310 Classification of Coal Measures (Scoble and Moftuoglu, 1984), Excavatability Index Rating Scheme (Hadjigeorgiou and Scoble, 1990), Diggability Index (Karpuz, 1990), Revised Excavatability Graph (Pettifer and Fookes, 1994), Cuttability index (Dey and Ghose, 2008) and many more. A new cuttability index is developed based on the case studies by the authors and compared the performance with existing models of Bilgin et.al. (1988), Gehring (1989) and Copur et, al. (1997). The details of these models are given in the Table 2. Table 2 – Cuttability index and roadheader performance predictive models Bilgin et.al. (1988), 2/3 100 = RQD RMCI cσ ICR = 0.28×P×0.974 RMCI where, RMCI = rockmass cuttability index (kg/cm2) RQD = rock quality designation (%) σc = unconfined compressive strength (kg/cm2). P = Motor Power, HP, ICR = Instantaneous cutting rate (bcm/h) Gehring (1989) N k L cσ * = For Roadheader model VASM-2D; N k k k L cσ 3 1 2 * × × = where, L* = production or cutting performance (bcm/h) N = cutter head power (kW) k = a factor for consideration of relative cuttability or tuning effect between road header and rock σc = unconfined compressive strength (MPa). k1 = relative cuttability of intact rock and, = 6 for very tough and plastic rock = 7 for tough and plastic rock = 8 for average rock = 9 for brittle rock = 10 for very brittle rock = 10 – 15 for coal k2 = influence of discontinuity such as joint, bedding plane etc and, = 1 for massive and discontinuity distance > 25 cm = 1.5 – 2 for layered/fissured, thinner bed rock, discontinuity 10 – 25 cm = 2.5 for layered/fissured/interbedded rock discontinuity <5 cm
RkJQdWJsaXNoZXIy MTM0Mzk2