FOUNDATIO

N
DEFINITION OF
FOUNDATION
A foundation is that part of the structure
which is in direct contact with the ground
to which the loads are transmitted.
Purpose of foundations.
Foundations provide the structure's stability from the ground: To distribute the weight of the
structure over a large area in order to avoid overloading the underlying soil (possibly causing
unequal settlement).
Requirements of
foundations.
• Foundation shall be constructed to sustain the dead and imposed
loads and to transmit these to the subsoil in such a way that pressure
on it will not cause settlement which would impairs the stability of
the building or adjoining structures.

• Foundation base should be rigid so that differential settlements

are minimised ,specially for the case when super imposed loads
are not evenly distributed.

• Foundation should be taken sufficiently deep to gurd the building

against
damage or distress caused by swelling or shrinkage of the sub
soil.

• Foundation should be so located that ,its performance may not be

affected due to any unexpected future influence.
Requirement of
foundations
Critical design considerations include foundation depth, soil bearing
capacity, soil type, frost protection, foundation materials, and load
transfer. A poorly designed foundation can lead to problems like
foundation settling, cracking, and even structural failure.
Functions of
foundations
1. REDUCTION OF LOAD INTENSITY
Foundation distributes the load of super
structure to a larger area so the intensity of load
at its base.

Even distribution of load

foundation distributes non-uniform load of the
super structure evenly to the sub soil
.
for example ,2 differently loaded columns is
connected together with combined footing. The
load will distributed evenly with uniform soil
pressure. Due to this ,unequal or differential
settlements are minimised.
Provision of level surface.
Foundation provides levelled and hard surface over which the super
structure can be built

Lateral stability
It anchors the super structure to the ground,thus imparting lateral
stability to the super structure.

Safety against undermining

It provides the structural safety against undermining or scouring burrowing
and flood water.

Protection against soil movements

Special foundations minimises the distress or cracks in the super
structure due to expansion or contraction of the sub soil because
of moisture movements in some problematic soils.
TYPES OF
FOUNDATIONS
• Shallow foundations
• Deep foundations

According to Terzaghi , A foundation is shallow if its

depth is less than or equal to its width and;
if its depth is greater than or equals to its
width is called deep foundation.
Shallow foundation
Shallow foundations are of 4
types.

1.Spread footing.
2. Combined footing.
3.Strap footing
4. Mat foundations.
Spread footing
Spread footings are those which spread the super imposed
load of wall or column over a large area. Spread footings
supports ,either a column or wall.
• Single footing for a column
• Stepped footing for a column
• Sloped footing for a column.
• Wall footing without step.
• Stepped footing for wall.
• Grillage foundation.
1. Single footing for a column in which the loaded area
of the column has been spread to the size
through a single spread. the base is generally
made of concrete.

2. Stepped footing for a heavily loaded column, which

requires
greater spread. the base is generally made of
concrete.

3. Concrete base does not have uniform thickness ,but

is made slopped with greater thickness at its
junction with column and smaller thickness at its
ends.

4. Spread footing for a wall, consisting of concrete base

without steps.
GRILLAGE
FOUNDATION

It is a special type of isolated footing generally provided for heavily

loaded steel stanchions and used in these locations where bearing
capacity of soil is poor. The depth of such foundation is limited to I to 1.5
m.the load of the stanchion is distributed over a large area by means of
two or more tiers of rolled steel joints
,each layer being laid at right angles to the layer below it, Both the tiers
of the joists are then embedded in cement concrete to keep the joists in
position and to prevent their corrosion.
mat footing, also known as a raft foundation, is a thick, reinforced
concrete slab that serves as the base for a building's
columns and beams

Mat footings are used when the soil is weak, the building is heavy, or the
columns are closely spaced. They're also used to reduce settlement caused by
uneven load distribution or construction on non-homogenous soils
Deep
foundations
Deep foundation

Deep foundations are structural elements that extend

below the ground surface to transfer building loads to
deeper, more stable soil or rock layers. They are typically
used when surface soils are insufficient to support the
weight of a structure. Here are some common types of
deep foundations
Deep foundations
1.Deep strip rectangular or square
footing.
2.Pile foundation
3.Pier foundation or drilled caisson
foundation
4.Well foundation or caissons.
Strip foundations
Strip foundations (or strip footings) are a type of shallow foundation
that are used to provide a continuous, level (or sometimes stepped)
strip of support for
linear structures such as walls or closely-spaced rows of
columns that are built on top of the foundation, placed
centrally along their length.

