On the interpretation of shear parameter uncertainty with a linear regression approach

Abstract Interpretation of the triaxial testing results of soil shear strength parameters is a particular case of simple linear regression. In triaxial testing the parameters of the regression have certain physical interpretation (i.e. the intercept is the cohesion and the slope is the tangent of the internal friction angle). Another important issue is that the fitting of the line is carried out on the other plane to the plane of the Mohr-Coulomb criterion. The results of the fitting needs to be later transformed into the soil parameters. This makes the uncertainty analysis of the parameters nontrivial. This study focuses on the two abovementioned issues. Firstly, the transformation formulae for different planes are briefly presented. The methodology of confidence interval estimation is then described. The validity of our approach is verified by computer simulation. The results of the simulation are discussed and the conclusions regarding recommendations for laboratory test planning are drawn.