Soil is defined as the uncemented aggregate of minerals grain and decayed organic matter i.e, solid particles with liquid and gas in the empty spaces between the solid particles.
Soil mechanics is defined as the application of laws of mechanics and hydraulics to the engineering problems dealing with sediment and other unconsolidated accumulation of solid particles produced by the mechanical and chemical disintegration of rocks regardless of whether or not they contain an admixtures of organic constituents. This definition was given by Terzaghi,father of soil mechanics.
Geotechnical engineering is the sub discipline of civil engineering that involves natural material found close to the surface of the earth. It includes the application of the principle of soil mechanics and rock Mechanics to the design of foundations, retaining structures and Earth structures.

Purposes of soil mechanics:

Soil is defined as the uncemented aggregate of minerals grain and decayed organic matter i.e, solid particles with liquid and gas in the empty spaces between the solid particles.
Soil mechanics is defined as the application of laws of mechanics and hydraulics to the engineering problems dealing with sediment and other unconsolidated accumulation of solid particles produced by the mechanical and chemical disintegration of rocks regardless of whether or not they contain an admixtures of organic constituents. This definition was given by Terzaghi,father of soil mechanics.
Geotechnical engineering is the sub discipline of civil engineering that involves natural material found close to the surface of the earth. It includes the application of the principle of soil mechanics and rock Mechanics to the design of foundations, retaining structures and Earth structures.

Purposes of soil mechanics:

1. To perform engineering soil surveys.
2.  To develop rational sampling devices and soil sampling methods.
3. To develop suitable soil testing equipment and soil testing methods.
4. To investigate physical properties of soil by means of field and laboratory test.
5.  To analyse and interpret soil test data and classify soils.
6. To understand the effect of various factor on soil such as static and dynamic loads, ice, water and temperature.
7. To solve the practical engineering problems by applying the principal of soil mechanics.

1. To perform engineering soil surveys.
2.  To develop rational sampling devices and soil sampling methods.
3. To develop suitable soil testing equipment and soil testing methods.
4. To investigate physical properties of soil by means of field and laboratory test.
5.  To analyse and interpret soil test data and classify soils.
6. To understand the effect of various factor on soil such as static and dynamic loads, ice, water and temperature.
7. To solve the practical engineering problems by applying the principal of soil mechanics.

The basic geotechnical problem associated with soil mechanics are:

• Problem of stability 
• Problem of elastic and plastic deformations 
• Problem due to failure of various structure like pavement, retaining structures, dams, foundations etc.

In case of stability, problem arises due to sudden collapse of resisting capacity of the soil. To prevent failure due to stability, the following questions need to be answered:

• What load is imposed on soil?
• What magnitude of stress does the load induce to the subsoil?
• How much resistance the soil can sustain?

Similarly, in the problem of deformation,the magnitude of elastic and plastic deformation and rate of deformation need to be assessed. The magnitude of deformation should be kept within a certain limit in which a structure can tolerate.

The various problems associated with pavement design, foundation failure etc are fatigue failure, frost, heave and thaw etc.

The basic geotechnical problem associated with soil mechanics are:

• Problem of stability 
• Problem of elastic and plastic deformations 
• Problem due to failure of various structure like pavement, retaining structures, dams, foundations etc.

In case of stability, problem arises due to sudden collapse of resisting capacity of the soil. To prevent failure due to stability, the following questions need to be answered:

• What load is imposed on soil?
• What magnitude of stress does the load induce to the subsoil?
• How much resistance the soil can sustain?

Similarly, in the problem of deformation,the magnitude of elastic and plastic deformation and rate of deformation need to be assessed. The magnitude of deformation should be kept within a certain limit in which a structure can tolerate.

The various problems associated with pavement design, foundation failure etc are fatigue failure, frost, heave and thaw etc.

soils are formed by either:

• Physical disintegration
• Chemical decomposition of rocks

Physical Disintegration:

Physical disintegration of rocks is due to the action of various agents such as expansive forces of freezing water in fissures, due to sudden changes of temperatures or due to abrasion of rocks by moving water or glaciers.This type of rock weathering takes place in very significant manner in arid climates where free, extreme atmospheric radiation brings about considerable variation in temperature at sunrise and sunset.

Erosion by wind and rain is very important factor and is a continuous event. Cracking force by growing plants and roots in voids and crevasses of rock can force fragments apart. Coarse grained soils, such as gravel and sand are formed by process of physical disintegration.

Chemical Decomposition:

When chemical decomposition or chemical weathering of rocks takes place, original rock minerals are transformed into new minerals by chemical reactions. Chemical decomposition can transform hard rock minerals into soft, easily erodible matter. The principle types of decomposition are hydration,oxidation,carbonation,desilication, and leaching. Chemical decomposition of rocks results in the formation of clayey soils.

soils are formed by either:

• Physical disintegration
• Chemical decomposition of rocks

Physical Disintegration:

Physical disintegration of rocks is due to the action of various agents such as expansive forces of freezing water in fissures, due to sudden changes of temperatures or due to abrasion of rocks by moving water or glaciers.This type of rock weathering takes place in very significant manner in arid climates where free, extreme atmospheric radiation brings about considerable variation in temperature at sunrise and sunset.

