This document discusses foundations for structures. It defines foundations as the lowest part of a structure that transfers loads to the soil below ground level. Foundation engineering involves evaluating soil bearing capacity and determining the proper type, size, and depth of footings. The purpose of foundations is to transfer structural loads to the underlying soil without causing failure or excessive settlement. Shallow foundations spread loads laterally near the surface, while deep foundations distribute loads vertically to deeper soil layers using piles, piers or caissons when the upper soil cannot support the loads. Different types of shallow and deep foundations are described, along with their uses in different soil and load conditions.

1. FOUNDATION
Prepared by
Er. Ankaj Kumar
Lecturer & Head
Civil Engg. Deptt.

2. INTRODUCTION
 Foundation is the lowest part of a structure which is
constructed to below the ground level.
Or
 The foundation of a structure is the lowest part of the
sub-structure interfering with the soil and the
structure. It consists of some structural element (pad
or base) the soil underneath.
Or
 The structure below the ground is collectively called as
“foundation

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Every structure consist of two parts
Sub Structure Super Structure

6. FOUNDATION ENGINEERING
Foundation engineering is the branch of civil
engineering which deals with the following two types
of problems
 Evaluation of the ability of soil or bearing capacity of
soil.
 Decision of the proper type of footing, size of footing
and at what depth it should be placed.

7. PURPOSE OF FOUNDATION
The purpose of foundation is to
transfer the load of the structure to
the underlying soil without causing
the danger of failure in shear and
excessive settlement.

8. CLASIFICATION OF FOOTING
 Shallow foundation: A shallow foundation is a type of
building foundation that transfers structural load to the earth
very near to the surface, rather than to a subsurface layer or a
range of depths, as does a deep foundation.
Customarily, a shallow foundation is considered as such when
the width of the entire foundation is greater than its depth.
In comparison to deep foundations, shallow foundations are
less technical, thus making them more economical and the
most widely used for relatively light structures.

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 Deep foundation : A deep foundation is a type of foundation that
transfers building loads to the earth farther down from the surface than
a shallow foundation does to a subsurface layer or a range of depths.
 If the depth of footing greater or equal to the Width of footing, it is
known as the deep Foundation. Deep Foundation is used Where the
bearing capacity of the soil is very low. The load coming from the
superstructure is further transmitted vertically to the soil. There are
Three Major Types of Deep Foundation, and Their uses in construction
are discussed below
 Shallow foundations spread the load laterally
 Deep foundations distribute the load vertically rather than
horizontally

10. Types of Shallow & Deep
foundation

11. Isolated footing
It is used to support the load of a
single column. These are provided
where loads are relatively light and
columns are far spaced.

12. 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 center 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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14. Deep foundation
 If bearing capacity of the upper soil layer is insufficient for a
spread foundation but firmer strata is available at greater depth
then the piles are used to transfer the load to the deeper layer.
 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).

15. 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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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.
• Piles may be cast-in-situ or precast.
• They may be cased or uncased.

17. Pile foundations are used in the following
situations
 The load of the super structure is heavy and its
distribution is uneven
 The top soil has poor bearing capacity
 The subsoil water level is high
 There is large fluctuations in subsoil water level
 Canal or deep drainage lines exist near the foundation
 The structure is situated on the sea shore or river bed

19. Types of Pile Foundation

20. Timber pile

21. Concrete pile

24. Pier Foundation
 A pier foundation is a series of vertical pillars or
piles that transfer the building load to the soil.
Beams are then built on top of these columns. They lift
the house off the ground and are very popular in
coastal regions where rising tides are a problem

25. Pier foundations

26. Caissons
The word caissons derived from the French
word caisse meaning a box
Box like structure, round or rectangular
which sunk from the surface of either land
or water to some desired depth
Used for placing foundation under water

29. Box Cassion
Box caissons are typically box-shaped prefabricated structures that
are open at the top but closed at the bottom.
• Strong water tight vessel
• Built on land and floated up to site and then sink in to the water
• Used when loads are not heavy
• Bearing stratum is available at shallow depth
• Water depth is 6 to 8 m
• Foundation bed not required
• Material is loose

31. Open Cassion or Well
 The open caissons are open both at the top and at
the bottom and these caissons are hollow chambers.
The bottom of the caisson has a cutting edge.
• Used for buildings and bridge where soil liable to scour
• No firm bed is available

33. Pneumatic caisson
 A pneumatic caisson is a watertight box or cylinder-
like structure that is closed at the top and open at the
bottom, resting on the bed of the waterbody. They are
used for underwater construction of foundations for
bridge piers, abutments in rivers, and foundations for
large multi-story buildings. They are designed to keep
water out of the construction zone and act as a seal
that keeps the inside of the caisson dry for workers to
carry out work safely.

35. Any Questions ?