Question

What is the purpose of pile caps in deep foundation systems?

• A. To provide lateral support to the piles
• B. To distribute the load from the superstructure to the piles
• C. To increase the length of the piles
• D. To resist uplift forces

Hint:

Pile caps are an integral part of pile foundations, serving as a critical interface between the heavy, concentrated loads from the building and the individual piles. Proper design of pile caps ensures uniform load distribution to the piles, preventing differential settlement and ensuring the overall stability of the foundation.

Answer 1

The Correct Option is B

Step 1: Understand the components of a pile foundation system.
A deep foundation system typically consists of piles and a pile cap.

• Piles: Long, slender structural members that transmit loads from the superstructure through weak or compressible soil strata to stronger, deeper soil or rock.
• Pile Cap: A thick concrete slab that connects the tops of a group of piles.

Step 2: Analyze the primary function of a pile cap.
The main purpose of a pile cap is to act as a bridging element between the column/wall from the superstructure and the individual piles. It receives the concentrated load from the superstructure and distributes it evenly among the piles in the group. This ensures that each pile carries its share of the load and that the load transfer to the soil occurs effectively and safely.
Step 3: Evaluate the given options.

• (1) To provide lateral support to the piles: While pile caps do offer some degree of lateral restraint, their primary function is not lateral support. Lateral support is primarily provided by the surrounding soil and the stiffness of the piles themselves.
• (2) To distribute the load from the superstructure to the piles: This aligns perfectly with the primary function described in Step 2.
• (3) To increase the length of the piles: This is incorrect. Pile caps are constructed on top of the piles and do not increase their length.
• (4) To resist uplift forces: While pile caps can contribute to uplift resistance in certain configurations (e.g., if piles are tension piles), their fundamental and most common purpose is compressive load distribution. Uplift resistance is primarily provided by the piles themselves through skin friction and/or end bearing in tension.

Step 4: Select the correct option.
Based on the primary function of pile caps, the correct option is to distribute the load from the superstructure to the piles. $$\boxed{\text{To distribute the load from the superstructure to the piles}}$$