Equation 2 shows that, as the length of the accumulation increases, the force

level reaches an asymptotic value that is related only to the water drag and cover

width (friction and lateral stress coefficients being constant). Kennedy's formula-

tion, however, neglected the streamwise component of the weight of the pulpwood

and assumed that the depth (and therefore water shear) was constant. Consequently,

the force through the jam would be independent of the thickness and bulk density

of the pulpwood accumulation.

Berdennikov (1964) investigated the forces exerted on an ice boom retaining an

ice accumulation. While he initially identified the weight component of the ice mass

parallel to the water surface as one of the forces to be considered, he dismissed this

force and the hydrodynamic pressure against the leading edge of the cover *f*1 as

being so small as to be negligible. His expression for the normal stress in the ice

field σx, assuming that σx = 0 at *x *= 0, is

-2λ*k*0x

σx =

1 - exp

.

* B *

(3)

2λ*k*0η

Pariset and Hausser (1961), then Pariset et al. (1966), advanced Kennedy's for-

mulation by including the streamwise components of the weight of the cover and

an assumed "cohesive" stress acting between the ice and the banks. Summation of

the forces acting on the ice cover (Fig. 13) gives

(4)

where

force per unit width acting in the downstream direction

τc =

cohesive stress per unit area at the banks

η =

cover thickness

downstream component of the weight of the cover per unit area and *B*, *k*0,

λ, and τi are defined as above, so that

(5)

where

specific gravity of ice

ρ =

density of water

acceleration due to gravity

slope.

f3

F+ F

F

(τ c η + k o λ F)

τi

13

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