Document Type : Original Research Paper

Authors

1 Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran.

2 Department of Mining Engineering, Higher Education Complex of Zarand, Shahid Bahonar University of Kerman, Kerman, Iran.

3 Department of Mine Exploitation Engineering, Faculty of Mining and Metallurgy, Institute of Engineering, Yazd University, Yazd, Iran.

4 Department of Mining Engineering, Shahid Bahonar University of Kerman, Kerman, Iran.

Abstract

In this paper, the effect of variations in the number and area of the rock bridges on the non-persistent discontinuities is investigated. In this regard, blocks containing rock bridges and joints with dimensions of 15 cm * 15 cm * 15 cm are prepared from plaster. The available rock bridges that have occupied 0.2, 0.4, and 0.6  of the shear surface show latitudinal extension along the shear surface. There are variations in the number and extension of the rock bridges in the fixed area. For each of the samples, tests are performed on three blocks of the same material, by putting it under various direct normal stresses. Normal stresses were 3.33, 5.55, 7.77 kg/cm2. Also the obtained shear strength by laboratory tests was compared with the outputs of Jenning's criterion and Guo and Qi's criterion to determine the accuracy of these criteria for predicting the shear strength of non-persistent joints. The results show that the tensile crack started in the rock bridge under normal stress of 3.33 kg/cm2. Mixed-mode tensile shear cracks were propagated in the rock bridge under a normal stress of 5.55 kg/cm2, while a pure shear crack developed in the rock bridge under a normal stress of 7.77 kg/cm2. With the increase of normal stress, the number of microfractures increased. The variance in the number of rock bridges in the fixed area of the rock bridge does not affect the friction angle along the shear surface. Furthermore, the cohesion along the shear surface shows a small decrease with the increasing number of rock bridges. Also by the increase in the area of rock bridges, the friction angle along the shear surface remains constant, while at the same time, there is an almost linear increase in cohesion. Guo and Qi's criterion predicts the shear strength of the non-persistent joint exactly close to the shear strength of the physical samples.

