LECTURE NOTES
CO1: DETERMINE THE PHYSICAL AND INDEX PROPERTIES OF
SOIL
SOIL,SOIL MECHANICS AND SOIL ENGINEERING
The term 'Soil' has various meanings, depending upon the general professional field in which
it is being considered.
To an agriculturist, soil merely means the top layer of the earth which is responsible for
supporting plant life. Even to a geologist. soil is the thin outer layer of loose sediments within
which plant roots are present. A geologist refers to the rest of the earth's crust as rock,
irrespective of how strong or weak the bonding forces of the sediments are.
The material which is called soil by the agronomist or the geologist is known as top soil in
geotechnical engineering or soil engineering. The top soil contains large quantity of organic
matter and is not suitable as a construction material or as a foundation for structures. The top
soil is removed from the earth's surface before the construction of structures.
For a civil engineer, soils mean all naturally occurring, relatively unconsolidated earth
material-organic or inorganic in character-that lies above the bedrock. According to Terzaghi,
soils can be broken down into their constituent particles relatively easily, such as by agitation
in water. On the other hand, rocks are an agglomeration of mineral particles which are bonded
together by strong molecular forces.
DEFINITION OF SOIL: The term 'soil' in soil engineering is defined as an unconsolidated
material, composed of solid particles, produced by the disintegration of rocks. The void space
between the particles may contain air, water or both. The solid particles may contain organic
matter.
Soil Mechanics is the branch of civil engineering that concerns the application of the principles
of mechanics, hydraulics and to a smaller extent, chemistry, to engineering problems related to
soils.
Rock Mechanics is defined as the science dealing with the application of the principles of
mechanics to the understanding of the behaviour of rock masses.
Soil engineering in an applied science dealing with the applications of principles of soil
mechanics to practical problems. It has a much wider scope than soil mechanics, as it deals
1
Department of Civil engineering, GPC Muttom
,with all engineering problems related with soils. It includes site investigations, design and
construction of foundations, earth-retaining structures and earth structures.
Geotechnical engineering is a broader term which includes soil engineering, rock mechanics
and geology. This term is used synonymously with soil engineering.
CIVIL ENGINEERING PROBLEMS RELATED TO SOILS
A civil engineer has to deal with soils in their diverse roles
Every civil engineering structure, whether it be a building, a bridge, a tower, an embankment,
a road pavement, a railway line, a tunnel or a dam, has to founded on the soil .Soil is, therefore,
the ultimate foundation material which supports the structure.
Soil is also the most abundantly available construction material. From ancient times, man has
used soil for the construction of tombs, monuments, dwellings, and barrages for storing water.
In modern times, the use of earth for building dams and for constructing pavements for
highways and airfields is an important aspect of civil engineering.
In the design and construction of underground structures such as tunnels, conduits, power
houses, bracings for excavations and earth retaining structures, the role of soil is again very
crucial.
For designing foundations for machines such as turbines, compressors, forges etc., which
transmit vibrations to the foundation soil, one has to understand the behaviour of soil under
vibratory loads.
The effect of quarry blasts, earthquakes and nuclear explosions on structures is greatly
influenced by the soil medium through which the shock waves traverse.
In those parts of the world which experience freezing temperatures, structures are designed to
withstand the effects of freezing and thawing.
SOIL FORMATION AND SOIL TYPES
On the basis of the geological origin of their constituent sediments, soil can be divided into two
main groups-those which owe their origin to the physical and chemical weathering of the
parent rocks, and those which are chiefly of organic origin (This type is extremely compressible
and their use as foundation material is best avoided)
Soils which are a product of physical weathering or mechanical disintegration, retain the
minerals that were present in the parent rocks and are coarse grained. Gravels and sands fall
into this category.
The agencies responsible for physical weathering are the impact and grinding action of flowing
water, ice, wind and splitting actions of ice, plants and animals.
As against this, chemical weathering or decomposition of rocks is caused mainly by oxidation,
hydration, carbonation and leaching by organic acids and water. Clays and, to some extent,
silts are formed by chemical weathering.
If the products of rock weathering are still located at the place where they originated, they are
called residual soils.
2
Department of Civil engineering, GPC Muttom
,Any soil that has been transported from its place of origin by wind, water, ice or any other
agency and has been redeposited, is called a transported soil. Residual soils are not as common
as transported soils.
