Three-dimensional physical modeling of deep-seated landslides: New technique and first results

[1] A new technique for physical ( experimental) modeling of landsliding and the first results are presented. The technique is based on the use of new elasto-brittle-plastic analogue materials and an original vertical accelerator device enabling an increase in the "gravity acceleration.'' This technique allows slope stability to be addressed in a full three-dimensional, large strain formulation involving brittle and ductile rupture of the material. Three sets of experiments on the scale of a mountain similar to 1 km high are presented. The first one was designed to define the conditions and the mode of instability ( deformation) in a homogeneous unfractured model. Instability occurs when the effective compressive strength sigma(c) of the mountain is as small as 10(7) Pa, i.e., about 1 order of magnitude lower than the typical strength of small rock samples. The deformation and rupture involve the whole mountain and correspond to well-known, deep-seated gravitational slope deformation. In the second set of experiments we introduced inherited "tectonic'' faults, which considerably reduce mountain stability, with deformation again developing at the mountain scale. The introduction of the local small-scale fractures and weak zones in the last set of experiments resulted in smaller-scale shallow landslides.