hydrate. It is proved that the proposed coupling method can simulate the installation problem of the suction caisson in MHBS successfully. It is found that the existence of under-pressure can significantly reduce the penetration resistance because of seepage. In the MHBS case, the penetration resistance is affected by both seepage and the dissociation of MH. On one hand, the seepage itself can reduce the penetration resistance. On the other hand, the under-pressure will decompose and desaturate hydrate, which diminishes the strength of the sediment and facilitates the penetration process. In addition, a higher height of the soil plug appears in MHBS case than in clean soil case.
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