Assessing progressive mechanical instability of submarine slopes caused
by methane hydrate dissociation
Abstract
Large amounts of gas hydrates exist on continental slopes, and pose a
significant risk of triggering submarine landslides, subsequently
impacting offshore infrastructures. While the infinite slope model is
widely used for submarine slope stability analysis, it overlooks the
potential for initial small failures to develop into large landslides.
Our study integrates slip nucleation with excess pore pressure during
gas hydrate dissociation, establishing a model for progressive slope
failure triggered by hydrate dissociation. Focusing on the Shenhu
hydrate site GMGS3-W19, our results show that even 1% gas hydrate
dissociation contributing to about 1 MPa overpressure can induce
progressive landslides. Notably, deeper failure surfaces with gentler
slopes and collapsible sediments require higher pore pressures to induce
progressive failure, reducing the risk of developing into catastrophic
landslides. The results indicate that the infinite slope model may
overestimate slope stability, and that submarine landslides caused by
progressive failure may occur on slopes previously considered stable,
such as the Ursa Basin in the northern Gulf of Mexico. This extension of
the infinite slope model sheds light on potential limitations in current
stability assessments, providing crucial insights for submarine
landslide studies and offshore infrastructure development.