UNDERWATER CONSTRUCTION PPT BY AJITA PANDEY & SACHIN RAMANI

1. DEPT. OF CIVIL ENGINEERING GCET
JAMMU 1

2. Presented by:
Ajita Pandey
Sachin Mansharamani
2
Construction
Underwater...

3.  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.
3

4. UNDERWAT
ER
CONSTRUC
TION
Constructi
on
technique
s
Caissons
Cofferda
ms
Methods
of
Placing
of
concrete
Tremie
method
Pump
method
Toggle
bags
Bag
works 4

5. DEPT. OF CIVIL ENGINEERING GCET
JAMMU 5

6. Caissons:
 Watertight 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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7. 7
Working inside a caisson

8. 8
Control post
pontoon
Ballast water
grab
Ground
water
level
Circumferential
gap
shoe
Box caisson
Open caisson
TYPES OF CAISSONS

9. 9
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.

10.  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
10

11.  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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12. DEPT. OF CIVIL ENGINEERING GCET
JAMMU 12
Working inside a cofferdam

13.  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
13
Bracing frame
Sheet piles

14. 1. Pre-dredge to remove soil or soft sediments and level the area of the
cofferdam
2. Drive temporary support piles.
3. Temporarily erect bracing frame on the support piles
4. Set steel sheet piles.
5. Drive sheet piles to grade.
6. Block between bracing frame and sheets, and provide ties for sheet
piles at the top as necessary
7. Excavate inside the grade or slightly below grade, while leaving the
cofferdam full of water
8. Drive bearing
9. Place rock fill as a levelling and support course.
10. Place Tremie concrete seal .
14

15. PLACEMENT
METHODS:
Tremie method. Pump method. Toggle bags. Bags work.
15
It is a process in which the prepared concrete is
poured below the water surface by using
suitable methods.

16.  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.
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17. DEPT. OF CIVIL ENGINEERING GCET
JAMMU 17

18. Laying of concrete by using Tremie
18
Basic principle behind Method
of underwater concreting -
Tremie method
Method of underwater
concreting— Tremie
method (inside view)

19.  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

20. TOGGLE BAGS: BAGWORK:
• 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.
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Used only in special cases like repair works, etc.

21.  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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22. DEPT. OF CIVIL ENGINEERING GCET JAMMU
22