Blast design for underground mining applications1 R. HOLMBERG R. Holmberg Lima Nov 2011 Contents 2 Contents: 1. Purpose - applications 2. Surface blasting 3. Surface - underground 4. Tunneling 5. Function of cut 6. Design of parallel cut 7. Tunnel rounds 8. Contour blasting 9. Divided faces 10. Shaft sinking R. Holmberg Lima Nov 2011 11. 12. 13. 14. 15. 16. 17. Mining methods Ring layouts Design formula Explosives Decoupled charges Pointers Acknowledgements Purpose & applications -1 3 The purpose is to: Efficiently excavate rock so that the pieces removed can be handled economically Avoid ore losses and waste rock intrusion Obtain the planned contour with no underbreak and as little overbreak as possible Leave the remaining rock stable for as long as the operation requires. R. Holmberg Lima Nov 2011 parking garages. R. hydropower and water tunnels. power house caverns etc Other applications.Purpose & applications -2 4 The main applications are Mining. well springing. seismic operations etc. Holmberg Lima Nov 2011 . shelters. traffic tunnels. drifting and development work plus full workings Raise blasting and shaft sinking Quarrying Infrastructure. BS pattern. Holmberg Lima Nov 2011 . same diameter and same burden and spacing. like quarry but contour holes . typically identical holes. essentially like road cuts but vertical holes.5-0. smaller hole diameters. Road cut. parallel.9 kg/m3. q = 0.Surface blasting -1 5 Quarry. same charging. smaller charges and on flatter angle Foundations. R. like road cut but larger holes and contour gets special emphasis.Surface blasting -2 6 Open cast mine. 7540 7520 1st row production 7500 holes 17 m Ø311 mm 7480 7460 7440 7420 helper & contour Ø152 mm 15 m bench R. sometimes smaller holes of different angles and depths. Holmberg Lima Nov 2011 7400 4480 4500 4520 4540 presplit Ø127 mm 4560 4580 4600 4620 4640 . OP: ore < waste.Surface vs underground . UG: ore >> waste 7 R. Holmberg Lima Nov 2011 .1 Worldwide: OP >> UG. • Other mines and crushed stone. ~80Mton •Makes about 180 Mton or 6 m3 per capita •70 kton explosives makes about 8 kg per capita R. 20 Mton waste • Aitik open pit mine: 28 Mton Cu-ore. 30 Mton waste.2 8 Annually excavated volumes in Sweden • LKAB UG mines: 25 Mton Fe-ore.Surface vs underground . Holmberg Lima Nov 2011 . infrastructure projects etc. 3 9 Tunnelling: Underground blasting.Surface vs underground . Holmberg Lima Nov 2011 . often more complicated drilling patterns and combinations of blasting methods fire-in-the-hole! blasting plan charged & primed R. Tunnelling . Holmberg Lima Nov 2011 .1 10 What has happened in tunnelling recent 25 years? R. Holmberg Lima Nov 2011 . small part of total excavation work but outcome often decisive for downstream operations R.2 11 blasting = (38% 2007).Tunnelling . 3 m.Tunnelling . min 0.first one free face . Holmberg Lima Nov 2011 .5-2 kg/m3 R.2-0. Blasting is confined and specific charge is high q = 1. design burden applied to hole bottom (toe) and at face deduct look-out Start.the tunnel face.3 12 look-out angle needed to make room for drilling next round. 4 13 Tunnel round with parallel holes enlargement of cut part larger empty (void. reamer or burn) holes cut blasting starts with cut = opening part of round R. Holmberg Lima Nov 2011 .Tunnelling . 