The spill slope riprap rock size is obtained by iteration from assuming Dm and calculating
successively Equations 6.16, 6.4, 6.6, and 6.3 until the stability factor, S.F. equals 1.5. As a
first approximation, a stone size of 0.3 ft is used. From Figure 3.4, φ ≅ 40.
From Equation 6.16,
0.3 x 6 2
η=
= 0.68
(2.65 - 1) x (32.2) x (0.3)
Figure 6.38. Safety factors for various side slopes.
From Equation 6.4,
cos 20
-1
β = tan
= 32.8
2 sin 18.5
+ sin 20
0.68 tan 40
From Equation 6.6,
6.69
Previous Page
