Construction methods · Bored piles and deep foundations

Percussion rotary drilled (PRD) steel pipe piles

A down-the-hole hammer inside a steel pipe advances the pipe through soil and into rock; the socket is then cleaned, a cage lowered and the pipe filled with concrete. It gives a driven pile's steel section with a bored pile's rock socket, quietly, in a small footprint: a Korean answer to shallow weathered rock, boulders and city sites.

How bridges get built · Bored piles and deep foundations · Percussion rotary drilled (PRD) steel pipe piles

Also called: PRD pile, rock-socketed steel pipe pile, DTH pile

Concept diagram (TheBridgeEng)

How it is done

Set the pipe with a rotary head; the DTH hammer drills ahead of the pipe shoe with air flush, pulling the pipe down.
Continue into rock to the socket depth; clean out with air or water.
Lower the cage, concrete the pipe and socket; the pipe is permanent.

Where it fits

Shallow weathered rock, boulder beds, urban sites, marine trestles with rock close to the bed, small groups under viaduct piers.

Where it does not

Deep soft soil where shaft friction on the pipe is the main resistance (the pipe is not driven, friction is low).
Very large diameters.

Plant, pace and money

PlantPRD rig with rotary head and DTH hammer, air compressors, service crane.

Productivity3-8 piles of 20-30 m per rig per shift.

CostUSD 250-500 per metre for 600-800 mm.

Risks and controls

What goes wrong

Air flush blowing out soil around the pipe, socket cleanliness, dust and noise from the compressor.

Quality assurance

Drilling logs with rock penetration rates, socket depth verification, load tests.

Examples

Korean urban viaducts and coastal trestles; Hong Kong 'socketed H-piles' are the H-section cousin.