Steel sheet piling retaining wall

A steel sheet pile retaining wall is a retaining structure composed of interlocking steel sheet piles. By driving or statically pressing the sheet piles into the ground, a continuous wall is formed to resist lateral pressure from soil or water. Among various retaining wall materials, steel sheet piles stand out due to their versatility, strength, and ease of construction, making them the preferred material for various projects.

Structure and Working Principle of Steel Sheet Pile Retaining Walls

1. Basic Structure
Steel sheet piles are typically hot-rolled steel sections with interlocking fasteners (such as U-shaped, Z-shaped, or straight types) on both sides, forming a continuous wall through mechanical interlocking. The stability of the retaining wall depends on two parts:

Fixed Section: The pile body is embedded in stable strata, utilizing passive earth pressure to provide anchoring force.

Support Structure: Cantilevered sections or auxiliary components such as anchor bolts and cap beams enhance stability.

2. Working Mechanism
One end of the steel sheet pile wall ("high side") bears the pressure of the protected soil, while the other end ("low side") transmits the pressure to the underground soil layer or structure through the pile sheet. In some cases, the wall operates as a cantilever; at greater depths or under pressure, an anchored wall is used to increase stability.

If used for water retention or seepage prevention, the seepage path at the interlocking joints must be controlled. Studies have found that the wall itself is almost impermeable; seepage mainly occurs through the interlocking joints.

Material Types and Selection Factors

Type Classification:

Z-shaped sheet piles: The cross-section is "Z"-shaped, with the interlocking joints far from the neutral axis; commonly used in applications requiring high load-bearing capacity.

U-shaped sheet piles: The cross-section is "U"-shaped; a traditional and commonly used type.

Straight-web type: Suitable for structures with low deflection requirements, shallow depths, or temporary structures.

Composite or box-type types: For particularly large loads or deep-water environments, box-shaped or H-shaped steel structures with interlocking walls may be used.

Selection Factors:

Stress requirements (e.g., bending moment, shear, lateral pressure);
Installation depth, geological conditions (hard soil, rock, groundwater);
Installation method (pile driving, static pressure, vibration);
Waterproofing or seepage prevention requirements: For high permeability control, choose a more tightly interlocked or welded joint;
Economy and reusability: Steel sheet piles are reusable, making them particularly suitable for temporary projects.

Applicable Conditions and Limitations

Geological Conditions:

Suitable for rock foundations (bedrock integrity coefficient > 0.6) or dense sand layers.

Soft soil foundations require an additional anchoring system; otherwise, insufficient embedment can lead to displacement (displacement limit ≤ 1/100 of cantilever height).

Application Scenarios:

Permanent projects: Wharf embankments, revetments, breakwaters, etc.

Temporary projects: Foundation pit support, cofferdams, trench retaining/water blocking (e.g., bridge cofferdams).

Disaster emergency response: Flood control and diversion, landslide protection.

Limitations:

Retaining height: Permanent structures are typically ≤10m; exceeding this limit requires special design.

Earth pressure value: Applicable earth pressure ≤100kPa; high pressure requires combination with other structures.

Summary

Although the initial cost of sheet piles may be higher than other types of retaining walls, their long-term benefits, including low maintenance and long service life, make them an economical, efficient, safe, and versatile solution.