Document Type : Original Research Paper

Authors

1 Rock Mechanics Division, School of Engineering, Tarbiat Modares University, Tehran, Iran

2 Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran

3 Faculty of Civil Engineering, University of Minho, Braga, Portugal

Abstract

The tensile strength of rocks plays a noteworthy role in their failure mechanism, and its determination can be beneficial in optimizing the design of the rock structures. Schistose rocks due to their inherent anisotropy in different foliation directions show a diverse strength at each direction. The purpose of this work was to compare and assess the tensile strength of phyllite, which was obtained in direct and indirect tensile tests in different foliation directions. To this end, several phyllite specimens with different foliation angles (0º, 30º, 45º, 60º, and 90º) related to the loading axis (β) were prepared. Finally, the direct tensile test, diametrical and axial point load tests, Brazilian test, and Schmidt hammer test were conducted on 188 samples. The results of the experimental tests revealed that the maximum and minimum tensile strengths in direct tensile testing tension were directly related to the angles of 0º and 90º. Also it was observed that the Brazilian tensile strength overestimated the tensile strength. Furthermore, an exponential correlation was introduced between the direct tensile strength and the Brazilian tensile strength.

Keywords

[1]. Hudson, J.A., Brown, E.T. and Rummel, F. (1972, March). The controlled failure of rock discs and rings loaded in diametral compression. In International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts (Vol. 9, No. 2, pp. 241-248). Pergamon.‏
[2]. A. Coviello, R. Lagioia, and R. Nova, “On the Measurement of the Tensile Strength of Soft Rocks”, Rock Mechanics and Rock Engineering, Vol. 38, No. 4, 2005, pp 251–273.
[3]. Nova, R. and Zaninetti, A. (1990, August). An investigation into the tensile behaviour of a schistose rock. In International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts (Vol. 27, No. 4, pp. 231-242). Pergamon.‏
[4]. Goodman, R.E. (1989). Introduction to rock mechanics (Vol. 2). New York: Wiley.‏
[5]. Liao, J.J., Yang, M.T. and Hsieh, H.Y. (1997). Direct tensile behavior of a transversely isotropic rock. International Journal of Rock Mechanics and Mining Sciences. 34 (5): 837-849.‏
[6]. Nazerigivi, A., Nejati, H.R., Ghazvinian, A. and Najigivi, A. (2018). Effects of SiO2 nanoparticles dispersion on concrete fracture toughness. Construction and Building Materials, 171, 672-679.
[7]. Ghazvinian, A., Nejati, H.R., Sarfarazi, V. and Hadei, M.R. (2013). Mixed mode crack propagation in low brittle rock-like materials. Arabian Journal of Geosciences. 6 (11): 4435-4444.‏
[8]. Gurocak, Z., Solanki, P., Alemdag, S. and Zaman, M.M. (2012). New considerations for empirical estimation of tensile strength of rocks. Engineering Geology, 145, 1-8.‏
[9]. Amadei, B. (1996, April). Importance of anisotropy when estimating and measuring in situ stresses in rock. In International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts (Vol. 33, No. 3, pp. 293-325). Pergamon.‏
[10]. Cho, J. W., Kim, H., Jeon, S. and Min, K.B. (2012). Deformation and strength anisotropy of Asan gneiss, Boryeong shale, and Yeoncheon schist. International journal of rock mechanics and mining sciences (1997), 50, 158-169.‏
[11]. Dai. F. and Xia, K. (2009). “Tensile strength anisotropy of Barre Granite”, ROCKENG09: Proceedings of the 3rd CANUS Rock Mechanics Symposium, Toronto, May 2009 (Edition: M. Diederichs, and G. Grasselli) 2009.
[12]. Barla, G. and Innaurato, N. (1973). Indirect tensile testing of anisotropic rocks. Rock mechanics, 5(4), 215-230.‏
[13]. Nazerigivi, A., Nejati, H.R., Ghazvinian, A. and Najigivi, A. (2017). Influence of nano-silica on the failure mechanism of concrete specimens. Computers and Concrete, 19(4), 429-434.‏
[14]. Nejati, H.R. and Ghazvinian, A. (2014). Brittleness effect on rock fatigue damage evolution. Rock mechanics and rock engineering, 47(5), 1839-1848.‏
[15]. Tien, Y.M., Kuo, M.C. and Juang, C.H. (2006). An experimental investigation of the failure mechanism of simulated transversely isotropic rocks. International journal of rock mechanics and mining sciences, 43(8), 1163-1181.‏
