UNIVERSITY OF MELBOURNE
DEPARTMENT OF INFRASTRUCTURE ENGINEERING
CVEN30010 SYSTEMS MODELLING AND DESIGN
This experiment is designed to facilitate an understanding of the principles involved when water flows through a pervious material such as soil.
A. THE SAND TANK MODEL
Note: Tamp the sand lightly to obtain uniform compaction and to get rid of trapped air. Ensure no air is trapped in all piezometer tubes.
B. THE EXPERIMENT
PART I - SEEPAGE FLOW
1. Maintain a constant water level (head) difference between the two sides of the tank as shown in the diagram by allowing water to overflow through the overflow and outflow tubes. Measure the water level (head) difference.
2. Once the flow reaches its…show more content… The final result when all the dye emerges at the downstream side is shown in Figure 1.
Figure 1 : Traced Flow Lines
4. The flow velocity increases as the flow gets closer to the barrier wall and reduces as it moves away from the wall. This is because as the flow rate is constant (Conservation of mass) while the area of the flow cross section decreases when it gets closer to the barrier wall, the flow velocity increases. This is best understood by referring to the continuity equation,
Alternatively, it can also be explained by referring to the equation , where the k value is constant while the hydraulic gradient i defined by i = ΔH/L increases because the head difference ΔH is constant while the flow length L becomes shorter when it gets closer to the barrier wall.
5. The final result when all the dye emerges at the downstream side is shown in Figure 1.
6. The outflow rate is measured by using a measuring cylinder. It is measured 3 times and averaged for a more accurate result. The results are shown in Table 2.
Flow rate (l/sec)
Table 2 : Flow rate measurement
The result is converted to m3/sec per unit width as shown below
7. With the preceding flow net information, a flow net is sketched and presented in Figure 3 of the attached Appendix 1.
8. From the flow net in Figure 3, the flow rate is calculated as shown