The failure criteria and failure models of slopes in the numerical calculations of slope stability were discussed extensively by using theoretical analysis and two typical examples.Qualitative mechanical analyses showed that, if subjective factor was avoid, the frequently-used three types of criterion could reflect concordantly the slope failures under strict convergence criteria,which was verified by the numerical example 1. Failure modes of the slope were determined by the yield criterion of rock and soil mass. In order to make the numerical analyses satisfied with the engineering practice,the tensile modification should be carried out in the yield criterion based on shear failure like Mohr-Coulomb yield criterion. On the basis of shear and tensile composite failure of rock and earth mass,a numerical strength reduction process was set up, and this process was proved more reasonable and justified by the calculation example 2.
