The aim of this paper is to report the results of rock stress measurements performed, by means of the hydraulic fracturing (HF) technique, at two ornamental stone quarry sites. The two sites where the tests was carried out are: a pillar in a underground exploitation (quarry A) and a quarry located at a bottom of a valley (quarry B). A general description of the HF principles & techniques that were applied for the measurement and the evaluation of the key parameters used in a classical breakdown model (a specific MATLAB code was set up) are reported. The tensile strength was determined accurately under HF conditions (σ_(tHF)) by making tests in boreholes (38 mm diameter) that were drilled in marble blocks without confining stress. In the A case, the experimental results are compared with those obtained using FEM 2-D and BEM 3-D numerical models.
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