CPT-Angle of Internal Friction

[scottm8]

Hello All,

Would anyone be able to explain why there would be results for friction angle for just a single CPT? I have output from a data forensics software package and am wondering if the different values for Phi'(1), Phi'(2), etc. just represent different methods of correlating CPT raw data to strength parameters? I have attached an image of the output results. Any advice is appreciated.

Thanks!

 

[moe333]

The two high phi values are likely based on two different empirical methods. The very low one (below 10 degrees) is unusual and the values are in line with a residual clay friction angle...but a lot of the soil appears granular (Su is undefined). I would ask for background on the low phi method, it looks suspect to me. Typically there is an appendix with CPT reports that explains the interpreation methodology.

 

[scottm8]

Thanks moe333! That is what I suspected. There is no supporting documentation accompanying the CPT results. These tests were performed in very soft mine tailings. Unsually soft even for tailings because the coars fraction was screened and removed, so I am actually confused by the higher Phi value.

 

[moe333]

Empirical correlations developed for soil sometimes do not translate well to mine tailings. You may need to do some additional specialized correlation.