Issue 40

K. Kaklis et alii, Frattura ed Integrità Strutturale, 40 (2017) 18-31; DOI: 10.3221/IGF-ESIS.40.02 25 (a) (b) (c) (d) (e) (f) Figure 8: (a) Uniaxial compression strength, (b) Intact rock modulus, (c) Poisson’s ratio, (d) Strain energy density, (e) Lateral peak strain and (f) Axial peak strain with respect to the diameters of the specimens. Results from a typical circular disc specimen with diameter D =100 mm are presented in Fig. 9a-e. The difference between the strain values measured by the strain rosettes on opposite sides of the specimen is shown in Fig. 9b. This has also been observed in other experimental unpublished data by the authors and, currently, it is attributed to a number of experimental difficulties such as: material inhomogeneity, imperfections in the geometry of the disc specimens, which may result in eccentric loading of the discs through the steel jaws, as well as minute differences in the orientation and location of the strain gages with respect to the vertical axis and the center of the specimen respectively. Fig. 9c presents the curves constructed by averaging the respective curves in Fig. 9a; these are the values used in subsequent calculations. Fig. 9 d, e present the variation of the intact rock modulus and Poisson’s ratio respectively (as calculated by eq. 2 and 3) with respect