Investigations of high-speed avalanche dynamics and Hugoniot of ice by the high-speed impact experiments of snow

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High-speed impact experiments of snow and ice were conducted in a large cold room maintained at -18ﾟC.A light gas gun was used to impact an ice projectile (15 mm cylinder with a round cap of radius 8 mm) on snow and ice plates. The impact speed was varied between 50 and 600 m/s. Observations of crack growth in the ice target was possible by eliminating reflections from walls. The impact phenomena were photographed with an image-converter camera at 200,000 and 500,000 frames per second. The lighting system used was Schlieren and shadow photograpy.From the photographic observations, the following results were obtained. In the impact experiment between an ice projectile and ice plate, cracks developed semicircularly, and the propagation velocity of craks amounted to roughly 3 km/s when the impact speed was 139 m/s. The propagation velocity varies between 2.1 and 4.0 km/s at the impact speed of 139-528 m/s.In the high-speed impact experiments between an ice projectile and snow paltes (thickness of 3,5,10,20,30 mm and porosity of 15 and 30%), it was found that the free surface particle velocity decreased with distance and that of snow was larger than that of ice at the same impact velocity.