Method of underwater repair for the damaged structure

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NATIONAL INSTITUTE OF CONSTRUCTION MANAGEMENT & RESEARCH, PUNE

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INTRODUCTION
UNDERWATER CONSTRUCTION TECHNIQUES:
1.CAISSONS
2.COFFERDAMS
UNDERWATER CONCRETING
Placement Methods
1. TREMIE 3. TOGGLE BAGS
2. PUMP METHOD 4. BAG WORKS
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CAISSONS
 The term caisson has been derived
from the French word ‘CAISSEE’,
meaning BOX.
 Watertight retaining structure,
permanent in nature.
 Large & hollow that is sunk down
through the earth.
 Constructed in such a manner so that
the water can be pumped out.
 Used to work on foundation of bridge
pier, building columns, construction of
concrete dam or for the repair of
ships.
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Working inside a Caisson

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BOX CAISSON
OPEN CAISSON
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Control post
Pontoon
Ballast water
Grab
Ground water
level
Circumferential
gap
Shoe
TYPES OF CAISSON

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SUCTION CAISSON
PNEUMATIC CAISSON
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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.
• 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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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

8. Dangers encountered:
• Caisson disease is so named since it appeared in
construction workers when they left the compressed
atmosphere of the caisson and rapidly re entered
normal (decompressed) atmospheric conditions.
• Construction of the Brooklyn Bridge, which was built
with the help of caissons, resulted in numerous workers
being either killed or permanently injured by caisson
disease during its construction.
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COFFERDAMS
 Temporary structure, designed to keep water
and/or soil out of the excavation area.
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TYPES OF COFFERDAMS
• Dikes
• Cellular cofferdams
• Rock-filled crib cofferdams
• Concrete cofferdams
• Suspended cofferdams

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DEPT. OF CIVIL ENGINEERING GCET JAMMU
Working inside a Cofferdam

11. 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.
• Bracing frame
• Concrete seal
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Bracing frame
Sheet piles

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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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Comparison Between Caisson And
Cofferdam
CAISSON
• Permanent structure
• Plan of small area
• Water height more
than 12m
COFFER DAM
• Temporary structure
• Plan of larger area
• Water height up to
12m
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UNDERWATER CONCRETING
PLACEMENT METHODS:
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• Tremie Method
• Pump Method
• Toggle Bags
• Bagwork
• It is a process in which the prepared concrete
is poured below the water surface by using
suitable methods.

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TREMIE METHOD
• A Tremie is a watertight
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.
Fig: schematic of a tremie method

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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
labor.
• For massive underwater concrete
construction of navigation
structures, the pump method
should be prohibited.

17. 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 1cum bags can
be placed using a crane.
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Used only in special cases like repair works, etc.

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A CASE STUDY ON BRIDGE FOUNDATION
Akashi Kaikyo
Bridge, Japan
(Completed in
1998)
The two main tower foundations are large double-wall steel
caissons filled with tremie concrete.

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• The project required that a large volume of tremie
concrete be placed up to 57m below the water
surface.
CASE STUDY

20. • All the tremie concrete was produced on a
floating batch plant.
• Each tremie placement was carried out
continuosly day and night for 3days.
• Each tremie pipe covered a 100-m2 area.
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21. • The total of 50,000 cum of concrete was
placed in the steel caisson.
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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. 22

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THANK YOU!
Presented By:
SUNAY JAISWAL AP14101
ANKUSH SINGH AP14125
SIDDESH HUPRIKAR AP14126
NITIN KUMAR AP14137
AMIT SINGH AP14192