Consider the following statements about the under-reamed pile in swell...
Under-reamed pile is a special type of bored pile which is provided with a bulb/pedestal at the end. The usual size of such piles are 150 to 200 mm shaft diameter, 3 to 4 m long. The diameter of under-reamed portion is usually 2 to 3 times the shaft diameter.
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Consider the following statements about the under-reamed pile in swell...
Introduction:
The under-reamed pile is a type of deep foundation used in swelling soils to provide stability and resist movement due to volume changes. It is characterized by a bulb-shaped enlargement at the base of the pile, which acts as an anchor against soil movement. In this question, we have to determine which statements about the under-reamed pile are correct.
Statement 1: Its bulb provides anchor against movement due to volume changes of soil.
Explanation:
The under-reamed pile is specifically designed for use in swelling soils, which are prone to volume changes due to moisture content variations. The bulb-shaped enlargement at the base of the pile acts as an anchor against such movement. When the soil swells, the pressure against the bulb increases, providing resistance and preventing the pile from being displaced. Therefore, statement 1 is correct.
Statement 2: It is a driven pile.
Explanation:
Driven piles are installed by driving them into the ground using impact or vibration. Under-reamed piles, on the other hand, are not driven piles. Instead, they are installed by excavating a hole to the desired depth and diameter, and then placing the pile in the hole. The hole is backfilled with concrete or grout, which provides support to the pile. Therefore, statement 2 is incorrect.
Statement 3: Its bulb diameter is 2.5 times its shaft diameter.
Explanation:
The diameter of the bulb at the base of the under-reamed pile is typically larger than the diameter of the pile shaft. However, the exact ratio between the bulb diameter and the shaft diameter can vary depending on the design requirements and soil conditions. While a ratio of 2.5:1 is commonly used, it is not a universal standard. Therefore, statement 3 is incorrect.
Conclusion:
From the explanations above, we can conclude that statement 1 and statement 3 are correct, while statement 2 is incorrect. Therefore, the correct answer is option 'D' - 1 and 3 only.