Soil Permeability Test: Constant and Falling Head Methods, Study notes of Building Materials and Systems

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CONSTANT AND

FALLING HEAD

permeability test

CONSTANT AND FALLING HEAD

PERMEABILITY TEST

Definitions: Permeability: The ability of a substance to allow another substance to pass through it. The permeability of soil is expressed by coefficient of permeability or hydraulic conductivity (k). 𝒒 = 𝒌𝒊𝑨 Where: q: flow rate (volume / time). i: hydraulic gradient = difference in elevation / length of path = Δh/l (unitless). A: cross-sectional area for specimen.

• Apparatus:

1. Constant head test.
2. Falling head test
3. Graduated cylinder.
4. Thermometer.
5. Stop watch.
6. Rubber tubing.
7. Balance.

• Falling Head test:
• Supply water to the funnel till the specimen is saturated and remove air

bubbles.

• Allow the water to flow through sample for some time, when the funnel is

full, the water will flow out of it into the sink.

• Close the flow of water through the sample. Measure the head difference

h1 (cm).

• Open the pinch chock. Water will flow through the burette to the

specimen and then out of the funnel. Record time (t) and the head

difference h2 (cm).

• Determine the water volume (V) that is drained from the burette in (cm3).