Using effective or total stress for shear strength

[ketanco]

Hello,

On question 33 of six minute solutions for geotechnical, why do they take the total stress and not effective stress for shear strength calculation, can anyone tell me?

for those who dont have that book, It is a question that basically gives the thickness of a cohesive soil with also angle of friction . they give dry density, moisture content and depth also. they want us to calculate the shear stress mid point of the layer.

 

[Lomarandil]

I only dabble in geotech, but I'm also surprised by this.

The fluid won't have any shear strength, so effective stress should definitely drive the shear strength.

I assume that the water table is above the midpoint of the layer?

 

[MikeMcC215]

The shear strength and shear stress in the soil are not the same thing, maybe you are getting these terms confused. I don't have the book anymore though so maybe I am missing something in the problem statement.