5 14 Charge calculations for tunnelling can be made according to Chapter 7 in “Rock Blasting and Engineering” by Persson. Holmberg & Lee. Holmberg Lima Nov 2011 .Tunnelling . R. In these OHs simplified rules of thumbs by Finn Oucterlony at Swebrec is used. Design of parallell hole cut . Holmberg Lima Nov 2011 .∆100 ms R.1 15 #3 reamer hole = first swelling volume #1 #2 rock to be broken #4 . Holmberg Lima Nov 2011 .Design of parallell hole cut .2 16 In principle. choose burden a according to diagram but: • If burden a too large → breakage failure (rifling) or choking of flow of rock fragments • If burden a too small → burning of rock fragments Drilling accuracy is most essential! R. 5W2√2 R.5W3√2 .Design of parallell hole cut .5Ø + 2nd quadrangle: B1 B1 = W1 a W1= √2a 0. Holmberg Lima Nov 2011 4th quadrangle: B3 = W3 & W4 =1.5W1 W2 =1.5W1√2 W1 3rd quadrangle: B2 = W2 & W3 =1.3 17 Geometric considerations for cartridged explosives: 1st quadrangle: a = 1. 0. R.4 18 Charge concentration lb = lp in first quadrangle: Advance.Design of parallell hole cut . Use an uncharged part at the collar of h0 = a.15+34.1 Ø39.4Ø2) In case of several (n) empty holes (d) in the cut use: Ø = d√n when estimating advance.95*(0. Holmberg Lima Nov 2011 . 5B. 2. Holmberg Lima Nov 2011 . 3 Max burden B. Bottom part may need lb=2lp to height of 1. kg/m 19 lp Bi. m Stemming or uncharged length 10d or 0. R. i =1.25B.5 Charge concentration lp for 2nd-4th quadrangles: Charge concentration lp.Design of parallell hole cut . Correct B for look-out of 0. or lift cut position 5. same for downward stope and adjust to even breakage volumes. match size of cut to side stope.2-0. If cautious blasting see below. spacing should not exceed design value S. use same side stope Burden B burden < B in all rows. Helpers. Cut. Place cut to minimize no.3 m 2.20.Tunnel rounds . width/S = 11. Wall+roof.1 20 Design of parts of round: Roof or back holes Downward stoping Wall or rib holes Side stoping 1.g. balance contour damage . Cut holes Helper row 3. same for spacing and subtract look-out distance 0. e.3 m from design burden B. of side stope rows. Holmberg Lima Nov 2011 4. Lifters. Floor holes or lifters Spacing S R.4 means round up to 12 and add 1 hole. Stoping. if B3 > B0 (next OH) then decrease B3. Tunnel rounds .5 x B 0 Floor /Lifter Contour: Wall Roof Stoping: Upwards Horiz.5 x lb 0. R.9 x B 0 1 x B0 1 x B0 1 x B0 Note: The explosive chosen (density and charge diameter) determines the charge concentration lb.1 x B 0 1. Diagram in next OH gives B0.5 x B 0 0. Calculate lp and use next larger cartridge or pipe size for real column charge.2 x B 0 Bottom Charge concentration Stemming charge length bottom lb column lp not charged Lb.9 x B 0 0./Side Downwards 1 x B0 0.5 x lb 0.1 x B 0 1. kg/m.1 x B 0 1.3 x lb 0. Holmberg Lima Nov 2011 . m 1/3 x H 1/6 x H 1/6 x H 1/3 x H 1/3 x H 1/3 x H kg/m lb lb lb lb lb lb kg/m 1.0 x lb 0. m 0.2 x B 0 0.5 x lb h0.1 x B 0 1.5 x B 0 0.1 x B 0 1.4 x lb 0.5 x B 0 0. Helpers may be designed as stoping holes or with consideration for damage depth.5 x B 0 0.2 21 Part of round Burden B m Spacing S m 1. burden at hole bottom or toe vs equiv. bottom charge same emulsion but in longer pipes. suitable for bottom charges dynamite.mm R. charge con-centration lb (kg/m) needed for breakage. e. Holmberg Lima Nov 2011 .mm blasthole.3 22 B0 lb cartridge. used for column charges bulk ANFO like SSE fills hole. and a proper primer is needed shifted scales on lines because densities are different cartridge.mm pipe. Deduct look-out for perimeter holes cartridged emulsion with alu.Tunnel rounds .g.mm B0. Tunnel rounds – 4 23 Priming and initiation sequence principles Do not initiate two holes on same delay no. In practice it is not usual to have the same delay time between all intervals. see Nonel LP series R. Holmberg Lima Nov 2011 . in first two quadrangles. Detonator no:s #1-22 tell the initiation sequence. 