Erosion by wind and rain is very important factor and is a continuous event. Cracking force by growing plants and roots in voids and crevasses of rock can force fragments apart. Coarse grained soils, such as gravel and sand are formed by process of physical disintegration.

Chemical Decomposition:

When chemical decomposition or chemical weathering of rocks takes place, original rock minerals are transformed into new minerals by chemical reactions. Chemical decomposition can transform hard rock minerals into soft, easily erodible matter. The principle types of decomposition are hydration,oxidation,carbonation,desilication, and leaching. Chemical decomposition of rocks results in the formation of clayey soils.

On the basis of the origin of their constituents, Soils can be divided into following two groups:

• Residual Soils
• Transported Soils

Residual Soils:

Residual soils are those soils that remains at the place of their formation as a result of the weathering of the parent rocks. The depth of residual soils depends primarily on climatic conditions and the time of exposure. An important characteristics of the residual soil is that the sizes of the grains are indefinite. For example- when the residual soil is sieved, the amount passing through any given sieve size depends greatly on the time and energy expended in shaking, because of partially disintegarated conditions.

Transported Soils:

Transported soils are the soils that are found at locations far from their place of formation. The transporting agencies of such soils are glaciers, wind and water. The soils are named according to the mode of deposition as:

• Alluvial deposit
• Lacustrine deposit
• Marine deposit
• Aeolian deposit

Soils that has been deposited from suspension in running water are alluvial deposits.

Lacustrine deposit:

Soils that has been deposited from suspension in still, fresh water of lakes are lacustrine deposits.

Marine deposit:

Soils that has been deposited from suspension in sea water.

Aeolian deposit:

Soils that have been transported by winds are aeolian soils.
 Glacial soils:

Soils that have been transported by ice are glacial soils.

Soils are also classified as :

• Organic Soils
• Inorganic Soils

On the basis of the origin of their constituents, Soils can be divided into following two groups:

• Residual Soils
• Transported Soils

Residual Soils:

Residual soils are those soils that remains at the place of their formation as a result of the weathering of the parent rocks. The depth of residual soils depends primarily on climatic conditions and the time of exposure. An important characteristics of the residual soil is that the sizes of the grains are indefinite. For example- when the residual soil is sieved, the amount passing through any given sieve size depends greatly on the time and energy expended in shaking, because of partially disintegarated conditions.

Transported Soils:

Transported soils are the soils that are found at locations far from their place of formation. The transporting agencies of such soils are glaciers, wind and water. The soils are named according to the mode of deposition as:

• Alluvial deposit
• Lacustrine deposit
• Marine deposit
• Aeolian deposit

Soils that has been deposited from suspension in running water are alluvial deposits.

Lacustrine deposit:

Soils that has been deposited from suspension in still, fresh water of lakes are lacustrine deposits.

Marine deposit:

Soils that has been deposited from suspension in sea water.

Aeolian deposit:

Soils that have been transported by winds are aeolian soils.
 Glacial soils:

Soils that have been transported by ice are glacial soils.

Soils are also classified as :

• Organic Soils
• Inorganic Soils

The development of soil mechanics can be divided into following periods as:

• Ancient to Medieval period,
• Period of early development
• Modern era
• Recent developments

Ancient to Medieval period:

In this period, the civil engineering constructions were constructed using thumb rule. The authorized theories on soil mechanics were not found in this period, but some complex challenging constructions were done during that time which still exists.

1. Hanging garden was built in Babylonian.
2. During Roman times, many heavy structures were built.
3. Taj Mahal at Agra was built.

Periods of Early Developments:

The eighteenth century can be considered as the real begining of soil engineering. In this period,

1. A french engineer gave a theory of earth pressure on retaining walls.
2. Culmann gave a general graphical solution for earth pressure.
3. Boussinesq gave the theory of stress distribution due to externally applied load.
4. Atterberg give some simple test for determining consistency of cohesive soils.

Modern Era:

The modern era began in 1925 with the publication of book by Karl Terzaghi giving thetheory of consolidation and effective stress.In this era,

1. Pactor did pioneering work on compaction of soils.
2. tayler made major contribution on consolidation of soils,shear strength and stability of slopea.

Recent Development:

Recent development is concerned with:

1. ground improving techniques.
2. application of finite element and numerical methods to study soil mechanics.
3. Computer programming to study soil and structure interaction.
4. Dynamic soil mechanics.

The development of soil mechanics can be divided into following periods as:

• Ancient to Medieval period,
• Period of early development
• Modern era
• Recent developments

Ancient to Medieval period:

In this period, the civil engineering constructions were constructed using thumb rule. The authorized theories on soil mechanics were not found in this period, but some complex challenging constructions were done during that time which still exists.

1. Hanging garden was built in Babylonian.
2. During Roman times, many heavy structures were built.
3. Taj Mahal at Agra was built.

