13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- underneath rock mass. The disc edges are assumed to behave as artifact cracks. The propagation and coalescence mechanism of the micro cracks emanating from each artifact crack tips are investigated by discretizing it into three ordinary and three special crack tip elements at the tip. The maximum tangential tensile stress criterion (σθ-criterion) is implemented into HOSDD2D code. In the present research, the effects of erosion on the Mode I and Mode II stress intensity factors and specific energy (SE) for TBM disc cutters are investigated by simulating the penetrating artifact cracks (disc cutters) into a rock mass. The main purpose of the present modeling was to compare the results obtained for the eroded disc cutters with those of non-eroded disc cutters. As a result, for the eroded disc cutters, higher forces (more specific energy) are required to propagate the micro cracks emanating from the artifact cracks compared to those for non-eroded disc cutters 6.References [1] X. C. Tan, S. Q. Kou, P. A. Lindqvist, Simulation of Rock Fragmentation by Indenters Using DDM and Fracture Mechanics, Rock Mechanics, Tools and Techniques; Aubertin M., Hassani F., and Mitri H. (Eds.); Balkema, Roterdam, 1996 [2] J.Rostami, , L. Ozdemir, A new model for performance prediction of hard rock TBMs. In: Proceedings, Rapid Excavation and Tunneling Conference (RETC), 1993, pp. 793–809. [3] O. Acaroglu, L. Ozdemir, B. Asbury,. A fuzzy logic model to predict specific energy requirement for TBM performance prediction. Tunn. Undergr. Space Technol, 23 (2008) 600–608. [4] J.W. Cho, S. Jeon, S.H. Yu, S.H. Chang, Optimum spacing of TBM disc cutters: A numerical simulation using the three-dimensional dynamic fracturing method, Tunnelling and Underground Space Technology 25 (2010) 230–244. [5] N.G.W. Cook, M. Hood, F. Tsai, Observations of crack growth in hard rock loaded by an indenter. Int. J. Rock Mech. Min. Sci. Geomech. Abstr, 21 (1984) 97– 107. [6] Y. Uga, K. Sakoi, S. Sugiyama, Y. Kondo, K. Nishimura, H. Ono,. Development of new tunnel boring machine with slurry transport system – penetration efficiency of disc cutters, Kawasaki Heavy Industry Report 91, 1–8 (in Japanese), 1986. [7] B. Nilsen, L. Ozdemir, Hard rock tunnel boring prediction and field performance. In: Proceedings, Rapid Excavation and Tunneling Conference (RETC), 1993, pp. 833–852. [8] N. Bilgin, H. Tuncdemir, C. Balci, H. Copur, S. Eskikaya, A model to predict the performance of tunneling machines under stressed conditions, In: Proceedings, AITES-ITA 2000 World Tunnel Congress, 2000, pp. 47–53. [9] H.Y. Liu, S.Q. Kou, P.A. Lindqvist, C.A. Tang, Numerical simulation of the rock fragmentation process induced by indenters. Int. J. Rock Mech. Min. Sci. 39 (2002) 491–505. [10] S.H. Baek, H.K. Moon, A numerical study on the rock fragmentation by TBM cutter penetration. Tunn. Undergr. Space (J. Korean Soc. Rock Mech.) 13 (2003) 444–454 (in Korean). [11] N. Bilgin, C. Feridunoglu, D. Tumac, M. Cinar, Y. Palakci, O. Gunduz, L. Ozyol, The performance of a full face tunnel boring machine (TBM) in Tarabya (Istanbul). In: Proceedings, 31st ITA-AITES World Tunnel Congress, 2005, pp. 821–826. [12] S. Eskikaya, N. Bilgin, C. Balci, H. Tuncdemir,. From research to practice – development of rapid excavation technologies. In: Proceedings, 31st ITA-AITES World Tunnel Congress, 2005, pp. 435–441.
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