18100 ms same as new LP 1800 e. • LP 0 at 25 ms exception • don‟t use intervals shorter than 100 ms in tunnel rounds without trials R. 100.Tunnel rounds – 5 24 Nonel® plastic tube with 17 mg/m of explosive VoD 2100 m/s Nonel® LP detonators suitable for UG work New series Nonel LP detonators: • delays up to 6000 ms in steps of 50. 200 and 400 ms • old series detonator no.g. Holmberg Lima Nov 2011 . 45 17 0.3 Stoping 2.8 0.2 Contour 1. Holmberg Lima Nov 2011 4.92 0.6 0.60 0. m m 9 special list 28 0.02 0.38 3.9 29.4 0.60 10 0.92 0.38 3.5 Lifter 2.1 30.50 0.38 4.8 25.2 0.Tunnel rounds – 6 Drilling and charging plan data: from Äspö TASS tunnel.2 Helper 1.60 1m 1m Part of round Cut Stoping Lifter Helper Contour Bottom charge Dynomit Dynomit Dynomit Dynomit Dynomit ØxL mm 30×380 30×380 30×380 30×380 30×190 Column charge Dynorex Dynorex Dynorex Dynotex 1 Dynotex 1 ØxL mm 25×1100 25×1100 25×1100 22×1000 17× 460 R.8 75.8 32.2 .60 0.45 0.55 28 0.19 4.92 0.3 m Part of Charge Total Charge length Unround weight part bottom column charged kg/hole kg m m m Cut 2.0 0.21 0.38 3. note look-out 25 Part of round Cut Stoping Lifter Helper Contour Holes Spacing Burden no. • Parallel holes in good rock and small tunnels to achieve long pull (parallel & burn hole cuts). tight hole burdens and spacings (high specific charge) • Cut design requires special considerations like avoidance of sympathetic detonations and dead pressing • Long delays to avoid choking of flow of fragmented rock. Holmberg Lima Nov 2011 .Tunnel rounds – 7 26 In summary: • Only 1 free face to start with when cut fires. R. up to 6000 ms or more. fan and plow cuts possible to use if face wide enough to angle booms • Depending on local conditions packaged or bulk explosives may be used. and primer should be used. • Contour and helper row holes are usually more lightly charged than stoping holes. e. angled holes. R.g.g. lp = lb. plastic pipe charges or string emulsion. Holmberg Lima Nov 2011 . ctd: • Poor rock requires shorter rounds. e.Tunnel rounds – 8 27 In summary. With bulk there is no special pipe charge. Contour blasting .1 Why cautious blasting? 28 • Extent of cautions blasting depends on expected life time of tunnel /cavern /drift etc • Less dilution. less shotcrete or concrete to cast • Increased safety • Less rock to haul. better ore recovery • Less support work. less bolting. without caution with R. Holmberg Lima Nov 2011 . saves time and money • Smooth blasting method used UG to reduce overbreak and blast damage. Holmberg Lima Nov 2011 . The cracking caused by the stoping and helper holes inside the perimeter helpers or must not reach farther into the stoping holes remaining rock than the cracking from the perimeter/contour holes. zone radius R. holes fired last in round.Contour blasting – 2 29 Cautious and smooth blasting: By cautious blasting is meant that the cracking in the remaining rock due to blasting. or contour Smooth blasting uses light decoupled charges in contour