Sheet Pile Design for River Training Works

You are designing a river training structure—a guide bank, a groyne, or a cut-off wall. The river is unpredictable, with changing flows and eroding banks. You need a solution that can withstand the forces of water and soil.

Sheet pile design for river training works requires careful consideration of flow velocities, scour depths, and soil conditions. U-type sheet piles¹ with Larssen interlocks are the standard choice for river training because they provide water tightness, can be installed in flowing water, and resist erosion. The design must account for both normal flow and flood conditions.

I have supplied sheet piles for river training projects across Southeast Asia and the Middle East. The riverbank project in Southeast Asia was a classic example—a guide wall that stabilized the river course and prevented erosion. Let me walk you through the design considerations for river training works.

---

What is the rule of thumb for sheet pile depth¹?

The rule of thumb for sheet pile depth¹ in river training works accounts for flow velocities², scour potential³, and soil conditions.

For sheet piles in river training works, the rule of thumb for embedment depth (D) is 1.2 to 1.8 times the exposed height (H) for cantilever walls⁴. In river applications, the depth must also account for potential scour—the embedment should extend below the expected scour depth. For high-velocity rivers, embedment may need to be 2.0 times H or more.

River-Specific Embedment Rules

Let me explain how river conditions affect the rule of thumb.

Base Rule for Cantilever Walls
For river training works, cantilever walls⁴ are most common:

• D = 1.2 to 1.8 H (higher than land-based walls)
• The higher range accounts for scour and dynamic water forces

Scour Factor
Scour is the erosion of riverbed around structures. Sheet piles must be embedded below the expected scour depth.

• Low velocity rivers ( 4 m/s): Add 3-5 m below scour depth

Flow Velocity Factor

Flow Velocity	Additional Embedment
4 m/s	+40-50%

Example Calculation
Given:

• Exposed height (H) = 5 m
• Flow velocity = 3 m/s
• Scour depth = 2 m

Base D = 1.5 × H = 7.5 m
Velocity factor: +30% = 2.25 m
Scour allowance: 2 m below scour depth? Actually, piles must go below scour depth. If scour depth is 2 m, embedment below original bed must be at least 2 m deeper.

Final D = 7.5 + 2.25 + 2.0 = 11.75 m

My Experience
For the riverbank project, the river velocity was moderate (2.5 m/s), and scour depth was estimated at 1.5 m. We used D = 1.5 × H + 2 m = 7.2 m + 2 m = 9.2 m. The piles have stayed in place through several flood seasons.

---

What are the disadvantages of using sheet piles?

Sheet piles are excellent for river training, but they have limitations that engineers must consider.

The main disadvantages of sheet piles for river training works are corrosion in freshwater (though slow), potential for scour undermining the toe of the wall, difficulty driving through cobbles or rock, and the need for guide frames to maintain alignment in flowing water. In high-velocity rivers, the wall may need additional scour protection at the toe.

Addressing the Disadvantages

Let me discuss each disadvantage and how to mitigate it.

Corrosion¹
In freshwater rivers, corrosion is slow (0.02-0.05 mm/year). For a 50-year design life:

• Add 1-2 mm corrosion allowance to wall thickness
• Use standard carbon steel (A328, S270GP) for freshwater
• For brackish or tidal rivers, use marine grade A690

Scour Undermining²
Scour can erode the soil at the toe of the wall, reducing embedment and causing failure.

• Design piles to extend below expected scour depth
• Install scour protection (riprap or concrete) at the toe
• Monitor scour after flood events

Driving Difficulties³
Rivers may have cobbles, boulders, or rock that make driving difficult.

• Conduct geotechnical investigation before design
• Pre-drill through hard layers
• Use impact hammers instead of vibratory
• Consider alternative pile types if rock is near surface

Alignment in Flowing Water⁴
Maintaining alignment in flowing water requires careful planning.

• Use guide frames mounted on barges or temporary piles
• Drive piles in calm water conditions if possible
• Use heavier piles that resist water forces during driving

Flow-Induced Vibration
In high-velocity rivers, sheet piles can vibrate.

