1. TYPES OF DEEP FOUNDATION
SOIL MECHANICS
5th CIVIL
DIV:B
Batch:B3
L.D. COLLEGE OF ENGINEERING

2. Presented by:- Name Enrollment no Hitesh Rathava 130280106101
Dasharath Sagar
Kiranmoy Samanta
Axit Shah
Deep Shah

3. INDEX
Foundation
Caisson
Pile Foundation
Coffer Dams

4. FOUNDATION
A foundation is the element of an architectural structure which connects it to the ground, and transfers loads from the structure to the ground.
There are mainly two types of foundation.
1> Shallow Foundation ( D<= B)
2> Deep Foundation ( D> B)
Deep Foundation may be further divided into three parts:
1> Caisson
2> Pile Foundation
3> Coffer Dams

5. CAISSON 1> Introduction:
CAISSON is a prefabricated hollow box or cylinder sunk into the ground to some desired depth and then filled with concrete thus forming a foundation which is often used in construction of bridge piers and other structures beneath any water body.
A caisson is a retaining, watertight structure used, for example, to work on the foundations of a bridge pier, for the construction of a concrete dam, or for the repair of ships. These are constructed such that the water can be pumped out, keeping the working environment dry.

6. 6
2> Installation:
Builders construct a water- tight caisson, over fifty feet long and nine feet high. It is made of oak timbers and covered with plate iron.
Containe d within the caisson are three open- bottome d air chamber s that allow the structure to act as a diving bell.

7. To sink the caisson, several ton blocks are placed at the top its roof.
Wooden pilings are made which guides its decent.
Workboats are used to support the machinery and move the blocks into place.
As caisson is installed into the water, the man starts to go inside through the airlocks.

8. They begin to excavate the riverbed, shovelling sand into a sand pump that suctions it up through a shaft and out through an opening at the top of the structure.
Compressed air is pumped into the chamber to keep water out ‚ the deeper the caisson sinks, the greater the air pressure needed.

9. 3> Types of caisson: Types of caisson Pneumatic Open Single
Cylindrical
Box
Dredging well
Monolithic
3> Types of caisson:

10. Pneumatic
Open cylindrical
Caissons
Box

11. 4> Uses: As breakwaters Bridge piers and abutments in river
Quay walls
Structures for shore protection
Large water front structures(pump houses)
For closure dams(closed caisson, sluice caisson)

12. PILE FOUNDATION
Piles are structural members that are made of steel, concrete, and/or timber. They are used to build pile foundations, which are deep and which cost more than shallow foundations . Despite the cost, the use of piles often is necessary to ensure structural safety.

13. Lateral forces are relatively prominent.
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When is it needed?
Top layers of soil are highly compressible for it to support structural loads through shallow foundations.
Lateral forces are relatively prominent.
In presence of expansive and collapsible soils at the site.
For structures near flowing water (Bridge abutments, etc.) to avoid the problems due to erosion.

14. Cont..
A pile foundation consists of two components: Pile cap and single or group of piles.
Piles transfers the loads from structures to the hard strata, rocks or soil with high bearing capacity.
These are long and slender members whose length can be more than 15m.
Piles can be made from concrete, wood or steel depending on the requirements.

15. PILE MATERIALS

16. Classification of piles:
Based on material:
Concrete
Timber
Steel
Based on method of construction:
Displacement pre cast piles
Displacement cast in situ piles
Replacement pre cast piles
Replacement cast in situ piles

17. Based on load transfer mechanism:
End bearing piles
Friction piles
Bearing cum friction piles
Based on sectional area:
Circular
Square H
Octagonal
tubular

18. Function of Pile Foundation:
 To transmit the buildings loads to the foundations and the ground soil layers whether these loads vertical or inclined.
To install loose cohesion less soil through displacement and vibration.
To control the settlements; which can be accompanied by surface foundations.
To increase the factor of safety for heavy loads buildings

19. Coffer Dam
A cofferdam is a structure that retains water and soil that allows the enclosed area to be pumped out and excavated dry.
Cofferdams are commonly used for construction of bridge piers and other support structures built within water.
Cofferdams walls are usually formed from sheet piles that are supported by waters and internal braces, and cross braces.
Since cofferdams are usually constructed within water, the sheet piles are installed using preconstructed templates that permit the correct positioning of each sheet pile from a barge.

20. Requirements Of a Cofferdam
The Cofferdam should be reasonably watertight.
It should be generally constructed at site of work.
The design and layout of a cofferdam should be such that the total cost of construction, maintenance and pumping is minimum.
It should be stable against bursting, overturning and sliding, under the floods and waves.

21. Types of Cofferdam Earth-fill Cofferdams Rock-fill Cofferdams
Rock-fill Crib Cofferdams
Single-Walled Cofferdams
Double-Walled Sheet Pile Cofferdams
Cellular Cofferdams
Hybrid Cofferdams

22. Earth-Fill Cofferdam
It is essentially consist of an earthen embankment built around the area to be enclosed.
It is constructed in places where the depth of water is not much say 1.3 to 1.8, and the velocity of flow is low.
The top of embankment should be about 1m above the water level.

23. 2323
Rock-fill Cofferdams
If the depth of water to be retained by the embankment of cofferdam is of order 1.8 to 3 m, stone or rubble is used for the embankment.
The construction is adopted only if the stone is easily available in the nearby areas.
An impervious layer of earth is laid on the outer face of the cofferdam, which makes it impervious.

24. Single-Wall Cofferdams
It is used in very small area and the depth of water is more, say 4.5 to 6 m.
Timber pipes are driven into the firm ground below the water bed.
Spacing of the piles may vary between 1.8 to 4 m.
Wales are the bolted to guide piles and sheets on the two faces are braced by struts.

25. Rock-fill Crib Cofferdams
A rockfill crib dam is comprised of timber cribs.
A crib is a framework of wooden horizontal and cross beams laid in alternate courses.
The cribs are open at the bottom and are filled with rock or earth or gravel. This gives stability to the crib against overturning.

26. Double-Walled Sheet Pile Cofferdams
They are cofferdams comprising two parallel rows of sheet piles driven into the ground and connected together by a system of tie rods at one or more levels. The space between the walls is generally filled with granular material such as sand, gravel or broken rock.

27. Hybrid Cofferdams

28. COFFERDAM CONSTRUCTION SEQUENCE:
For a typical cofferdam, such as for a bridge pier, the construction procedure generally is:
Pre-dredge to remove soil or soft sediments and level the area of the cofferdam 
Drive temporary support piles for template
Temporarily erect bracing frame on the support piles for the template
Install steel sheet piles, starting at all four corners and meeting at the center of each side
Drive sheet piles to grade

29. Cont..
Block between bracing frame and sheets, and provide ties for sheet piles at the top as necessary.
Excavate inside the grade or slightly below grade, while leaving the cofferdam full of water. Then lower the water inside and progressively install internal bracing as required by the design.
Drive piles within the cofferdam (if required).
Place rock fill as a leveling and support course.
Place tremie concrete seal.

30. Thank You