Issue 40

K. Kaklis et alii, Frattura ed Integrità Strutturale, 40 (2017) 18-31; DOI: 10.3221/IGF-ESIS.40.02 30 Figure 13: Variation of the UCS with the specimen diameter. Results show that almost all the mechanical parameters used to describe the behavior of the building stone depend on the size of the specimens, with the exception of the intact rock modulus and Poisson’s ratio which appear to be constant with varying specimen diameters. The values of UCS for the Alfas stone that were experimentally determined are in full agreement with the formula published by Hoek and Brown [28]. In addition, an almost perfect linear correlation between UCS and diameters in a double logarithmic chart was developed, which indicates that when specimen spalling and axial splitting rather than specimen shearing is the predominant failure mode, the dependence of UCS to specimen size may follow Carpinteri’s fractal law [29]. Furthermore, experimental results indicate that the splitting tensile strength of Alfas stone is not a linear function of the specimen diameter, but it exhibits a non-monotonic pattern. Although this non-monotonic behavior has also been previously presented in the literature [12], it is clear that additional research needs to be performed to reach definite conclusions regarding the dependence of the splitting tensile strength to specimen diameter. A CKNOWLEDGEMENTS his research has been co-financed by the European Union (European Social Fund-ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program: THALES: Reinforcement of the interdisciplinary and/or inter- institutional research and innovation. The authors would also like to thank the anonymous reviewers of this paper for their constructive comments and recommendations. R EFERENCES [1] Dufour, F., Size effect in geomaterials. Revue Europénne de Génie Civil., 11 (7-8) (2007) 963-975. [2] Weibull, W., A statistical theory of the strength of materials. Royal Swedish Academy of Eng. Sci. Proc., 151 (1939) 1- 45. [3] Barla, G., Goffi, L., Direct tensile testing of anisotropic rocks. Proceedings of the Third International Congress of Rock Mechanics, 2, Part A (1974) 93-98. [4] Nova, R., Zaninetti, A., An investigation into the tensile behavior of a schistose rock. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 27 (1990) 231-242. [5] Hondros, G., The evaluation of Poisson’s ratio and the modulus of materials of a low Tensile resistance by the Brazilian (indirect tensile) test with particular reference to concrete. Australian Journal of Applied Science, 10 (1959) 243-264. [6] Pinto, J.L., Determination of the elastic constants of anisotropic bodies by diametral compression tests. Proceedings of the Fourth ISRM Congress, Montreux, 2 (1979) 359-363. T