Armfield S12-MKII, Инструкция по эксплуатации

Страница: 52 / 67

Armfield Instruction Manual
48
The experiment may be varied by altering the position of the obstruction within the
width of the channel, and by using multiple obstructions.
Results
Diagrams of the channel planform, flow obstructions, flow turbulence and scour
features should be made for each set of conditions.
Valley slope
(%)
River discharge
(l/min)
Sediment yield
(g/min)
One method of making diagrams of the channel requires two rulers or measuring
sticks, both of which must be rigid and one of which must be at least 1 metre in
length. This long ruler should be laid across the top of the tank from one side to the
other, parallel to the end, and then moved along the tank in steps of 10cm. At each
position, the second ruler is then used to measure the distance from the top line of
the tank to the sand surface, in steps across the entire width of the tank. Reference
points should be recorded for notable features such as the positions of the channel
sides and any flow turbulence and eddies. More detailed sketches should be made of
scour hole geometry.
Conclusion
Describe the way in which the shape of an obstruction influences the amount of
scouring of the river bed and sides. If multiple obstructions were investigated,
comment on the effect of spacing, both across the channel and down its length. Can
any conclusions be drawn from the experimental model on the best positioning of
bridge piers across a river to minimise scour, and on the best cross-section for the
base of such piers? What other factors may need to be considered when designing
an artificial river structure such as a bridge or groyne?