Hydro-mechanical modelling of the process system acting on a coastal landslide

Malet, J.-P. (1), Spickermann, A. (1), Lissak, C. (2), Maquaire, O. (2)

(1) Institut de Physique du Globe de Strasbourg, CNRS UMR 7516, Université de Strasbourg, 5 rue Descartes, F-67084 Strasbourg Cedex, France
(2) Laboratoire LETG-Geophen, Littoral, Environnement, Télédétection, Géomatique, CNRS UMR 6554, Université de Caen-Basse-Normandie, Caen, France

In Normandy, the 12 km long Pays d’Auge coastal slopes are periodically affected by rotational and translational landslide since several centuries. These landslides occurred in marly formations covered by chalks and quaternary deposits. In January 1982, major landslides have caused several damages (roads, destroyed houses) and a retrogression of the hillslopes. The affected slopes are the Cirque des Graves at the West of the city of Villervile and the Fosses du Macre at the East of the city of Cricqueboeuf. Since this major event, the Cirque des Graves landslide is intensively monitored through campaigns of measurements and permanent instrumentation. In particular, a representative cross-section, of nearly 200 m in length, located in the most active sub-unit of the landslide is monitored by permanent GNSS, inclinometers, soil humidity sensors and piezometric sensors, and a detailled geotechnical cross-section is available. Further, the analysis of the relationships between effective rainfall, groundwater table variations and landslide displacements indicates clearly that the landslide mechanism is controlled by slope hydrology that further influences the mechanical response of the slope. The objective of this work is to simulate the observed landslide behaviour due to external hydraulic and/or mechanical perturbations using the multi-physics modelling framework Abaqus. Stress-strain simulations are performed using a visco-plastic rheology to represent the bevahiour of the slip surfaces developed in the marly formation. The different deformation analyses allow to estimate the influence of triggering factors on the slope response.