• Emil Sørensen
4. term, Structural and Civil Engineering, Master (Master Programme)
The purpose of this report is to derive and implement a strain hardening Mohr-Coulomb model based on return mapping in principal stress space by the use of boundary planes. The report aims at modeling strain hardening rock material through a Mohr-Coulomb approximation of the generalized Hoek-Brown criterion.

Firstly, the classification of rock materials as well as the generalized Hoek-Brown criterion are presented. Afterwards follows an introduction to the Mohr-Coulomb criterion and the approximations used for the generalized Hoek-Brown criterion.

Next, the fundamentals of plasticity and hardening is presented along with the theory behind return mapping in general stress space, including the derivation of the consistent constitutive matrix used in the global FEM equilibrium iterations. Then the advantages of return mapping in principal stress space is outlined.

Following is the derivation of a non-associated isotropic strain hardening Mohr-Coulomb model based on the introduced theory.

Finally, the derived model is implemented in two examples. The first example tries to model a strip footing while the second example models a tunnel excavation. The obtained results are compared with perfectly plastic solutions utilizing the peak and residual strength of the rock material.
Publication date8 Jun 2012
Number of pages70
ID: 63641171