Module 17
Pile groups, settlement and negative skin friction
Nine piles are not nine times one pile — in capacity, in settlement, or in what they carry.
What this module covers
- Compute group efficiency and say what physical effect it represents
- Check block failure of a group in clay and recognise when it governs
- Use the equivalent raft to estimate group settlement, and explain why it exceeds a single pile's
- Compute downdrag from negative skin friction and explain why it is a settlement problem
Lessons
- 17.1
Group capacity
Efficiency, and the failure mode that ignores the individual piles.
Start lesson → Two problems that are both about movement, not strength.
Start lesson →
Module checkpoint
Check what you have taken in
2 questions
Question 1
A 0.6 m pile passes through 6 m of fill with γ′ = 10 kN/m³ and β = 0.3, all of it above the neutral plane. What downdrag load does it attract, in kN?
Question 2
Which remedy addresses the cause of downdrag rather than its symptom?