Influence of weathering and pre-existing large scale fractures on gravitational slope failure: insights from 3-D physical modelling

International audienceUsing a new 3-D physical modelling technique we investigated the initiation and evolution of large scale landslides in presence of pre-existing large scale fractures and taking into account the slope material weakening due to the alteration/weathering. The modelling technique is based on the specially developed properly scaled analogue materials, as well as on the original vertical accelerator device enabling increases in the "gravity acceleration" up to a factor 50. The weathering primarily affects the uppermost layers through the water circulation. We simulated the effect of this process by making models of two parts. The shallower one represents the zone subject to homogeneous weathering and is made of low strength material of compressive strength sl. The deeper (core) part of the model is stronger and simulates intact rocks. Deformation of such a model subjected to the gravity force occurred only in its upper (low strength) layer. In another set of experiments, low strength (sw) narrow planar zones sub-parallel to the slope surface (sw