BeginnerTopic 36 of 112Civil & Structural
Deep foundations
Piles and caissons transfer load to deeper strong layers.
In depth
Piles (driven, bored, CFA, micropiles) transfer load through weak layers to stronger strata by end bearing and shaft friction: Q_u=Q_b+Q_s. Pile groups, negative skin friction and lateral loads need checking. Testing: static, dynamic, integrity tests. Caissons and piers serve for bridges.
Key points
- Pile cap
- Group efficiency
- Settlement of piles
ExampleBridge piers over rivers are founded on large-diameter bored piles.
What is Deep foundations?
Piles and caissons transfer load to deeper strong layers.
Why is it important to understand deep foundations?
Deep foundations transfer load to firm layers deeper down, which is essential when the surface soil is weak or the load is high.
What is the difference between end-bearing and friction piles?
End-bearing piles transfer load to a firm layer at the tip. Friction piles carry load mainly by shaft friction along their length.
What is a caisson?
A large deep foundation, often a hollow shaft or box, sunk into the ground to reach a strong layer, sometimes under water.
How is Deep foundations used in practice?
Typical applications include supporting a high-rise tower on bored piles to bedrock, founding a bridge pier on caissons in a river and carrying a port structure on driven piles through soft clay.
What should I learn before Deep foundations?
Study "Shallow foundations" first (topic 35 of 112 in Civil & Structural). It covers the groundwork this topic builds on.
What are the key points of Deep foundations?
Pile cap. Group efficiency. Settlement of piles.
Can you give an example of Deep foundations?
Bridge piers over rivers are founded on large-diameter bored piles.
What comes after Deep foundations?
The next topic is "Retaining walls", which builds directly on this one.
How difficult is Deep foundations?
It is classed as Beginner in Civil & Structural (topic 36 of 112). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.