Keywords

Main Subjects

[1]. Eberhardt, E., Kaiser, P., & Coggan, J.S. (2004). Numerical analysis of initiation and progressive failure in natural rock slopes—the 1991 Randa rockslide. International Journal of Rock Mechanics and Mining Sciences, 41(1), 69-87.
[2]. Cai, M., Kaiser, P.K., Uno, H., Tasaka, Y., & Minami, M. (2004). Estimation of rock mass deformation modulus and strength of jointed hard rock masses using the GSI system. International Journal of Rock Mechanics and Mining Sciences, 41(1), 3-19.
[3]. Einstein, H.H., Veneziano, D., Baecher, G.B., & O’Reillly, K.J., (1983). The effect of discontinuity persistence on rock slope stability. International Journal of Rock Mechanics and Mining Sciences, 20(5), 227–36.
[4]. Wong, R.H.C., Chau, K.T., Tang, C.A. & Lin, P. (2001). Analysis of crack coalescence in rock-part I: experimental approach. International Journal of Rock Mechanics and Mining Sciences, 38, 909–924.
[5]. Lajtai, E.Z. (1974). Brittle fracture in compression. International Journal of Fracture, 10, 525–536.
[6]. Lee, H. & Jeo, S. (2011). An experimental and numerical study of fracture coalescence in precracked specimens under uniaxial compression. International Journal of Solids and Structures, 48: 979–999.
[7]. Wong, L.N.Y. & Einstein, H.H. (2009). Crack coalescence in molded gypsum and carrara marble: part 2—microscopic observations and interpretation. Rock Mechanics and Rock Engineering, 42 , 513–545.
[8]. Park, C.H. & Bobet, A. (2010). Crack initiation, propagation and coalescence from frictional flaws in uniaxial compression, Engineering Fracture Mechanics, 77, 2727–2748.
[9]. Wong, R., Chau, K., Tang, C., Lin, P. (2001). Analysis of crack coalescence in rock-like materials containing three flaws—part I: experimental approach. International Journal of Rock Mechanics and Mining Sciences, 38, 909–924.
[10]. Zhou, X.P., Cheng, H., & Feng, Y.F. (2014). An experimental study of crack coalescence behaviour in rock-like materials containing multiple flaws under uniaxial compression, Rock Mechanics and Rock Engineering, 47 (6), 1961–1986.
[11]. Yang, H. & Liu, J., Wong, L.N.Y. (2017). Influence of petroleum on the failure pattern of saturated pre-cracked and intact sandstone. Bulletin of Engineering Geology and the Environment, 77, 767–774.
[12]. Bobet, A., (2000). The initiation of secondary cracks in compression. Engineering Fracture Mechanics, 66, 187-219.
[13]. Bobet, A. (2000). Modeling of crack initiation، propagation and coalescence in uniaxial compression. Rock Mechanics and Rock Engineering, 33(2), 119–39.
[14]. Li, Y.P., Chen, L.Z., & Wang, Y.H. (2005). Experimental research on pre-cracked marble. International Journalof Solids and Structures, 42, 2505-2516
[15]. Wong, R.H.C. & Chau, K.T. (1998). Crack coalescence in a rock-like material containing two cracks, International Journal of Rock Mechanics and Mining Sciences, 35(2), 147–164.
[16]. Savilahti, T., Nordlund, E., & Stephansson, O. (1990). Shear box testing and modeling of joint bridge. In: Proceedings of international symposium on shear box testing and modeling of joint bridge Rock Joints, Loen, Norway, pp. 295–300
[17]. Ghazvinian, A., Nikudel, M.R., & Sarfarazi, V. (2007). Effect of rock bridge continuity and area on shear behavior of joints. In: Proceedings of the 11th Congress of the international society for rock mechanics, Lisbon, Portugal, 3, 247–250.
[18]. Xia, C.C., Xiao, W.M., & Ding, Z.Z. (2010). Modification of Jennings strength criterion for intermittent joints considering rock bridge weakening and joint surface undulating angle. Chinese Journal of Rock Mechanics and Engineering, 29, 485–492.
[19]. Tang, Z.C., Xia, C.C., & Liu, Y.M. (2012). Modified Jennings shear strength criterion based on mechanical weakening model of rock bridges. Chinese Journal of Geotechnical Engineering, 34, 2093–2099.
[20]. Zhang, H.Q., Zhao, Z.Y., Tang, C.A., & Song L. (2006). Numerical study of shear behavior of intermittent rock joints with different geometrical parameters. International Journal of Rock Mechanics and Mining Sciences, 43(5), 802–816
[21]. Einstein, H.H., Veneziano, D., Baecher, G.B., & O’Reillly, K.J. (1983). The effect of discontinuity persistence on rock slope stability. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 20(5), 227–23.
[22]. Lajtai, E.Z., Carter, B.J., & Duncan, E.J.S. (1994). En echelon crack-arrays in potash salt rock. Rock Mechanics and Rock Engineering, 27(2), 89–111.
[23]. Li, S., Feng, X,T., Li, Z., Chen, B., Zhang, C., & Zhou, H. (2012). In-situ monitoring of rockburst nucleation and evolution in the deeply buried tunnels of Jinping II hydropower station. Engineering Geology, 137, 85–96.
[24]. Huang, D., Cen, D., Ma, G., & Huang, R. (2015). Step-path failure of rock slopes with intermittent joints. Landslides, 12(5), 911–926.
