Document Type : Original Research Paper


School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran


The uniaxial compressive strength (UCS) of intact rocks is one of the key parameters in the course of site characterizations. The isotropy/anisotropy condition of the UCS of intact rocks is dependent on the internal structure of the rocks. The rocks with a random grain structure exhibit an isotropic behavior. However, the rocks with a linear/planar grain structure generally behave transversely-isotropic. In the latter case, the UCS of intact rocks must be determined by a set of laboratory tests on the oriented rock samples. There are some empirical relations available to describe the strength of these rocks. Though characterization of transversely-isotropic rocks is practically a 3D problem, but these relations provide only a 2D description. In this paper, a method is proposed to provide a 3D description of UCS of transversely-isotropic rocks. By means of this formulation, one can determine UCS along with any arbitrary spatial direction. Also, a representative illustration of UCS is proposed in the form of contour-plots on a lower hemisphere Stereonet. The method is applied to an actual case study from the Kanigoizhan dam site located in the Kurdistan Province (Iran). Application of the proposed method to the phyllite rocks of this site show that the direction perpendicular to the dam axis exhibits the most anisotropic behavior. Hence, it is essential to take the strength anisotropy into account during the relevant analysis. The results obtained, together with the statistical variation of UCS, provide a practical approach to select the proper values of UCS according to the scope of the analysis.


[1]. Al-Karni, A.A. and Al-Shamrani, M.A. (2000). Study of the effect of soil anisotropy on slope stability using method of slices. Comput. Geotech. 26: 83–103.
[2]. Majdi, A. and Amini, M. (2008). Effects of geostructural weaknesses on flexural toppling, Proc, Fifth Asian Rock Mechanics Symposium (ARMS5), Tehran, 24-26 November, 611–618.
[3]. Majdi, A. and Amini, M. (2011). Analysis of geo-structural defects in flexural toppling failure. Int. J. Rock Mech. Min. Sci. 48: 175–186.
[4]. Majdi, A. and Hassani, F. (1989). Access tunnel convergence prediction in longwall coal mining. Int. J. Min. Geol. Eng. 7: 283–300.
[5]. Satici, O. and Ünver, B. (2015). Assessment of tunnel portal stability at jointed rock mass: A comparative case study. Comput. Geotech. 64: 72–82.
[6]. Barton, N. and Quadros, E. (2014). Most rock masses are likely to be anisotropic. Proc, Rock Mechanics for Natural Resources and Infrastructure- ISRM Specialized Conference. CBMR/ABMS and ISRM, Goiania, 9-13 September.
[7]. Wittke, W. (2014). Rock mechanics based on an anisotropic jointed rock model (AJRM), Wiley Blackwell, Berlin, 875 P.
[8]. Donath, F.A. (1964). Strength variation and deformational behavior in anisotropic rock. In: Judd, W. (Ed.) State of Stress in the Earth’s Crust, New York, pp. 281–298.
[9]. Hoek, E. (1964). Fracture of anisotropic rock. J. South African Inst. Min. Metall. 64: 501–518.
[10]. McLamore, R. and Gray, K.E. (1967). The mechanical behavior of anisotropic sedimentary roks. J. Eng. Ind. 89: 62–76.
[11]. Attewell, P.B. and Sandford, M.R. (1974). Intrinsic shear strength of a brittle, anisotropic rock- I: Experimental and mechanical interpretation. Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 11: 423–430.
[12]. Brown, E.T., Richards, L. and Barr, M. (1977). Shear strength characteristics of Delabole slates. Proc, Conference on Rock Engineering, New Castle Upon Tyne, 33–55.  
[13]. McCabe, M.W. and Koerner, R.M. (1975). High pressure shear strength investigation of an anisotropic mica schist rock. Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 12: 218–228.
[14]. Nasseri, M.H., Rao, K.S. and Ramamurthy, T. (1997). Failure mechanism in schistose rocks. Int. J. rock Mech. Min. Sci. Geomech. Abstr. 34: 460.
[15]. Nasseri, M.H.B., Rao, K.S. and Ramamurthy, T. (2003). Anisotropic strength and deformation behavior of Himalayan schists. Int. J. Rock Mech. Min. Sci. 40: 3–23.
[16]. Singh, V.K., Singh, D. and Singh, T.N. (2001). Prediction of strength properties of some schistose rocks from petrographic properties using artificial neural networks. Int. J. Rock Mech. Min. Sci. 38: 269–284.
[17]. Saroglou, H. and Tsiambaos, G. (2008). A modified Hoek- Brown failure criterion for anisotropic intact rock. Int. J. Rock Mech. Min. Sci. 45: 223–234.
[18]. Ramamurthy, T., Rao, G. and Singh, J. (1988). A strength criterion for anisotropic rocks, Proc, Fifth Australia-New Zealand Conference on Geomechanics, Sydney, 22-26 August, 253–257.
[19]. Al-Harthi, A.A. (1998). Effect of planar structures on the anisotropy of Ranyah sandstone, Saudi Arabia. Eng. Geol. 50: 49–57.
[20]. Colak, K. and Unlu, T. (2004). Effect of transverse anisotropy on the Hoek-Brown strength parameter “mi” for intact rocks. Int. J. Rock Mech. Min. Sci. 41: 1045–1052.
[21]. Ajalloeian, R. and Lashkaripour, G.R. (2000). Strength anisotropies in mudrocks. Bull. Eng. Geol. Environ. 59: 195–199.
[22]. Ramamurthy, T. (1993). Strength and modulus responses of anisotropic rocks. In: Brown, E.T. (Ed.), Comprehensive rock engineering. Pergamon press, pp. 313–329.
[23]. Singh, K.B. and Singh, T.N. (1998). Ground movements over longwall workings in the Kamptee coalfield, India. Eng. Geol. 50: 125–139.
[24]. Franklin, J.A. (1985). Suggested method for determining point load strength. Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 22: 51–60.
[25]. Tsidzi, K.E.N. (1997). Propagation characteristics of ultrasonic waves in foliated rocks. Bull. Int. Assoc. Eng. Geol. 56: 103–114.
[26]. Saroglou, H., Marinos, P. and Tsiambaos, G. (2003). The anisotropic nature of selected metamorphic rocks from Greece. Proc, ISRM 2003-Technology roadmap for rock mechanics. South African Institute of Mining and Metallurgy, 8-12 September, 1019–1024.
[27]. Saroglou, H. and Tsiambaos, G. (2007). Classification of anisotropic rocks. Proc, 11th Congress of the International Society for Rock Mechanics, Lisbon, 09-13 July, 191–196.
[28]. Jaeger, J.C. (1960). Shear failure of anisotropic rocks. Geol. Mag. 97: 65–72.
[29]. Donath, F.A. (1961). Experimental study of shear failure in anisotropic rocks. Geol. Soc. Am. Bull. 72: 985–990.
[30]. Garagon, M. and Can, T. (2010). Predicting the strength anisotropy in uniaxial compression of some laminated sandstones using multivariate regression analysis. Mater. Struct. 43: 509–517.
[31]. Saeidi, O., Rasouli, V., Geranmayeh Vaneghi, R. and Gholami, R. (2014). A modified failure criterion for transversely isotropic rocks. Geosci. Front. 5: 215–225.