Nielsen Saga: Analyse de la zone de glissement de l’Abefet et analyse de risque.

Nielsen Saga
Co-supervisors: Prof. Michel Jaboyedoff, Dr. Pierre Gex

The Abefet zone is situated in the Solalex-Anzeinde valley, on top of Bex in the right bank of the Rhône (canton of Vaud). According to the geologic map, the Abefet is a landslide surmounted by a zone of collapse. The Master Thesis consists of characterizing the danger, the landslide, and to make a risk analysis.

The characterization of the landslide zone was made with the following methods:

  • Geomorphology and geology: field observations, geological map and sections, and digital model of ground.
  • Geophysics: PS, EM 31, electric soundings and measures of temperatures and conductivities of waters. All those results do not confirm the information of the geologic map. There is a need of finding a new working hypothesis to explain the morphology and the geophysics measures.
  • Computing: a new delimitation of the Abefet zone was chosen. The hypothesis of a deep landslide making one system with the zone of collapse surmounted partially by two superficial landslides (slide of morainics deposits) is put.

The risk analysis part is not complete, to many data were missing. The field observations on the ground tend to prove that the zone is asleep. Leaving the principle that the deep landslide can slide again, two essays of danger maps are made, according to two scenarios of gliding and according to the elements at risk.

To conclude, the geophysics methods used, surrounded with computing methods, show their value in the framework of the landslides analysis. In relation to the landslides, the risk analysis advances that the Abefet zone is not dangerous.