under water construction

1. By
1. N.Abu Bakker Siddeeq
2.M.Bowjoor Rehman
Department Of Civil Engineering
Nandha College Of Technology
Underwater
Construction
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Guided By
V.Aravind, M.E.(Geotech)
AP/Civil Engg Dept.,
Nandha College of Technology

2. Contents
 Introduction
 Underwater construction techniques
 Caissons
 Types
 Advantages
 Cofferdams
 Types
 Components
 Advantages
 Underwater lying of concrete
 Tremie method
 Pump method
 Toggle bags
 Bagwork
 Conclusion
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3.  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.
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4. UNDERWATER
CONSTRUCTION
Construction
techniques
Caissons
Cofferdam
s
Methods of
Placing
concrete
Tremie
method
Pump
method
Toggle
bags
Bag works
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5. Caissons
 Water light retaining structure .
 Permanent in nature.
 Used to work on foundation of bridge pier, construction of
concrete dam or for the repair of ships.
 Constructed in such a manner so that the water can be pumped
out.
 Keeps working environment dry.
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Working inside a caisson

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Control post
pontoon
Ballast water
grab
Ground
water
level
Circumferential
gap
shoe
Box caisson
Open caisson
TYPES OF CAISSONS

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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 quicksand's.

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• More suitable for off shore construction.
• Upturned bucket embedded in marine sediment.
• Embedment achieved by pushing or by creating negative
pressure.
Suction caisson

10. 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
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11. Cofferdams
 Temporary structure
 Built within or in pairs across a body of water
 Allows the enclosed space to be pumped out, creating a dry work
environment .
 Enclosed coffers are commonly used for construction and repair
of oil platforms, bridge piers and other support structures built
within or over water.
 A cofferdam involves the interaction of the structure, soil, and
water. The loads imposed include the hydrostatic forces of the
water, as well as the dynamic forces due to currents and waves.
 Used for shallow constructions having depth less than 10m.
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Working inside a cofferdam

13. Components Of Cofferdam
 Sheet piling
Sheet piling is a manufactured
construction product with a
mechanical connection
“interlock” at both ends of the
section. These mechanical
connections interlock with one
another to form a continuous
wall of sheeting.
 Brace piling
 Concrete seal
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Bracing frame
Sheet piles

14. Advantages Of Cofferdam
 Allow excavation and construction of structures in otherwise
poor environment.
 Provides safe environment to work.
 Contractors typically have design responsibility.
 Steel sheet piles are easily installed and removed.
 Materials can typically be reused on other projects.
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15. Underwater Concreting
PLACEMENT
METHODS:
Tremie method. Pump method. Toggle bags. Bags work.
It is a process in which the prepared concrete is poured
below the water surface by using suitable methods.
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16. Tremie Method
A Tremie is a water light pipe
Generally 250mm in dia.
Funnel shaped hopper at its upper end
and a loose plug at the bottom.
It is supported on a working platform
above water level.
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17. Laying Of Concrete By Using Tremie
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Basic principle behind Method
of underwater concreting -
Tremie method
Method of underwater
concreting— Tremie
method (inside view)

18. 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 time and labour.
 For massive underwater concrete
construction of navigation structures,
the pump method should be
prohibited.
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Pump Method Of Laying Concrete

19. TOGGLE BAGS
• 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.
BAGWORK
• 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.
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20. 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.
 At present, the Tremie placement method is the standard way of placing
high-quality concrete underwater. 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.
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21. THANK YOU
ANY QUERIES?
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