| Measurement of Friction Coefficient on a Powder Layer and Fluid Dynamic Study |
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Application of the model to the actual debris avalanche
In
this section, the dynamic pressure model is applied to the debris avalanche of
Mt. St. Helens which occurred in 1980. In the Mt. St. Helens debris avalanche, debris-avalanche blocks
ranged from 1 m to 170 m in diameter (Voight et al., 1981), and the average density
of the source area and the deposits are 2.31´103
kg/m3 and 1.85´103 kg/m3,
respectively (Glicken, 1998). Assuming that the disk height, disk density, and
density of the powder is 100 m, 2.31´103
kg/m3, and 1.85´103 kg/m3,
respectively, the floating critical speed is
estimated as 49 m/s. The average velocity of Mt. St. Helens debris avalanche was 35 m/s and the maximum
speed was 70 m/s (Voight et al., 1983). It is considered that
the
dynamic pressure model gives a realistic value for the critical speed.
Measurement of Friction Coefficient on a Powder Layer and Fluid Dynamic Study |
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