Open-pit mining is one of the most common methods in mining engineering. This type of excavations is experimenting a general trend of increasing in depth in recent years reaching hundreds or thousands of meters. This increase in size is being accompanied by an increase in the number of slope failures. Some researchers suggested that large scale slopes present damage of the rock mass that may be originated by several causes such as excavation technique and quality, and change on the stress trajectories, among others. These effects are increased with the size of the slope and that is why the study of the influences of the damage on the stability is important. Recently, Silva and Gomez (2015) presented a simple geometrical method to consider the damage of the rock mass in slopes by means of the perturbance factor D of the Hoek Brown model. In this context, this paper presents the application of the method proposed by Silva and Gomez (2015) to a real case study. A FLAC3D routine that incorporates the damage according the cited method was implemented using Python and FISH programming. Each element of the numerical is evaluated as a function of its relative position and the value of the perturbance factor is saved to be used in later calculations of the Hoek-Brown parameters mb, s and a as well as the deformation modulus of the rock mass. The Poisson ratio was estimated following the recommendations of Vasarhelyi (2009). The mechanical constitutive model of the rock mass was considered as elastic perfectly plastic. Initially, synthetic Hoek-Brown models are tested and finally the real case uses Hoek-Brown, Mohr-Coulomb and Ubiquitous Joints models. The failure criteria were chosen based on the rock mass classification and properties. The results of geometrical analogous slopes in undamaged and damaged rock masses are contrasted in order to evaluate the magnitude of the differences in terms of the factor of safety and maximum displacements. Displacements presented increments in more than 50% for the damaged conditions and factor of safety was degraded between 20 to 50%. Also, failure mechanisms tend to be shallower for the damaged condition coinciding with field evidences. Finally, these results might explain the common consideration of practitioners of considering reduced design parameters.

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