Abstract: It is obvious phenomenon that cracks exist in the upper part of slope. This paper considers
that the failure of slope is caused by composition of crack and shear, but not single shear failure.
Tension and Mohr-Coulomb shear failure is discussed in the analysis of slope and the just connection
between the shear failure zone, and crack is regarded as the criterion of sliding failure of slope.
Extended finite element method is adopted to simulate the cracking of tension. Unified enrichment
function is used in the approximation of discontinuous field in which mixing element is avoided and
the enrichment freedom has significance. The simulation results show that if the tension failure is not
taken into account, the factors of safety of slope stability are higher. Therefore, it is necessary to
consider the tension failure of soil. Meanwhile, the length of the crack of tension is longer than the
theoretical ones. It can be used as reference for the judgment of critical sliding surface.

Key words: numerical simulation, slope stability, extended finite element