Deep Strip foundations are the least expensive and are used when ground
conditions are good. A concrete strip, sometimes reinforced with steel mesh,
supports the walls. The trench depth is variable but in most cases should be at
least 1m with a width of 600mm. The concrete should have a minimum depth of
225mm
• The usual strip ,rectangular or square
footing comes under the category of
deep foundations
,when the depth of the foundation is
more than
the width of the footing
Piles: Long, slender columns made of concrete, steel,
or wood, driven into the ground. They can be driven
piles (installed using a pile driver) or drilled shafts
(excavated and then filled).

Caissons: Large, cylindrical foundations that are often used in

water or soft soil conditions. They are typically drilled into the
ground and filled with concrete

Drilled Shafts: Also known as drilled piers, these are deep

foundations created by drilling a hole into the ground and
filling it with concrete
Socketed Piles: Piles that extend into bedrock,
providing extra stability for structures in areas with
challenging soil conditions
Deep foundations are crucial for tall buildings, bridges,
and other heavy structures, ensuring safety and stability
by anchoring them in more reliable sub-surface materials
Pile
foundations
Pile
foundation
purpose: Pile foundations are used to support structures when the top
soil layers aren't strong enough to support the structure on their
own. They can also be used to improve the load-bearing capacity of
the soil
Materials: Pile foundations are typically made of concrete or steel
Benefits: Pile foundations offer deep support, high load capacity, access
in difficult soils, minimal vibration, and are adaptable to various ground
conditions

Depth: Piles can be driven up to 50 meters deep in the ground, but the
minimum depth is usually around 3-4 meters

Use: Pile foundations are commonly found in

coastal areas
 Pile and Pier foundation
• PILE FOUNDATION
• Pile foundation is that type of deep foundation
in which the loads are taken to a low level by
means of vertical member which may be of
timber ,concrete or steel .Pile foundation may
be adopted

• PIER FOUNDATION
A pier foundation is a construction technique that uses a series
of vertical pillars or piles to support a building's weight and
transfer it to the soil. Beams are then built on top of the pillars
to raise the house off the ground. Pier foundations are often
used in situations where traditional foundations are difficult to
build, such as in coastal areas, around trees, or on slopes
Caisson
• The usual strip ,rectangular or square footing comes under the category of
deep foundations ,when the depth of the foundation is more than the width
of the footing.
• Well foundations are generally adopted for bridge pier etc. And not for
building
foundations.

• PILE FOUNDATION
• Pile foundation is that type of deep foundation in which the loads are taken to a
low level by means of vertical member which may be of timber ,concrete or
steel .Pile foundation may be adopted

• PIER FOUNDATION (DRILLLED CAISSON FOUNDATION )

• A pier foundation consists of a cylindrical column of large diameter to support
and transfer
large super imposed loads to the firm strata below.
• The difference between pile foundation and pier foundation lies in the
method of construction.
• Pile foundation transfer the load through friction and/or bearing ,pier
transfer the load
PIER FOUNDATION

A pier foundation is a foundation that lifts a structure off the

ground creating a space underneath. You've probably seen
houses near bodies of water raised high on piers. They look kind
of like they're sitting on a deck. Those are pier foundations. They
protect homes from flooding and the rising tide
Piles and piers
The main differences between piles and piers are their function, size, and material,
but the terms are often used interchangeably in the geotechnical industry
Function
Piles transfer loads from a building or structure into the ground, while piers are raised structures
that provide access to offshore areas.
Size
Piles can be as small as 2 inches in diameter, while piers are deep foundations with a larger
diameter, ranging from 2 to 30 feet.
Material
Piles can be made from steel, wood, or other materials, while piers are usually made
from concrete
Use
Piles are often used in situations where the soil lacks firm strata, such as bedrock, and are typically
used to support greater loads. Piers are usually used for smaller applications, such as sheds and
small living units
Piles and piers
Piles and
piers
Piles and
piers
Pile and pier
The main differences between pier and pile foundations are the
materials used, their diameter, and where they're typically used:
•Materials
•Piles can be made of steel or wood, while piers are usually
made
of concrete.
•Diameter
•Piles can be as small as 2 inches in diameter, while piers are
typically larger, ranging from 2 to 30 feet in diameter.
• Location
Pile foundations are often used in coastal areas with weak soil, while
post and pier foundations are common in coastal pre-FIRM
structures.
Here are some other differences between pier and pile foundations:
• Construction: Piles are driven into the ground until they reach
"refusal".
• Cost and time: Pile foundations are generally more expensive and
time-consuming than pier foundations.
• Support: Piers are designed to support between 120% to 150% of
the structure's weight
Caisson

A prefabricated, watertight structure made of wood, steel, or reinforced

concrete that is built above ground and then sunk into the
ground. Caissons are also known as drilled piers, drilled shafts, or bored
piles. They are often used for large structures like bridges and concrete
dams.
• Well foundations are generally adopted for bridge pier
etc. And not for building foundations.