+1 vote
in Irrigation Engineering by (75.2k points)
Calculate the ratio of the tractive critical stress to the average shear stress if the water flows at a depth of 0.8 m in a wide stream having a bed slope of 1 in 3000. The median diameter of the sand bed is 2 mm.

(a) 0.53

(b) 1.86

(c) 0.86

(d) 1.53

I have been asked this question during an online exam.

Enquiry is from Irrigation Channels Design topic in section Sediment Transport and Irrigation Channels Design of Irrigation Engineering

1 Answer

0 votes
by (106k points)
The correct option is (a) 0.53

The explanation is: The critical tractive stress is given by (d < 6 mm) –

Tc = 0.155 + [0.409 d2/(1 + 0.177 d2)^0.5]

= 0.155 + [0.409 x 22/(1 + 0.177 x 22)^0.5] = 1.40 N/m^2.

The average shear stress = Yw. RS = 9.81 x 0.8 x 1/3000 = 2.616 N/m^2

Ratio = 1.40/2.616 = 0.53.

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