The document provides information on the basics of civil engineering foundations. It discusses the objectives and types of foundations, including shallow foundations like isolated and combined footings, and deep foundations such as pile and pier foundations. Pile foundations can be friction piles or load bearing piles. Factors that determine the size and bearing capacity of foundations are also covered. The document contains diagrams to illustrate foundation components and construction methods.

1. Basic Civil Engineering-Foundation
By
Mr.B.Ramesh, M.E.,(Ph.D),
Research Scholar, CEG, Anna University, Chennai.
Associate Professor, Department of Mechanical Engineering,
St. Joseph’s College of Engineering,
Jeppiaar Trust, Chennai-119

2. Foundation

3. Foundation
• Introduction :
• A structure essentially consists of two parts, namely the super
structure which is above the plinth level and the substructure which is
below the plinth level.
• Substructure is otherwise known as the foundation and this forms the
base for any structure. Generally about 30% of the total construction
cost is spent on the foundation.
• The soil on which the foundation rests is called the “foundation soil”.
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• Objectives of a foundation :
A foundation is provided for the following purposes:
• To distribute the total load coming on the structure on a larger
area.
• To support the structures.
• To give enough stability to the structures against various
disturbing
forces, such as wind and rain.
• To prepare a level surface for concreting and masonry work.

4. Foundation…
• Types of foundation :
The two main types of foundation
are :
• Shallow foundation (spread
foundation) and
• Deep foundation
Types of Shallow foundation :
• Isolated footing (single footing,
Column footing)
• Combined footing
Types of Deep foundation :
• Pile foundation
• Pier foundation
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Types of Pile foundation :
• Friction pile
• Load bearing pile
Note : Under-reamed piles is a
type of load bearing pile

5. Foundation…
• Shallow foundation (spread
foundation):
• Depth of foundation is less than
or equal to its width.
• Isolated footing (single footing,
column footing):
• In framed structures where
several columns are to be
constructed, isolated footings
can be adopted.
• The columns involved can be
provided with masonry or
concrete footing.
• If masonry footing is provided,
steps are given and the
foundation area is thus
increased so that the stresses
developed at the base is within
the limit.4 November 2010
• In case of masonry footing, the
projection of each step must be ½
brick thick and each step is made
of 1 or 2 bricks put together.
• Concrete can be moulded to any
shape and hence a concrete
footing may be a sloping one to
provide sufficient spread.

6. Foundation…
• Isolated footing (single footing, column footing)…
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7. Foundation…
• Isolated footing (single footing, column footing)…
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8. Foundation…
• Isolated footing (single footing, column footing)…
wall footing
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9. Foundation…
• Combined footing:
• This type of footing is
adopted when the space
between two columns is so
small that the foundation for
individual columns will
overlap.
• Combined footings are
proportioned in such a way
that the centre of gravity of
the loads coincides with the
centre of gravity of the
foundation. Hence these
footings have either a
trapezoidal or a rectangular
shape.
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Footing :
Footings are structural members
used to support columns and walls
and to transmit and distribute their
loads to the soil in such a way that
the load bearing capacity of the
soil is not exceeded. Also
excessive settlement, differential
settlement or rotation are
prevented and adequate safety
against overturning or sliding is
maintained.

10. Foundation…
• Size of footing :
• The area of footing can be determined from the actual
external
loads, such that the allowable soil pressure is not exceeded.
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11. Foundation…
• Pile :
• A slender, structural member
consisting steel or concrete or
timber.
• It is installed in the ground to
transfer the structural loads to
soils at some significant depth
below the base of the structure.
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12. Foundation…
Pile caps are thick slabs used
to tie a group of piles together
to support and transmit column
loads to the piles.
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13. Foundation…
• Deep foundation :
• Deep foundation consists of
pile and pier foundations.
• This consists in carrying down
through the soil a huge
masonry cylinder which may be
supported by the sides of soil
or may be supported on solid
rock (hard stratum).
• Pile foundation :
• Pile is an element of
construction used as
foundation. It may be driven in
the ground vertically or with
some inclination to transfer the
load safely.
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14. Foundation…
• Pile foundation…
• Loads are supported in two
ways.
• If the load is supported by the
effect of friction between the
soil and the pile skin, it is called
friction pile.
• Friction piles may be made of
cast iron, cement concrete,
timber, steel, wrought iron and
composite materials.
• If the load is supported by
resting the pile on a very hard
stratum, it is called load bearing
pile.
• Load bearing piles are steel
sheet piles, concrete piles and
timber piles.
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• Piles may be cast-in-situ or
precast.
• They may be cased or
uncased.