and helpers with balanced damage damage zone depths. shall be limited to the „damage zone depth Rc‟ that has been prescribed for perimeter the perimeter in question. q < 0.0 1.5 2.5 2. multiply real q by 0. m Rc= 1.5). R.5 1.3 m often required • Damage zone table gives charge concentration for Swedish bedrock conditions.Contour blasting – 3 30 In Swedish tunneling: • Rc < 0.0 Rc = 1.9·q. q > 0.0 0. Holmberg Lima Nov 2011 2.5 1.0 Charge concentration q. Ø45-51 mm holes. kg DxM/m .9*q 0.0 0.5 kg/m Rc = 0.95·(q+0.5 Damage zone depth Rc.0 1. • Note: q is given in Dynamite equivalents.73 for Gurit • Contour and helper damage zones can be read off curve • Holmberg-Persson theory behind line.5 kg/m 0. electronic dets or cord.3 m = 0.17 eq kgDxM/m New Swebrec approach explicitly includes effect on Rc of • Blast hole diameter and coupling factor • Water in blast hole and rock properties • Simultaneous initiation using e.Damage zone Contour blasting .4 31 Recommended charging of countour holes Notes: Connect charges and use small primer to initiate them *: Damage zone e.230.g. R. Holmberg Lima Nov 2011 .73 ≈ 0. from 17 mm Gurit Rc = 1.90.g. stoping R. Holmberg Lima Nov 2011 . Solution = more lightly charged helper row with adjusted burdens and spacings! When cracks from holes inside the contour reach no further than the cracks from the contour holes. the damage zones are balanced.Contour blasting – 5 32 normal stoping holes If stoping holes too heavily charged then the cracks will extend beyond damage zone of contour holes. Holmberg Lima Nov 2011 .Contour blasting – 6 33 Does it matter? Take Ø22 mm Gurit • Crack length in dry Ø64 mm hole 15-20 cm • Crack length in wet Ø64 mm hole 45-60 cm • Crack length with no decoupling 90-100 cm! Crack lengths with electronic dets shorter than for Nonel detonators if • Charge concentration q < 0. R.6 kg/m and spacing S/B < 1 • If decoupling is sufficient and holes are proven dry • Initiation simultaneous well within 1 ms. 7 34 Extremely cautious blast with hybrid initiation plan Nonel + electronic dets (EDD) in contour and helpers • Lightly charged lifters and helpers R. Holmberg Lima Nov 2011 Note half casts in floor! .Contour blasting . Contour blasting .8 35 R. Holmberg Lima Nov 2011 . Divided faces .1 36 R. Holmberg Lima Nov 2011 . uncertain about geology.the span is able to support the rock-load .can‟t otherwise maintain stability of and at face . Holmberg Lima Nov 2011 . access to many faces • Length of rounds . pilot gathers information • Productivity.the support measures can be installed in due time.Divided faces .2 37 Reasons for dividing face: • Stability reasons . R. Divided faces . Löttinge traffic tunnel.5 m. 2-lane 1058 m Sthlm 2005-6 188. leaving plug to prevent noise coming out and winter cold in • Rd 4-7 Widen to full section ca 5m 1:a överlapp ca 7m 10 ca 5m • Rd 8-9 side pilots • Rd 10-123 side pilot and trailing side stope in same round.3 38 West portal 10 Ex. Holmberg Lima Nov 2011 . ca 3m saved plug 6000 1 R. 152 m2: • E & W access • Rd 1-3 Side pilot. 