Construction methods · Ground improvement

Sand compaction piles

A steel casing is vibrated into the ground, sand is fed and compacted by repeated withdrawal and re-driving, leaving dense sand columns 0.6-0.8 m in diameter that improve soft clay and loose sand. A Japanese and Korean standard for port and coastal works.

How bridges get built · Ground improvement · Sand compaction piles

Also called: SCP, compacted sand piles

Sand compaction piles — concept diagram — Concept diagram (TheBridgeEng)

How it is done

Drive the casing to depth with a vibro-hammer; fill with sand.
Withdraw partly while compressed air holds the sand, re-drive to compact it, repeat to the surface.
Replacement ratios of 20-70 % depending on the target strength.

Where it fits

Soft marine clay under quay walls, approach embankments and small abutments; liquefaction mitigation in loose sand.

Where it does not

Sites where the vibration is unacceptable; very deep soft layers beyond 30-35 m.

Plant, pace and money

PlantMarine or land SCP rig with vibro-hammer, sand barge or hopper.

Productivity30-60 piles of 15-25 m per rig per shift.

CostUSD 50-100 per metre of pile.

Risks and controls

What goes wrong

Heave of the adjacent seabed or ground; sand supply logistics.

Quality assurance

Sand consumption per pile, post-treatment CPT and SPT.

Examples

Kansai and Incheon airport reclamations, Korean west-coast port bridges.