Soil displacement is the pushing of the ground sideways and downwards when an object is driven into the subsoil, without that soil being excavated or removed. The idea matters mainly for foundation piles: a displacement pile pushes the soil aside, whereas a bored (replacement) pile removes soil.
Displacement piles versus bored piles
- Displacement piles — are driven, vibrated or screwed into the ground without removing soil. Examples are the driven precast concrete pile, the vibro pile and the screw pile. The surrounding soil is compacted sideways, which increases the bearing capacity (shaft friction).
- Bored (replacement) piles — a hole is first bored and the soil removed, after which concrete is placed. Example is the auger pile. These cause less vibration.
Application and points to watch
Soil displacement has advantages and risks:
- Advantage — the compaction around the pile raises the bearing capacity, and there is no spoil to cart away.
- Vibration and noise — driving with displacement causes vibration that can damage neighbouring buildings; a vibration survey and condition survey are often carried out beforehand.
- Heave — in dense or cohesive soil the displaced ground can push up the subsoil or nearby piles.
- Choice in urban areas — in vibration-sensitive surroundings, low-vibration bored or screw piles are often preferred.
The choice between displacement and removal depends on the soil type, the surroundings and the required bearing capacity.
Related terms
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