Introduction
When we are thinking about any kind of construction
like a small house to skyscraper, foundation is base of the construction,
foundation is the most important part of the structure, which transferred whole
load of structure to the soil safely and provide stability to the structure.
Design of foundation is the most essential part when
a structure is designed. After the study of topography, geology, and size of
structure and other factors consideration the type of foundation is decided.
Ø What Is Foundation?
·
Foundation is the basic component of
structure through which the whole load of structure is transferred to the soil,
the solid ground on which foundation is rested, is called foundation bed.
·
Stability
is provided by Foundation to the structure, by distributing the load of
superstructure to the earth.
·
Strong
and well-designed foundation prevent settlement of structure and increase the stability.
Ø Types Of Foundations
On the earth
surface different kind of soil, sediment, stones are found. By studying their characteristics,
and so many factors geotechnical engineers recognized how these factors affects the structure, and which type of design of structural element should be done.
So there are two
type of foundation
1.
Shallow Foundation
2. Deep Foundation
1.
Shallow
Foundation
ü Shallow
foundation is the foundation in which width of foundation is greater than the
depth of foundation.
ü It is more
economical than deep foundation because it requires less digging.
ü Shallow
foundation is suitable where the soil can bear the weight of structure at a
shallow depth.
ü Shallow
foundation again divided into following types,
Types of Shallow
Foundation
A.
Individual
foundation and isolated foundation
C.
Strip
foundation
D.
Raft
or mat foundation
A. Individual Foundation And Isolated Foundation
ü Individual
foundation or isolated foundation is the type of shallow foundation, which is
used for building construction.
ü This foundation is
constructed for single column.
ü It is the most
economical type of footing, because the column placed at a particular distance.
ü The shape of footing may be square or
rectangular.
ü Material used
for it may be reinforced or non-reinforced.
ü The size of footing
is depending on the safe bearing capacity of soil and load of superstructure
come on column.
ü Simply, the size
of footing calculated by dividing the total load at the column base by the
allowable bearing capacity of soil
ü
The
combined footing is the combination of a different footing.
ü
It
is not differing from the isolated footing, only difference is that one base or
footing is sharing weight of two columns.
ü
It
happened because the two footing area come very close to each other.
ü
The
shape of footing can be rectangular, square trapezoidal.
ü This
type of footing is used in load bearing structure, in which wall distributing
the load of structure, not the column or pillars and beam.
ü In
this footing, the base of footing is wider than the load bearing wall because
the foundation runs the entire length of load bearing wall.
ü This
wider base of footing transferred load safely to soil and provide better
stability.
ü It
is made up of reinforced concrete, bricks, etc.
ü This
type of foundation is used when the bearing capacity of soil is weak.
ü The
Mat foundation is spread across the entire area of building.
ü This
foundation is used where load of the structure coming from wall and column is too
high.
ü To
prevent settlement of structure this foundation is used.
ü This
is costly structure; this footing is constructed when there is no other type of
footing is suitable.
ü The
columns are placed closely to each other.
ü Deep foundation
is used when building on the soft soil and sand which cannot carry the load of
structure safely.
ü Up to getting
hard strata, the foundation is deeper.
ü The foundation
is situated at the deep underground or underwater.
ü For bridges,
piers and dams such foundation is used.
ü Deep foundation
gain divided into following types:
Types of Deep Foundation
E. Pile foundation
F. Drilled shafts or caissons
G. Pier foundation
E. Pile Foundation
ü Pile foundation is the most common type of deep foundation,
which is used where the hard strata of soil are deeper, and to carry load of structure
the plies are used.
ü Pile length is more than its cross-sectional
area.
ü Pile transferred load to soil trough friction or
bearing.
ü They are helped to reduce cost of construction.
ü The types of piles are as follows
a. Based on their function or use
1.
Sheet piles
2.
Load bearing piles
3.
End bearing piles
4.
Friction piles
5.
Soil compactor piles
b. Based on the material and construction method.
1. Timber piles
2. Concrete piles
3. Steel piles
4. Composite piles.
F.
Drilled Shafts or Caissons
ü A drilled shafts also known as
caissons, which is mostly used at the construction of bridge, pier and mostly at
the structure over water.
ü They have the characteristics of
floating at a desired location then sunk into the place.
ü By digging the loose land with an
auger up to getting bedrock, sand while digging, hollow steel casing is fixed to
prevent the sand or soil from caving, the reinforced mesh rebar is then
centered inside the casing, and then
concrete poured. Concrete is filled from bottom to the top of casing, so that all
the groundwater out from the top. Caisson
foundation can be done by this way
ü Also by using mesh grid of rebar
filled with concrete, caisson can be constructed on site.
ü Main types of caissons are as
follows:
1) Open caissons
2) Pneumatic caissons
3) Monolithic caissons
4) Sump caissons
5) Box caissons
G. Pier Foundation
ü The load which is not transmitted by
the shallow foundation, for transferring such massive load pier foundation is
used.
ü It is not as deep as piles; it is
used in multistory structure.
ü It transferred load to soil through
end bearing.
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