by RA Dick · Cited by 73 — Information Circular 8925. Explosives and Blasting Procedures. Manual. By Richard A. Dick, protective mats may be used to contain flyrock. However, this.
112 pages
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Information Circular 8925 Explosives and Blasting Procedures Manual By Richard A. Dick, Larry R. Fletcher, and Dennis V. D’Andrea US Department of Interior Office of Surface Mining Reclamation and Enforcement Kenneth K. Eltschlager Mining/Blasting Engineer 3 Parkway Center Pittsburgh, PA 15220 UNITED STATES DEPARTMENT OF THE INTERIOR James G. Watt, Secretary BUREAU OF MINES Robert C. Horton, Director Phone 412.937.2169 Fax 412.937.3012 [email protected]
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As the Nation’s principal conservation agency, the Department of the Interior has responsibility for most of our nationally owned public lands and natural resources. This includes fostering the wisest use of our land and water reŁ sources, protecting our fish and wildlife, preserving the environmental and cultural values of our national parks and historical places, and providing for the enjoyment of life through outdoor recreation. The Department assesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. The Department also has a major re· sponsibility for American Indian reservation communities and for people who live in Island Territories under U.S. administration. This publication has been cataloged as follows: Dick, Richard A Explosives and blasting procedures manual, (Bureau of Mines Information circular ; 8925) Supt. of Docs. no.: I 28.27:8925. 1. Blasting-Handbooks, manuals, etc, 2. Explosives-Haodbooks, manuals, etc, I. Fletcher, Larry R. II. D’Andrea, Dennis V. Ill, Title, IV. Series: Information circular (United States, Bureau of Mines) ; 8925, TN295,U4 [TN279] 622s [622′.23] 82·600353 For sale by the Superintendent of Documents, U.S. Government Prin£ing Office Washington, D.C. 20402
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CONTENTS Abstract . . Introduction . Chapter 1.-Explosives Products Page 1 2 Chemistry and physics of explosives .. . .. 3 Types of explosives and blasting agents . . 4 Nitroglycerin-based high explosives 5 Dry blasting agents . , 7 Slurries.. 9 Two-component explosives. 10 Permissible explosives . .. .. .. .. . .. .. . .. .. .. . .. .. 11 Primers and boosters .. .. .. .. .. . .. . .. .. . 1 1 Liquid oxygen explosive and black powder. 13 Properties of explosives. 14 Strength.. 14 Detonation velocity .. .. .. .. .. .. .. . .. . 14 Density .. .. . .. .. . . . .. . .. .. .. .. .. .. .. .. .. . . .. . . 14 Water resistance 15 Fume class .. , 15 Detonation pressure . . .. .. .. . 16 Borehole pressure 16 Sensitivity and sensitiveness.. 16 Explosive selection criteria 17 Explosive cost .. .. 17 Charge diameter 16. Cost of drilling.. 16 Fragmentation difficulties.. 18 Water conditions 18 Adequacy of ventilation. 18 Atmospheric temperature .. .. 19 Propagating ground. 19. Storage considerations . , 19 Sensitivity considerations .. . .. .. 19 Explosive atmospheres . 20 References 20 Chapter 2.-lnitiation and Priming Initiation systems .. .. . . .. 21 Delay series .. . . . .. . .. . .. 21 Electric initiation .. . . .. .. .. .. . .. .. .. .. .. .. . .. .. . .. .. .. .. .. .. 22 Types of circuits . .. .. .. . . 23 Circuit calculations . .. . .. .. 25 Power sources ··25 Circuit testing.. 28 Extraneous electricity . .. .. .. . .. . . . .. .. . . . .. 30 Additional considerations.. 30 Detonating cord initiation .. .. .. .. .. . 30 Detonating cord products. 31 Field application 31 Delay systems 33 General considerations . 34 Detaline system. 34 Cap-and-fuse initiation . .. 35 Components 35 Field applications.. 35 Delays 36 General considerations . .. .. .. .. . . .. . .. . .. .. . . .. .. .. . .. . .. .. 36 Other nonelectric initiation systems .. .. .. .. .. 36 Hercudet 37 Nonel.. 39 Page Chapter 2.-lnitiation and Priming-Con. Priming 43 Types of explosive used 43 Primer makeup.. 45 Primer location .. . . .. .. . .. .. . 46 Multiple priming .. . . 47 References 47 Chapter 3.-Biasthole Loading Checking the blasthole.. . . . .. .. .. . .. .. .. . .. .. .. .. 49 General loading procedures. 49 Small-diameter blastholes. 50 Cartridged products. 50 Bulk dry blasting agents .. .. .. . .. .. .. .. .. .. . .. .. 