Maria Elena Fonticoba: Etude structurale et GPR de la région de Varneralp (Valais)

Maria Elena Fonticoba
Co-supervisors: Prof. Michel Jayboyedoff, Prof. Dr. François Marillier
Assistants: Andrea Pedrazzini, Jehanne Correia-Demand

This work aims the understanding and characterization of a possible deep seated gravitational slope deformation in Sierre (Valais, Switzerland). A catastrophic rock avalanche occurred a long time ago causing the deposit of about 1 km3 of material in the Rhone valley close to the town of Sierre.

The uphill area of this collapse is the subject of this master thesis. The area is occupied by the pastures of Varneralp and underwent significant displacements. Their chronology relative to the collapse has not yet been established.

This work has two main objectives:

  • The characterization of the mechanisms and magnitude of displacements.
  • The study area is used to test the contribution of GPR to highlight fractures in deep seated gravitational slope deformations.

This study was carried out using different methodologies:

  • A structural analysis based on field observations proves the presence of deep and surface deformations. 5 joints families have been highlighted in the region. Two of them are actively involved in landslide mechanisms.
  • The creation of a geomecanical model has been used to check the chronology of deformations. The movements in Varneralp seem to appear after the collapse start.
  • 20 GPR profiles have been carried out. Two joint networks have been highlighted. They correspond to joint families which are present in the region. Despite of acquisition difficulties, the GPR has brought complementary information.