Lateral spreading processes in mountain ranges: Insights from an analogue modelling experiment

The results of a study on gravitational induced lateral spreading phenomena are here reported. The lateral spreading processes are widely represented in the Italian Apennines due to the widespread overlapping of stiff rock masses on more ductile ones. The stress-strain evolution of these processes was investigated by combining an analogical and a numerical modelling approach. The analogue modelling reproduced the evolution of a carbonate ridge thrust over a clayey flysch with reference to the case-study of Mt. Roccatagliata-Mt. Sant'Angelo ridge. The rock mass juxtaposition was reproduced in a laboratory experiment by overlapping a brittle concrete on a viscous ductile material; these materials were selected with rheological properties, physically scaled with respect to the natural rock mass prototypes. The spreading phenomenon was modelled by opening horizontal panels in sequential stages and monitoring the resulting stresses within the ductile material during the experiment. A stress-strain modelling was also performed by an FDM numerical solution; this modelling replied the laboratory experiment by testing the use of different rheological constitutive laws. The resulting stresses and morphological evolutions are comparable with the analogical laboratory experiment only if a time-dependent rheological behaviour is assumed for the ductile material. The results show that lateral spreading processes can be properly investigated by combining analogue and numerical modelling techniques which take into account the viscous-plastic behaviour of the used materials.