Failure mechanics of snow layers through image analysis

This paper is devoted to analyze the micro-mechanical behavior of snow layers subjected to shear force. A number of cold laboratory tests were performed on reconstructed snow samples on a specially designed direct shear apparatus and the loading process leading to the failure was recorded by a high-speed camera. The specimens were prepared under isothermal conditions and immediately tested in order to avoid sintering between the snow grains. Image analysis techniques (digital image correlation and particle image velocimetry) were applied on the camera records in order to obtain the snow strain history (during the loading phase) and the velocity field after the failure. Sequences of jamming and unjamming phases with the formation of vortices were observed. These observations confirm that snow layer failure process is similar to the one observed in other natural materials (e.g., sands). These results give an insight into triggering and failure propagation in a weak snow layer.