[25]. Gehle, C. & Kutter, H.K. (2003). Breakage and shear behavior of intermittent rock joints. International Journal of Rock Mechanics and Mining Sciences & Geomechanics, 40, 687–700.
[26]. Gerolymatou, E., & Triantafyllidis, T. (2016). Shearing of materials with intermittent joints, Rock Mechanics and Rock Engineering, 49(7), 2689–2700.
[27]. Asadizadeh, M., Moosavi, M., Hossaini, M.F., & Masoumi, H. (2018). Shear strength and cracking process of non-persistent jointed rocks: an extensive experimental investigation. Rock Mechanics and Rock Engineering, 51, 415–428.
[28]. Yaylacı, M., Abanoz, M., Yaylacı, E.U., Ölmez, H., Sekban, D.M., & Birinci, A. (2022). Evaluation of the contact problem of functionally graded layer resting on rigid foundation pressed via rigid punch by analytical and numerical (FEM and MLP) methods. Archive of Applied Mechanics, 92, 1953–1971.
[29]. Yaylaci, E. U., Oner, E., Yaylaci, M., Ozdemir, M. E., Abushattal, A., & Birinci, A. (2022). Application of artificial neural networks in the analysis of the continuous contact problem. Structural Engineering and Mechanics, 84(1), 35–48.
[30]. Yaylacı, M., Şabano, B.Ş., Özdemir, M.E., and Birinci, A. (2022). Solving the contact problem of functionally graded layers resting on a HP and pressed with a uniformly distributed load by analytical and numerical methods. Structural Engineering and Mechanics, 82(3), 401-416.
[31]. Golewski, G.L. (2023).Combined Effect of Coal Fly Ash (CFA) and Nanosilica (nS) on the Strength Parameters and Microstructural Properties of Eco-Friendly Concrete. Energies, 16(1), 452. https://doi.org/10.3390/en16010452.
[32]. Golewski, G.L., (2023). Mechanical properties and brittleness of concrete made by combined fly ash, silica fume and nanosilica with ordinary Portland cement, AIMS Materials Science, 10(3), 390-404.
[33]. Golewski, G.L. (2023). Study of strength and microstructure of a new sustainable concrete incorporating pozzolanic materials. Structural Engineering and Mechanics, 86(4), 431-441.
[34]. Golewski, G.L. (2023). The Phenomenon of Cracking in Cement Concretes and Reinforced Concrete Structures: The Mechanism of Cracks Formation, Causes of Their Initiation, Types and Places of Occurrence, and Methods of Detection—A Review. Buildings,13(3), 765. https://doi.org/10.3390/buildings13030765.
[35]. Özdemir, M.E. & Yaylac, M. (2023). Research of the impact of material and flow properties on fluid-structure interaction in cage systems. Wind and structures, 36 (1), 31-40.
[36]. Turan, M., Uzun, Y.E., & Yaylacı, M. (2023). Free vibration and buckling of functionally graded porous beams using analytical, finite element, and artificial neural network methods. Archive of Applied Mechanics, 93, 1351–1372.
[37]. Yaylacı, M., Yaylaci, E.U., Ozdemir, M.E., Ozturk, Ş., & Sesli, H. (2023). Vibration and buckling analyses of FGM beam with edge crack: Finite element and multilayer perceptron methods. Steel and Composite Structures, 46(4), 565-575.
[38]. Yang, X.X. & Kulatilake, P.H. (2019). Laboratory investigation of mechanical behavior of granite samples containing discontinuous joints through direct shear tests. Arabian Journal of Geosciences, 12(3), 79.
[39]. Jennings, J.E. (1970). A mathematical theory for the calculation of the stability of open cast mines, In Proceedings of the Symposium on the Theoretical Background to the Planning of Open Pit Mines, Johannesburg, South Africa, 1 January, pp. 87–102.
[40]. Guo, S. & Qi, S. (2015). Numerical study on progressive failure of hard rock samples with an unfilled undulate joint, Engineering Geology, 193:173–182.
[41]. Martin, C. (1997). Seventeenth Canadian geotechnical colloquium: The effect of cohesion loss and stress path on brittle rock strength. Canadian Geotechnical Journal, 34, 698–725.
[42]. Hajiabdolmajid, V., Kaiser, P., & Martin, C. (2002). Modelling brittle failure of rock. International Journal of Rock Mechanics and Mining Science, 39, 731–774.
[43]. Wong, R.H.C. & Wang, S.W. (2002). Experimental andn umerical study on the effect of material property, normal stress and the position of joint on the progressive failure under direct shear. NARMS-TAC2002. In Proceedings of the Mining and Tunneling Innovationand Opportunity. Toronto,ON,Canada,7–10 July, pp.1009–1016.
[44]. Guo, S.F., Qi, S.W., Zhan, Z.F., & Zheng, B.W. (2017). Plastic-strain-dependent strength model to simulate the cracking process of brittle rocks with an existing non-persistent joint. Engineering Geology, 231, 114–125.
[45]. Huang, X.L. Qi, S.W., Zheng, B.W., Guo, S.F., Liang, N., & Zhan, Z.F. (2020). Progressive failure characteristics of brittle rock under high-strain-rate compression using the bonded particle model. Materials, 13, 3943, https://doi.org/10.3390/ma13183943.