Transported soils are further classified according to the transporting agency and method of
deposition:
(a) Alluvial deposit-soils that have been deposited from suspension in running water.
(b) Lacustrine deposit-soils that have been deposited from suspension in still, fresh water of
lakes.
(c) Marine deposit-soils that have been deposited from suspension in sea water.
(d) Aeolian deposit-soils that have been transported by wind.
(e) Glacial deposit-deposits have been transported by ice.
FIELD APPLICATIONS OF SOIL MECHANICS
Soil engineering has vast application in the construction of various civil engineering works.
Some of the important applications are as under
1) Foundations-Every civil engineering structure, whether it is a building, a bridge, or a
dam, is founded on or below the surface of the earth. Foundations are required to
transmit the load of the structure to soil safely and efficiently.
2) Retaining Structures-When sufficient space is not available for a mass of soil to spread
and form a safe slope, a structure is required to retain the soil. An earth retaining structure is
also required to keep the soil at different levels on its either side. Soil engineering gives the
theories of earth pressure on retaining structures.
3) Stability of Slopes-If soil surface is not horizontal, there is a component of weight of the
soil which tends to move it downward and thus causes instability of slope. The slopes may be
3
Department of Civil engineering, GPC Muttom
, natural or man-made Fig shows slopes in filling and cutting. Soil engineering provides the
methods for checking the stability of slopes.
(4) Underground Structures-The design and construction of underground structures, such as
tunnels, shafts, and conduits, require evaluation of forces exerted by the soil on these structures.
These forces are discussed in soil engineering.
Fig shows a tunnel constructed below the ground surface and a conduit laid blow the ground
surface.
(5) Pavement Design-A pavement is a hard crust placed on soil (subgrade) for the purpose of
providing a smooth and strong surface on which vehicles can move. The pavement consists of
surfacing, such as a bitumen layer, base and subbase (Fig). The behaviour of subgrade under
various conditions of loading and environmental changes is studied in soil engineering.
6) Earth Dam-Earth dams are huge structures in which soil is used as a construction material
The earth dams are built for creating water reservoirs and its construction requires a thorough
knowledge of soil engineering.
4
Department of Civil engineering, GPC Muttom
CO1: DETERMINE THE PHYSICAL AND INDEX PROPERTIES OF
SOIL
SOIL,SOIL MECHANICS AND SOIL ENGINEERING
The term 'Soil' has various meanings, depending upon the general professional field in which
it is being considered.
To an agriculturist, soil merely means the top layer of the earth which is responsible for
supporting plant life. Even to a geologist. soil is the thin outer layer of loose sediments within
which plant roots are present. A geologist refers to the rest of the earth's crust as rock,
irrespective of how strong or weak the bonding forces of the sediments are.
The material which is called soil by the agronomist or the geologist is known as top soil in
geotechnical engineering or soil engineering. The top soil contains large quantity of organic
matter and is not suitable as a construction material or as a foundation for structures. The top
soil is removed from the earth's surface before the construction of structures.
For a civil engineer, soils mean all naturally occurring, relatively unconsolidated earth
material-organic or inorganic in character-that lies above the bedrock. According to Terzaghi,
soils can be broken down into their constituent particles relatively easily, such as by agitation
in water. On the other hand, rocks are an agglomeration of mineral particles which are bonded
together by strong molecular forces.
DEFINITION OF SOIL: The term 'soil' in soil engineering is defined as an unconsolidated
material, composed of solid particles, produced by the disintegration of rocks. The void space
between the particles may contain air, water or both. The solid particles may contain organic
matter.
Soil Mechanics is the branch of civil engineering that concerns the application of the principles
of mechanics, hydraulics and to a smaller extent, chemistry, to engineering problems related to
soils.
Rock Mechanics is defined as the science dealing with the application of the principles of
mechanics to the understanding of the behaviour of rock masses.
Soil engineering in an applied science dealing with the applications of principles of soil
mechanics to practical problems. It has a much wider scope than soil mechanics, as it deals
1
Department of Civil engineering, GPC Muttom
,with all engineering problems related with soils. It includes site investigations, design and
construction of foundations, earth-retaining structures and earth structures.
Geotechnical engineering is a broader term which includes soil engineering, rock mechanics
and geology. This term is used synonymously with soil engineering.
