Geoscience Reference
In-Depth Information
15
10
5
0
-5
-10
-15
-20
-25
-30
0
20
40
60
80
100
120
140
160
180
200
Distance (cm)
Fig. 5 Longitude profile of scour hole flow discharge equal to 20 L/s
4 Results and Discussion
To predict the scour dimensions downstream of the gabion stepped spillway,
experimental program was conducted. Three types of spillways with a slope of
1(V):3.5(H), were tested under different flow conditions and two bed material sizes.
The results obtained from these tests reveal that the scour hole dimensions in type
I spillway, or simple spillway, is generally larger than the other two types of
spillway. This is because the energy dissipation in pooled stepped spillway is greater
than the simple stepped spillway. By analyzing data obtained from this study, three
equations were developed by regressional method. These equations are as follows:
1. For simple gabion stepped spillway:
1
:
39
d
s
D
50
¼
y
1
D
50
0
:
95
0
:
125
ðÞ
SN
(5)
r
2
¼
0
:
97
2. For pooled stepped spillway (end sill at the middle of downstream apron):
0
:
98
d
s
D
50
¼
y
1
D
50
0
:
92
0
:
43
ðÞ
SN
(6)
r
2
¼
0
:
84
