ABSTRACT
The exploitation of marble in Greece is extended lastly underground. Its productivity is largely dependant on the ability to excavate large stable openings. The prediction of the mechanical response of such an exploitation is endeavoured with the observational method. Numerical models and closed form solutions provided by the voussoir beam theory are used to analyse the structural behaviour of the excavation. The necessary initial estimates for the deformability data of the in-situ surrounding rock are evaluated by back- analysing the response of a pilot tunnel. These data are used then to calculate at a first stage the stability of the enlarged opening. This observational method may be repeated then contiguously at the various subsequent stages of the excavation enlargement, which is performed in slices, by using the updated data evaluated at each stage of the underground structure, to the analysis of the following ones.
