I have found the hyperbolic parameters (K and n) according to Duncan and Chang model. However, I have no idea how to fit a hyperbolic model into a failure envelope to get the friction angle.
I believe you need several tests to graph the relationship between (s1+s3)/2 and (s1-s3)/2 at failure (p, q coordinates in American literature [Lambe]).
The failure envelope may be simplified as "qf = c*cos(phi)+p*sin(phi)" or, in cohesionless materials, by a nonlinear function of "phi" versus "s3" like "phi = phi0 + Dphi * log(s3 / patm)".
A single test, duly adjusted to the hyperbolic model for (s1-s3) versus the axial strain, cannot provide the failure envelope. More than three tests in the stress range of your problem may improve the geotechnical analysis with a non-linear failure envelope.
Hello,
some suggestions can be found at the link:
https://www.rocscience.com/help/rs2/theory/Material_Model_Manuals/7-Duncan-Chang_Model.pdf
Take into account that strength parameters should be selected according to the applied stress path, resulting from the loading sequence.
Regards
Claudio Oggeri Thanks a lot for the suggestions. Really helpful.
Luis R. Vasquez-Varela Thanks a lot for the detailed answer. Will try this.
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