A Coupled elastoplastic-logarithmic damage model to numerical analysis of rocks failure mechanism
The logarithmic damage model has already been proposed in literature. But in this paper, the logarithmic damage model was coupled with plasticity theory. Therefore, stiffness degradation and irreversible strain can be taken into account simultaneously especially on post-peak region of rock behavior. The coupled elastoplastic-logarithmic damage model was used to simulate the irreversible deformations and stiffness degradation of rock materials under loading. In this model, damage evolution & plastic flow rules were formulated in the framework of irreversible thermodynamics principles. To take into account the stiffness degradation and softening on post-peak region, logarithmic damage variable was implemented. Also, a plastic model with Drucker-Pruger yield function was used to model plastic strains.
Then, the algorithm was proposed to calculate the numerical steps based on the proposed coupled plastic and damage constitutive model. The developed model has been programmed in VC++ environment. Then, it was used as a separate and new constitutive model in DEM code (UDEC). Finally, the experimental Oolitic limestone rock behavior was simulated based on the developed model. The irreversible strains, softening and stiffness degradation were reproduced in the numerical results. Furthermore, the confinement pressure dependency of rock behavior was simulated in according to experimental observations.
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