1. B.V.Patel Institute of Technology-Diploma studies
cofferdam

2. ADVANCE COSTRUCTION TECHNOLOGY
NAME OF SUBJECT:
ADVANCE COSTRUCTION TECHNOLOGY
SUBJECT OF SEMINAR :
COFFERDAM

3. NAME OF STUDENTS :- PATEL PRANAV R. (106560306127)
PATEL SANJAY B ( )
NAYI VISHAL A ( )
BHAGAT HARSH G. ( )
PATEL DENISH D ( )
PATEL VISHAL P ( )
DESAI MOHIT D ( )

4. Contents :- Introduction Requirement of a cofferdam
Necessity of cofferdam
Use of cofferdam
Factor affecting selection of cofferdam
Types of cofferdam
Forces acting on cofferdam
Economical height of cofferdam

5. Introduction :-
A cofferdam is a temporary structure which is built in a river, lake etc. to remove water from an area and make it possible to carry on the construction work under reasonably dry conditions.
Cofferdams are usually required for project such as dams and construction of piers and abutment.

6. Requirement of a cofferdam :-
The cofferdam should be reasonably watertight.
It should be generally constructed at site of work.
The design and layout of a cofferdam should be such that the total cost of construction, maintenance and pumping is minimum.
It should be stable against bursting, overturning and sliding, under the floods and waves.
The water to be excluded by a coffer dam may be either ground water of water lying above ground level, it may be deep or shallow and still or running.
The materials used in construction of a cofferdam are earth, timber, steel and concrete.

7. Necessity of cofferdam :-
The coffer dams are required in the following situation:
When it is required to construct a structure in the river bad.
When structure is to be constructed on a sea shore.
When it is required to construct a structure one a bank of the lake or inside the lake.
When deep excavation are carried out in a course grained soil.
When excavation is carried out below ground water table.
During deep excavation, when sides of the trenches are likely to collapse.

8. Use of cofferdam To facilitate pile driving operation
To place grillage and raft foundation
To construct foundations for piers and abutments of bridge, dams, locks, etc.;
To enclose a space for the removal of sunken vessels
To provide a working platform for the foundation of building when water is met with; and
To provide space for carrying out the foundation work without disturbing or damaging the adjoining structure such as buildings, pipelines, sewers, etc.

9. Factor affecting selection of cofferdam
The selection of a type of cofferdam depends upon the following factors:
The size of area which is protect by cofferdam
Depth of water
Flow of water
velocity of flowing water.
The nature of bed on which the cofferdam is to rest.
Availability of materials at the site
The Possibility of overtopping by floods, tides etc.
Transportation facility of machine equipment and materials

10. Types of cofferdam :- Earthen cofferdam Rock-filled cofferdams
Sand bags cofferdam
Single wall cofferdams
Double wall cofferdams
Cellular cofferdam
Crib cofferdam
Concrete cofferdam
Suspended or floating cofferdam

11. Earthen cofferdam :-
This is the simplest form of cofferdam. It essentially consist of an earthen embankment built around the area to be enclosed.
Suitable for low, 1.2 to 1.5 m and moderate head of water.
The top of embankment should be 1m above the water level.

12. Rock-filled cofferdams :-
Suitable for turbulent flow and up to 3m depth of water.
Stone or rubble is used for the embankment.
It construction is adopted only the stone is easily available in the nearby areas.

13. Sand bags cofferdam :-
The method of using laminated sand bags to build cofferdam are easy to construct, cost-efficient and economic friendly

14. Single wall cofferdams
This type of cofferdam is used in places where the area to be enclosed is very small and the depth of water is more, say 4.5 to 6 m.
It can be used for up to 25m depth of water.

15. Double wall cofferdams :-
Two-parallel rows of steel sheet piles driven into the ground
Tied together with anchors and wales, then filled with soil
There are two types of this type of cofferdams:
ohio river type wood sheeting cofferdam
Wood or steel sheeting cofferdam with wales and tie rods

16. Cellular cofferdams :-
Circular cells are connected by diaphragms
Deep excavations
Used when the construction area is very large
Also used when internal bracing is impractical
There are two types of this type of cofferdams:
Circular
Diaphragm

17. Crib cofferdam
In deep water where it is difficult to penetrate the guide piles or sheet
Piles into the hard bed below ,crib cofferdam is used.
In these type of construction ,the sheet piles are supported by a series of wooden cribs.

18. Concrete cofferdam
when construction must take place below the water level, a cofferdam is built to give works a day work environment.
sheet piling is driven around the work site, seal concrete is placed into the bottom to prevent water from seeping in from underneath the sheet piling, and the water is pumped out.

19. Suspended Cofferdam
cofferdam which is freely suspended and has a characteristics of floating.
it is a box type cofferdam.

20. Forces acting on cofferdam :-
Self weight of cofferdam
Water pressure
Earth pressure from out side soil
Uplift pressure
Scouring action
Ice pressure
Other action

21. Economical height of cofferdam
The maximum height of cofferdam for which its total cost is minimum is known as the most economic height of cofferdam.
When cofferdam is constructed in a river. It is necessary to determine the height that will most satisfactory. Usually the height of cofferdam is determined based on the height of the average normal flood during every year.

22. GUIDE BY :-
N.R.SHAH
M.M.PATEL
……BYE