BeginnerTopic 32 of 112Civil & Structural
Consolidation
Slow squeezing of water from saturated clay causes settlement over time.
In depth
Loading saturated clay causes excess pore pressure that dissipates as water drains, leading to settlement over time. Terzaghi's theory: degree of consolidation vs time factor T_v=c_v t/H_d². Primary settlement S=C_c H/(1+e₀) log(σ'_f/σ'_0). Secondary compression follows.
Key points
- Oedometer test
- Preconsolidation pressure
- Prefabricated vertical drains speed up settlement
ExampleA building on soft clay may settle several hundred millimetres over years.
Consolidation explains why clays settle slowly under load, which affects buildings, embankments and reclaimed land for many years.
What is Consolidation?
Slow squeezing of water from saturated clay causes settlement over time.
Why is it important to understand consolidation?
Consolidation explains why clays settle slowly under load, which affects buildings, embankments and reclaimed land for many years.
What causes consolidation?
Water is slowly squeezed out of the clay pores as excess pore pressure dissipates, which transfers load to the soil skeleton and causes settlement.
Why does consolidation take so long in clay?
Clay has very low permeability, so water takes a long time to drain, which makes the settlement gradual.
How is Consolidation used in practice?
Typical applications include predicting the long-term settlement of a building on soft clay, planning a waiting period before building on reclaimed land and using vertical drains to speed up settlement of an embankment.
What should I learn before Consolidation?
Study "Effective stress" first (topic 31 of 112 in Civil & Structural). It covers the groundwork this topic builds on.
What are the key points of Consolidation?
Oedometer test. Preconsolidation pressure. Prefabricated vertical drains speed up settlement.
Can you give an example of Consolidation?
A building on soft clay may settle several hundred millimetres over years.
What comes after Consolidation?
The next topic is "Shear strength of soil", which builds directly on this one.
How difficult is Consolidation?
It is classed as Beginner in Civil & Structural (topic 32 of 112). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.