underwater construction

2. Introduction
Underwater constructiontechniques
 Caissons
Types
Advantages
Dangersencountered
Cofferdams
Types
Components
Advantages
Underwater lying of concrete
Tremie method
Pump method
Toggle bags
Bag work
Conclusion

3. INDTRODUCTION
During the construction of bridges, dams or any
other structure where the foundation part of the
structure is most likely to lie underwater , we have
to opt for underwater construction
Construction in water poses many difficulties
especially in the places where there the depth is
considerable.
During underwater construction our main objective
is to create dry and water free environment for
working in such a manner that the structural
stability of the structure is not compromised.

4. UNDERWATER CONSTRUCTION
CONSTRUCTION
TECHNIQUES
1. CAISSON
2. COFFERDAMS
METHODS OF PLACING
OF CONCRETE
1. TREMIE METHOD
2. PUMP METHOD
3. TOGGLE BAGS
4. BAG WORKS

5. UNDERWATER CONSTRUCTION
TECHNIQUES
CAISSONS
 Watertight retaining structure
 Permanent in nature
 Used to work on foundationof bridge pier, construction of
concrete dam or for therepair of ships
 Constructed in such a manner so that the water can be
pumped out
 Keeps working environment dry.

9. TYPES OF CAISSONS
 OPEN CAISSON
 BOX CAISSON
 PNEUMATIC CAISSON
 SUCTION CAISSON

10. OPEN CAISSON
Similar to box but does not have bottom face .
Used in soft clays not having large obstructions
beneath.
It may fill with water during sinking.

11. 1. GRAB
2. GROUNDWATER
LEVEL
3. CIRCUMFERENTIAL
GAP
4. SHOE

14. BOX CAISSON
Prefabricated concrete box , it is set down on
prepared bases.
Once in place it is filled with concrete to
become part of the permanent works.

17. PNEUMATIC CAISSON
Large inverted box on which pier is built.
Compressed air is used to keep the water and
mud out.
Used to work on riverbed or quicksands.

21. SUCTION CAISSON
More suitable for off shore construction.
Upturned bucket embedded in marine sediment.
Embedment achieved by pushing or bycreating
negative pressure.

28. ADVANTAGES OF CAISSONS
Economic.
Slightly less noise and reduced vibrations.
Easily adaptable to varying site conditions.
High axial and lateral loading capacity.
Minimal handling equipment is required for
placement of reinforcing cage.
Placement is sometimes possible in types of soil
that a driven pile could not penetrate.

29. DANGERS ENCOUNTERED
CAISSON DISEASE is so named since it appeared
in construction workers when they left the
compressed atmosphere of the caisson and
rapidly reentered normal (decompressed)
atmospheric conditions.
Construction of the Brooklyn Bridge , which was
built with the help of caissons , resulted in
numerousworkers being either killed or
permanently injured bycaisson diseaseduring its
construction, including thedesigners son and Chief
Engineer of the project.

30. BROOKLYN BRIDGE

33. COFFER DAM
Coffer dams are temporary enclosures to keep out
water and soil so as to permit dewatering and
construction of the permanent facility in the dry
Meaning of Coffer Dam :Coffer=Box
To take up the foundation works in the Marine
Region, it is necessary to obstruct the water
f low by means of Coffer Dam.

34. PURPOSE TO USE COFFER DAM
STRUCTURE
To retain Soil & Water
Can be used as either Temporary or Permanent
Main purpose is to provide dry working area for
workers
It is constructed to facilitate piledriving operations.
theraft
It is used to place grillage as well as
foundation
It is used, whenthe foundation for piers and
abutments of a bridge , dams, locks, etc.. are tobe
constructed.
Some times it is also provided to storewater
temporarily

35. Cofferdams can be used in the all
sectors as explained below
A. Civil Engineering: Underground Car Parking,
Foundation, Basement Construction
B. Transport Engineering: Bridge Pier, Support Wall,
Ramps, Ground Water Retention, Tunnel Worketc.
C. Water Engineering: Weirs, Culverts, Flood
Protection Walls, Scour Protection Walls,Securing
Embankmentetc..
D. Port Construction: Dock Works, Jetty Worksetc..

36. TYPES OF COFFERDAM
1. Earth fill cofferdams: Mainly for low level water
2. Sand Bag Coffer Dam: Todivertcoarse of water
3. Rock fill cofferdams
4. Timber Cribor Rock filled cribcofferdams
Construction on land and than f loated into place,
which is also known as Gravity Dam
5. Braced/Sheet Pile Coffer Dam: Consisting of Sheet Piles,
mainly used in shallow water depth
a) Single wall cofferdams
b) Double wall cofferdams
c) Cellular cofferdams
6. Movable or Suspendedcofferdams

37. UNDERWATER CONCRETING
It is a process in which the prepared concrete is
poured below the water surface by using suitable
methods.
PLACEMENT METHODS
TREMIE METHOD
PUMP METHOD
TOGGLE BAGS
BAGS WORK

38. TREMIE METHOD
 A Tremie is a watertight pipe
 Generally 250mm in Dia
Funnel shaped hopperat its upper end and a
loose plug at the bottom
It is supported on a working platform above water
level

39. PUMP METHOD
Pumping concrete directly into its final position,
involving both horizontal and vertical delivery of
concrete.
Pumping concrete has the advantage of operational
efficiency with potential savings of timeand labour.
For massive underwater concrete construction of
navigation structures , the pump method should
be prohibited.

40. TOGGLE BAGS BAG WORK
 Toggle bags are ideal for
small amounts of concrete
placement.
 The bag is filled in the dry
with wet concrete.
 Used for repair work.
 The concrete is squeezed
out by a diver.
 Bags are made of open
weave material.
Diver- handled bags are
usually of 10 to 20 litres
capacity but 1cub . m bags
can be placed using a
crane.

41. CONCLUSION
 Cofferdams are temporary structures and used in
cases where the plan area of foundation is very
large, depth of water is less and for the soft soils,
where soils allow easy driving of sheet piles.
 Caissons are permanent structures and becomes
economical in cases where the plan area of
foundation is small, large depth of water and for
loose soils.
 Suction caisson anchors are gaining considerable
acceptance in the offshore industry.

42.  At present, the Tremie placement method is the
standard way of placing high-quality concrete.The
other placement method are not able to reliably
place high- quality underwater concrete for major
structures, although they may find application in
special cases.
 For massive underwater concrete construction of
navigation structures, the pump method should be
prohibited.