Experimental Assessment of Rock Cutting Characteristics by Strength-Driven Mechanism H Munoz, A Taheri & E Chanda AusIMM Africa Australia Technical Mining Conference, Jun 11-12 215 Adelaide, Australia
Outline 1. Previous studies on rock properties & Drilling Performance 2. Rock-tool Interaction Laws 3. Specific Energy and Intrinsic Specific Energy 4. Lab Experiments on Rock Compression & Cutting 5. Stress-Strain Energy on Rock Cutting 6. Final Remarks 4
Background: Rock Properties & Cutting Performance (Hoseinie, 29) 5
Background: Rock Properties & Drilling Performance Rock properties and drillability: not a strong relation in all cases Drilling Rate & rock parameters in rotary-percussive drilling (Thuro, 1996a) 6
Rock-tool Interaction Laws Background: - First concept of Specific Energy in drilling by Teale (1965) - Cutting mechanism in rocks by Nishimatsu (1972) - Cutting mechanism in metals & other materials by Atkins (1974) - Polycristalline Diamond Compact (PDC) drilling response by Detournay et al. (1992) - Cutting in metals in modern fracture mech by Atkins (23) - PDC drilling response model by Detournay et al. (28) - ID (Impregnated Diamond) drilling response model by Franca et al. (215) 7
Specific Energy and Intrinsic Specific Energy Full bit and equivalent two-dimensional cutter Fs F n PDC cutting ID cutting 25 2. = weight on the bit, = torque on the bit = area of the hole or excavation, = depth of cut per revolution, = rate of penetration, = angular velocity of the bit Specific energy, SE (MPa) 2 15 1 5 A B D C Intrinsic specific energy= 45 MPa 5 1 15 2 25 w/d, (MPa) E diss = Dissipation on friction (wear flat area: Diamond+matrix) = Intrinsic Specific Energy: energy strictly used in cutting 8
New Approach on Drilling Performance Some drawbacks from previous methods include: 1. Not taking into account the rock-tool interaction laws (i.e. the Intrinsic Specific Energy) to find rock properties in cutting & optimisation. 2. In addition, to the lack of knowledge in the nature of SE. 3. Strength classification on UCS alone (UCS alone does not fully describe rock strength, but the strain energy does). 9
New Approach on Drilling Performance 1) Rock-tool interaction laws, 2) Energy balance & 3) Stress-strain energy in UC tests 1 Plastic yielding (strength-related failure mechanism) d) (MPa) N = (F C s ) peak /(w c 1 1 = 221 = 88 = 42 = 26 = 9 J/cm 3 Mantina Brukunga Hawksbury Mountain Gold 1.1 1 1 d (mm) Tuffeau 1. ε is the minimum energy consumed in cutting 2. Strength-related failure mechanism is predominant 3. External work provided by Fs: dw external =dw fracture +dw shear +dw friction 4. Shear work (dw shear ) is the major contributor to dissipate external work, & 5. Beside UCS, stress-strain energy characterises rock plastic yield 1
Rock Types Tested Rock types from relatively soft to hard rocks Rock name Rock type Grain size Dry density (g/cm 3 ) Young s modulus (GPa) UCS (MPa) Tuffeau Limestone Fine 1.53 3.4 9 Castlegate Sandstone Fine 1.94 4.6 16 Mountain Gold Sandstone Fine 2.11 7.4 35 Hawksbury Sandstone Fine 2.26 14.4 45 Massangis Sandstone Fine 2.45 31.4 87 Brukunga Phyllite Fine 2.81 39.1 13 Mantina Basalt Fine 2.73 52.7 249 Harcourt Granite Medium-coarse 2.7 67.8 169 Radiant Red Granite Medium-coarse 2.62 75.1 262 American Black Granite Fine-medium 3.6 99.4 27 11
Uniaxial Compressive Tests Test details 4 tests in total Uniaxial monotonic compression & Single-cycle uniaxial compression UCS (MPa) 3 25 2 15 1 PDC tests ID tests 5 Young Modulus at 1 =1-5 (GPa) 12 1 8 6 4 2 Sandstones Limestones Siltstones Granites 12
Test details PDC Cutting Tests 7 tests in total PDC single cutter, Steady-state conditions (no wear takes place) & kinematic control (depth of cut d constant) Rock name Rock type Intrinsic specific energy ( ) (J/cm 3 ) PDC cutter = 5 = 3 = 45 degrees degrees degrees Tuffeau Limestone 9 11 19 Castlegate Sandstone 15 - - Mountain Gold Sandstone 26 - - Hawksbury Sandstone 42 57 97 Brukunga Phyllite 88 151 25 Mantina Basalt 221 314 495 Cutting machine & Single PDC cutter cutter width of 1 mm = 15 = 3 = 45 13
ID Cutting Tests Test details 3 tests in total ID leached segment, Steady-state conditions (no wear takes place) & kinematic control (depth of cut d constant) Rock name Rock type Intrinsic specific energy ( ) (J/cm 3 ) Leached ID segment Massangis Sandstone 3 Harcourt Granite 5 Radiant Red Granite 75 American Black Granite 45 Cutting machine & ID leached segment 14
