Steel Sheet Pile Applications in Offshore Terminal Projects

You are designing an offshore terminal for oil, gas, or bulk cargo. The structure is exposed to waves, currents, and ship impacts. The foundation must be strong, durable, and reliable for decades in a harsh marine environment.

Steel sheet piles are widely used in offshore terminal projects for quay walls, dolphin structures, cofferdams, and scour protection. Z-type piles (AZ series) are preferred for deep water quay walls. U-type piles are used for dolphin structures. Combination walls are used for very deep water and heavy loads. Marine grade steel (ASTM A690) is essential for seawater corrosion resistance.

I have supplied sheet piles for offshore terminals across the Middle East and Southeast Asia. A terminal in the UAE used AZ 26 piles for the quay wall. Another project used sheet pile cofferdams for foundation construction. Let me walk you through the key applications of steel sheet piles¹ in offshore terminal projects.

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How are sheet piles used for quay walls in offshore terminals?

Sheet piles are used to construct the main quay wall in offshore terminals. The quay wall provides the vertical face where ships berth and cargo is transferred.

In offshore terminals, sheet pile quay walls¹ are typically anchored walls with tie rods or ground anchors. The piles are driven to depth below the seabed, and the wall is anchored to resist lateral pressure from soil and water. For water depths of 10-15 meters, AZ 26 or AZ 34 Z-type piles are used. For depths of 15-20 meters, AZ 42 or AZ 50 piles are used. Combination walls may be used for depths over 20 meters.

Quay Wall Design for Offshore Terminals

Let me explain the key design considerations for sheet pile quay walls¹ in offshore terminals.

Typical Quay Wall Sections by Water Depth

Water Depth	Recommended Section	Wall Type	Anchor Type
8-10 m	AZ 18 or AZ 26	Anchored	Single tie rod
10-12 m	AZ 26	Anchored	Single tie rod
12-15 m	AZ 34	Anchored	Single or double tie rod
15-18 m	AZ 42	Anchored	Double tie rod
18-20 m	AZ 50	Anchored	Double tie rod
Over 20 m	Combination wall	Anchored	Multiple tie rods

Key Components of a Sheet Pile Quay Wall

• Sheet piles: Primary retaining wall
• Tie rods: Connect sheet piles to anchor wall
• Anchor wall: Driven behind the quay wall to resist pullout
• Concrete capping beam: Distributes loads and provides deck support
• Fender system: Absorbs ship berthing energy
• Bollards: Mooring points for ships

Design Loads for Offshore Terminals

Load Type	Source	Design Consideration
Soil pressure	Retained soil	Active and passive earth pressure
Water pressure	Tides, waves	Hydrostatic and hydrodynamic
Surcharge	Crane loads, cargo	Heavy equipment on deck
Berthing loads	Ships	Impact energy absorption
Mooring loads	Ship lines	Pullout forces on bollards
Wave loads	Storms, cyclones	Extreme event design

My Experience
For an offshore terminal in the UAE with 16 m water depth, we used AZ 42 sheet piles² for the quay wall. The piles were driven to 25 m total length (16 m exposed + 9 m embedment). Double tie rods at 3 m and 8 m below the deck provided the necessary support.

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What is the role of sheet piles¹ in dolphin and breasting dolphin² structures?

Sheet piles are used to construct dolphin structures, which are isolated mooring points for ships. Breasting dolphins absorb berthing energy, while mooring dolphins provide tie-off points.

In dolphin structures, sheet piles¹ are driven in a circular or rectangular pattern to form a cellular cofferdam³. The cells are filled with sand or gravel to create a stable mass. U-type sheet piles⁴s](https://www.escpile.com/single-post/top-five-advantages-of-using-vinyl-sheet-pile-for-marine-construction)[^1] with Larssen interlocks are commonly used because they can form curved cells. The cell diameter typically ranges from 5 to 15 meters depending on the berthing energy requirements.

Dolphin Design and Construction

Let me explain how sheet pile dolphins are designed and built.

Types of Dolphins

Type	Function	Sheet Pile Configuration
Breasting dolphin	Absorbs berthing impact	Circular cell, larger diameter
Mooring dolphin	Provides tie-off points	Smaller circular or rectangular
Berthing dolphin	Combination of both	Circular cell with fenders

Cellular Cofferdam Design for Dolphins

• Sheet piles are driven in a circle to form a cell
• The cell is filled with granular material (sand or gravel)
• The fill provides stability and weight
• The sheet pile interlock transfers tension around the cell

Recommended Sheet Pile Sections for Dolphins

Cell Diameter	Recommended Section	Wall Thickness	Fill Material
5-8 m	U 400 x 125	13 mm	Sand or gravel
8-10 m	U 400 x 170	15.5 mm	Sand or gravel
10-12 m	U 400 x 170	15.5 mm	Gravel
12-15 m	U 600 x 180	13.4 mm	Gravel

Advantages of Sheet Pile Dolphins

• Fast construction compared to concrete
• Can be built in deep water
• Fill material provides stability without heavy foundation
• Sheet piles can be extracted and reused for temporary dolphins

My Experience
For an offshore terminal, we constructed breasting dolphin²s using U 400 x 170 sheet piles¹ in 10 m diameter circles. The cells were filled with gravel, and fenders were mounted on the face. The dolphins have handled ship berthing for over a decade without issues.

