Simulation of crack coalescence mechanism underneath single and double disc cutters by higher order displacement discontinuity method

Abstract

The present research is focused on the numerical crack coalescence analysis of the micro-cracks and cracks produced during the cutting action of TBM disc cutters. The linear elastic fracture mechanics (LEFM) concepts and the maximum tangential stress criterion are used to investigate the micro crack propagation and its direction underneath the excavating discs. A higher order displacement discontinuity method with quadratic displacement discontinuity elements is used to estimate the stress intensity factors near the crack tips. Rock cutting mechanisms under single and double type discs are simulated by the proposed numerical method. The main purposes of the present modeling are to simulate the chip formation process of indented rocks by single and double discs. The effects of specific disc parameters (except speed) on the thrust force F_r, the rolling force F_r, and the specific energy E_S are investigated. It has been shown that the specific energy (energy required to cut through a unit volume of rock) of the double disc is less than that of the single disc. Crack propagation in rocks under disc cutters is numerically modeled and the optimum ratio of disc spacing S to penetration depth P_d (i.e. S/P_d ratio) of about 10 is obtained, which is in good agreement with the theoretical and experimental results cited in the literature.

Keywords

TBM disc cutter / double discs / cracks coalescence / higher-order displacement discontinuity method / specific energy

References

[1] HowarthD F, RoxborughF F. Some fundamental aspects of the use of disc cutters in hard rock excavation [J]. J South Afric Inst Min and Metall, 1982, 11: 309-315

[2] CookN G, HoodM, TsaiF. Observations of crack growth in hard rock loaded by an indenter [J]. Int J Rock Mech Min Sci & Geomech Abstr, 1984, 21: 97-107

[3] GuoH, AzizN I, SchmidtL C. Rock cutting study using linear elastic fracture mechanics [J]. Engineering Fracture Mechanics, 1992, 41: 771-778

[4] RostamiJ, OzdemirL. A new model for performance prediction of hard rock TBMs [C]. Proceedings of Rapid Excavation and Tunneling Conference (RETC). Boston, 1993793-809

[5] TanX C, KouS Q, LindqvistP AAubertinM, HassaniF, MitriH. Simulation of rock fragmentation by indenters using DDM and fracture mechanics [C]. Rock Mechanics, Tools and Techniques, 1996, Roterdam, Balkema

[6] AcargluO, OzdemirL, AsburyB. A fuzzy logic model to predict specific energy requirement for TBM performance prediction [J]. Tunneling Underground Space Technology, 2008, 23: 600-608

[7] BilginN, BalaciC, Acaroglu, TuncdemirH, EskikayaNatoT U. Development of rapid excavation technologies for the Turkish mining and tunnelling industries [C]. Excavation Project Report, 2000, Turkey, Istanbul Technical University: 172

[8] BenardosA G, KaliampakosD C. Modeling TBM performance with artificial neural networks [J]. Tunneling and Underground Space Technology, 2004, 19: 597-605

[9] ParkK I, ChangS H, ChoiS W, JeonS. Prediction of the optimum cutting condition of TBM disc cutter in Korean granite by the linear cutting test [C]. Proceedings of Korean Society for Rock Mechanics Conference, 2006217-236

[10] Fatehi MarjiMCrack propagation modeling in rocks and its application to indentation problems [D], 1990, Ankara, Turkey, Middle East Technical University

[11] GertschR, GertschL, RostamiJ. Disc cutting tests in Colorado red granite: Implications for TBM performance prediction [J]. Int J Rock Mech Min Sci, 2007, 44(2): 238-246

[12] AlehosseinH, DetournayE, HuangH. An analytical model for the indentation of rocks by blunt tools [J]. Rock Mech Rock Engin, 2000, 33: 267-284

[13] HaeriH, ShahriarK, Fatehi MarjiM, MoarefvandP. A coupled numerical-experimental study of the breakage process of brittle substances [J]. Arabian Journal of Geosciences, 2013

[14] Fatehi MarjiMModeling of cracks in rock fragmentation with a higher order displacement discontinuity method [D], 1997, Ankara, Middle East Technical University (METU)

[15] Fatehi MarjiM, Hosseini-nasabH, HosseinmorshedyA. Numerical modeling of the mechanism of crack propagation in rocks under TBM disc cutters [J]. J Mech Mater Struct, 2009, 2: 439-457

[16] ShouK J, CrouchS L. A higher order displacement discontinuity method for analysis of crack problems [J]. Int J Rock Mech Min Sci & Geomech Abstr, 1995, 32: 49-55

[17] HaeriH, ShahriarK, Fatehi MarjiM, MoarefvandP. An experimental and numerical study of crack propagation and cracks coalescence in the pre-cracked rock-like disc specimens under compression [J]. International Journal of Rock Mechanics and Mining Sciences, 2014

[18] CrouchS L, StarfieldA MBoundary element methods in solid mechanics [M], 1983, London, Allen and Unwin

[19] Fatehi MarjiM, Hosseini-NasabH, KohsaryA H. On the uses of special crack tip elements in numerical fracture mechanics [J]. Int J Solids Struct, 2006, 43: 1669-1692

[20] Fatehi MarjiM. Numerical analysis of quasi-static crack branching in brittle solids by a modified displacement discontinuity method [J]. Int J Solids Struct, 2014, 5(19): 1716-1736

[21] HaeriH, Fatehi MarjiM, ShahriarK, MoarefvandP. On the HDD analysis of micro crack initiation, propagation and coalescence in brittle materials [J]. Arabian Journal of Geosciences, 2014

[22] WhittakerB N, SinghR N, SunGRock fracture mechanics, principles, design and applications [M], 1992, Netherlands, Elsevier

[23] BowieO LSihG C. Solutions of plane crack problems by mapping techniques [C]. Mechanics of Fracture, 1973, Leyden, Noordhoff International Publishing