Have you ever wondered how bridge piers stand tall amidst rushing waters, defying natural forces? Are you curious to unveil the mystery hidden beneath? Let’s delve into the realm of the braced cofferdam uncover this engineering wonder and understand what is braced cofferdam.
Definition of Braced Cofferdam
Braced cofferdams are specialized structures built where underwater or near-water construction is required. Braced cofferdams have diagonal braces or struts positioned between vertically driven sheet piles.
Components of Braced Cofferdam
There are various components of cofferdams:
- Laggings: wooden planks that are placed in the horizontal direction as excavation proceeds
- Sheet Piling: Timber, steel, or concrete piles are vertically driven into the ground.
- Soldier beam: These Vertical Beams are provided to support the leggings. In the case of sheet piles, a soldier beam is not required.
- Wales/Waler beam: These are horizontal beams that transfer loads from sheet piles or leggings to struts.
- Struts: Struts are compression members that help distribute the load from one side to the other side of the excavation.
Factors Affecting the Selection of Cofferdam
Besides braced cofferdam, several other types of cofferdams exist, such as Earth-filled cofferdams, rock-filled cofferdams, water-inflated cofferdams, single-wall cofferdams, double-wall cofferdams, and cellular cofferdams. Engineers and project managers must consider the following factors while choosing the appropriate type of cofferdam.
- The dimensions of the area to be covered by a cofferdam.
- Depth of water
- Fluctuations of outside water level
- Subsoil conditions
- Cofferdam construction cost
- Possibility of scouring
- Availability of construction materials
- Duration of cofferdam construction
Hence, designing a cofferdam requires great consideration of the above-mentioned factors, ensuring an absolute absence of potential accidents.
Benefits of Cofferdam
Standing as engineering marvels, braced cofferdams are more than mere structures. Their applications extend across various construction scenarios.
- To facilitate pile-driven operations
- Providing facility to grillage and raft foundations
- To construct foundations for piers and abutments of bridges, dams, etc.
- To provide space for carrying out the foundation work without disturbing or damaging the adjoining structures such as buildings, pipelines, sewers, etc.
Remember that cofferdams are temporary structures removed after construction, whereas caisson forms part of the permanent structure. However, the function of both cofferdams and caissons is the same: to create a dry environment for construction.
Constraints of Cofferdam
Highlighting the strength of braced cofferdam is essential, yet it is equally important to know their constraints, for as everything has pros and cons, the same applies to braced cofferdams.
- Installation and alignment of diagonal braces can be complex and time-consuming.
- Struts reduce the available space for construction activities.
- Regular maintenance and checks are required to ensure water tightness.
- Removing coffer dams and braces takes time and effort.
- Construction can affect the environment and aquatic ecosystems.
- Only suitable if the riverbed is hard.
Braced cofferdams are evidence of engineering marvels and ingenuity, offering solutions to the complexities of underwater construction. Braced cofferdam continues to be helpful in various construction circumstances despite some limitations. Engineers must carefully review the project’s requirements and then examine the site conditions, and constraints to decide whether a braced cofferdam is the best option, or another form of cofferdam should be considered.
Conclusion
Braced cofferdams are of utmost importance in the construction industry. Cofferdam provides a dry area for the construction of structures. Furthermore, cofferdams are divided into various components that have their own importance. As everything has advantages and disadvantages, cofferdams also have them. Engineers should keep in mind the factors that affect the selection of the types of coffer dams.
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