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Why are sheet pile cofferdams¹ essential for constructing offshore terminal foundations?

Sheet pile cofferdams are essential for creating dry work areas during the construction of offshore terminal foundations. They allow workers to build pile caps, foundations, and other structures in the dry.

A sheet pile cofferdam is a temporary enclosure made by driving sheet piles in a circle or rectangle around the foundation area. The enclosure is dewatered using pumps, creating a dry work environment. After the permanent foundation is built, the cofferdam is removed and the sheet piles are extracted for reuse.

Cofferdam Design for Offshore Construction

Let me explain how sheet pile cofferdams¹ are designed and used.

Types of Cofferdams for Offshore Terminals

Type	Shape	Best For
Single-walled	Rectangular or circular	Shallow water, small areas
Cellular	Interlocking circular cells	Deep water, large areas
Braced	With internal struts	Deep excavations in soft soil

Cofferdam Design Considerations

Factor	Consideration
Water depth	Determines pile length and wall thickness
Soil conditions	Affects embedment and dewatering
Wave action	Requires robust design for exposed sites
Dewatering	Pump capacity for seepage control
Access	Space for construction equipment

Recommended Sheet Pile Sections for Cofferdams

Water Depth	Recommended Section	Bracing Required?
Up to 5 m	U 400 x 125	No (cantilever)
5-8 m	U 400 x 170	Yes (single brace)
8-10 m	U 600 x 180	Yes (single or double brace)
10-12 m	U 600 x 210	Yes (double brace)

Construction Sequence

1. Drive sheet piles around the foundation area
2. Install bracing (if needed)
3. Dewater the enclosure using pumps
4. Excavate to foundation depth (if needed)
5. Construct pile caps or foundations
6. Backfill and remove bracing
7. Extract sheet piles for reuse

My Experience
For an offshore terminal foundation, we used a sheet pile cofferdam 15 m in diameter. The water depth was 8 m, and we used U 600 x 180 piles with one level of internal bracing. The cofferdam was dewatered in 24 hours, and the foundation was built in two weeks.

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What sheet pile sections are recommended for cyclone and wave load resistance?

For offshore terminals in cyclone-prone regions, sheet pile sections must be designed to resist extreme wave loads, storm surge, and wind forces.

For cyclone and wave load resistance, use Z-type sheet piles¹ (AZ 34, AZ 42, or AZ 50) with high section modulus and thick walls. The embedment depth² should be increased by 20-30% to account for storm surge and scour. Marine grade steel (ASTM A690) is essential for corrosion protection. For very extreme conditions, combination walls with H-piles³ may be required.

Design for Extreme Wave and Cyclone Loads

Let me explain how to select sheet piles for cyclone-prone regions.

Design Loads for Cyclone Conditions

Load Type	Design Consideration
Wave height	Extreme storm waves (10-15 m+)
Storm surge	Elevated water levels (2-5 m above tide)
Wind forces	Direct pressure on wall and structures
Scour	Erosion at the toe of the wall
Debris impact	Floating objects hitting the wall

Recommended Sections for Cyclone-Prone Regions

Water Depth	Recommended Section	Additional Protection
8-10 m	AZ 26 or AZ 34	Increased embedment by 20%
10-12 m	AZ 34 or AZ 42	Increased embedment by 25%
12-15 m	AZ 42 or AZ 50	Increased embedment by 30%
15-18 m	AZ 50 or combination	Increased embedment by 30%
Over 18 m	Combination wall	Special design

Design Modifications for Cyclone Resistance

• Increase embedment depth² by 20-30% to account for scour
• Add scour protection (riprap or concrete mat) at the toe
• Use thicker wall sections for corrosion allowance
• Add tie rods at multiple levels for deep water
• Design for wave impact pressures

Steel Grade for Cyclone-Prone Regions

Environment	Recommended Grade
Seawater, cyclone zone	ASTM A690 (marine grade)
Splash zone	A690 + coating
Below water	A690 + corrosion allowance

My Experience
For an offshore terminal in a cyclone-prone region, we used AZ 42 sheet piles with 20 mm wall thickness. The embedment depth² was increased by 30% from 9 m to 12 m. Riprap scour protection was placed at the toe. The terminal has survived multiple cyclones without damage.

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Conclusion

Steel sheet piles are essential for offshore terminal projects. Use Z-type piles¹ for deep water quay walls. Use sheet pile dolphins for mooring and berthing. Use cofferdams for foundation construction. For cyclone-prone regions, increase embedment depth and use marine grade steel².

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