Permeability of soil -
The property of a soil which permits flow of water or any other liquid through it, is called permeability.
Application for soil -
It is a very important engineering property of soil. It is essential in a number of engineering problems, such as settlement of buildings, yield of wells, seepage through and below the earth structures. It controls hydraulic stability of soil masses. It is also required in the design of filters used to prevent piping in hydraulic structures.
Determination of coefficient of permeability -
Laboratory methods
(a) Constant Head Permeability Test.
(b) Falling Head Permeability test.
(a) Apply in Darcy's Law, we get q=kiA
Q/t=K.h/L.A
K=QL/Aht
A = Area of cross section of soil specimen.
L = Length of soil specimen.
h = Constant head.
The constant head, h, causing flow is the vertical distance between water levels in the overhead and bottom tank. After ensuring that the soil specimen is fully saturated the flow has become steady, the quantity of water, Q flowing through the specimen known interval of time t is found.
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| Constant head test setup |
Short Answer Type Questions
1. Darcy's law is applicable to seepage if a soil is –
(a) Homogeneous (b) Isotropic the above
(c) Incompressible (d) All
Answer: (d)
2. The phreatic line in an earthen dam may be -
a) Parabolic (b) Elliptical (c) Straight line (d) Circular
Answer: (a)
3. The quantity of seepage of water through soils is proportional to -
(a) coefficient of permeability of soil
(b) total head loss through the soil
(c) neither (a) nor
(b) (d) both (a) and (b)
Answer: (d)
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