Analysis of massif fracturing during Deep-Seated Gravitational Slope Deformation by physical and numerical modeling

Both 3-D physical modeling and 2-D numerical modeling were used to analyze the development of Deep-Seated Gravitational Slope Deformations. We focused especially on the link between fracturing and morphological features such as Sagging/Sackung. Physical modeling was performed by using properly scaled analogue materials as well as an original vertical accelerator device. This device enables cyclic loading of the model, and to advance step by step in the deformation process. This technique is thus particularly well suited to analyze rupture initiation and evolution. Surface deformation is registered with a high resolution digital camera. Internal model deformation was studied by making cross-sections at different experiment stages. The failure of one or both mountain sides was observed, with a deep-seated failure zone that follows an almost circular trajectory. It intersects the surface perpendicularly in the upper part. Other fractures are generated in the moving mass in response to its motion. Fracture network becomes wider and morphological features such as counterscarps are generated. Numerical models were performed with a 2-D finite element code named Adeli. We tried to reproduce physical modeling results by using the same mechanical behaviour and parameters of the analogue material. The results reproduced failure initiation well, but poorly described moving mass deformation. Furthermore rupture initiation in the 2-D numerical models occurs more easily (e.g. for a lower acceleration value) than in the 3-D physical models, confirming the importance of the three dimensional analysis.