Application & History of Soil Mechanics, you must know

First of all, thanks for giving everyone so much love in the previous article. I didn’t think the article would look like this. For those who haven’t read the article yet, read here.

But in this article, I will talk about another topic of civil engineering, that’s Soil Mechanics. It is one of the very important subjects in civil engineering. 

 

This is also important for any Govt (India) examinations, such as GATE, IES, SSC-JE, RRB-JE, and many other state-level exams. Just like a site engineer, Soil Mechanics needs to be very well known.

So after reading this article, you will be gained on basic concepts of soil mechanics. This article is going to be very interesting. So if you are a civil engineer or student then don’t miss it. 

 

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History of Soil Mechanics –

Prehistoric times, when man started constructing a home for living and roads for transportation, then they had a basic knowledge of using soil extends. The knowledge of soils for the foundation and roads was grained by trial and error experience.

 

The use of both timber and stone caissons shaft construction was known in Egypt in 2000 B.C. The cutting edge was made of a round limestone block with a vertical hole bored into its middle.

One of the greatest structures in ancient times was the famous ‘hanging garden’ built by the Babylonian King Nebuchadnezzar. 

 

After, the Romans built many notable structures, such as harbors, moles, break-waters, aqueducts, bridges, buildings, sewage, etc. The Roman engineer Vitruvious wrote his Ten Books on Architecture sometimes in the first century B.C. Discussing the stability of buildings, Vitruvious writes that “... the greatest care must be taken piled against them”. 

 

In India, Mansar, Mayamata, Visvakarma, Agastya, Santakumara, Mandana, Srikumara, etc. wrote books laying down rules of construction. Mansar’s ‘Silpa Sastra,’ written sometimes in the sixth or seventh century, became very popular. Mansar recommended compaction of soil by cows and oxen and dewatering of foundations.

 

In the later of the 17^th century, France Military engineers contributed some empirical and analytical data pertaining to earth pressure on retaining wall for the design of revetment of fortifications. France established a Department of Roads and Bridge in 1715, and in 1747, the Famous Ecole des Ponts et chausses were started.

 

Coulomb was the first to introduce the concept that shearing the resistance of soil is composed of two components, namely, cohesion and friction. Poncelet (1788-1866), a famous geometer, extended Coulomb’s theory, giving a graphical method of finding the magnitude of earth pressure on the wall, vertical as well as for inclined wall surface on the backfill side, and for arbitrary broken polygonal surfaces. 

 

Two important laws – Darcy’s law for the flow of water through soils and Stoke’s Law for settlement of solid particles in liquid – were put forward in 1856. 

 

In 1857, Rankine presented his theory for calculating earth pressure and the safe bearing capacity of the foundation.

 

In 1871, O Mohr gave a graphical representation of stress at a point, popularly known as Mohr’s stress circle. In soil mechanics, Mohr's stress circle is extensively used in the analysis of the shearing strength of soils.

 

Attterberg was the first to propose in 1911 the different stages of consistency in which a clay soil may exist, depending upon its water content.

 

Dr. Terzaghi published his theory of consolidation in 1923 and the term Soil Mechanics was coined by him in 1925 when his book under the equivalent German title Erdbaumechanik was published. Dr. Terzaghi’s contributions in the field of soil engineering have been immense and he is fittingly called the ‘Father of Soil Mechanics’.

 

During World War 2 (1939-1945) and after, a great development of soil engineering has been made by various scientists and engineers of different countries of the World, and today it is recognized as a well established branch of engineering.

What is Soil Mechanics?

So before studying soil mechanics, we need to have a clear the idea of what soil mechanics is and its definition. 

 

The term ‘Soil’ has various meanings, depending upon the general professional field in which it is being considered. According to an agriculturist, the soil is the substance existing on the earth’s surface, which grows and develops plant life. To the geologist also, the soil is the material in the relatively thin surface zone within which roots occur, and all the rest of the crust is grouped under the term rock irrespective of its hardness. And according to an engineer, the soil is the unaggregated or uncemented deposits of mineral and/or organic particles or fragments covering a large portion of the earth’s crust.

 

According to Terzaghi(1948): “ Soil Mechanics is the application of the law of mechanics and hydraulics to engineering problems dealing with sediments and other unconsolidated accumulations of solid particles produced by mechanical and chemical disintegration of rocks regardless of whether or not they contain an admixture of the organic constituent.”

Application/Importance of Soil Mechanics:-

We know that soil mechanics is an important subject of civil engineering at present. So indifferent construction places, we have to apply the formula of soil mechanics. And as a civil engineer, you must know those things. It is also necessary to know where its application is most applicable.

The following are described in detail below –

 

Foundation and Construction –

We all civil engineers know the foundation is the first element of all structures. Every structure in your surroundings like a residential house, bridge, road, industrial building, school, college, tunnel, canal or dam is founded in or on the surface of the earth.  It is necessary to know the probable settlement of the foundation, the the pattern of stress distribution in the soil, bearing capacity of the soil and ground water effects.

Pavements Design –

Pavement can be either be flexible or rigid, and its performance depends upon the subsoil on which it rests. The design depends upon certain characteristics of the subsoil.

Apart from these, other problems of pavement design are : frost, heave and thaw with their associated problems of frost damage to pavements; frost penetration depth; the problem of ‘pimping’ of clay subsoil and suitability of a soil as a construction material for building highways or railways, earth fills or cuts, etc.

Underground Structure and earth retaining structures –

The examples of underground structures include tunnels, underground buildings, drainage structures, and pipelines.

The example of earth retaining structures is gravity retaining wall, anchored bulkheads, and cofferdams. Knowledge of soil-structure interaction is essential to design properly such structures subjected to soil loadings. 

Design of earth dams –

Since soil is used as the only construction material in an earth dam, which may be homogeneous or of the composite section, its design involves the determination of the following physical properties of soil: index properties, such as density, plasticity characteristics, and specific gravity, particle size distribution and gradation of the soil; permeability, consolidation and compaction characteristics, and shear strength parameters under various drainage conditions.

 

The determination of the optimum water content at which maximum density will be obtained on compaction, is probably the most essential the aspect of the design.

The consolidation characteristics help in predicting the long-range behavior of the dam towards settlement.

 

Lastly, the possible effect of vibrations during an earthquake should also be taken into account while designing.

Design of embankments and excavation – 

Thorough knowledge of shear strength and related properties of soil is essential to design the slope and height (or depth) of the embankment (or excavation). The possibility of the seeping groundwater reducing the soil strength while excavating must also be taken into account. It may sometimes be essential to drain the subsoil water, to increase the soil strength and reduce the seepage forces. Deep excavations require lateral braces and sheet walls to prevent caving in.

At last,

So, this is the article on history and application of soil mechanics, Hope you like it. I’ve tried to make it as simple as possible and simple English language.

 

As you read the textbook you will understand how difficult these are. There is a lot of information in the textbook we don’t need to read. So, I have discussed the most important points in this article.

In the coming days, you will find important articles on Soil Mechanics. So, if you like this post, please share and subscribe and have any quarry please comment below, I can try to solve it. One more small request, If you are not following us on Instagram, then please follow us on Instagram, because most of all time we are online on Instagram.