Observation of the microstructural evolution of snow under uniaxial compression using X-ray computed microtomography

Abstract

The relationship between snow microstructure and its mechanical properties is crucial for modeling the microstructural cause of snow avalanches. In this paper, the knowledge gap between snow microstructural evolution and overburden is bridged by combining compression tests with X-ray computed microtomography (micro-CT). Continuous compression tests and interrupted compression tests were performed on three types of snow (fresh low-temperature snow, fresh high-temperature snow, and sintered low-temperature snow with densities ranging from 100 to 350 kg/m3) to investigate the effects of initial structure on both the stress-displacement curve and structural changes during the compression test. Three-dimensional micro-CT images and scanning electron microscopy images showed that well-connected structures of sintered snow contribute to a more rapid stress increase during deformation. By combining the analyses of the specific surface area, structure model index, and structure thickness, it is shown that compression tests at a fixed temperature, loading rate, and density snow metamorphism can be regarded as an accelerated pressure sintering process. However, when extremely low-density snow (50 kg/m 3) was subjected to compression testing, the same evolution of structure parameters was again found, but fracture of snowflakes was also observed. The overall process of low-density snow deformation can be explained as a combination of fracturing and sintering but with the sintering predominating. Key Points Sintered snow has more rapid load increase during compression test Snow metamorphism under overburden is an accelerated sintering process Low-density snow under compression has both sintering and fracturing processes ©2013. American Geophysical Union. All Rights Reserved.