CFA Piles vs. Sheet Piles in Excavation Support

Advantages of Columnar Piles Over Sheet Piles

Columnar piles used in excavation support systems (retaining structures, nailing, anchoring, micropiles, top-down, etc.) offer several advantages over sheet piles:

  • Less noise and vibration

  • Higher stiffness

  • Eliminate the need for excessive bulk excavation

  • Better control of ground deformation

Types of Embedded Pile Walls

  • Contiguous Wall

  • Secant Wall

  • Tangent Wall

  • شمع

Features of Contiguous Pile Walls (CFA Walls)

These piles are constructed with very narrow spacing between them. Their cost-effectiveness comes from the use of inexpensive augers and suitable drilling equipment for creating separated piles.

Key Factors Influencing Pile Diameter and Spacing

  • Soil type

  • Groundwater level

  • Design pressure magnitude

Large gaps between piles must be avoided, as they can lead to soil collapse between the piles in excavation support systems.

These piles are commonly referred to as CFA (Contiguous Flight Auger) piles. Their diameter typically ranges from 300 to 1000 mm.

CFA piles are preferred over diaphragm walls in small to medium excavations due to:

  • Faster and more economical installation

  • No need for bentonite slurry

  • Suitability for urban environments where vibrations and movements may affect nearby structures

They are highly effective in controlling ground movement behind the excavation, especially in densely populated urban areas.