Foundation Engineering / module 13
Load transfer: shaft and base
How shaft and base resistance develop with pile movement, and what that means when their capacities are combined.
What you will understand
- Split a pile's ultimate capacity into shaft and base contributions
- Explain why shaft and base mobilise at very different displacements
- Describe the load transfer curve and what it implies at working load
- Decide when a pile's self-weight matters and when it does not
Lessons
The two resistances
Where the load actually goes.
Mobilisation
Why the sum is a fiction, and a useful one.
Module summary
- Ultimate capacity is shaft plus base — equilibrium, even though the two numbers added are empirical
- The example pile carried 848 kN on its shaft and 153 kN on its base: 85% shaft
- Shaft resistance is fully mobilised at a few millimetres; base resistance needs 5–10% of the diameter
- At 10 mm of settlement the pile offered 886 kN, and 96% of it came from the shaft
- Shaft and base resistances must be combined at a compatible displacement; separately quoted peak values may not occur together
Teaching basis and review status
These are educational models and exercises. Check their assumptions before using the results. The full technical content and every diagram have not yet been independently verified.
Concrete and steel calculations retain their stated first-generation Eurocode teaching basis. Use the standards and amendments specified for your project; do not mix generations without an appropriate design basis.
Read the lesson register and outstanding review notesCheck your understanding
Practice
A bored pile 0.6 m in diameter and 15 m long is in clay with su = 60 kPa and α = 0.5. What is its shaft resistance, in kN?
Check yourself
At working load, which component is a typical slender pile in clay actually relying on?