1. A caisson foundation is a type of foundation constructed by sinking a watertight chamber into the ground and filling it with concrete. 2. There are three main types of caissons: open caissons which are open on both ends, box caissons which are open at the top and closed at the bottom, and pneumatic caissons which use air pressure inside a sealed chamber. 3. Pneumatic caissons are constructed by building a sealed working chamber, excavating the soil inside while maintaining air pressure equal to outside water pressure, and repeatedly sinking the chamber to the desired depth before filling it with concrete.

1. CAISSON FOUNDATION

2. INTRODUCTION
• The term caisson has been derived from the French
word ‘CAISSEE’, meaning BOX.
• It can be round or rectangle in plan.
• It is commonly used where foundation under water is
done.
• It can sunk from surface of either land or water to the
desired depth.

3. TYPES OF CAISSON
• Open caisson
• Box caisson
• Pneumatic caisson

4. OPEN CAISSON
• Also called as well caisson.
• They are open at both the ends.
• These are boxes of timber, steel or R.C or masonry.
• Small caisson consists of one opening or well, while
larger one contain a series of wells.

5. PROCEDURE
• The caisson is cast and flatted to the site and sunk.
• When it reaches the required depth concrete is
deposited through water to some depth.
• After the concrete gets hardened, the water will be
pumped out.
• The caisson is finally filled completely with concrete.

6. BOX CAISSON
• Also called as Floating caisson.
• They are open at top and closed at bottom.
• They can be made of steel, R.C or timber.

7. • The caisson is built on land, then launched and brought
to the site where they have to be sunk.
• They are filled with concrete or stone masonry and
sunk until it rests on the river bed, which has been
prepared to receive it, or on a pile cluster to form a
lower part of a bridge pier.
PROCEDURE

8. TOWING OF CAISSON

9. APPLICATIONS OF BOX CAISSON
• Bearing stratum is available at shallow depth
• Loads are not heavy
• For wharfs and break waters

10. PNEUMATIC CAISSON
• “Pneumatic" means "with air" “Caisson" means "a box“
• The pneumatic caisson method works on the same
principle as a cup pressed into some water upside
down

11. 1.Preparation of the ground for installation
We level surface of working site where the
caisson is to be installed and improve the surface
conditions so that appropriate supporting force can be
supplied.
2.Construction of working chamber
We construct a working chamber at a bottom of
the caisson, in which earth is excavated and removed.
The chamber is pressurized to the same pressure as
the ground water pressure to make it watertight
EXECUTION OF THE PNEUMATIC CAISSON

12. 3. Rigging
Cylindrical steel shafts are used for workers to
enter or exit the pressurized working chamber and to
remove excavated earth. These shafts have locks (for
both men and materials) to regulate the difference
between the atmospheric pressure on the ground and
the pressure in the chamber. Installation of such
locks and shafts is called "rigging work".
4. Repeated excavation to sink & construct
caisson
We excavate and construct the caisson every 4m
height, and repeatedly sink it by excavating the
ground and constructing it to the desired depth.
EXECUTION OF THE PNEUMATIC CAISSON

13. 5. Testing the bearing capacity of soil
After the caisson has sunk to the specified depth,
we test and confirm that if sufficient bearing
capacity of soil has been obtained.
6. After concrete filling for working
chamber
After confirming the bearing capacity, we remove
equipments in the working chamber and fill
concrete, which means completion of works.
EXECUTION OF THE PNEUMATIC CAISSON

14. 1.PREPARATION OF THE GROUND FOR
INSTALLATION

15. 2.CONSTRUCTION OF WORKING
CHAMBER

16. 3.RIGGING

17. 4a.REPEATED EXCAVATING TO SINK
AND CONSTRUCT THE CAISSON

18. 4b.REPEATED EXCAVATING TO SINK
AND CONSTRUCT THE CAISSON

19. 5.TESTING THE BEARING CAPACITY OF
SOIL

20. 6.AFTER CONCRETE FILLING FOR
WORKING CHAMBER

21. APPLICATIONS
The Pneumatic Caisson Method is used for many
different structures:
• Foundations of road and railway bridges
• Subway tunnels facilities
• Basements and foundations buildings
• Water supply and sewage facilities
• Other facilities (e.g. garbage pits)

22. FOUNDATIONS OF ROAD AND RAILWAY
BRIDGES

23. BRIDGES CONSTRUCTED AT THE
WATER DEPTH OF 50 TO 60 M.

24. SUBWAY TUNNELS FACILITIES

25. BASEMENT AND FOUNDATION BUILDINGS
(Eg. UNDERGROUND PARKING ZONES)

26. WATER SUPPLY AND SEWAGE FACILITIES
(Eg. TREATMENT PUMP BUILDING)

27. OTHER FACILITIES (E.G. GARBAGE PITS)

28. OTHER TYPES
There are few more methods in caisson foundation.
• Jacking caisson method
• Space System Caisson

29. JACKING CAISSON METHOD
Jacking caisson method is to sink large scale caisson
thruster into ground by using jacks with rods connected to
earth anchor.

30. Intake shaft of 14 meter ø. is thrusted in
the ground at 50.7 meter below by using
12 jacks of 240 ton thrust force. The
caisson itself is constructed on the
ground by each rot of 5 meter.
Dimension of 26x19 meter is sunk by 8
jacks in the ground depth 18.5 meter,
while inside of caisson is excavated by
clam shell
JACKING CAISSON METHOD

31. SPACE SYSTEM CAISSON
• The gravel is filled between wall
surface and ground, and the
skin friction resistance is
reduced.
• The SS caisson method gently
and accurately install the
caisson in non-loading.
• The problem of the conventional
open caisson method is solved.

32. FEATURES OF THE SS CAISSON METHOD
• It is gently installed only at the dead weight at the good
accuracy.
• Subsidence and collapse of the ground in the
circumference are not caused.
• It is applicable for various geology.