Geoscience Reference
In-Depth Information
3. For pooled stepped spillway (end sill at the downstream end of apron):
0
:
94
d
s
D
50
¼
y
1
D
50
0
:
61
ðÞ
SN
(7)
r
2
¼
0
:
99
5 Design Procedure
The following procedure is presented to estimate the maximum scour hole depth:
1. Upon knowing the unit discharge and the height of spillway, determine the
energy loss through stepped spillway by applying one of the equations presented
in Table
2
. For example, for the case of
h
=' ¼
3
:
5, we get:
0
:
28
q
2
gH
3
1
H
¼
1
:
736
(8)
1
D
E
=
2. Determine the amount of energy downstream of the spillway from (
9
):
y
c
D
E
3
2
E
1
¼
(9)
1
=
3
q
2
in which
y
c
¼
ð
=
g
Þ
3. By simultaneously solving equations of energy (
10
) and continuity (
11
), one
can obtain
y
1
and
V
1
:
V
1
E
1
¼
2
g
þ
y
1
(10)
q
¼
V
1
y
1
(11)
4. Determine the stability number from (
4
).
5. Determine the scour depth applying the proper equation (
5
-
7
, whichever
applies).
6 Conclusion
In this study, three types of gabion stepped spillways under different flow condi-
tions and bed materials were tested. Based on stability analysis of a particle at the
point of incipient motion, a general formula was developed to predict the scour hole
depth. With the help of regression analysis technique and the use of experimental