Under-reamed piles as per IS 2911 Part III have an enlarged bulb at the base. The main advantage over straight shaft bored piles is:
Choose the correct answer
Easier construction
Increased uplift and lateral load resistance; bulb interlocks with soil, preventing withdrawal
Reduced cost
Smaller diameter shaft needed
Correct Answer
B. Increased uplift and lateral load resistance; bulb interlocks with soil, preventing withdrawal
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Under-reamed piles: one or more enlarged bulbs (1.5 to 2.5 times shaft diameter) formed in-situ by reaming tool. Main advantages: higher bearing capacity (bulb end bearing in hard stratum), resistance to uplift forces (bulb anchors into soil), resistance to heave (expansive soils). Common in black cotton soil (expansive) and for transmission tower foundations.
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