Risk Assessment for Submarine Slope Stability: Numerical Modeling of Flow around a Sliding Soil Mass

摘要

Submarine landslides present an important risk to offshore structures and related facilities such as oil and gas pipelines. Although submarine slides have many similarities to their subaerial counterparts, there are important differences. Hance (2002) conducted a comprehensive survey of submarine slides and developed an extensive database of slope failures. He reported that out of 399 slides examined, 334 occurred on slopes flatter than 10 degrees. He also reported that among a total of 434 slides, 194 slides involved the slide mass traveling a distance of 10 km or more; three slides were reported to have traveled more than 500 km. The reasons for slides on such flat slopes and with such large travel (run-out) distance are only partially understood. Hydroplaning is one possible mechanism that explains the large run-out distances exhibited by some submarine slides. This research is focused on the mechanism of slide hydroplaning and developing methodologies that can be used to predict the run-out distances of submarine slides. Such information is necessary for designers to predict the likelihood of a given submarine slide impacting a project site. Once the extent of a slide movement is known, designers will either need to design to resist the soil forces imposed by a slide or avoid the area of impact. The current research reported on here is focused in particular on the influence of the fluid surrounding a moving slide mass. Previous studies of hydroplaning of submarine slides have employed empirical equations and assumptions to describe the forces exerted by the fluid on the soil mass. This was reported on in the previous progress report for this project. Most of the empirical equations and assumptions have not been verified and in some cases there are contradictions between the theoretical models and experimental observations.