Module 13
Critical-state soil behaviour
One framework that ties the course together: the critical state a soil reaches at large strain, the critical-state line, and how a soil's state relative to it predicts strength, volume change and pore-pressure response.
What this module covers
- State the critical state: continuous shearing at constant volume and constant stress
- Draw the critical-state line in q–p′ (q = Mp′) and relate M to φ′cs
- Distinguish soils wet of critical (contractive) from dry of critical (dilative)
- Predict the sign of undrained pore-pressure change and the presence of a peak from the state
- See how consolidation, stress history and strength are unified by one framework
Lessons
The unique end-point of shearing, and the critical-state line.
Start lesson →State relative to the CSL, and what it predicts.
Start lesson →- 13.3
One framework
How consolidation, stress history and strength join up.
Start lesson →
Module checkpoint
Check what you have taken in
2 questions
Question 1
A soil has φ′cs = 27°. What is its critical-state stress ratio M? (M = 6 sinφ′/(3 − sinφ′).)
Question 2
A loose, saturated sand (well wet of critical) is sheared undrained by rapid loading. What is the danger?