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Existence of discontinuities causes higher deformability and lower strength in rock masses. Thus joints can change the rock mass behaviour due to the applied loads. For this reason properties and orientation of the joint sets have a great effect on the stability of rock slopes. In this paper, after introducing some numerical methods for evaluating the factor of safety for the stability of slopes, stability of jointed rock slopes in the plane strain condition is investigated with the strength reduction technique this method is modified and applied in the multilaminate framework. First of all, stability of one homogeneous rock slope is investigated and compared with the limit equilibrium method. Then stability of a layered rock slope is analyzed with some modifications in the strength reduction technique. Effects of orientation, tensile strength and dilation of layered joint sets on the factor of safety and location of the sliding block are explained.

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A semi-micromechanical multilaminate model is introduced here to predict the mechanical behavior of soils.

This model is like a bridge between micro and macro scale upon the satisfaction of minimum potential energy level

during any applied stress/strain increments. The concept of this model is based on a certain number of sampling planes

which constitute the elastic-plastic behavior of the soil. The soil behavior presents as the summation of behavior on

these planes. A simple unconventional constitutive equations are used in each of the planes to describe the behavior

of these planes separately. An unconventional plasticity can predict the soil behavior as a smooth curve with

considering plastic deformation due to change of stress state inside the yield surface. The model is capable of

predicting softening behavior of the soil in a reasonable manner due to using unconventional plasticity. The influences

of induced anisotropy are included in a rational way without any additional hypotheses owing to in-nature properties

of the multilaminate framework. Results of this model are compared with test data and reasonable agreement is found.