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Measurement of permeability in situ: pit method
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The “pit method” is a simple method that can give a first idea of the permeability of a subgrade soil. For more accurate results the measurement needs to be performed by the “open-end test” method. In the “pit method” a hole 50 cm x 50 cm in area is dug down to the formation level of the structure. An thin layer (2 to 3 cm) of crushed stone is laid on the bottom. The pit is then filled with water, so as to just submerge the crushed stone. Immediately after that 5 l of water is poured into the pit and the time is measured until the water level just reaches the crushed stone.
The test is repeated at least three times.
Permeability is determined as: