Document Type: Original Research Paper

Authors

Rock Mechanics Gr., Mining Dept., Eng. Faculty, Tarbiat Modares University, Tehran, Iran

Abstract

One of the methods used to investigate the damaged zone in rock structure is the acoustic emission method. This method is based on receiving the elastic waves that are produced by deformation and cracking of the rock mass around the underground excavation. In this research, a study is conducted on the rock samples by a numerical method to investigate the damaged zone caused by the excavation of circular space on it. For this purpose, 33 cube samples of three different material types including sandstone, concrete, and cement-plaster mortar are prepared. A circular hole is drilled in the center of each sample. The hole diameter is 20 or 25 mm. The samples are loaded uniaxially or biaxially with different stress rates. It is tried to study the acoustic events occurring in the samples during the test, and their locations are investigated. Then the experiments are evaluated by a numerical method using the FLAC3D software and some developed codes. The relation between the sample damaged zone where the acoustic events have occurred during the loading period and the numerical elements that reach a degree of tensile and shear yield is studied. The results obtained show that the amount of cumulative acoustic parameters in cement-plaster mortar specimens is more than the others. In fact, the finer grains, the more amounts of energy and counts will be produced. Also, the results show that with increase in the lateral pressure and loading rate, the amount of cumulative energy and counts decreases.

Keywords

Main Subjects

[1]. Fattahi, H., Shojaee, S. and Farsangi, E. (2013). Application of adaptive neuro-fuzzy inference system for the assessment of damaged zone around underground spaces. International journal of optimization in civil engineering, 3 (4): 673-693.

[2]. Tsang, CF., Bernier, F. and Davies, C. (2005). Geohydromechanical processes in the excavation damaged zone in crystalline rock, rock salt, and indurated and plastic clays—in the context of radioactive waste disposal. International Journal of Rock Mechanics and Mining Sciences, 42 (1): 109-125.

[3]. Sato, T., Kikuchi, T. and Sugihara, K. (2000). In-situ experiments on an excavation disturbed zone induced by mechanical excavation in Neogene sedimentary rock at tono mine, central Japan. Engineering Geological. 56 (2): 97-108.

[4]. Shen, B. and Barton, N. (1997). The disturbed zone around tunnels in jointed rock masses. International Journal of Rock Mechanics and Mining Sciences, 34 (1): 117-125.

[5]. Suzuki, K., Nakata, E., Minami, M., Hibino, E., Tani, T., Sakakibara, J. and Yamada, N. (2004). Estimation of the zone of excavation disturbance around tunnels, using resistivity and acoustic tomography. Exploration Geophysics, 35 (1): 62-69.

[6]. Ji, M., Zhang, Y.D., Liu, W.P. and Cheng, L. (2014). Damage evolution law based on acoustic emission and Weibull distribution of granite under uniaxial stress. Acta Geodynamica et Geomaterialia, 175 (3): 1-9.

[7] Fakhimi, A., Carvalho, F., Ishida, T. and Labuz, J.F. (2002). Simulation of failure around a circular opening in rock. International Journal of Rock Mechanics and Mining Sciences, 39, 507-515.

[8]. Zhu, W.C., Liu, J.S., Tang, C.A., Zhao, X.D. and Brady, B.H. (2005). Simulation of progressive fracturing processes around underground excavations under biaxial compression. Tunnelling and Underground Space Technology, 20 (3): 231-247.

[9]. Zhu, W.C. and Bruhns, O.T. (2008). Simulating excavation damaged zone around a circular opening under hydromechanical conditions. International Journal of Rock Mechanics and Mining Sciences. 5 (45): 815-830.

[10]. Wang, S.Y., Sloan, S.W., Sheng, D.C. and Tang, C.A. (2012). Numerical analysis of the failure process around a circular opening in rock. Computers and Geotechnics, 39, 8-16.

[11]. Zhao, X.D., Zhang, H.X. and Zhu, W.C. (2014). Fracture evolution around pre-existing cylindrical cavities in brittle rocks under uniaxial compression. Transactions of Nonferrous Metals Society of China. 24 (3): 806-815.

[12]. Liu, J.P, Li, Y.H., Xu, S.D., Xu, S. and Jin, C.Y. (2015). Cracking mechanisms in granite rocks subjected to uniaxial compression by moment tensor analysis of acoustic emission. Theoretical and Applied Fracture Mechanics, 75, 151-159.

[13]. Xu, S.D., Li, Y.H. and Liu, J.P. (2017). Detection of cracking and damage mechanisms in brittle granites by moment tensor analysis of acoustic emission signals. Acoustical Physics. 63 (3): 359-367.

[14]. Shokri, T. (2013). Health Monitoring and Crack Source Location in Reinforced Concrete Based on Acoustic Emission. PhD Thesis, University of Miami.

[15]. Miller, R.K. and Mclntire, P. (1987). Non-Destructive Testing Handbook: Acoustic Emission Testing. American Society for Nondestructive Testing.

[16]. Salinas, V., Vargas, Y., Ruzzante, J. and Gaete, L. (2010). Localization algorithm for acoustic emission. Physics Procedia, 3 (1): 863-871.

[17]. Shull, P.J. (2002). Nondestructive evaluation: theory, techniques, and applications. CRC press.

[18]. Vallen CO. (2010). AMSY-5 Manual. www.Vallen.de.

[19]. Tan, X. (2013). Hydro-mechanical Coupled Behavior of Brittle Rocks: Laboratory Experiments and Numerical Simulations (Doctoral dissertation, Institute für Geotechnik).

[20]. Hu, J. and Xu, N. (2011). Numerical analysis of failure mechanism of tunnel under different confining pressure. Procedia Engineering, 26, 107-112.

[21]. Itasca. (2010). FLAC‐3D (Version 5.0) user manual.

[22]. Zhou, Z.L., Zhou, J., Dong, L.J., Cai, X., Rui, Y.C. and Ke, C.T. (2017). Experimental study on the location of an acoustic emission source considering refraction in different media. Scientific Reports 7, Article number: 7472 (2017).