1. It reduces the number of piles needed by spreading loads wider
2. It ties the piles together to share loads and resist uneven settlement
3. It increases skin friction along the piles in wet soil
4. It simplifies pile installation in saturated conditions

Explanation

Explanation: A pile cap connects multiple piles into a cohesive unit, distributing the pier’s load evenly among them to prevent differential settlement in saturated clay, where soil strength can vary. It enhances “group efficiency” (how piles share forces per codes like AASHTO) and manages moments from eccentric loads—not reducing pile count (A), which design dictates, nor boosting friction (C), which comes from pile-soil contact. Installation (D) isn’t simpler; it’s an added step.

Learning Resources

• Review AASHTO LRFD, 9th Edition (2020), Section 10.7 for pile group efficiency calculations; CHBDC S6-19, Section 6.8.6 covers pile group behavior.
• Study the Sunshine Skyway Bridge (Florida, 1987) for pile cap use in marine clay.
• Tip: Align pile cap reinforcement with eccentric load paths during design.