15. Load
Bearing
Pile
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Friction Piles

16. 4 November 2010
Load bearing
pile
Friction Pile

17. Batter Piles
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18. Foundation…
Under-reamed piles:
• Structures built on expansive soils often
crack due to the differential movement
caused by the alternate swelling and
shrinking of soil. Under-reamed piles
provide a satisfactory solution to the
above problem.
• The principle of this type of foundation is
to transfer the load to a hard strata which
has sufficient bearing capacity to take the
load.
• Single and double under-reamed piles
may also be provided for foundations of
structures in poor soils overlying firm soil
data. In such soils if double under-reamed
piles are provided, both the under-reams
shall rest within the firm soil data.
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19. Cast in situ
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20. PILE FOUNDATION IS USED WHEN:
• The soil near the surface doesn’t have sufficient bearing capacity
(weak) to support the structural loads.
• The estimated settlement of the soil exceeds tolerable limits
• Differential settlement due to soil variability or non-uniform structural
loads is excessive.
• Excavations to construct a shallow foundation on a firm soil are
difficult or expensive.
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Foundation…

21. Distribution of Soil Pressure
Soil pressure distribution in
non-cohesive soil.
Soil pressure distribution in
cohesive soil.
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22. Foundation…
• Bearing capacity of soil :
• It is defined as the maximum load per unit area which the soil will
resist safely without displacement
• The bearing capacity of the soil can be found by loading the soil,
noting the settlement and by dividing the maximum load by the area on
which the load is applied. The maximum load is obtained from the
graph between the settlement and load.
• Safe bearing capacity of soil = [Ultimate bearing capacity of soil] /
[Factor of safety]
• On completion of a structure there may be some displacement in the
position of the foundation.
• For ordinary framed structures of concrete, the permissible angular
distortion is 1/500 and the desirable value is 1/1000.
• The maximum differential settlement should not exceed 25 mm in case
of foundations on sandy soil and 40 mm in case of foundations on
clayey soil.
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23. Foundation…
Bearing capacity of soil…
• In case of non-cohesive soils, such as sand and gravel, the allowable
bearing capacity should be reduced by 50%, provided that the water
table is above or near the bearing surface of the soil.
• The bearing capacity of reclaimed soils or shrinkable soils can be
taken as 50kN/m2 in the absence of the site data.
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24. Artificial methods to improve bearing
capacity of soil
• By increasing the depth of foundation.
• By draining the sub-soil water.
• By compacting the soil.
• By confining the soil mass.
• By cement grouting.
• By injecting chemicals like silicates etc.
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Essential requirements of a good foundation:
• The foundation should be so located that it is able to resist any
unexpected
future influence which may adversely affect its performance.
• The foundation should be stable or safe against any possible failure.
• The foundation should not settle or deflect to such an extent that will
impair
its usefulness.

25. PIERS
• It’s a vertical bridge support.
• It’s a foundation for carrying a heavy structural load which is
constructed
in site in a deep excavation.
• Among the things to be taken in consideration during construction of
pier are as follows:
– Drilling through wet or caving soils may need use of temporary steel
casing. May also require the use of a tremie & a pump to dewater the
hole & place concrete. This is more expensive and require a large
diameter hole.
– For the purpose of reinforcing, it’s difficult to get bars to the full depth
of the pier with the proper concrete cover in deep holes. Use
centralizes. Use large diameter bars versus more bars.
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26. c) Don’t leave holes open for any length of time even in dry condition.
Have concrete on site and fill right after drilling and cleaning.
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27. Foundation…
Videos and Animations
1. Basement forming
– Foundation
– Types of foundation
– Pile foundation
– Sheet piling
– Raft foundation
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28. TYPES OF PILES
• Concrete Piles
i) Cast-In-Situ Concrete Piles
a) Cased cast-in-situ b) Uncased cast-in-situ
ii) Precast Concrete Piles
• Steel Piles
i) H-Piles ii) Cylindrical piles iii) Tapered piles
• Timber Piles
• Composite Piles
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29. TYPES OF PILE CONSTRUCTION
1. Displacement Piles
It cause the soil to be displaced radially as well as vertically as pile
shaft is driven or jacked into the ground.
b) Non Displacement Piles (Replacement piles)
It cause the soil to be removed and the resulting hole filled with
concrete or a pre cast concrete pile is dropped into the hole and
grouted in.
Displacement Pile Non Displacement pile
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30. METHOD OF INSTALLATION
• Dropping Weight or Drop Hammers
- commonly used method of insertion of displacement piles
• Diesel Hammers
-Most suitable to drive pile in non cohesive granular soil
• Vibratory Hammers or vibratory method of pile driving
-very effective in driving piles through non cohesive granular soil
• Jacking Method Of Insertion
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31. 4 November 2010
Pile installation using Drop Hammer

32. Pile Driving Rig - temporarily support the pile that
being
driven and to support the pile hammer.4 November 2010

33. Jacking Method Of Insertion
• Jacked Piles are most commonly used in underpinning structures
• By excavating underneath a structure short lengths of pile can be
inserted and jacked into the ground using the underside of the existing
structure as a reaction.
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34. NON DISPLACEMENT PILES
There are four types:
1. Small Diameter Cast-In- Situ
– Large Diameter Cast-In-Situ
– Partially Preformed Piles
– Grout or Concrete Intruded
Piles
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35. 4 November 2010
Thank You