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Plan
flow
6.00
Section
1.00
GATE
Ho
Ytw
GABION
Y1
SAND
Fig. 2 Plan and section view of the experimental flume
TYPE 1
0.375
0.4375
0.4375
0.7500
0.125
0.125
0.125
0.125
2.000
TYPE 2
0.3750
0.3750
0.1250
0.125
0.0625
TYPE 3
Fig. 3 Three types of stepped spillway tested in this study
high, in the hydraulic laboratory of the Shahid-Chamran University. Figure 2 shows
the plan and section view of the flume. Three types of gabion stepped spillways
(Fig. 3 ) were tested under different flow conditions. Two different sizes of bed
materials, A and B, were placed inside the gabion mesh and three types of bed
materials, C, D, and E, were placed downstream of the spillway. Figure 4 shows
the size distribution of these materials.
After placing the desired gabion spillway and bed material, the required flow
discharge was established by simultaneous adjusting of the inflow valve and the
downstream gate. In all tests, the flow type was the nape or pooled flow. Upon the
establishment of the desired flow and tail water depth, the flow characteristics and
the scour depth were measured. During the test, when little or no removal of bed
material from the scour hole was observed, usually 90 min from the start of the test,
the pump was shut down. At the same time, the downstream gate gradually was
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