4 39 Drilling of pilot at East portal and side stopes (slashes). R.Divided faces . Holmberg Lima Nov 2011 . Holmberg Lima Nov 2011 .Divided faces – 5 40 Excavation sequence for hydro power house cavern R. Holmberg Lima Nov 2011 .Shaft sinking .1 41 2 m bench with confined toe and fanned rows R. Shaft sinking . Holmberg Lima Nov 2011 .2 42 5 m full face round with cut and parallel holes easier drilling. pulls deeper and produces finer muck than bench round 200 mm pilot (reamer) hole drilled 0.3 m deeper than rest of round to ensure 100% pull. R. metal mines & underground quarries cross cut = tunnel round drift heading = tunnel round vertical bench upward stoping = horizontal bench Depending on the mining method a mine uses several blasting methods.Mining methods -1 43 Room and pillar. Holmberg Lima Nov 2011 . R. R.Mining methods -2 44 Drift and (multiple) benching. Zinkgruvan Parallel drill holes that follow the ore. Holmberg Lima Nov 2011 . R.Mining methods -3 45 Panel stoping. Zinkgruvan 2 1 2 1 2 1 2 1 2 2 1 2 2 1 2 1 2 1 rings or fans with Ø89 mm angled holes of different lengths 1 2 1 1 2 1 2 Panels 1 filled with paste fill before # 2 between blasted. Holmberg Lima Nov 2011 . Holmberg Lima Nov 2011 .Mining methods -4 Sublevel caving or SLC at LKAB 46 blasting against confinement of caving masses SLC rings with angled holes of different lengths high grade iron ore 4500 kg/m3 R. 15-58 m long. 3 m burden. typically opened at center. R. 2 holes every 100 ms. Holmberg Lima Nov 2011 .Ring layouts – 1 47 Different SLC ring layouts at LKAB water hydraulic ITH. Ø115 mm holes. initiation sequence stemming charge in hole separated into decks by stemming and detonated separately in sequence 3. Holmberg Lima Nov 2011 flow . 4 etc R.Ring layouts – 2 48 Deck charging sometimes used for • • breakage sequence + flow delay number = Vibrations. Holmberg Lima Nov 2011 .Explosives -1 49 Types of explosives used R. 0 MJ/kg 2400 m/s 970 l/kg poor compressed air charging equipm.2 50 Anolit (ANFO) Anolit Density Weight strength Volume strength Expl. Holmberg Lima Nov 2011 .Explosives .9 MJ/kg volume strength = 125 % R. Anolit A with 6-7% Al expl. energy VOD Gas volume Water resistance Use primer 850 kg/m3 100 % 100 % 4. energy = 4. Holmberg Lima Nov 2011 . less restricted transportation R.Explosives .3 51 Emulsion matrix is not an explosive which means safer. Explosives .4 52 Reaction kinetics Emulsion –finer structure rendering in higher VoD R. Holmberg Lima Nov 2011 . 5 53 Site Sensitised Emulsion Oxidizer Solution Slurry Station Gassing agents Fuel and Emulsifier Emulsion mixer Dosage pumps Control panel Pump Emulsion matrix R. Holmberg Lima Nov 2011 .Explosives . Explosives - 6 54 Titan® SSE system (site sensitized emulsion) under ground in Ø45-51 mm holes R. Holmberg Lima Nov 2011 Explosives - 7 55 Slurry Station Gassing agents AN Aluminum Prills Oxidizer Solution Fuel and Emulsifier Control panel Blender Pump - Emulsion mixer Dosage pumps R. Holmberg Lima Nov 2011 Explosives - 8 56 Bore hole diameter : Quarries : 2” - 6” Mining : 6” - 12” Max pump heigth : 40 m Max hose length : 150 m Slurry Station Gassing agents AN - Prills Aluminum Oxidizer Solution Fuel and Emulsifier Control panel Blender Pump Emulsion mixer Dosage pumps above ground in holes Ø64-320 mm R. Holmberg Lima Nov 2011 Holmberg Lima Nov 2011 . Roger R.Prills Aluminum Control panel Blender Pump Emulsion mixer Dosage pumps Emulsions have higher water resistance and AN prills may be added to raise density • Energy content per m3 roughly the same but • Lower price of ANFO ideal for dry hole conditions.9 57 Comparing ANFO and emulsion explosives • • • Emulsion matrix less restricted in transportation Pumped emulsions have higher charging capacity