Piles with Enlarged Shafts – Identification of bulbs on the vertical pile A pile that has one or more enlarged bulbs formed along its vertical shaft is generally known as:

Introduction / Context:
Under-reamed piles are widely used in expansive clays to resist uplift and improve load capacity. They feature one or more “bulbs” (under-reams) created by reaming out the soil and filling with concrete, enlarging the pile cross-section locally.

Given Data / Assumptions:

• Bulb(s) formed along the vertical shaft of the pile.
• Pile constructed in soils where uplift or low bearing capacity is a concern.
• Concrete bulbs increase bearing area and uplift resistance.

Concept / Approach:
The defining feature is the local enlargement(s) below ground. This distinguishes under-reamed piles from plain friction or end-bearing piles and from sheet piles (used as earth-retaining elements).

Step-by-Step Solution:
Recognize “bulb” geometry → under-ream.Connect to application: expansive soils, uplift resistance.Rule out other pile types that lack bulbs.

Verification / Alternative check:
Design guides specify minimum bulb spacing (e.g., about 1.5 du) and reinforcement detailing between bulbs, confirming typical under-reamed practice.

Why Other Options Are Wrong:

• Friction/bearing piles: defined by load transfer mode, not bulb geometry.
• Sheet piles: thin interlocking members for retaining, not vertical foundation piles with bulbs.

Common Pitfalls:
Confusing enlarged base piles (single belled base) with multi-bulb under-reamed piles; both enlarge area but differ in geometry and terminology.

Final Answer:
Under-reamed pile