Object
Determination of the coefficient of permeability of a soil using constant head apparatus or variable head apparatus.

Apparatus
Permeameter mould and accessories, Circular filter papers, Compaction device, Constant head reservoir, Graduated glass standpipes along with support frame and clamps, Measuring flask, Stop-watch.

Procedure for Constant Head Test
1. Take 2.5 kg of dry soil and prepare it to obtain desired water content.

2. Apply little grease on to the interior sides of the permeameter mould.

3. Keep a solid metal plate in the groove of the compaction base plate. Assemble the base plate, mould and collar. Compact the soil into the mould.

4. Remove the collar and base plate, and replace the solid metal plate with a porous stone covered with filter paper.

5. Trim off excess soil from the top of the mould and place another porous stone with filter paper on it. Attach the top cap of the permeameter.

6. Connect a constant head reservoir to the bottom outlet of the mould. Open the air vent of the top cap, and allow water to flow in and upwards till the soil gets saturated.

7. Disconnect the reservoir from the bottom outlet and connect it to the top inlet. Close the air vent and allow water to establish a steady flow.

8. Collect the water in a measuring flask for a convenient time interval. For similar time intervals, measure the flow quantity for at least three times.

9. After the test, measure the temperature of the water.

Procedure for Variable Head Test
1. Follow the same steps 1 to 6 as for the constant head test.

2. Disconnect the reservoir from the bottom outlet and connect a selected standpipe to the top inlet.

3. Fill the standpipe with water, close the air vent and allow water to flow .

4. Open the bottom outlet and record the time interval required for the water surface in the standpipe to fall between two levels as measured from the centre of the outlet.

5. Measure time intervals for similar drops in head at least three times after re-filling the standpipe.

6. At the end of the test, measure the temperature of the water.