Density regulated by gassing during pumping • • Decoupled „string‟ emulsion in horizontal holes Slurry Station Oxidizer Solution Gassing agents Fuel and Emulsifier AN .Explosives . YZ-snitt KI-28-849-o3030-19 6 Explosives . contains aluminum • Water used to lubricate inside of charging hose.10 Uphole ring charging at LKAB • KR0500 („Kimulux Repumpable 0500‟). Holmberg Lima Nov 2011 -40 40-50 m 5 7 4 8 -35 58 -30 -25 2 11 -20 3 10 9 8 8 8 9 9 10 10 11 -15 1 9 12 8 9 12 11 10 8 12 8 11 -10 11 -5 10 12 0 -10 -5 0 5 10 . running water creates problems. mixed in at nozzle • Staying in place is a balance between viscosity and adhesion • Emulsion is tixotropic and blast shock is too fast to cause liquefaction • But. sensitized by glass microballoons. R. in wet holes etc.11 DynoRex® Dynamite with NG. nitrocellulose and AN 59 used as bottom charge.Explosives . primer & booster. R. Holmberg Lima Nov 2011 also available as 1100 mm pipe charges 59 . nitroglycol. 12 60 Kemix A® used as bottom and column charge (pipe) .Explosives . R. primer & booster. contour blasting. Holmberg Lima Nov 2011 . Holmberg Lima Nov 2011 .1 61 R.Decoupled charges . Decoupled charges .2 62 Dynotex® pipe charges Ø17-32×460/1000 mm R. Holmberg Lima Nov 2011 . Holmberg Lima Nov 2011 .3 63 String emulsion by balancing emulsion flow through nozzle and hose retraction an even string is deposited in hole string 0.Decoupled charges .35 kg/m mini SSE R. 45m Innerkontur (hjelpekontur) : 3.3m E R.5 kg D C D Konturhull m/hjørneliggere : 1. SSE emulsjon i hele salven Strossehull oppe : 4.2m 1.3m 3.2 m 4.1 kg/m A B A B C 0.3 kg E 0.4 64 Selmer Anläggning AB Chalmers-tunnelen Strengladning SSE Ladeplan 4.4 kg/m : 3.8 kg/m 0.1 kg/m 0.3m Kutt m/hjelpehull : 4.8 kg/m 0.3m 3.15m Liggerhull : 3.9 m 0.45m 0. Holmberg Lima Nov 2011 .6m Emulsjon Tennpatron 0.05 m 0.7m 3.steg .45m 0.3m 3.Decoupled charges .0 kg 0.7 kg 0.7m 3.0 kg 1.0 kg Innerkontur (hjelpekontur) 0. 1 65 Underground blasting: • Often more complicated drilling patterns and blasting methods used than in surface blasting • Special considerations for cuts and openings. R. stability. Holmberg Lima Nov 2011 . spillage & non-detonating explosives are sources.Pointers . rock stress and water complicate work • Separation between fragmented rock (ore) and remaining rock mass (waste) hard to maintain • Short life span of drifts and cavities in mining but long span in infrastructure tunnels and cavern • Nitrate leakage from explosives is coming into focus. water removes cushion effect for decoupled charges. e.g.Pointers . SLC. One doesn't . know how the ring fired or even which ring the ore loaded comes from • High quality blast designs.see the drilling quality.bad charging practice mixes emulsion & water. R.2 66 Quality of blasting work: • Blasting never gets better than drilling and drill hole deviations are frequently large • Water problem in charging also with emulsions . Holmberg Lima Nov 2011 . drilling and charging work needed to achieve good blasting results. may cause detonation failure. wet upholes cause emulsion to slip etc • Some cases „black holes‟. Holmberg Lima Nov 2011 . Swebrec and LTU who provided a lot of the sources for the material presented in this lecture R.Accknowledgements 67 The author wishes to acknowledge Prof Finn Ouchterlony . THANKS! 68 R. Holmberg Lima Nov 2011 .
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