What is secant pile? Explain in details with work procedure and its use.
A secant pile is a type of retaining wall used in deep excavation projects to provide support to the sides of an excavation. The wall is constructed by installing a series of interlocking concrete piles, which are drilled or driven into the ground. These piles are then connected by a concrete lagging or by steel beams to form a continuous barrier that resists soil pressure and prevents the sides of the excavation from collapsing.
The work procedure for constructing a secant pile wall typically involves the following steps:
- Excavation: The excavation is carried out to the desired depth, and the soil is removed to make way for the pile installation.
- Pile installation: The piles are then drilled or driven into the ground using an impact hammer, rotary drill, or other piling equipment. The piles are installed at close intervals along the excavation, and the spacing between them is determined by the load-bearing capacity of the soil and the strength of the piles.
- Concrete placement: Concrete is then poured into the holes created by the piles to form a solid mass. The concrete is usually reinforced with steel bars to provide additional strength.
- Interconnection: Once the concrete has cured, the piles are interconnected by a concrete lagging or by steel beams to form a continuous wall.
- Backfilling: After the wall has been completed, the excavation is backfilled with soil, and the secant pile wall becomes a permanent structure that provides support to the sides of the excavation.
Secant pile walls are commonly used in deep excavation projects where the soil is unstable, or where the excavation is too deep for conventional retaining walls to be used. They are also used in situations where there is limited space available for the construction of a retaining wall. Secant pile walls are relatively expensive compared to other types of retaining walls, but they provide a high degree of stability and reliability, making them a popular choice for complex and challenging excavation projects.