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Common Blast Design Pitfalls Trouble Shooting The 19th Annual Surface Mined Land Reclamation Technology Transfer Seminar Jasper, Indiana December 5 th & 6 th, 2005 Wm. J. Reisz
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Improper Hole Placement holes to close to the face optimal burdens & spacings Transient Pressures/Dynamic Shock deadpress basic blast design insufficient decking Electronic Initiation Systems why electronics? pyrotechnic demonstration Common Blast Design Pitfalls
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Hole Placement
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Spoil
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Optimum Burdens & Spacings Determine Bench Parameters bench height width length hole diameter explosives type retangular 1:1.2 staggered 1:1.5
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105’ 25’ 15’ Non-Proportional Burdens
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105’ 105’ ÷ 4.7 = 22.3’ 82.7’ 60.4’ 38.1’ 15.8’ 105’ 16.4’ Crest burden ≈.7 X inner row burden 110’ 110’ ÷ 4.7 = 23.4’ 110’ 86.6’ 63.2’ 39.8’ 16.4’ Proportional Burdens & Spacings 153’ ÷ 6 = 25.5’ 153’ 7 holes = 6 inner hole spacings
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Blast Design ISEE Certificate Program, Level One-Practical Blasting Fundamentals
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Transient Pressures Deadpress Fire at a low order Total failure of the explosive charge Dynamic Shock Damage the initiator Destroy the booster Fire at the wrong time Sympathetic Detonation
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Bottom FirstInsufficient Decking
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Bottom First Bottom Up ↔ 12 - 15 times borehole diameter For example: 9” dia. X 15 = 135” ÷ 12” = 11 ¼ ’ Stemming Between Decks Rule of Thumb
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Top Deck First
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Top First Top Down ↔ 1 foot for every inch of borehole diameter For example: 9” dia. X 1’ = 9’ stem Stemming Between Decks Rule of Thumb
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Why Electronics?
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Why Electronic Detonator Systems? Eliminate pyrotechnic scatter poor rock fragmentation high ground vibration levels high air blast levels greater flyrock potential
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Why Electronic Detonator Systems? Eliminate pyrotechnic scatter Delay selection, site specific Safety immunity to RF, EMI and Stray Current completely testable automated self-test and disarm features requires specific blast machine to fire
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Eliminate pyrotechnic scatter Delay selection, site specific Safety Optimized Blast Performance Why Electronic Detonator Systems? Vibration Control Flyrock Control Floor Control Wall Control Improved Cast Percentage
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Eliminate pyrotechnic scatter Delay selection, site specific Safety Autonomous Operation Optimized Blast Performance Inventory Control Why Electronic Detonator Systems?
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overcome poor blast design make your job easier What Electronic Detonator Systems Will Not Do
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Comparison to pyrotechnic dets
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Detonators Attached to Grade Stake Shock Tube 400 ms Daveytronic 400 ms
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Comparison to pyrotechnic dets Daveytronic
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Comparison to pyrotechnic dets
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Grade Stake 12345678910 Pyrotechnics/ms405411417383428405413412419421 Daveytronics/ms400 Grade Stake Actual Firing Times Daveytronic/ms Pyrotechnics/ms
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4110 42134 51 6885102119 136 405153 428451434 496 490 515531 555 405574 417 383428 405413 412 41917 1 2 4 3 6 5789 10 - 4.25%+ 7% Avg. dev. + 2.85% Blast Simulation Using Actual Shock Tube Firing Times Out of Sequence Holes Poor Fragmentation Zone If we add 17ms between holes we have.... Potential FlyrockHigher Air & Ground VibrationsColumn Disruption 6ms
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Blast Design ISEE Certificate Program, Level One-Practical Blasting Fundamentals
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Questions or Comments?
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Thankswww.daveytronic.com Wm. J. Reisz
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