The 'under-reamed pile' (IS 2911 Part 3) is specifically used for:
Choose the correct answer
Rock-anchored high-rise buildings
Expansive (black cotton) soils — under-ream bulbs anchor pile below active swelling zone to resist heave
Marine structures in saline water
Only for very long piles > 50 m
Correct Answer
B. Expansive (black cotton) soils — under-ream bulbs anchor pile below active swelling zone to resist heave
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Under-reamed pile: driven or bored cast-in-situ pile with one or more bulb enlargements (under-reams) formed by a mechanical cutter at the base. Mainly used in: expansive soils (black cotton soil — high swelling). The bulb below the active zone anchors the pile against upward movement (heave). Also: single bulb piles for settlement-sensitive structures.
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