Question

Q3. Explain the concept of permeability, the factors affecting permeability along with some examples of how permeability plays a vital role in engineering structures. Please mention the examples......

Answer 1

Permeability is the property of the soil, by the virtue of which it allows the flownof fluids through it. It is also termed as Hydraulic Conductivity.

When water tries to flow through a soil medium, permeability is that standing out property which determines the ease with which the water will flow through it. If the permeability is less, then the water might face lot of difficulty in flowing through the soil and if it is more, the water might flow easily.

Different soils, based on their different properties, show different permeability values.

The factors which effect the permeability of soils are,

1) Particle size of the soil.

2) Specific surface area of the soil.

3) Void ratio of the soil.

4) Properties of the fluid supposed to flow through the soil, such as temperature, density, viscosity etc.

5) Entrapped gases in the soil.

6) Degree of Saturation of the soil.

7) Presence of foreign impurities.

8) Presence of absorbed water.

Coming to applications.

In case of seepage of water below the dams, permeability helps in partial transfer of water from upstream to downstream.

It sometimes, also provides the uplifting pressure on the dam at the base.

In case of borewells, due to the permeability of soils only, is there the flow of water in the soil resulting in the draw down of water table only at the location of borewell.

The effect of permeability is also seen on the effective stress of soil.