Numerical analyses of submarine slope failure due to gas hydrate dissociation

Upon gas hydrate dissociation, following environmental changes and/or industrial activities, a vast amount of gas and a small quantity of water is generated. This can cause pore water pressure increase in gas hydrate bearing sediments, which results in the decrease of an effective stress and in the degradation of stiffness and strength of soil in a submarine slope. A method based on the Small Hydrate Concept (SHC) is proposed in order to predict the generated excess pore water pressure due to gas hydrate dissociation. The method is then used to calculate excess pore water pressure in the Storegga slide of which gas hydrate dissociation may have contributed. The slope failure that occurred at the Storegga slide is simulated by considering the predicted excess pore water pressures due to assumed gas hydrate dissociation. Since the excess pore water pressure calculated by the SHC resulted in the considerable loss of stiffness and strength in the gas hydrate zone, the submarine slope failure that occurred at the Storegga slide was successfully simulated. Results of the analyses show that the SHC can be incorporated into slope stability problems that involve gas hydrate dissociation, even though several assumptions should be made.