جستجوی مقالات مرتبط با کلیدواژه "متغیر خرابی لگاریتمی" در نشریات گروه "عمران"

The rock materials surrounding the underground excavations typically demonstrate nonlinear mechanical response under high stress states. The dominant causes of irreversible behavior are plastic flow and damage process. The plastic flow is controlled by the presence of local shear stresses which cause dislocation to some preferential elements due to existing defects. During this process, the net number of bonds remains practically unchanged. The main cause of irreversible changes in quasi-brittle materials such as rock is the damage process occurring within the material.
In this paper, a coupled logarithmic damage and plastic model was used to simulate irreversible deformations and stiffness degradation of rock materials under loading. In this model, damage evolution and plastic flow rules were formulated in the framework of irreversible thermodynamics principles. To take into account the stiffness degradation and softening in post-peak region, logarithmic damage variable was implemented. Also, a plastic model with Drucker-Pruger yield function was used to model plastic strains. Then, an algorithm was proposed to calculate the numerical steps based on the proposed coupled plastic and damage constitutive model. The developed model was programmed in VC environment. Then, it was used as a separate and new constitutive model in DEM environment 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.