| The debris flow is classified in three categories as the stony debris flow, mud turbulent debris
flow and viscous debris flow from the different flow mechanism. The mud turbulent debris
flow is discussed in this research. This debris flow ha some specific characteristics things.
One is the high concentrated flow with sediment on the gentle slope channel, and
some debris flow occur in short period. The occurrence condition of mud turbulent
debris flow has been not studied clearly. In this research, the theoretical occurrence
condition is obtained from the instability flow condition and Arai-Takahashi mud
flow velocity equation. The result on the roughness bottom condition is as follows.
[( ) { ( ) ( )
3 -1 -1-H- -1 -1-bks
2 - β + sinh Ï02d - sinh Ï02 d
- -------(--)-- ( )}
2 -d 2 d- - 1
- 1+ Ï0 H + Ï0 H
{ ( ) ( ) - ------(---)-}
2 d- 2 -d 2 d- 2
à 1+ Ï0 H - Ï0 H 1+ Ï0 H
- ------(---)2-]2
à 1+ Ï 2 d- - β (β - 1) -¥ -1-
0 H Fr2
here, Ï02 = (λ2aisinα)
κ2, λ = {(C-*)13 - 1}
C-1 : linear concentration, H : depth of
flow, d : particle size, ks : equivalent roughness , b=1/30, β : momentum correction
coefficient, Fr : Froude number, κ : Karman constant, Ï : dencity of solid particle,
Ïm : mean density of flow, C* : concentration of packed solid particles, C : mean
concentration.
The result indicates that if the ratio of the flow dept and particle size is less, the
occurrence is less Froude number, and if the concentration is higher, the occurrence is less
Froude number. |