CIVIL ENGINEERING PROBLEMS RELATED TO SOILS
A civil engineer has to deal with soils in their diverse roles
Every civil engineering structure, whether it be a building, a bridge, a tower, an embankment,
a road pavement, a railway line, a tunnel or a dam, has to founded on the soil .Soil is, therefore,
the ultimate foundation material which supports the structure.
Soil is also the most abundantly available construction material. From ancient times, man has
used soil for the construction of tombs, monuments, dwellings, and barrages for storing water.
In modern times, the use of earth for building dams and for constructing pavements for
highways and airfields is an important aspect of civil engineering.
In the design and construction of underground structures such as tunnels, conduits, power
houses, bracings for excavations and earth retaining structures, the role of soil is again very
crucial.
For designing foundations for machines such as turbines, compressors, forges etc., which
transmit vibrations to the foundation soil, one has to understand the behaviour of soil under
vibratory loads.
The effect of quarry blasts, earthquakes and nuclear explosions on structures is greatly
influenced by the soil medium through which the shock waves traverse.
In those parts of the world which experience freezing temperatures, structures are designed to
withstand the effects of freezing and thawing.
SOIL FORMATION AND SOIL TYPES
On the basis of the geological origin of their constituent sediments, soil can be divided into two
main groups-those which owe their origin to the physical and chemical weathering of the
parent rocks, and those which are chiefly of organic origin (This type is extremely compressible
and their use as foundation material is best avoided)
Soils which are a product of physical weathering or mechanical disintegration, retain the
minerals that were present in the parent rocks and are coarse grained. Gravels and sands fall
into this category.
The agencies responsible for physical weathering are the impact and grinding action of flowing
water, ice, wind and splitting actions of ice, plants and animals.
As against this, chemical weathering or decomposition of rocks is caused mainly by oxidation,
hydration, carbonation and leaching by organic acids and water. Clays and, to some extent,
silts are formed by chemical weathering.
If the products of rock weathering are still located at the place where they originated, they are
called residual soils.
2
Department of Civil engineering, GPC Muttom
,Any soil that has been transported from its place of origin by wind, water, ice or any other
agency and has been redeposited, is called a transported soil. Residual soils are not as common
as transported soils.
Transported soils are further classified according to the transporting agency and method of
deposition:
(a) Alluvial deposit-soils that have been deposited from suspension in running water.
(b) Lacustrine deposit-soils that have been deposited from suspension in still, fresh water of
lakes.
(c) Marine deposit-soils that have been deposited from suspension in sea water.
(d) Aeolian deposit-soils that have been transported by wind.
(e) Glacial deposit-deposits have been transported by ice.
FIELD APPLICATIONS OF SOIL MECHANICS
Soil engineering has vast application in the construction of various civil engineering works.
Some of the important applications are as under
1) Foundations-Every civil engineering structure, whether it is a building, a bridge, or a
dam, is founded on or below the surface of the earth. Foundations are required to
transmit the load of the structure to soil safely and efficiently.
2) Retaining Structures-When sufficient space is not available for a mass of soil to spread
and form a safe slope, a structure is required to retain the soil. An earth retaining structure is
also required to keep the soil at different levels on its either side. Soil engineering gives the
theories of earth pressure on retaining structures.
3) Stability of Slopes-If soil surface is not horizontal, there is a component of weight of the
soil which tends to move it downward and thus causes instability of slope. The slopes may be
3
Department of Civil engineering, GPC Muttom
, natural or man-made Fig shows slopes in filling and cutting. Soil engineering provides the
methods for checking the stability of slopes.
(4) Underground Structures-The design and construction of underground structures, such as
tunnels, shafts, and conduits, require evaluation of forces exerted by the soil on these structures.
These forces are discussed in soil engineering.
Fig shows a tunnel constructed below the ground surface and a conduit laid blow the ground
surface.
(5) Pavement Design-A pavement is a hard crust placed on soil (subgrade) for the purpose of
providing a smooth and strong surface on which vehicles can move. The pavement consists of
surfacing, such as a bitumen layer, base and subbase (Fig). The behaviour of subgrade under
various conditions of loading and environmental changes is studied in soil engineering.
6) Earth Dam-Earth dams are huge structures in which soil is used as a construction material
The earth dams are built for creating water reservoirs and its construction requires a thorough
knowledge of soil engineering.
4
Department of Civil engineering, GPC Muttom
