Sheet Pile Shear Strength of Soils

[LearningAlways]

Hello All,

I am developing soil parameters for a sheet pile, and one needed parameter is shear strength.

Is there a way to determine the shear strength of a soil from the internal friction angle and moist density? If not, how should we estimate the shear strength given SPT N-value, or is there another way outside of running an actual shear strength test.

I've looked through many textbooks and articles online but am having a tough time finding anything that helps. We have a chart at work that give parameters of certain soils/rocks. For example, the given ultimate shear strength of limestone, depending on SPT N-value, is between 4 and 15 ksf. I need the same parameter for sand and clay.

I've read that the shear strength of a clay is the unconfined compressive strength divided by 2, qu/2 = Tf.

I am hoping to find some empirical data or a formula.

Thoughts?

Thank you for the help!

 

[oldestguy]

The US Navy NAVFAC documents on line probably have these figures.

However, I have copied from an older version and perhaps between the two you can get what you want.

 

[oldestguy]

Guess we can onl load one at a time. Here is the other one.

 

[oldestguy]

Here is what they have published now, shown via one of our members.
Figure 3 on page87 may help.

http://web.mst.edu/~rogersda/umrcourses/ge441/dm7_01.pdf

 

[LearningAlways]

Thank you oldestguy for the replies.

Is there a way to calculate the shear strength of a soil without knowing the effective stress being put on it? From what I've found shear strength is as follows:

τ_f = σ*tan(Φ)

Internal friction angle (Φ) is found from SPT N-values. What I don't understand is that somehow in previous reports that our company has issued we have given the shear strength of sand to be 390 psf at a depth of 4 feet. But this isn't coming from the above equation because the shear strength in the same boring at a depth of 30 feet is given as 400 psf, thus neither the depth nor the effective stress play a role. GWT = 2.0 ft

Is there a correlation between density and shear strength? Or passive and active pressures and shear strength? Has you can tell I am grabbing at straws here.

Thank you again for the help!!!

 

[oldestguy]

It appears that who ever was writing the past should have explained more. However, angle of friction may change a little as more confinement takes place.

In your case, I'd see if you can find a mentor that is more experienced, since you may be missing something that could be important. Using blow count alone is rather crude and sometimes all we have, but it is a very approximate indicator of soil properties. Get out with a drill crew and you may see how the number can be affected by many things.