The Chartership Forum

Foundation Engineering / module 12

Why piles, and what kinds

The decision that comes before the calculation — and the one that costs most to get wrong.

What you will understand

  • List the situations that genuinely call for piles rather than a shallow foundation
  • Distinguish displacement from replacement piles and describe what installation does to the ground
  • Explain why the same pile in the same soil has different capacity depending on how it was installed
  • Choose a pile type against ground conditions, loads and site constraints

Lessons

  1. When piles

    Six reasons, only one of which is about strength.

  2. Kinds of pile

    Displacement or replacement — and why the ground can tell the difference.

Module summary
  • Piles are for weak near-surface ground, concentrated loads, uplift, lateral load, scour and settlement control
  • The example pile resistance is about 1000 kN at ultimate; a separate 1000 kN service-load pad calculation gives 2.6 m square. These are not equivalent design capacities.
  • Driven piles displace soil and raise horizontal stress; bored piles remove it and relax it
  • Installation is not a detail: it changes the capacity of the finished pile substantially
  • Pile type is chosen against ground, load, access, noise, vibration and groundwater — rarely against capacity alone
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 notes

Check your understanding

Check yourself

Which is the most common reason that ordinary buildings end up on piles?

Check yourself

A city-centre site is surrounded by sensitive Victorian buildings, with restricted headroom and a high water table. Which pile type is indicated?