50 Bulk slurries. 52 Permissible blasting . . .. . . 52 Large-diameter blastholes.. .. 52 Packaged products.. 52 Bulk dry blasting agents .. .. .. . .. .. .. .. .. . 53 Bulk slurries. 54 References 56 Chapter 4.-Biast Design Properties and geology of the rock mass,,.. 57 Characterizing the rock mass .. :: 57 Rock density and hardness. 57 Voids and incompetent zones 57 Jointing.. 58 Bedding. 58 Surface blasting. 59 Blasthole diameter 59 Types of blast patterns.. 61. Burden 61 Subdrilling. 62 Collar distance (stemming).. 62 Spacing. 63 Hole depth 64 Delays 64 Powder factor . . .. . . .. .. .. .. . . . .. 65 Secondary blasting .. :.. 65 Underground blasting.. 66-0penlng cuts . .. . . .. . .. . . .. . .. 66 Blasting rounds.. 68 Delays 69 Powder factor .. .. .. . . . .. .. .. . . .. . .. . .. .. . 70 Underground coal mine blasting . .. 70 Controlled blasting techniques 70 Line drilling . .. . .. .. .. .Ł .. .. .. . . 70 Presplitting .. . . . .. .. . . . .. . 71 Smooth blasting. 73 Cushion blasting 74 References :.. 74 Chapter 5.-Environf1lental Effects of Blasting Flyrock .. 77 Causes and alleviation .. . .. . .. . .. . .. .. .. . .. . .. .. .. . .. .. . .. . 77 Protective measures.. 77
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IV Page Chapter 5.-Environmental Effects of Blasting-Con. Ground vibrations . . Causes . . Prescribed vibration levels and measurement techniQues . ; .. . Scaled distance equation . Reducing ground vibrations . Airblast .. . Causes .. Prescribed airblast levels and measurement techniques . . Reducing airblast . . Dust and gases .. References .. . Chapter 6.-Biasting Safety Explosives storage . .. 77 78 79 80 80 80 81 82 82 83 83-85 Chapter 6.-Biasting Safety-Con. Transportation from magazine to jobsite .. . PrecaUlions before loading .. Primer preparation . .. Borehole loading .. . Hooking up the shot . Shot firing . . P?stsh?t .. : .. Dtspostng of mtsf1res . .. Disposal of explosive materials . . Principal causes of blasting accidents . .. Underground coal mine blasting .. . References .. . Bibliography . Appendix A.-Federal blasting regulations .. Appendix B.-Glossary of terms used in explosives and blasting . ILLUSTRATIONS Page 85 86 88 88 90 90 92 92 92 92 93 93 94 96 99 1. Energy released by common products of detonation .. .. . . .. . .. .. .. .. .. . .. .. .. .. . .. .. .. .. . .. .. .. .. .. .. .. . . .. . .. .. 3 2. Pressure profiles created by detonation in a borehole 4 3. Relative ingredients and properties of nitroglycerin-based high explosives. 5 4. Typical cartridges of dynamite 6 5. Types of dry blasting agents and their ingredients · .. 7 6. Porous ammonium nitrate prills , 8 7. Water-resistant packages of AN·FO for use in wet boreholes .. ::.. 9 8. Formulations of water-based products.. 1-0 9. Slurry bulk loading trucks .. . . . .. 11 10. Loading slurry-filled polyethylene bags :. 12 11. Cast primers for blasting caps and detonating cord . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. . .. . .. .. .. . .. .. . 13 12. Delay cast primer .. . .. . . . .. .. .. .. .. .. . .. . .. .. . .. .. . . . .. . . .. .. .. . . .. . .. .. .. .. .. 13 13. Effect of charge diameter on detonation velocity.. 14. 14. Nomograph for finding loading density.. 15 15. Nomograph for finding detonation pressure .. .. . . . .. .. .. . .. . .. .. .. . .. . .. .. . .. .. . .. .. .. .. .. .. .. 16 16. Field mixing of AN-FO . . .. .. . .. .. .. .. .. .. .. . .. .. .. .. .. .. . .. .. .. .. . .. . .. . .. .. .. .. . . . .. .. .. .. . .. .. . . . .. . .. .. .. . .. . 17 17. Instantaneous detonator . :. 21 18. Delay detonator. 22 19. Electric blasting caps.. 23 20. Delay electric blasting cap 23 21. Types of electric blasting circuits.. 24 22. Recommended wire splices .. :. 24 23. Calculation of cap circuit resistance . . .. . .. . .. .. 25 24. Capacitor discharge blasting machine 26 25. Sequential blasting machine 27 26. Blasting galvanometer 28 27. Blasting multimeter. . .. . . . .. . . . . .. . .. . . . .. . .. . . . .. .. . . . . . . . .. .. .. . . . . . . . . .. .. . . . . . . .. .. .. . . . . .. . . . . . . .. .. . . . . . . 29 28. Detonating cord. 31 29. Clip-on surface detonating cord delay connector . .. .. . . .. .. .. .. .. .. .. . . .. .. .. . .. .. .. . .. .. .. .. . . .. .. .. . . .. . . .. . .. . .. 32 30. Nonel surface detonating cord delay connector . .. .. . 32 31. Recommended knots for detonating cord. 33 32. Potential cutoffs from slack and tight detonating cord lines. 33 33. Typical blast pattern with surface delay connectors .. . .. . . .. 33 34. Misfire caused by cutoff from burden movement.. 34 35. Blasting cap for use with safety fuse.. 35 36. Cap, fuse, and lgnitacord assembly . . . . . . .. . . . .. .. . .. . . . .. . .. . 36 37. Hercudet blasting cap with 4-in tubes. 37 38. Extending Hercudet leads with duplex tubing. 38 39. Hercudet connections for surface blasting 38 40. Hercudet pressure test module . .. . .. .. .. . . .. . . . . .. . . . .. . .. .. . 39
