Seepage Tank Lab Report 2012 Edit
UNIVERSITY OF MELBOURNE
DEPARTMENT OF INFRASTRUCTURE ENGINEERING
CVEN30010 SYSTEMS MODELLING AND DESIGN
SEEPAGE MODEL
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 steady state (i.e. when a constant outflow rate is maintained), record the elevation head (by reference to an arbitrary datum such as the base of the tank) and the pressure head at each piezometer. Also measure the water and sand levels (relative to your datum), and the dimensions (length, depth and width) of the tank.
3. By injecting a small dose of dye just below the surface of the sand (against the glass) on the upstream side, trace the path of the flow line by marking its movement with time on the glass.
4. Observe the change in velocity of the flow as it travels from the upstream sand surface to the downstream sand surface. Explain why the velocity increases as the flow gets closer to the barrier wall and reduces as it moves away from the wall.
5. Repeat the above to trace a few more flow lines with an aim to provide enough information to assist you to sketch a flow net.
Comment:
LAMINAR FLOW - note the flow through the sand is laminar as the path traced by each shot of dye is a streamline flow and is not dispersed as in a turbulent situation. Confirm this by putting a shot of dye into the sand but this time away from the glass. The dye will reappear at a mirror position on the other side of the barrier wall. Also note that
DEPARTMENT OF INFRASTRUCTURE ENGINEERING
CVEN30010 SYSTEMS MODELLING AND DESIGN
SEEPAGE MODEL
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 steady state (i.e. when a constant outflow rate is maintained), record the elevation head (by reference to an arbitrary datum such as the base of the tank) and the pressure head at each piezometer. Also measure the water and sand levels (relative to your datum), and the dimensions (length, depth and width) of the tank.
3. By injecting a small dose of dye just below the surface of the sand (against the glass) on the upstream side, trace the path of the flow line by marking its movement with time on the glass.
4. Observe the change in velocity of the flow as it travels from the upstream sand surface to the downstream sand surface. Explain why the velocity increases as the flow gets closer to the barrier wall and reduces as it moves away from the wall.
5. Repeat the above to trace a few more flow lines with an aim to provide enough information to assist you to sketch a flow net.
Comment:
LAMINAR FLOW - note the flow through the sand is laminar as the path traced by each shot of dye is a streamline flow and is not dispersed as in a turbulent situation. Confirm this by putting a shot of dye into the sand but this time away from the glass. The dye will reappear at a mirror position on the other side of the barrier wall. Also note that