PERMEABILITY, FLOW NETS AND DARCY'S LAW
The apparatus is a transparent-sided tank, mounted on a steel-framed bench with worktop.
The tank is clear so students can see the flow patterns. The sides are plate glass to resist abrasion from the permeable medium. The rear of the tank contains pressure tappings. Each tapping has filters that stop any unwanted particles. The tappings connect to a bank of piezometer tubes at the side of the apparatus which allow measurement of the head distribution along the tank.
Removable stainless-steel mesh baffles at each end of the tank hold the permeable medium (usually sand) in place. At each side of the baffles are end compartments with adjustable overflow pipes for setting the water levels at each end of the model. The top of the tank is open to allow students to fill the tank and set up model structures.
Supplied are clear, self-sealing plates for students to build models of sheet piling, walls and simulated dams. Included is a dye-injector system to help show flow lines. Around the front edge of the glass tank are scales to help students position and measure flow nets correctly. The self-contained apparatus needs only a mains water supply and drain.
Learning outcomes
- Determination of seepage beneath a structure
- Construction of flow nets and determination of coefficient of permeability
- Flow under a sheet pile and determination of critical seepage force at which ‘piping’ occurs
- Seepage flow under an impermeable dam
- Flow through an earth dam with and without a toe drain
- Drawdown in horizontal flow (simulation of ground water flow into a river or well)
- Determination of uplift pressures on structures such as building foundations
- General studies of seepage and drainage
- Flow through a porous medium (Darcy’s law)
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PERMEABILITY, FLOW NETS AND DARCY'S LAWPermeability, Flow Nets and Darcy's Law Experiment