Building piers in the ocean involves carefully constructing a stable structure that can withstand water, currents, and weather.
Key Steps in Ocean Pier Construction
Constructing a pier in the challenging marine environment requires specialized techniques and careful planning. One historical method, still relevant today for creating a dry work area, involves using cofferdams.
Here are the fundamental steps often involved:
- Site Survey and Preparation: Before any construction begins, detailed surveys of the seabed and water conditions are conducted to determine the best location and foundation type.
- Foundation Installation: The pier's foundation is critical for stability. This usually involves driving large piles (columns made of steel, concrete, or timber) deep into the seabed. Alternatively, pre-made concrete caissons might be sunk into position.
- Creating a Dry Workspace (Dewatering): To build the lower parts of the pier foundation or superstructure in a dry environment, the construction area needs to be dewatered. As a reference states, "Historically, construction sites have been dewatered by sinking a prefabricated cofferdam at the construction site." The reference further clarifies, "Cofferdams are enclosed structures from which water is pumped to expose the bed of a water body, allowing the construction of piers or other hydraulic works." This enclosed space provides a safe, dry area for workers to operate.
- Building the Substructure: Within the dewatered area created by methods like a cofferdam, workers can construct the pile caps, beams, or other elements that connect the piles and support the deck.
- Deck Construction: Once the substructure is complete, the deck of the pier is built on top. This involves placing girders, beams, and the deck surface itself (often concrete or timber).
- Adding Amenities and Finishing: Handrails, lighting, seating, and any necessary utility lines are installed to complete the pier.
- Removing Temporary Structures: If used, temporary structures like cofferdams are carefully removed once the permanent structure is stable.
Methods for Working in Water
Working directly in or above the water requires specific engineering solutions. Besides the historical use of cofferdams, modern techniques include:
- Pile Driving: Using large hammers (hydraulic, diesel, or vibratory) from barges or temporary trestles to drive piles into the seabed.
- Floating Equipment: Utilizing barges and cranes to transport materials and equipment and perform tasks from the water surface.
- Precast Elements: Constructing large sections of the pier (like deck sections or pile caps) on land and then floating them out and lifting them into place.
- Temporary Trestles: Building a temporary bridge from the shore out to the construction area to provide access for heavy machinery and vehicles.
Why are Cofferdams Important?
Cofferdams, as highlighted in the reference, play a crucial role in enabling construction below the waterline by providing a dry environment. This allows for:
- Precise foundation work.
- Construction using standard techniques and materials that are typically used on land.
- Easier inspection and quality control of the constructed elements.
While temporary, these structures are essential for the successful and safe construction of many marine structures like piers.
