Definition

A tangent pile wall is a type of retaining wall constructed by installing a series of closely spaced, vertically drilled piles. The piles are typically installed with a small gap between them, so that they are tangential to each other, hence the name “tangent” pile wall. This construction method provides lateral earth support, making it effective for retaining soil or water in various geotechnical applications. Tangent pile walls are commonly used in urban environments, where space is limited and noise and vibration must be minimized during construction.

Construction

The construction of a tangent pile wall involves several key steps:

• Site Preparation: The construction area is prepared by clearing and leveling the site and setting up equipment for drilling.
• Drilling and Installation: Piles are drilled vertically into the ground at regular intervals, with a small gap between adjacent piles. The piles are typically reinforced with steel and filled with concrete to provide the necessary strength.
• Spacing: The spacing between the piles is small, typically in the range of 100-200 mm, to ensure that the soil between the piles is effectively retained.
• Completion: After the piles are installed, any remaining gaps between them may be filled with grout or shotcrete to enhance the wall’s integrity and watertightness.

Context of Use

Tangent pile walls are particularly useful in various applications within geotechnical engineering, including:

• Urban Construction: Tangent pile walls are ideal for urban environments where space constraints and the need for minimal disturbance make traditional retaining wall methods impractical.
• Deep Excavations: These walls provide lateral support for deep excavations, ensuring the stability of surrounding structures and preventing soil movement during construction.
• Water Retention: Tangent pile walls can be designed to retain water, making them suitable for use in cofferdams and other temporary or permanent water-retaining structures.
• Temporary Structures: Tangent pile walls are often used as temporary retaining structures during construction projects, particularly in areas where excavation support is required before permanent structures are built.

Advantages

• Minimal Disturbance: The construction of tangent pile walls generates minimal noise and vibration, making it suitable for use in sensitive urban environments.
• Space-Efficient: Tangent pile walls require less space than other retaining wall types, making them ideal for use in areas with limited space.
• Versatile: These walls can be used in a variety of soil conditions and are adaptable to different site constraints and requirements.

Limitations

• Potential for Gaps: The small gaps between the piles can allow some soil or water seepage unless additional measures, such as grouting, are taken to seal the wall.
• Cost: Tangent pile walls can be more expensive than other retaining wall solutions due to the need for precise drilling and high-quality materials.
• Structural Limitations: These walls may not be suitable for extremely high loads or in situations where a completely watertight barrier is required without additional sealing.

Summary

Tangent pile walls are a versatile and effective solution for providing lateral earth support in urban construction, deep excavations, and water-retaining structures. By installing a series of closely spaced piles, these walls offer a space-efficient and minimally disruptive method of retaining soil or water. While they offer several advantages, including minimal noise and vibration during construction, tangent pile walls may require additional measures to ensure watertightness and may be more costly than other retaining wall options. Nonetheless, their adaptability and effectiveness make them a popular choice in challenging construction environments.