The stability of the submarine slope due to hydrate re-formation

Abstract

The dissociation of gas hydrate leads to the accumulation of excess pore pressure and the decrease of sediment strength, which may cause the instability of submarine slopes. Aiming at the risk caused by gas hydrate dissociation in offshore engineering, this study is conducted to propose a novel excess pore pressure model by improving the Grozic-Nixon model. Combined with the actual seismic and topographic data of the submarine slope in the northern South China Sea, the proposed excess pore pressure model is employed to numerically investigate the submarine landslide induced by gas hydrate dissociation. The corresponding safety factor is also obtained with the strength reduction method. The effects of water depth and the total amount of hydrate dissociation are discussed in detail on the stability of submarine slopes. The results show that the excess pore pressure caused by hydrate dissociation increases rapidly at the beginning, then increases slowly, and finally dissipates gradually. The hydrate re-formation of hydrate blocks the pore channels and slows down the dissipation of excess pore pressure to a certain extent. Hydrate dissociation amount, water depth, and sediment depth are crucial factors affecting the stability of submarine slopes.