Question

The shear stress required to move grain on the side slopes is less than the shear stress required to move the grain on the canal bed.

(a) True

(b) False

I had been asked this question in an international level competition.

The above asked question is from Irrigation Channels Design in portion Sediment Transport and Irrigation Channels Design of Irrigation Engineering

Answer 1

Right option is (a) True

Easy explanation: The actual shear stress on the channel bed is Yw.RS while on slopes this value is given by 0.75 Yw. R.S. The following equation shows that Tc’ < Tc.

Tc’ = {(1 – Sin^2Q/Sin^2R)^1/2.Tc } where Tc’ = shear stress on the side slopes, Tc = shear stress on the horizontal bed, Q = Angle of side slope with the horizontal, and R = angle of repose of the soil.