Geosynthetic polymeric barriers has been used in the impermeabilization of tailings dams, but causes concern regarding its performance under high loadings, especially in the interface with the dam and the foundation, due to the possibility of a low resistance or high deformability plane. Therefore, the interface between the dam material, underflow of tailings from a gold ore mining, and a texturized 1,5 mm HDPE geomembrane was evaluated numerically, using the finite element software RS2, in an interface shear test. It was observed that the interface did not respond to the elastic-plastic behavior and that therefore Mohr-Coulomb yielding criteria did not represent well the behavior of the experimental curve during shear. It was also observed the sensibility of the model to the loadings. The influence of the boundary conditions in the presented simulation also needs to be evaluated and probably better discretized.