Pocket Penetrometer in kg/cm^2

[deedub93]

thread261-237840

I read on here that people are using the direct conversion 1kg/cm^2 from a pocket penetrometer to 98.0665 kN/m^2. Whilst this is a correct conversion, if you are trying to calculate the undrained shear strength (Cu or Su)it is not correct. The pocket penetrometer test is analogous to sigma 1 in a triaxial test where sigma 3 is at or about zero. In other word the Cu value is 1/2 (sigma1-sigma3),(consider a mohr circle), which equates to half of the reading on the pocket penetrometer.

 

[BigH]

Divide the pocket penetrometer test result by 2 to get undrained shear strength - and don't do a whole lot of worrying about the 2# difference between kg/cm2 (tons per square foot) and kPa if you use 1 to 100.