Issue 40

K. Kaklis et alii, Frattura ed Integrità Strutturale, 40 (2017) 18-31; DOI: 10.3221/IGF-ESIS.40.02 22 (a) (b) Figure 3: (a) A series of cylindrical specimens with different diameters and constant ratio h/D = 2 for Alfas stone. (b) The position of the strain gages for cylindrical specimens. (a) (b) Figure 4: (a) A series of circular discs with different diameters and constant ratio D/t = 2 for Alfas stone. (b) The position of the strain gages attached to the circular discs. E XPERIMENTAL RESULTS AND DISCUSSION Uniaxial compression tests y processing the experimental data, the basic mechanical properties of the material were determined. The uniaxial compressive strength, intact rock modulus and Poisson’s ratio are presented in Tab. 2 for the three different sizes of the cylindrical specimens. Note that the intact rock modulus and Poisson’s ratio for each specimen was calculated at 50% of the UCS of that specimen. Furthermore, the lateral and axial peak strains and the strain energy density up to the peak load were calculated. Results from a typical cylindrical specimen with diameter D =100 mm are presented in Fig. 5a, b. It is observed that the strain values measured by the three strain gages are similar (Fig. 5a). It can also be observed that for small strains the constitutive law is almost linearly elastic. Fig. 5c, d present the variation with the uniaxial stress of the intact rock modulus and Poisson’s ratio respectively, for three specimens with diameter D =54 mm. The similarity of these results with respect to the trend and repeatability of the intact rock modulus is evident, at a region where stresses are about 50% of the strength. The variation of Poisson’s ratio with stress is consistent along the full stress path for all three specimens. B