Cast-in-situ piles: In which pile system is the concrete in a drilled hole compacted by compressed air?

Introduction / Context:
Cast-in-situ piles employ different mechanisms to place and compact concrete within a bore. Some methods rely on ramming; others use vibration or applied air pressure. Knowing which system uses compressed air helps match the method to ground conditions and quality requirements.

Given Data / Assumptions:

• Concrete must be placed and compacted effectively in a drilled hole.
• Compressed air is referenced as the compaction/placement medium.
• Common methods include Simplex, Franki, pressure, and vibro piles.

Concept / Approach:
Pressure pile techniques employ compressed air to force concrete into the bore and sometimes into the base or surrounding zone, ensuring compaction and counteracting inflow or loss into weak strata. Simplex and Franki methods use mechanical ramming and plugs; vibro piles use vibration to compact granular soils and concrete.

Step-by-Step Solution:
Identify the method explicitly associated with compressed air compaction.Pressure pile matches the description, as compressed air is integral to its placement process.Select “Pressure pile.”

Verification / Alternative check:
Construction method descriptions show the use of air pressure lines/nozzles in pressure piles for placement and densification, unlike the purely mechanical Franki/Simplex systems.

Why Other Options Are Wrong:
Simplex: Uses drop hammer ramming, not compressed air.Franki: Concrete is rammed with a plug; air pressure is not the primary compaction means.Vibro: Relies on vibration; compressed air is not central.Raymond: A thin-shell pile system; not defined by compressed air compaction.

Common Pitfalls:
Confusing pressure placement with ramming or vibration; assuming all cast-in-situ methods use the same compaction principle.

Final Answer:
Pressure pile.