Question

Determine the flow velocity (ft/s) a most hydraulically efficient trapezoidal channel (m=2) would be designed to carry water on a slope of 0.0015‐m/m excavated in coarse gravel with D75 of 1.2‐in (n=0.03). Consider the angle of repose for the gravel to be 40o and the critical shear stress of the coarse gravel to be 0.456lb/ft2.

Answer 1

solution: Given data from the problem ma2n=0.03 Angle of retire for the the gravel = $= 40" Water caring on slope = 0.0015mm shears fass=(T) = 0.456 lb/fx² We know that, To II- sino Substituting Trovala in above equation, Tous Site sinko *(0456) 0.71880.456 To = 0.3275 (blfa dow, To=f. R. So substituting to so, conds vale :(8=62-43) 0.3275 = (62.43X R (0.0015) 0.3275= 0.0936R 0.3275 0.0936 R = 3.497ft By applying the manning's formula :- V = + R²5 -3.492) V=2.974 falsec 12350.ools v=1.