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Sebastien Garziglia, IFREMER Centre de Brest (France)
Nabil Sultan, IFREMER Centre de Brest (France)
Antonio Cattaneo, IFREMER Centre de Brest (France)
Michel VOISSET, IFREMER Centre de Brest (France)
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A recent study conducted by Sultan et al (2007) in the detachment fold belt of the deep-water Niger delta reveals the occurrence of three submarine landslides expressed on the present day seafloor. These landslides lie on a mean slope angle of about 2° and are all located above the hinge of an anticline structure. Sultan et al (2007) used the cylindrical cavity expansion theory to simulate the compressional structure movements and to evaluate the strength generated within the upper sediment layers. Slope stability assessment conducted with the three dimensional slope stability model SAMU-3D has demonstrated that compressional deformation of the anticline could be a triggering mechanism for the observed slope failures in the area (Sultan et al., 2007).
These results leave an open question on how the displacement-rate of the compressional anticline affects the slope susceptibility to failure in the area. In an attempt to answer this question a further study is conducted using PLAXIS finite element code with two different constitutive models: Mohr-Coulomb and a more advanced constitutive model considering the Soft Soil Creep model which enables to account for stress-dependent stiffness and secondary (time-dependent) compression of the sediment. Different displacement-rates generated by the compressional structure movements are considered and applied at the base of the calculation domain in order to point out the importance of the time factor in terms of excess pore pressures, sediment deformations, and slope stabilities.
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