ABSTRACT
Underground cavities of cross sectional shapes circular, or non-circular are often used in mining and civil engineering. The elasto-viscoplastic constitutive equations became in last decades important tools of phenomenological description of the main physical phenomena encountered at geomaterials, like yield, failure, dilatancy, or compressibility of the volume. In the study of stress behaviour around underground cavities we could distinguish two time periods : the first one, in which the cavity is excavated, followed by the time interval in which the cavity is exploited. The first time period is usually much shorter than the second one. Thus, in the constitutive model we could emphasize two tipes of mechanical behaviour : one related to instantaneous elastic response of the rock mass, corresponding to the first period of time, resp. a creep deformation of the material that lasts over a long period of time.
