In this dissertation the study of the behavior of an underground cavern in jointed rock granite has been carried out. For this purpose, different analyses were developed, using Finite Element Method software for the modelling in two and three dimensions of the cavern. The main purpose of this master thesis was to create different continuum numerical models which could represent the weathered rock mass using different approaches. One possible approach followed in this project as means to incorporate the influence of joints on rock mass strength in numerical analysis was by modelling rock masses as equivalent continuum with reduced deformation and strength properties.