I d bl ti lt ith i Improved blasting results with precise initiation (Vinnova 2008-00862)

Finn Ouchterlony, LKAB prof. of detonics and rock blastingHåkan Hansson, Swebrec

• Industrial goal: To achieve a better fragmentation throw and other results in

timefragmentation, throw and other results in quarries and mines.

• Scientific goal: To identify the rock overlap of

tensile tails of overlap ofSc e t c goa o de t y t e ocvolumes within a blast where the shock wave interaction from neighboring blast-holes may create additional damage and

tensile tails of blast waves leading

compressive wave parts

holes may create additional damage, and thereby enhanced fragmentation, for varying bore-hole initiation delay times. blast-

holeS

P-wave frontsblast-hole

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hole hole

Boliden Mineral Aitik mine:18 Mton ore/yr will become 36 Mton/yr18 Mton ore/yr will become 36 Mton/yr

Blasting tests with raised specificcharge: 0,9 to 1,3 kg/m3 raisedcharge: 0,9 to 1,3 kg/m raised throughput in primary mills by 7%, gives large revenues:

Electronic dets have potential too. But, what delays are optimal?

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p , y pBlasting tests start Aug 2010.

• Duration: 2008-10-01 till 2011-12-31

Improved blasting results with precise initiation:

• Duration: 2008-10-01 till 2011-12-31

• Partners: Swebrec at LTU, LKAB & Boliden Mineral

• Personnel:Prof Finn Ouchterlony, project leaderHåkan Hansson, researcher,Prof Peter Moser, Leoben Österrike, intnl referenceLic Anders Nordqvist & Dr Zongxian Zhang, LKABLic Peter Bergman Boliden Mineral ABLic Peter Bergman, Boliden Mineral AB

• Tools:Simulation codes; Blo-Up ANSYS Autodyne & LS DynaSimulation codes; Blo Up, ANSYS Autodyne & LS DynaBlasting caps with electronic delays (EDD), delay intervals

down to 1 ms and precision down to ±0,13 ms

• Relevant parallel work:MinBas II (Swebrec) & HLRC (Daniel Johansson, LTU)

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• Volume: 8 3 Mkr; from Vinnova 4 15 LKAB 0 9 Boliden

Improved blasting results with precise initiation:Volume: 8,3 Mkr; from Vinnova 4,15, LKAB 0,9, Boliden 0,45, Swebrec 0,45 Mkr and in-kind 2,35 Mkr.

• Tasks:Tasks:1. ”Calibration” of simulation tool Blo-Up, completed2. Control point, completed----- reworking of project plan, accepted Nov -09 -----

3. Develop numerical methodology with new code for shock p gywave interaction and damage evaluation, on-going

4. Simulation of 3D shock wave interactions and damage in k f l t i bl t t Aitik d ti i ti i bl trock for electronic blasts at Aitik and participation in blasts

5. Simulation of model scale tests of timing effects, being done at Swebrec in HLRC project Optimized blasting ofdone at Swebrec in HLRC project Optimized blasting of SLC rounds (Daniel Johansson)

6. Optimisation of delay times with EDD detonators both in

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bench blasts at Aitik and in SLC ring blasts at LKAB.

“Calibration” of first simulation code, Blo-Up:

Cylinder w. single hole Mortar block with 2x5 holes shot w, delay

Results look reasonable but:Results look reasonable but:• New lattice formulation doesn’t permit correct stress representation• No pressure & rate dependent strength models included

D t il f d t ti b h l l d• Details of detonating borehole unresolved• Sometimes strange fragment geometries

I t i l ti f h k i t ti h d

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Incorrect simulation of shock wave interaction → change code

Pre processor: Solver: Post-processor:

Num. methodology for new code (explicit dyn FE):

Pre-processor:build model

mtrl prop. data

Solver:solve differential.

equations

Post-processor:graphs w. stress,

strain, damage

Test model for LS-Dyna;• Dimensions 17 × 17 × 6 5 m

bore-holesModel:

• Dimensions 17 × 17 × 6,5 m• Two 16 m bore-holes, Øh311 mm, • Bench height B = 15 m

stemming

5 m

• Non-reflective boundaries used to represent the semi-infinite rock.

• Approx 18x106 elements givesexplosive 15 m

• Approx. 18x10 elements gives resolution 40-50 mm

• Memory requirement 48 GB in one PC 2X Q dblast direction PC, 2Xeon Quad core proc.

• Goal run 4 holes on PC-cluster w. resolution ≈ 30 mm

blast direction

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Methodology development includes:

Verifications of:Verifications of:• Pre-processing capabilities.• Material model behaviour, both for rock and explosive.

