- Isolated Footing - Combined Footing - Mat or Raft Foundation - Pile Foundation - Piled Raft Foundation - Shore Pile or Sheet Pile Protection System

1. Presentation On
• Isolated Footing
• Combined Footing
• Mat or Raft Foundation
• Pile Foundation
• Piled Raft Foundation
• Shore Pile or Sheet Pile Protection System
Submitted By:
Farhan Sadek Efaz
Student ID: 1601124
Department of Civil Engineering
Chittagong University of Eng. & Tech.
Submitted To:
Ms. Nafisa Tabassum Subah
Lecturer,
Department of Civil Engineering
Chittagong University of Eng. & Tech.

2. Isolated Footing
• Isolated footing is defined as the
footing, which is provided beneath
the column to distribute the loads
safely to the bed soil. This kind of
footing is used to support single-
columns and when the columns
are arranged relatively at long
distance. This the most
inexpensive kind of footing.

3. Isolated Footing
Fig: Section of an Isolated Footing
Fig: Various Types of Isolated Footing

4. Isolated Footing
Advantages of Isolated footing:
(i) Isolated Footing is cost effective.
(ii) Construction is easy.
(iii) Material used is concrete.
(iv) Does not require skilled labors for construction.

5. Isolated Footing
Disadvantages of Isolated footing:
(i) It will have settlement.
(ii) It has limited capacity.
(iii) It can be subjected to torsion or tension forces
easily.

6. Combined Footing

7. Combined Footing
Whenever two or more columns in a
straight line are carried on a single
spread footing, it is called a
combined footing. A combined
footing is usually used to support
two columns of unequal loads. In
such a case, the resultant of the
applied loads would not
coincide with the centroid of the
footing, and the consequent the soil
pressure would not be uniform.

8. Combined Footing
Combined footings are provided only
when it is absolutely necessary, as
1. When two columns are close
together, causing overlap of adjacent
isolated footings
2. Where soil bearing capacity is low,
causing overlap of adjacent isolated
footings
3. Proximity of building line or existing
building or sewer, adjacent to a
building column.
Fig.: Section of a Combined Footing

9. Raft Foundation
Raft foundations (sometimes known as Mat Foundations) are a large concrete slab
which can support a number of columns and walls.The slab is spread out under the
entire building or at least a large part of it which lowers the contact pressure
compared to the traditionally used strip or trench footings.Because of the speed
and volume of houses required after the second world war, the raft foundation was
widely used. The raft foundation was cheaper, easier to install and most
importantly, did not require as much excavation as the usual strip
foundations.When the Building Regulations were introduced in 1965 there were no
generic rules for raft foundations as there were for strip foundations.This meant
that to use a raft foundation, it had to be designed and approved by Building
Control. This made the entire operation much more difficult and time consuming so
raft foundations became less widely used almost overnight.

10. Raft Foundation
Fig: Layout of Raft Foundation

11. Raft Foundation
When Are Raft Foundations Used
Rafts are most often used these days when the strata is
unstable or (because of this) a normal strip foundation would
cover more than 50% of the ground area beneath the
building. There are also situations (usually in areas where
mining has occurred) where there may be areas of movement
in the strata.
They are much more commonly used in the construction of
commercial building in the UK that they are for domestic
homes, but can be used very successful in both situations. To
understand when it is better to use raft foundations, you need
to understand how they work.
Fig: Section of a raft foundation

12. Raft Foundation
Advantages and Disadvantages of Raft Foundations
Raft foundations tend to be cheaper and quicker to
use than traditional footings. There are a number of
reasons why this is the case:
- The foundation and floor slab is combined, which
saves time and materials
- Less excavation is required
- Other reasons that make raft foundations preferable
to footings are due to their engineering benefits. They
are ideal for poor ground condition where normal
footings would not cope well as they cannot spread
the load as effectively.

13. Raft Foundation
Advantages and Disadvantages of Raft Foundations
Related to this is that raft foundations can reduce
differential settlement, where settlement occurs at
different rates across the ground surface of the
building, which reduces cracking and other more
serious problems.
The main disadvantage is that they can prone to edge
erosion if they are not treated properly. They are not
effective is the load of the building is going to be
focused on a single point, although this is rare in
domestic construction, so this isn’t generally of
concern.
Fig: Construction of Raft Foundation

14. Pile Foundation
A pile is basically a long
cylinder of a strong
material such as concrete
that is pushed into the
ground to act as a steady
support for structures
built on top of it.

15. Pile Foundation
Pile foundations are used in the following situations:
# When there is a layer of weak soil at the surface. This layer cannot support
the weight of the building, so the loads of the building have to bypass this
layer and be transferred to the layer of stronger soil or rock that is below the
weak layer.
# When a building has very heavy, concentrated loads, such as in a high rise
structure, bridge, or water tank.
# Pile foundations are capable of taking higher loads than spread footings.

16. Pile Foundation
There are two fundamental types of pile foundations (based on structural
behaviour), each of which works in its own way.
End Bearing Piles
In end bearing piles, the bottom end of the pile rests on a layer of especially
strong soil or rock. The load of the building is transferred through the pile onto the
strong layer. In a sense, this pile acts like a column. The key principle is that the
bottom end rests on the surface which is the intersection of a weak and strong
layer. The load therefore bypasses the weak layer and is safely transferred to the
strong layer.

17. Pile Foundation
Friction Piles
Friction piles work on a different principle. The pile transfers the load of the
building to the soil across the full height of the pile, by friction. In other
words, the entire surface of the pile, which is cylindrical in shape, works to
transfer the forces to the soil.
To visualise how this works, imagine you are pushing a solid metal rod of
say 4mm diameter into a tub of frozen ice cream. Once you have pushed it
in, it is strong enough to support some load. The greater the embedment
depth in the ice cream, the more load it can support. This is very similar to
how a friction pile works. In a friction pile, the amount of load a pile can
support is directly proportionate to its length.

18. Pile Foundation
Fig: Different Types Of Piles

19. Pile Foundation
Fig: Steps of Pile Foundation

20. Piled Raft Foundation
A piled raft foundation combines two
foundation-building techniques into a
hybrid design suitable for specialized
circumstances. The raft, or spread,
foundation spreads the load of the
building across the ground. Think of it as
a raft floating on the ground supporting a
structure. Piles are columns extending
below the ground surface that connect at
the top of the building. A piled raft
foundation uses both methods to
support the building.

21. Piled Raft Foundation
When a Piled Raft Foundation Is
Used
Builders use piled raft foundations
when the stability of the material that
anchors the piles is questionable or
when stable material does not extend
under the entire building. The piled
raft foundation offers the floating
foundation partially anchored for
support.

22. Shore Pile Or Sheet Pile Protection System

23. Shore Pile Or Sheet Pile Protection System

24. Shore Pile Or Sheet Pile Protection System
Sheet piles are sections of sheet materials with interlocking edges that are driven
into the ground to provide earth retention and excavation support. Sheet piles are
most commonly made of steel, but can also be formed of timber or reinforced
concrete. Sheet piles are commonly used for retaining walls, land reclamation,
underground structures such as car parks and basements, in marine locations for
riverbank protection, seawalls, cofferdams, and so on.
The selection of sheet piling is dependent on factors, such as:
- The type of work, for example. whether it is permanent or temporary.
- Site conditions.
- The required depth of piles.
- The bending moments involved.
- The nature of the structure.
- The type of protection required.

25. The End