Construction methods · Driven piles

Vibratory driving

Eccentric weights vibrate the pile at 20-40 Hz, liquefying the soil around it so the pile sinks under its own weight and the hammer's. Fast and quiet in sands, ideal for sheet piles, casings and steel pipes, but it does not prove bearing capacity, so the last metres are usually impact-driven.

How bridges get built · Driven piles · Vibratory driving

Also called: vibro-hammer, vibratory pile driver

Concept diagram (TheBridgeEng)

How it is done

Clamp the vibro-hammer to the pile head from a crane; vibrate down through sands and soft clays.
Switch to an impact hammer for the final drive into the bearing layer and for the set.
Also used to extract sheet piles and casings.

Where it fits

Sheet piles, temporary casings, steel pipe piles through sand and silt, extraction of temporary works.

Where it does not

Stiff clay and dense gravel (the pile stops); final bearing without an impact hammer; near structures sensitive to vibration and settlement.

Plant, pace and money

PlantCrane-hung vibro-hammer 20-300 kN eccentric moment, power pack; high-frequency resonance-free units near buildings.

ProductivitySheet piles at 20-60 per shift, casings in minutes.

CostCheaper per pile than impact driving where it works.

Risks and controls

What goes wrong

Settlement of adjacent ground by vibration, liquefaction of loose sand around existing foundations.

Quality assurance

Vibration monitoring at neighbours, penetration rate records.

Examples

Sheet-pile cofferdams everywhere; casing installation for bored piles.