Experimental Assessment of Rock Cutting Characteristics by Strength-Driven Mechanism. H Munoz, A Taheri & E Chanda

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1 Experimental Assessment of Rock Cutting Characteristics by Strength-Driven Mechanism H Munoz, A Taheri & E Chanda AusIMM Africa Australia Technical Mining Conference, Jun Adelaide, Australia

4 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

5 Background: Rock Properties & Cutting Performance (Hoseinie, 29) 5

6 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

7 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

= weight on the bit, = torque on the bit = area of the hole or excavation, = depth of

energy, SE (MPa) 2 15 1 5 A B D C Intrinsic specific energy= 45 MPa 5 1 15 2 25 w/d,

8 Specific Energy and Intrinsic Specific Energy Full bit and equivalent two-dimensional cutter Fs F n PDC cutting ID cutting = 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) A B D C Intrinsic specific energy= 45 MPa w/d, (MPa) E diss = Dissipation on friction (wear flat area: Diamond+matrix) = Intrinsic Specific Energy: energy strictly used in cutting 8

9 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

10 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 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

11 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 Castlegate Sandstone Fine Mountain Gold Sandstone Fine Hawksbury Sandstone Fine Massangis Sandstone Fine Brukunga Phyllite Fine Mantina Basalt Fine Harcourt Granite Medium-coarse Radiant Red Granite Medium-coarse American Black Granite Fine-medium

12 Uniaxial Compressive Tests Test details 4 tests in total Uniaxial monotonic compression & Single-cycle uniaxial compression UCS (MPa) PDC tests ID tests 5 Young Modulus at 1 =1-5 (GPa) Sandstones Limestones Siltstones Granites 12

Test details PDC Cutting Tests 7 tests in total PDC single

kinematic control (depth of cut d constant) Rock name Rock type

degrees degrees degrees Tuffeau Limestone 9 11 19 Castlegate

Sandstone 42 57 97 Brukunga Phyllite 88 151 25 Mantina Basalt

13 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 Castlegate Sandstone Mountain Gold Sandstone Hawksbury Sandstone Brukunga Phyllite Mantina Basalt Cutting machine & Single PDC cutter cutter width of 1 mm = 15 = 3 = 45 13

Intrinsic specific energy ( ) (J/cm 3 ) Leached ID segment Massangis Sandstone 3 Harcourt

14 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

15 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 = q cd U d = 34.6 Monotonic loading U= Strain Energy (1-3 J/cm 3 ) Strain (1-4 ) 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 = q peak U d = 3.2 Radiant Red Granite q peak = 262± or 3 (1-4 ) q cd 1 U= 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)

16 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 ) Reversal point Hawksbury Mountain Gold Tuffeau Castlegate 34.2 U = = 2/3 ( 1-3 ) (1-4 ) max = ( 1-3 )/2 (MPa) Absorbed Shear Strain Energy (1-3 J/cm 3 ) American Black p Radiant Red Harcourt Massangis at q peak Mantina Brukunga Reversal point U = = 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

17 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) 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= Intrinsic Specific Energy (J/cm 3 ) Mantina Brukunga Hawksbury Mountain Gold Castlegate (Roller-cone) Tuffeau 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= d (mm) Back-rake Angle (degrees) d ( mm/rev) 17

18 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 ) Intrinsic Specific Energy (J/cm 3 ) q peak (MPa) 3 9.3X.7, R 2 = X.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 Absorbed Strain Energy (1-3 J/cm 3 ) Intrinsic Specific Energy (J/cm 3 ) Intrinsic Specific Energy (J/cm 3 ) 21.84X.57, R 2 = X.86, R 2 = X.9, R 2 = X.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 Releasable Elastic Strain Energy (1-3 J/cm 3 ) 18

19 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 ) X.92, R 2 = X.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 ) X.59, R 2 = X.88, R 2 = X.91, R 2 = X.87, R 2 =.99 = 45 O ID Cutting = 3 O = 15 O PDC Cutting Absorbed Shear Strain Energy (1-3 J/cm 3 ) Elastic Shear Strain Energy (1-3 J/cm 3 ) 19

20 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

21 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

The University of Adelaide

The University of Adelaide Faculty of Engineering, Computer and Mathematical Sciences School of Civil, Environment and Mining Engineering A dissertation submitted to the School of Civil, Environment and