effective stress in unsaturated soils

[alai]

Dear All,

How's the development of effective stress in unsaturated soils? Is the effective normal stress increasing with suction? Is this increase in the stress at particle contacts reduce the possibility of slippage? If the effective stresses increase, does it imply that the consolidation increases with suction? Please correct me if I'm wrong in any of the above statements. Thank you.



Regards,
alai

 

[agus72indo]

Dear Alai,

In unsaturated soil mechanics, there are two stress state variables, namely, net normal stress which is defined as sigma-ua, and suction (or matric suction) defined as ua-uw, instead of one stress state variable (i.e., effective stress), as you have mentioned.

That is right that there are some literatures saying that the concept of effective stress is also valid in unsaturated soil cases. However, nowadays, more and more people realize that two stress state variables are more appropriate. For clarity about this and theory of consolidation for unsaturated soils, please read:

Soil Mechanics for Unsaturated Soils
Fredlund and Rahardjo, John Wiley, 1993

I hope this helps you.

Regards

Agus