• Design for dynamic loads
• Use stiffer sections (higher moment of inertia)
• Ensure proper embedment

Mitigation Summary

Disadvantage	Mitigation
Corrosion1	Corrosion1 allowance, marine grade steel
Scour	Embed below scour depth, scour protection
Hard driving	Pre-drilling, impact hammers
Alignment	Guide frames, calm water installation
Vibration	Stiffer sections, proper embedment

My Experience
For the riverbank project, we addressed scour by driving piles 2 m below the estimated scour depth. We also placed riprap at the toe to prevent erosion. The piles have not moved despite several floods.

---

What is the difference between U type and Z type sheet piles¹?

In river training works², the choice between U type and Z type sheet piles¹ depends on the wall alignment, height, and flow conditions.

U type sheet piles³ have interlocks at the neutral axis and are symmetric, making them ideal for curved river alignments and moderate heights. Z type sheet piles¹ have interlocks at the outer flanges, giving them higher structural efficiency for taller walls. For most river training works², U-type piles are preferred because they follow river curves easily and provide good water tightness⁴.

Comparison for River Training Applications

Let me explain which type works best for river conditions.

U Type Sheet Piles

• Profile: Symmetric, looks like a U
• Interlock: Larssen ball-and-socket at neutral axis
• Width: 400 mm or 600 mm
• Best for: Curved alignments, riverbanks, moderate heights (up to 8 m)
• Advantages: Easy installation, forgiving alignment, good water tightness⁴
• Common sections: U 400 x 125, U 400 x 170

Z Type Sheet Piles

• Profile: Asymmetric, looks like a Z
• Interlock: Ball-and-socket at outer flanges
• Width: 630-700 mm
• Best for: Straight alignments, tall walls (over 8 m)
• Advantages: Higher strength per kg, wider sections
• Common sections: AZ 18, AZ 26

River-Specific Considerations

Factor	U Type	Z Type
Curved alignments	Excellent	Difficult
Water tightness	Good (Larssen interlock)	Good (ball-and-socket)
Installation in flowing water	Forgiving	Requires more care
Height capability	Up to 8 m	Over 8 m
Cost for moderate heights	Lower	Higher

My Experience
For the riverbank project, the river had a curved alignment, so we chose U-type piles. The U 400 x 125 piles followed the curve easily and provided excellent water tightness⁴. For a straight river training wall over 8 m high, we would use Z-type piles.

---

What is the ASTM for sheet pile?

The ASTM standards for sheet piles define the material properties, chemical composition, and mechanical requirements.

The main ASTM standards for sheet piles are ASTM A328¹ (carbon steel sheet piles), ASTM A572 Grade 50 (high-strength sheet piles), ASTM A690² (marine grade sheet piles for brackish water), and ASTM A857 (cold-formed sheet piles). For freshwater river training works, ASTM A328¹ is the standard choice.

ASTM Standards for River Training

Let me explain which ASTM standards apply to river training works.

ASTM A328¹ – Carbon Steel Sheet Piles
This is the standard for standard carbon steel sheet piles.

• Yield strength: 240 MPa (35 ksi) minimum
• Tensile strength: 410 MPa (60 ksi) minimum
• Chemical composition: Standard carbon steel
• Best for: Freshwater rivers, moderate loads
• Cost: Lowest

ASTM A572 Grade 50 – High-Strength Low-Alloy
This standard covers higher strength steel.

• Yield strength: 345 MPa (50 ksi) minimum
• Tensile strength: 450 MPa (65 ksi) minimum
• Best for: Taller walls, higher loads
• Cost: Moderate

ASTM A690² – Marine Grade Sheet Piles
This standard covers steel with improved corrosion resistance.

• Yield strength: 345 MPa (50 ksi) minimum
• Tensile strength: 485 MPa (70 ksi) minimum
• Contains copper, nickel, phosphorus
• Best for: Brackish or tidal rivers
• Cost: Higher

Selection Guide for River Training

River Type	Recommended ASTM Standard
Freshwater, moderate loads	A328
Freshwater, tall walls	A572 Grade 50
Brackish water	A690
Tidal river	A690
Temporary works	A328 or A857

My Experience
For the riverbank project, the river was freshwater, so we used ASTM A328¹ sheet piles. The standard carbon steel with a 2 mm corrosion allowance provided the required 50-year design life.

---

Conclusion

Sheet pile design for river training works requires careful consideration of scour, flow velocity, and alignment. U-type piles¹ are preferred for curved river alignments. Embedment depth should account for scour potential. Use ASTM A328² for freshwater and A690 for brackish water.

---