| Measurement of Friction Coefficient on a Powder Layer and Fluid Dynamic Study |
Apparent friction coefficient is the ratio of the height of highest point on the breakaway rim (H) to the horizontal projection of distance form this point to the tip of the deposit (L). An apparent friction coefficient is equal to the friction coefficient under the condition that 1) the friction coefficient is constant during moving, 2) the kinetic energy of debris avalanche is lost only by friction and 3) the pathway is the minimum path. An apparent friction coefficient is empirically used as an indictor for the fluidity of a mountain collapse since it is obtained easily and gives information of significance (Hsü, 1975).