Why Soil Mechanics is Important in Civil Engineering

Why Soil Mechanics is Important in Civil Engineering

Soil mechanics is interrelated to civil engineering. Soil mechanics is a blend of soil physics and mechanics. 
Property, quality, behavior, and nature of soil can influence structure built on earth surface. Know more about the importance of soil mechanics in civil engineering.

Importance of soil in civil engineering is something unavoidable.

importance of soil in civil engineering

➤What is Soil Mechanics?

Before going into the discussion Lets learn from the basic.
The first question that triggers our mind is that 'What is Soil Mechanics is all about'?

Soil mechanics itself is a mixture of Soil physics and applied mechanics. In this branch of engineering, Soil behaviors are the main thing to discuss.

As civil engineering or geotechnical engineering is highly dependent on the foundation which is directly linked with rock, soil, clay minerals etc, It is necessary to know the actual behavior and the feature of soil compositions.

Well, in the case of foundation, retaining wall, dam, bridge-Soil mechanics is most useful from the civil engineering point of view.

Some of the most used terms in soil mechanics are listed below:

  • Dry/Wet density
  • Saturation of soil
  • Porosity
  • Void ratio
  • Moisture content...
[*Father of soil mechanics is 'Karl von terzaghi'.]

Geotechnical properties of soil related to civil engineering

After knowing the basics of soil mechanics, we must have detailed knowledge about soil properties.

The most important terms related to soil mechanics are given below-

1. Shear strength of soil -

 This term can be defined as how much the soil can resist shear stress. Due to friction and interlocking of particles soil gains some amount of shear strength.

Shear strength of soil can be depended upon grain size, void ratio, density, types of soil (silt, sand, silt, rock etc), loading condition, effective stress, drainage condition etc.

2. Bearing capacity -

Bearing capacity of the soil defined as soil capacity to support the load coming from the foundation.

Foundation of any structure exerts a certain amount of load( depends upon the type of structure)and the soil has to bear that load.

The first and foremost thing of constructing any structure is that knowing the soil strength and bearing capacity of the soil.

Three types of failure that come into the account-

  1. General shear failure
  2. Local shear failure
  3. punching shear failure.

3. Specific gravity -

The specific gravity of minerals gives us an idea about soil quality. The higher is specific gravity the better is soil in terms of strength.

The specific gravity of soil can be defined as the ratio of soil mass to the mass of an equal volume of water.

It is observed that the soil having high specific gravity value gives more strength and California bearing ratio.

For constructing the bridge, skyscraper or any heavy structure, soil with the higher value of specific gravity is most suitable.

4.Compaction of soil -

Compaction of soil is a very simple but important process for soil improvement.

In this process, soil gets densified by types of equipment like a vibratory machine, roller etc and the air is displaced between the soil grains.

Sometimes earth surface is not able to produce required bearing capacity or shear strength.
Thus the quality of soil needs to be improved to resist the load coming from the super-structure.

This is why compaction of soil is so necessary for civil engineering.

There are many ways to compact the soil, some are given below-

  • Vibrating
  • impact loading
  • static loading
  • rolling...

5.Consolidation of soil -

Purpose of consolidation is also same as compaction but there is a minor change in the process.
In the case of the consolidation, soil gets densified without changing the volume of air entrapped in the soil, only water is displaced from the soil grains.

6.The permeability of soil -

Permeability is a property of soil by which we can have an idea about how easily water can pass through the soil.
Similarly, the impermeable soil is that surface which does not allow fluid to pass through.

For an example, clay has low permeability where sand has high.

The permeability of soil depends upon many factors which are given below:

  • Particle size and shape
  • Void ratio
  • Degree of saturation
  • Water content
  • Water impurities

This property of soil generally most helpful in the construction of dam, bridges etc.

➤ Application of soil mechanics in civil engineering

Up to this, we have learned the geotechnical properties of soil that have influence in civil engineering work.

Here I mentioned some handpicked applications of soil mechanics -

1.Earth retaining wall -

Earth retaining structures are used to retain backfill soil. In this case, you must have proper knowledge and data about that particular soil that you're working on.

Because without knowing the types, permeability, void ratio and shear strength of soil it's too hard to design drainage and pipeline system of these structures.

2.Foundation -

We all know foundation acts as a connector between the super-structure and the soil surface.
By this, you can guess soil is playing an important role in the case of foundation design and the stability of soil also depends upon the soil.

Before the design process, you must conduct the soil test to know the parameters of soil such as bearing capacity, shear strength, the degree of compaction etc.

Well, the stability and durability of any structure depend upon the property of soil.

Sometimes soil fails to give the required amount of bearing capacity or strength, then we have to improve the soil's condition by a popular technique called 'Ground improvement techniques'.

3.Excavations, Embankments, and Dams -

One important part from soil mechanics is slope stability analysis which is required for excavations purposes.
Similarly, knowledge about soil behavior is required for dam and embankments.
The knowledge of soil mechanics is compulsory for excavation dams and foundation.


It is observed that the different properties of soil have a different influence on the structure.
For an example, specific gravity of soil influence the load carrying capacity and Compaction of coarse-grained soils is done by density index.

These geotechnical properties of soil mechanics are completely unavoidable when related to civil engineering.

Foundation work is first and the most basic in construction and property of soil like permeability of soil gives an idea about the stability of foundations, seepage, and drainage system.

The connection between soil mechanics and civil engineering can help the researchers while designing the structures that highly influenced by the property of the soil.

Here we have recommended a must buy the book to practice Soil Mechanics 


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If you have any unanswered question, Please do comment below -

Why Soil Mechanics is Important in Civil Engineering Why Soil Mechanics is Important in Civil Engineering Reviewed by Civil049seminar on October 11, 2018 Rating: 5


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