Stress-Strain & Stress-strain Energy Characteristics 3 = 1 Taheri s method for unloading Stress (MPa) 1 5 Peak stress E sec =Max U d U e q= 1-3 (MPa) 5 Mountain Gold Sandstone q peak = 35±1 Single-cycle loading q peak 3 vol = 1 +2 3 1 q cd U d = 34.6 Monotonic loading U= 77.2 25 Strain Energy (1-3 J/cm 3 ) 1 2 4 6 8 Strain (1-4 ) -75 75 1 at q peak 1p 1 or 3 (1-4 ) Stress-strain energy characterised by: Where is the total absorbed strain energy of unit volume rock, is the irreversible energy, & is the releasable elastic strain energy Uniaxial monotonic & single-cycle in well agreement q= 1-3 (MPa) 3 Monotonic loading Single-cycle loading 3 vol = 1 +2 3 q peak U d = 3.2 Radiant Red Granite q peak = 262±1-5 5 1 or 3 (1-4 ) q cd 1 U= 432.4 1 Strain Energy (1-3 J/cm 3 ) 15
Stress-Strain & Stress-strain Energy Characteristics 3 = ~ (σ 1 - σ 3 ) 1 1 By using the Cambridge invariants: - Shear stress, ~ (σ 1 - σ 3 ) & - Shear strain, = 2/3(ε 1 - ε 3 ) max = ( 1-3 )/2 (MPa) Absorbed Shear Strain Energy (1-3 J/cm 3 ) 25 75 Reversal point 53.8 51.9 Hawksbury Mountain Gold Tuffeau Castlegate 34.2 U = 14.2 5 1 = 2/3 ( 1-3 ) (1-4 ) max = ( 1-3 )/2 (MPa) Absorbed Shear Strain Energy (1-3 J/cm 3 ) 15 45 American Black p Radiant Red Harcourt Massangis at q peak Mantina Brukunga Reversal point 45.8 21.8 186.1 183.4 195.2 U = 93.4 1 = 2/3 ( 1-3 ) (1-4 ) Shear work per unit volume of rock can be obtained as the area under the shear stressstrain curve in terms of: 16
Intrinsic Specific Energy from PDC & ID Cutting PDC cutting: The intrinsic specific energy, is in well agreement with UCS when back-rake angle θ =15 o increases 1.2 to 2.3 times when θ= 3 & 45 o ID cutting: Linear regime: normalised cutting force, & The plot slope represents exceeds UCS of their respective rock (1.7 to 3.5 times UCS) 12 1 5 F C s (N) = 221 J/cm 3 = 88 = 42 = 26 = 9 1 Mantina UCS= 249 MPa Brukunga UCS= 13 Hawksbury UCS= 45 Mountain Gold UCS= 35 Tuffeau UCS= 9..1.2.3.4.5.6 Intrinsic Specific Energy (J/cm 3 ) 1 1 1 Mantina Brukunga Hawksbury Mountain Gold Castlegate (Roller-cone) Tuffeau 15 3 45 6 F C s (N/mm) = 75 J/cm 3 = 45 = 5 = 3 1 Radiant Red UCS= 262 MPa American Black UCS= 27 Harcourt UCS= 169 Massangis UCS= 87 1 2 3 4 d (mm) Back-rake Angle (degrees) d ( mm/rev) 17
Integrating 2 Streams: Cutting and Stress-Strain may relate to the stress-strain energy quantities by:,,,, takes into account,, the friction angle on rake face, the back-rake angle, and the orientation of shear plane Intrinsic Specific Energy (J/cm 3 ) 1 5 1 Intrinsic Specific Energy (J/cm 3 ) q peak (MPa) 3 9.3X.7, R 2 =.66 1.24X.9, R 2 =.94.6X.96, R 2 =.95.62X.88, R 2 =.95 R 2 =.5 ID Cutting = 45 O = 3 O = 15 O PDC Cutting 1 1 1 Absorbed Strain Energy (1-3 J/cm 3 ) Intrinsic Specific Energy (J/cm 3 ) 1 5 1 Intrinsic Specific Energy (J/cm 3 ) 21.84X.57, R 2 =.82 2.84X.86, R 2 =.98 1.51X.9, R 2 =.98 1.31X.85, R 2 =.98 R 2 =.79 5 Quartz content (%) Cervaiole Gioia Dionysios PDC Cutting ID Cutting = 45 O = 3 O = 15 O Back-rake angle 1 1 1 Releasable Elastic Strain Energy (1-3 J/cm 3 ) 18
Integrating 2 Streams: Cutting and Stress-Strain The external work: Considering that shear work is the major contributor to dissipative external energy, then,, 1 1 Intrinsic Specific Energy (J/cm 3 ) 5 4.37X.92, R 2 =.81 1.84X.93, R 2 =.98.93X.98, R 2 =.99.67X.95, R 2 =.97 ID Cutting = 45 O = 3 O = 15 O PDC Cutting Intrinsic Specific Energy (J/cm 3 ) 5 31.31X.59, R 2 =.86 5.5X.88, R 2 =.99 3.4X.91, R 2 =.98 2.42X.87, R 2 =.99 = 45 O ID Cutting = 3 O = 15 O PDC Cutting 1 1 1 Absorbed Shear Strain Energy (1-3 J/cm 3 ) 1 1 1 1 Elastic Shear Strain Energy (1-3 J/cm 3 ) 19
Final Remarks 1. Three concepts were adopted to build relations between rock properties & cutting performance: i) tool-rock interaction laws, ii) energy balance, and iii) stress-strain energy in uniaxial compression tests. 2. The intrinsic specific energy from PDC and ID cuttings was found to correlate well with the stress-strain energy absorbed by a unit volume of rock in uniaxial compression. 3. The results suggest that stress-strain energy is relevant to quantify indirectly the intrinsic specific energy on PDC and ID rock cutting. 2
Acknowledgements The work has been supported by the Deep Exploration Technologies CRC whose activities are funded by the Australian Government's CRC Programme. This is DET CRC Presentation 215/714