Evaluation of the risk of marine slope instability: A pseudo-3D approach for application to large areas

This article presents a methodology developed to evaluate the instability o f submarine slopes that extend over a large area. Special attention was pai d to (1) the complex geometry (bathymetry) and the expanse of the slope, (2 ) the heterogeneity of the sediment, and (3) the distribution of the pore p ressure. The safety factor was considered as a spatially varying quantity. The General Formulation (GLE, Fredlund and Krahn 1977), which fully satisfi es equilibrium conditions, was used for evaluating the stability of the mar ine slope. The submarine slope failure, which occurred on 16 October 1979 d uring the construction of the new Nice airport, was studied in order to tes t the developed model. Geotechnical parameters were taken from experimental tests carried out by IFREMER on 19 cores extracted at different depths (fr om 27 m to 1300 m) (Cochonat, Bourillet and Savoye, 1993; Mulder et al., 19 94). Many scenarios were proposed in order to explain the cause of the Nice slope failure (Habib, 1994). In this article, two of those scenarios were tested. Simulation results are presented and discussed.