CHARACTERIZATION OF SNOW MECHANICAL PROPERTIES USING A LASER ULTRASOUND: ROLE OF THE SNOW CRYSTAL

Quantifying snow mechanical properties is important for monitoring slope stability (avalanches), vehicle mobility across unknown snow terrains, and the evolution of seasonal snowpacks. To quantify the mechanical properties of snow, we developed a novel non-contacting ultrasound laser system. Our receiver laser, a PSV-400 Scanning Vibrometer by Polytec Inc, provides the capability to record ultrasonic wavefields that propagate through snow in a cold lab environment. To better understand the observed ultrasonic wavefield datasets collected on various snow samples, we control the microstructure of these snow samples since the microstructure influences wave velocity. By controlling supersaturation and temperature, different snow crystals (i.e., dendrites, needles, plates, columns, and subcategories) are made within the cold lab by an artificial snow making machine. In this research, we present the observations of the ultrasonic waves in various snow samples that are composed of different snow crystal classifications. Also, we investigate the quantified mechanical properties with cross validation from elastic waveform prediction (through physical and empirical relationships), comparison to previous studies, and accredited snow property measurement instruments (i.e., SnowMicroPen (SMP) and MicroCT scans). Lastly, we discuss the relationship between the observed velocity changes and snow crystal types.