Coffer dams are temporary structures that prevent water from entering excavation sites for construction, commonly used for bridge piers. Various types include braced, earth fill, rock fill, double-walled, and cellular coffer dams, each with specific characteristics and construction methods. Their advantages include a safe working environment, reusability of materials, and ease of installation, though they must withstand various forces like wind and water waves.

1. COFFER DAMS
Presented By
A.BHARAT KUMAR

2. Coffer dams
“A coffer dam is a temporary structure designed to
keep water and / or out of the excavation in
which a bridge pier (or) other structure is built”.
These coffer dam are usually welded
steel structure , wales and cross brace .such
structure are usually dismantled after the
construction work is completed.
meaning of coffer dam ; coffer= Box

3. Types of coffer dams
 Braced Coffer Dam
 Earth fill Coffer Dam
 Rock fill coffer dam
 Double-walled coffer dam
 Cellular coffer dam

4. Braced coffer dam
Formed from a single wall sheet pile
Drive into the ground and form a box
A round the excavation site
Interior is dewatered
Primarily used for bridge piers
Shallow water depth 30-35 feet

6. Earth fill coffer dam
It is the simplest type of coffer dam
Provide suitable drain
Free board 60 to 90 cm
1M width at top
Dry conditions clay embankment provided
Wet conditions sand materials suitable

8. Rock fill coffer dam
Depth about 3m
Availability of rock
Voids are filled by earth
Core wall clay (or) concrete
Some times , core wall (or) sheet pile is
used

10. Double-Walled
In large area and double walled sheet
The two parallel wall of coffer dams driven
into the ground and tie with system rods
The space between the walls is generally
filled with granular material such as sand,
gravel or broken rocks

12. Cellular coffer dam
Large areas
Steel sheet piles
Diaphragm cells and circular cells
Filling height equal, radius of 2500MM and
30-45 angel

14. Advantages
 Poor environment
 Safe environment
 Design responsibility
 Easy work
 Re-usability of material

15. Installation of coffer dam
 Pile driving hammer
 Vibratory (or) impact
 Crane of sufficient size
 Steel sheet piles are typically used
 H piles and walves , wide-flange beams

16. Forces acting on the coffer dam
 Wind waves
 Water waves acting on coffer dam
 Waves also produced by passing boats
and ships
 Seismic load