Read the given statements related to pile foundations and choose the correct option.

1. The load-carrying capacity of a pile depends upon both the skin friction and point resistance.

2. The negative skin friction on a pile develops when the soil surrounding it settles less than the pile.

3. The group efficiency of driven piles in sand at a close spacing may be greater than 100%. 

Explanation:

Pile Foundations

Pile foundations transfer loads from structures to hard strata deep underground. Understanding the behavior and interaction of piles with the surrounding soil is crucial for their design and application. Here, we analyze the given statements:

• Load-carrying capacity: The capacity of a pile is influenced by both the skin friction along the pile shaft and the point resistance at the pile tip.

• Negative skin friction: This occurs when the surrounding soil settles more than the pile, exerting a downward drag on the pile.

• Group efficiency: In sandy soils, the efficiency of closely spaced driven piles may exceed 100% due to the densification of the sand around the piles.

Analyzing the Given Statements

1. Statement 1: The load-carrying capacity of a pile depends upon both the skin friction and point resistance.

   • True. The capacity of a pile is a combination of the skin friction along the pile shaft and the point resistance at the pile tip.

2. Statement 2: The negative skin friction on a pile develops when the soil surrounding it settles less than the pile.

   • False. Negative skin friction occurs when the soil settles more than the pile, not less.

3. Statement 3: The group efficiency of driven piles in sand at a close spacing may be greater than 100%.

   • True. In sandy soils, closely spaced driven piles can densify the surrounding sand, resulting in a group efficiency greater than 100%.