A Simple THC Coupled Model for Assessing Stability of a Submarine Infinite Slope with Methane Hydrates

Methane hydrate (MH) is an ice-like clathrate compound of methane molecules trapped in cages of water molecules under high-pressure and low-temperature. In shallow marine region, MHs tend to dissociate due to seafloor temperature rise and massive submarine slope failure could be triggered or primed as a result of excess pore pressure buildup. This study develops a simple thermo-hydro-chemically (THC) coupled model to quantify the excess pore pressure buildup due to hydrate dissociation, and incorporates this model into the limit equilibrium method in order to analyze the stability of an idealized infinite slope embedding a hydrate layer. The results show that the presence of the overburden layer above the hydrate-bearing layer plays two opposite roles on the stability of the slope. It serves as a barrier that hampers excess pore pressure dissipation and therefore endangers the slope stability. Meanwhile it has beneficial effects by providing overburden pressure that mobilizes additional shear resistance in the slope. For the circumstances under consideration, the potential failure surface of the slope is constrained within a narrow band at to the top of the hydrate layer.