[SOIL PERMEABILITY] Definition / Test to Find Permeability

we discuss whereas types of water in soil on lesson capillary water, one of them is free water ( the water which flows from one point to other by the influence of gravity ). this free water gives permeability to the soil.

we also know soil mass contain pores or holes. if these porous are interconnected its called interstices, free water flow throw it from one place to other places on soil mass. 

Permeability of soil 

From the above discussion, we can say the property of soil which permits flow of water on it Called permeability.

However the velocity of water or say permeability may depend upon how much width of these interstices, for example, coarse grain soil give high permeability effect as compare to fine grain soil, because the particle gap is large in case of coarse grain as compared to fine grain.
generally, all type of soil is permeable, if the soil is a very low permeability its called impervious soil. permeability is very important engineering property. it helps in design filter, prevent hydraulic structure piping and seepage.

constant head permeability test 

For determining the coefficient of permeability of soil mass which is relatively sufficient amount of permeability, constant head permeability test is used, it is a laboratory method for determining permeability.

Procedure -

Take the mold and measure the dia, length, weight, volume properly for future calculation.

Take 2.5 Kg of a soil sample, mix it properly and convert it into a wet soil sample, then placed into in metallic mold, and level it properly.

calculate mold mass with the soil sample.

separate some amount of sample from our prepared sample for later water content determination.

Place porous disc at top and bottom of the sample and fix it properly.

from the base of the sample connect a pipe which collects the drain water to a reservoir.

Close the upward and downward valve, and apply vacuum so remaining air drains

allow water to fill mold from the top.

Connect a constant head reservoir to the inlet sample pipe.

star stopwatch
allows water to flow through the soil till the steady stage is attained.

take stopwatch reading and measure the time is taken or water is out in what time interval.

from how much supply of water and what time taken at the end in collecting jar we can find permeability.

repeat the test at least three times and collect mean value it gives an accurate result.