Small‐scale experimental simulation of talus evolution |
| |
| Authors: | Fabio Vittorio De Blasio May‐Britt Sæter |
| |
| Institution: | 1. Department of Geosciences, University of Oslo, Oslo, Norway;2. International Centre for Geohazards, Oslo, Norway;3. Present address: May‐Britt S?ter, Watercourse and Energy Directorate (NVE), Middelthunsgate 29, Oslo, Norway. |
| |
| Abstract: | We investigated a small‐scale laboratory model of a talus slope evolution. Five different size classes of basaltic rock were selected and marked with different colours. Homogenized mixtures of grains of different sizes were dropped from a fixed height onto a tilted experimental board covered with a loose granular layer. This was conducted in a series of regular sequences, and the resulting distribution on the board was studied after each sequence. At the beginning of the experiment, the grains developed a longitudinal gradation similar to natural talus slopes, where small grains settle at the top while the large ones roll down to the distal part. However, after a transient period dominated by single‐particle dynamics on the inert granular medium, the evolution proved to be more variable than expected. Due to the continuous shower of falling grains, the shear stress at the bottom of the upper granular layer increased. This resulted initially in a slow creep down slope that finally collapsed in large avalanches homogenizing the material. The slides occurred at the boundary between a weaker layer created by migration of small grains through the interstices, and marked by a vertical transition between small and large grains. We compare the experimental findings with observations from natural talus slopes, and suggest that similar experiments may be helpful in understanding the evolution of taluses. Copyright © 2009 John Wiley & Sons, Ltd. |
| |
| Keywords: | talus experimental geomorphology rockfall |
|
|
