The purpose of this master thesis is to numerically analyze, using a distinct element method, how the local distribution of stresses and the stability of the openings of an underground mining operation are influenced by the modification of the opening shape, based on the real life conditions found a room pillar scheme underground mine in Spain. In this thesis I evaluated 36 different models subjected to different geomechanical conditions, to a modified joint orientation, and with 4 different rectangular and horseshoe shaped openings to recreate the real life conditions on a section of the room and pillar mine. The results show that there is a direct relationship between the change of the openings shape and the attainment of a better overall structural stability, stress distribution, less strain and deformation, and a higher factor of safety. Therefore, the usage of horse shoe or similar shapes is recommended, as long as the methodology, equipment, logistics and other construction and operation conditions allow the excavation of a circular shaped opening.