Driven Prestressed Concrete Piles

Driven Prestressed Concrete Piles

Driven concrete piles are displacement piles where no (or minimal) spoil arises at the surface from their installation. Prestressed concrete piles offer several benefits compared to other driven pile systems. Tensile stresses, which can arise in a pile during driving, can be better resisted due to the prestressing forces, and the pile is less likely to be damaged during handling. Bending stresses during driving are also less likely to produce cracking than in conventional precast concrete piles.

Prestressed concrete piles are made from high-strength concrete, typically 50 MPa or more. As they are factory cast curing conditions can be strictly regulated. Special manufacturing processes such steam curing can be adopted to produce higher strength concrete.

This type of pile is generally less permeable than cast in situ reinforced concrete piles and hence offers superior performance in a marine environment.

Pointed Concrete or steel driving “shoes” can be used at the toe of jointed piles for protection when penetrating soils containing boulders, or in weak rock. When used in aggressive environments, piles can have improved durability by coating with epoxy bitumen. Slip layers can also be applied to remove the potential effects of negative skin friction.

Lateral forces can be resisted by installing piles on a rake.

Prestressed concrete piles are installed using driven track mounted rigs with modern efficient hydraulic hammers. Piles are typically supplied in lengths varying from 8 to 24m. Longer piles are installed using a jointing system.  Piling Contractors has developed a new form of joint for this pile.

Pile load capacity can be determined during driving using rig instrumentation, dynamic analysis and established methods of measuring the pile “set” per fixed number of hammer blows.
Piling Contractors has many years experience in installation of 550mm octagonal prestressed concrete piles on land and over water and our equipment allows us to pitch longer pile lengths than many others. Key advantages of the process are:

  •  Practically unlimited depth
  •  Not affected by Groundwater
  •  Factory Manufacture
  •  Self proving
  •  Immediate follow on construction
  •  Clean site / no spoil

In special circumstances a composite pile can be used made up of a lower section of steel column or H pile joined to an upper prestressed or precast concrete pile. This is particularly useful when the overall weight of the pile needs to be reduced (due to transport or handling constraints. For marine structures a composite concrete / steel pile provides a concrete section in the area where fluctuating sea water levels cause corrosion but also a cheaper steel section below this zone. The pile can be driven deep to provide uplift resistance. Composite piles are also suitable where hard layers of strata need to be driven into or through.