S l i l i h f h l d• Solution algorithms for the element types used.• Other numerical algorithms, e.g. boundary conditions.• Post-processing capabilities.Post processing capabilities.

Computer hardware speci-fications and simulation performance are also evaluated in this part of the projectthe project.

Plots of damage evolutionfor 2 ms initiation delay zero residualfor 2 ms initiation delaybetween holes:• plot 16 ms after initiation• runtime 38h on 4 CPU:s

zero residual tensile strength

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• runtime 38h on 4 CPU:s

The initial simulations needs determine, or account for:

Initial simulation requirements 1:The initial simulations needs determine, or account for:• The 3D stress states & 3D shock wave propagation in the rock.

agent of interaction, must be correctly modelled• Expansion of the borehole and explosive.

source of work on rock and hence energy content in waves e.g.• Coupling of fluid material to solid material within the model.

arbitrary Lagrange Euler and Euler multi-mtrl meshes needed for core Th t i l b h i d i hi h l di• The materials behaviour during high pressure loading.

rapid GPa level loading in bore-hole way exceeds strength plusinitial triaxial compression → strength pressure and rate dependentp g p p

• The large deformations of the near-field rock.distortion of Lagrange mesh requires remeshing

• A realistic geometric resolution.Øh/10 or 30 mm desirable but multiples of 107 elements pushes codes and compatibility beyond known regime of established functionality

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and compatibility beyond known regime of established functionality

Initial simulation requirements 2:

Experience so far:Experience so far:• The initial simulation requirements may cause compatibility

problems between solution algorithms and material models, p gand also regarding pre- and post-processing of simulation results.

• The set-up of test models show that that the first chosen explicit code, AUTODYN is not likely to comply to the initial i l ti i t B t th d LS DYNA tsimulation requirements. But, the code LS-DYNA seems to

be able to run our type of models with minor changes to the code itself and pre-/post-processing tools.p p p g

• Frequent interaction with code providers ANSYS and ERAB (LSTC’s Swedish representative) needed for removing bugs(LSTC s Swedish representative) needed for removing bugs and limitations that prevent desired functionality.

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Illustration of shock wave propagation:- model with stemming (brown) shot with 1,5 msdelay time; pressure contours at 1 ms intervalsdelay time; pressure contours at 1 ms intervals

free surface

stemming gdisplaced this much

grey = expansionmagenta = pressure

non-reflective boundary, sends magenta = pressure

above 400 MPaboundary, sends back no wave reflections'

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Illustration of tensile strength development:- model with stemming (brown) shot with 1,5 ms delay

time; “damage” contours at 1 ms intervalstime; damage contours at 1 ms intervals

red = total damage or id l t ilzero residual tensile

strengthblue = no damage or

intact tensile strengthintact tensile strength

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relationship between damage field and fragmentation size needs consideration

Limitations and possibilities:

Li it tiLimitations:• Since both the 3D stress states and shock wave propagation

need to be determined within the rock, it is necessary to use , ymodels with a large number of elements around each borehole. This limits the types of cases and number of blast-holes that are possible to study (four holes present goal)holes that are possible to study (four holes present goal).

• Further, both pre- and post-processing of the data from the simulations are likely to need enhancements of the currentlysimulations are likely to need enhancements of the currently available tools that do the pre-/post-processing.

H th i l ti th d l k it ibl tHowever, the simulation methodology makes it possible to:• Use any geometry, within the limits given earlier• Change properties for rock and explosive• Change properties for rock and explosive• Study the influence of shock wave interaction due to different

delay times

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delay times.

The following work is planned

Further work planned for 2010:g p

for the near future:

• Simulations of small scale• Simulations of small scaletests performed by Swebrec

• Bench blasting at the Aitik openpit mine, starting August 2010p t e, sta t g ugust 0 0

This will require the determination of material properties and q p pmodels for the rock and explosives. Further, running production simulations will require a migration from PC computers to a high performance Linux cluster to obtain reasonable calculation andperformance Linux cluster to obtain reasonable calculation and post-processing performance.

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Further work 2011:YZ-snitt KI-28-849-o3030-19

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• Study of SLC ring geometry usedby LKAB -35

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• More advanced material models may later have to be developed and usedf f i l i di

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for future simulation studies: e.gstochastic strength added and relationship between damage and 15

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1011

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11relationship between damage and fragmentation studied.

Alternative solution algorithms-10

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• Alternative solution algorithmsmay be of interest for future studies, incl. mesh-less methods. 1050510

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studies, incl. mesh less methods. 1050-5-10

Any questions?

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Any questions?