Les mouvements de versant de Séchilienne (Isère). Prise en compte de Théritage structural pour leur simulation numérique

Application of a Terrestrial Laser Scanner (TLS) to the Study of the Séchilienne Landslide (Isère, France)

“…Main schistosity is oriented N20°E with a subvertical dip angle. The landslide area is cut by several faults (Figure 1) and three sets of fractures [13]: Subvertical N20°E as parallel fracture set to the schistosity; subvertical N120°E; and N70°E 80°N. These N70°E 80°N fractures (main set of fractures in the RC area) form slices in the rock mass as shown by uphill facing scarps (up to 100 m long) associated with depressions in that direction.…”

“…These targets enable merging the four scans acquired from each scan position [13] and to georeference the total point cloud.…”

“…The entire RC area is moving down in a N150°E direction which is almost perpendicular to these massive N70°E structures. According to previous models developed [13], a first order conceptual interpretation ( Figure 10) can be drawn from the measurements of surface displacements and the main geological setting of the N70°E structures in the RC zone. Without clear information about their dip angle, N70°E structures are presumed to have a northern dip cut varying with depth.…”

“…Evolutions of the N70°E structures were identified as the main factor of instability in RC. Incidentally, numerical models with northern dip for N70°E structures have been developed [13,25] explaining depressions between N70°E structures. With TLS acquisitions, it is the first time that the evolution of each N70°E structure in RC can be described.…”

“…The Sé chilienne site is part of the external Belledonne chain, which mainly consists of micaschists [13]: Rocks forming the moving slope belong to an old sedimentary formation made of sandstones and siltic layers named -Sé rie Satiné e‖ [13]. Main schistosity is oriented N20°E with a subvertical dip angle.…”