Battered Pile Driving in Marine Construction

Marine construction is wrought with challenges, and installing piles as foundational supports within an aquatic environment is at the top of the list. There are different types of piles, and the material chosen depends greatly upon the structure's purpose, depth of the water, soil conditions, and more. For example, steel piles are common for docks and offshore platforms, and are often employed in deep water environments. Concrete piles may be used for piers, bridges, or jetties. Composite piles may be appropriate in especially environmentally sensitive areas.

The majority of piles are driven vertically (known as plumb piles); however, there are certain scenarios when a battered pile makes more sense.

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What is a battered pile?

Unlike traditional plumb piles (vertical), a battered pile is driven into the ground at an angle, creating unique installation challenges. Battered piles are often utilized to improve lateral stability required to resist seismic, berthing, wave, and wind imparted loads.  Also, when retrofitting existing structures with limited footprints, battered piles may be the only viable option to increase both lateral and vertical capacity.

In-water piles are commonly driven using crane barges or derrick barges (floating cranes).  A pile driven at a batter is moving both laterally and vertically adding to the challenge of holding position while floating in waves, current, and wind. Additionally, existing structures may reduce access for the crane, creating more conflict with rigging and crane positioning.

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A Battered Pile Case Study

Such was the case recently when Power Engineering Construction was building the foundation for a new loading system at an oil refinery in the Bay Area. Multiple battered piles were required in order to avoid conflict with the existing structural elements of a concrete wharf built almost 100 years ago. Several of the new battered piles needed to be intricately threaded through a sea of existing piles. It was a game of inches, and all conflicts were below water and even mudline.

A template was created to ensure accurate placement, alignment, and stability during the driving process. Power fabricated a template and pile driving tower at a 3:1 batter, which is a pretty significant angle (three vertical units for every horizontal unit). It was also necessary to develop a 3D model with existing pile locations to determine how and where to place the new battered piles without impacting the existing structure.  Based upon this model, the template and driving tower were designed, a process that took six months.

For this project, 24-inch square concrete precast piles were employed with lengths ranging from 128 feet to 148 feet, and a weight of 89,000 pounds each. Because the piles were fabricated of concrete, multiple rigging points were required when lifting them to avoid stress fractures in the concrete.

This was the second Power project at this oil refinery requiring battered piles. The initial project, entailed the installation of new seismic caps to withstand a 7.1 magnitude earthquake. This required 60-inch by 145-foot piles to be driven at a 3:1 ratio through active fuel lines and existing piles. Rather than concrete, however, this project utilized large-diameter steel pipe piles and a thick concrete cap structure to create a lateral resisting system. Similarly, the precise driving requirements and extreme weight and length of the steel battered piles resulted in the design and fabrication of a battered pile driving template and tower.

Because each driving tower is custom to the specific project, there is of course a cost associated with creating driving towers. Based upon lessons learned from the prior project, Power was able to fabricate a driving tower for the second project at roughly half the cost of the first.

For another project, Power constructed a breakwater designed to protect the newly built Treasure Island ferry terminal, and batter piles were essential. Here, an 815-foot-long precast concrete sheet pile wall required 24-inch octagonal piles every 6 to 18 feet to resist lateral wave and current forces on the breakwater wall. After exploring various options for locating, supporting, and driving battered piles, a custom hinge assembly was designed and fabricated to work in conjunction with standard pile driving leads for all battered piles. This custom hinge assembly was supported by the previously driven vertical concrete sheet pile, significantly reducing the cost of creating a much larger template tower.

Most of what happens with marine construction is not visible to the public – near, on, or under the water. And yet the challenges associated with this type of construction are significant and risky, requiring not only deep experience, but also extensive problem-solving capabilities and robust collaboration between the client, engineer, and contractor.

Do you have a challenging marine project in search of a solution? If so, we’d love to talk. Reach out to Wendy at pec@powerengconstruction.com to discuss how Power Engineering Construction can help make your project a reality.