[16]. Hobbs, D.W. (1964, May). The tensile strength of rocks. In International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts (Vol. 1, No. 3, pp. 385-396). Pergamon.‏
[17]. Gamaneh Kav Consulting Engineers, “Rock mechanics test results of water transmission system project of Azad dam to Ravansar”, Report No. 1, 2006.
[18]. Tavallali, A. and Vervoort, A. (2010). Effect of layer orientation on the failure of layered sandstone under Brazilian test conditions. International journal of rock mechanics and mining sciences. 47 (2): 313-322.‏
[19]. Debecker, B. and Vervoort, A. (2009). Experimental observation of fracture patterns in layered slate. International journal of fracture. 159 (1): 51-62.‏
[20]. Li, D. and Wong, L.N.Y. (2013). The Brazilian disc test for rock mechanics applications: review and new insights. Rock mechanics and rock engineering. 46 (2): 269-287.‏
[21]. Fairhurst, C. (1964, October). On the validity of the ‘Brazilian’test for brittle materials. In International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts (Vol. 1, No. 4, pp. 535-546). Pergamon.‏
[22]. Mellor, M. and Hawkes, I. (1971). Measurement of tensile strength by diametral compression of discs and annuli. Engineering Geology. 5 (3): 173-225.‏
[23]. Scull, P., Franklin, J., Chadwick, O.A. and McArthur, D. (2003). Predictive soil mapping: a review. Progress in Physical Geography. 27 (2): 171-197.
[24]. ‏ Bieniawski, Z.T. and Bernede, M.J. (1979, April). Suggested methods for determining the uniaxial compressive strength and deformability of rock materials: Part 1. Suggested method for determining deformability of rock materials in uniaxial compression. In International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts (Vol. 16, No. 2, pp. 138-140). Pergamon.‏
[25]. Franklin, J.A. (1985, April). Suggested method for determining point load strength. In International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts (Vol. 22, No. 2, pp. 51-60). Pergamon.‏
[26]. Chau, K.T. and Wong, R.H.C. (1996). Uniaxial compressive strength and point load strength of rocks. In International journal of rock mechanics and mining sciences & geomechanics abstracts (Vol. 33, No. 2, pp. 183-188). Pergamon.‏
[27]. Russell, A.R. and Wood, D.M. (2009). Point load tests and strength measurements for brittle spheres. International Journal of Rock Mechanics and Mining Sciences. 46 (2): 272-280.‏
[28]. Schmidt, E. (1951). A non-destructive concrete tester. Concrete, 59, 34-35.‏
[29]. Miller, R.P. (1965). Engineering classification and index properties for intact rock. PhD Thesis, University of Illinois.‏
[30]. Barton, N. and Choubey, V. (1977). The shear strength of rock joints in theory and practice. Rock mechanics, 10(1-2), 1-54.
[31]. ‏ Brown, E.T. (1981). Rock characterization testing and monitoring (No. BOOK). Pergamon press.‏
[32]. Hucka, V. (1965). A rapid method of determining the strength of rocks in situ. In International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts (Vol. 2, No. 2, pp. 127-134). Pergamon.‏
[33]. Poole, R.W. and Farmer, I.W. (1980). Consistency and repeatability of Schmidt hammer rebound data during field testing. International Journal of Rock Mechanics and Mining Science. 17 (3).‏
[34]. Fowell, R.J. and RJ, F. (1976). FACTORS INFLUENCING THE CUTTING PERFORMANCE OF A SELECTIVE TUNNELLING MACHINE.‏
[35]. Demirdag, S., Yavuz, H. and Altindag, R. (2009). The effect of sample size on Schmidt rebound hardness value of rocks. International Journal of Rock Mechanics and Mining Sciences. 46 (4): 725-730.‏
[36]. Brown, E.T. (1981). Rock characterization testing and monitoring (No. BOOK). Pergamon press.‏
[38]. Chau, K.T. (1998). Analytic solutions for diametral point load strength tests. Journal of engineering mechanics. 124 (8): 875-883.
[39]. ‏ Heidari, M., Khanlari, G.R., Kaveh, M.T. and Kargarian, S. (2012). Predicting the uniaxial compressive and tensile strengths of gypsum rock by point load testing. Rock mechanics and rock engineering, 45(2), 265-273.‏
[40]. Tsidzi, K.E.N. (1990). The influence of foliation on point load strength anisotropy of foliated rocks. Engineering Geology. 29 (1): 49-58.‏
[41]. Basu, A. and Aydin, A. (2004). A method for normalization of Schmidt hammer rebound values. International Journal of Rock Mechanics and Mining Sciences. 41 (7): 1211-1214.‏