Periods of Early Developments:

The eighteenth century can be considered as the real begining of soil engineering. In this period,

1. A french engineer gave a theory of earth pressure on retaining walls.
2. Culmann gave a general graphical solution for earth pressure.
3. Boussinesq gave the theory of stress distribution due to externally applied load.
4. Atterberg give some simple test for determining consistency of cohesive soils.

Modern Era:

The modern era began in 1925 with the publication of book by Karl Terzaghi giving thetheory of consolidation and effective stress.In this era,

1. Pactor did pioneering work on compaction of soils.
2. tayler made major contribution on consolidation of soils,shear strength and stability of slopea.

Recent Development:

Recent development is concerned with:

1. ground improving techniques.
2. application of finite element and numerical methods to study soil mechanics.
3. Computer programming to study soil and structure interaction.
4. Dynamic soil mechanics.

On the basis of the formation of soil, Soils can be divided into following two groups:

• Residual Soils
• Transported Soils

Residual Soils:

Residual soils are those soils that remains at the place of their formation as a result of the weathering of the parent rocks. The depth of residual soils depends primarily on climatic conditions and the time of exposure. An important characteristics of the residual soil is that the sizes of the grains are indefinite.

Transported Soils:

Transported soils are the soils that are found at locations far from their place of formation. The transporting agencies of such soils are glaciers, wind and water. The soils are named according to the mode of deposition as:

• Alluvial deposit
• Lacustrine deposit
• Marine deposit
• Aeolian deposit

Soils that has been deposited from suspension in running water are alluvial deposits.

Lacustrine deposit:

Soils that has been deposited from suspension in still, fresh water of lakes are lacustrine deposits.

Marine deposit:

Soils that has been deposited from suspension in sea water.

Aeolian deposit:

Soils that have been transported by winds are aeolian soils.
 Glacial soils:

Soils that have been transported by ice are glacial soils.

Soils are also classified as :

• Organic Soils
• Inorganic Soils

On the basis of the formation of soil, Soils can be divided into following two groups:

• Residual Soils
• Transported Soils

Residual Soils:

Residual soils are those soils that remains at the place of their formation as a result of the weathering of the parent rocks. The depth of residual soils depends primarily on climatic conditions and the time of exposure. An important characteristics of the residual soil is that the sizes of the grains are indefinite.

Transported Soils:

Transported soils are the soils that are found at locations far from their place of formation. The transporting agencies of such soils are glaciers, wind and water. The soils are named according to the mode of deposition as:

• Alluvial deposit
• Lacustrine deposit
• Marine deposit
• Aeolian deposit

Soils that has been deposited from suspension in running water are alluvial deposits.

Lacustrine deposit:

Soils that has been deposited from suspension in still, fresh water of lakes are lacustrine deposits.

Marine deposit:

Soils that has been deposited from suspension in sea water.

Aeolian deposit:

Soils that have been transported by winds are aeolian soils.
 Glacial soils:

Soils that have been transported by ice are glacial soils.

Soils are also classified as :

• Organic Soils
• Inorganic Soils

Soil is defined as the uncemented aggregate of minerals grain and decayed organic matter i.e, solid particles with liquid and gas in the empty spaces between the solid particles.

Soil mechanics is defined as the application of laws of mechanics and hydraulics to the engineering problems dealing with sediment and other unconsolidated accumulation of solid particles produced by the mechanical and chemical disintegration of rocks regardless of whether or not they contain an admixtures of organic constituents. This definition was given by Terzaghi,father of soil mechanics.

Importance Of Soil Mechanics:

It helps to perform engineering soil surveys.

It helps t0  develop rational sampling devices and soil sampling methods.

It helps to develop suitable soil testing equipment and soil testing methods.

It helps to investigate physical properties of soil by means of field in laboratory test.

 It helps to analyse and interpret soil test data and classify soils.

It helps to understand the effect of various factor on soil such as static and dynamic loads, ice, water and temperature.

 solve the practical engineering problems by applying the principal of soil mechanics.

Soil is defined as the uncemented aggregate of minerals grain and decayed organic matter i.e, solid particles with liquid and gas in the empty spaces between the solid particles.

Soil mechanics is defined as the application of laws of mechanics and hydraulics to the engineering problems dealing with sediment and other unconsolidated accumulation of solid particles produced by the mechanical and chemical disintegration of rocks regardless of whether or not they contain an admixtures of organic constituents. This definition was given by Terzaghi,father of soil mechanics.

Importance Of Soil Mechanics:

It helps to perform engineering soil surveys.

It helps t0  develop rational sampling devices and soil sampling methods.

It helps to develop suitable soil testing equipment and soil testing methods.

It helps to investigate physical properties of soil by means of field in laboratory test.

 It helps to analyse and interpret soil test data and classify soils.

It helps to understand the effect of various factor on soil such as static and dynamic loads, ice, water and temperature.

 solve the practical engineering problems by applying the principal of soil mechanics.