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v Page ILLUSTRATIONs-Continued 41. Hercudet tester for small hookups .. .. .. .. .. . .. . .. .. .. .. .. .. .. .. . .. . .. .. . .. .. . .. .. .. .. . . .. .. .. .. .. .. .. .. .. . .. .. .. . .. . .. . .. . . .. .. .. 40 42. Hercules bottle box and blasting machine 41 43. None I blasting cap 41 44. Nonel Primadet cap for surface blasting 42 45. None I noiseless trunkline delay unit .. .. .. .. .. .. . . . . . . .. . . . . . . . . . . . .. . . . . . . .. . 42 46. Noiseless trunkline using Nonel delay assemblies . .. . . . .. . . . . . .. .. .. . 42 47. Nonel noiseless lead-in line. 43 48. Highly aluminized AN-FO booster .. . . .. .. . . . .. . .. .. . .. .. . . . . .. .. . . . . . .. . .. . . . . .. . . . .. . .. . .. .. . . . . .. 44 49. Cartridge primed with electric blasting cap.. 45 50. Priming cast primer with electric blasting cap. 46 51. Priming blasting agents in large-diameter blastholes . 47 52. Corrective measures for voids 49 53. PneumatiC loading of AN-FO underground.. 51 54. Ejector-type pneumatic AN-FO loader 51 55. AN-FO detonation velocity as a function of charge diameter and density . . . . .. .. . .. .. . . . . . 52 56. Pouring slurry into small-diameter borehole 53 57. Pumping slurry into small-diameter borehole . 54 58. Slurry leaving end of loading hose .. ,.. 55 59. Loss of explosive energy through zones of weakness 58 60. Effect of jointing on the stability of an excavation. 58 61. Tight and open corners caused by jointing.. 58 62. Stemming through weak material and open beds .. .. . .. . . . .. . .. 59 63. Two methods of breaking a hard collar zone.. 59 64. Effect of dipping beds on slope stability and potential toe problems .. .. .. .. 59 65. Effect of large and small blastholes on unit costs. 60 66. Effect of jointing on selection of blasthole size .. . .. . . .. .. .. .. . .. . .. .. . .. . .. .. . .. .. .. .. . .. .. . .. . .. .. .. . .. .. . .. .. . .. . .. . .. 60 67. Three basic types of drill pattern . . . .. .. . .. .. .. .. .. .. . .. .. . .. .. . .. .. . .. . .. . . .. .. .. . . . .. . .. .. .. . .. . 61 68. Corner cut staggered blast pattern-simultaneous initiation within rows.. 61 69. V-echelon blast round. 61 70. Isometric view of a bench blast. 61 71. Comparison of a 12%-in-diameter blasthole (stiff burden) with a 6-in-diameter blasthole (flexible burden) in a 40-ft bench .. _ 62 72. Effects of insufficient and excessive spacing.. 63 73. Staggered blast pattern with alternate delays. 63 74. Staggered blast pattern with progressive delays ;. 63 75. The effect of inadequate delays between rows .. .. .. .. .. . .. . .. . .. . .. .. .. .. .. .. .. .. . .. .. .. .. . .. .. .. . .. .. .. .. .. .. .. 64 76. Types of opening cuts . .. .. .. . .. .. . .. .. .. .. . .. . .. . .. .. .. . .. .. . . .. .. . .. .. . .. .. .. . .. . . .. .. . .. . . . .. . .. . . .. . .. . . .. .. .. . .. .. . .. . .. . . 66 n. Six designs for parallel hole cuts.. 67 78. Drill template for parallel hole cut . .. .. .. . . .. . .. . .. .. .. .. . .. . .. .. .. .. . .. .. 67 79. Blast round for soft material using a sawed kerf 68 80. Nomenclature for blastholes in a heading round .. . .. . .. . .. .. . .. . . .. .. .. . . . . .. .. 68 81. Angled cut blast rounds. 68 82. Parallel hole cut blast rounds. 68 83. Fragmentation and shape of muckpile as a function of type of cut.. 69 84. Fragmentation and shape of muckpile as a function of delay. 69 85. Typical burn cut blast round delay pattern 69 86. Typical V-cut blast round delay pattern .. .. 69 87. Shape of muckpile as a function of order of firing. 69 88. Stable slope produced by controlled blasting .. .. . . . .. . .. .. .. .. .. . .. .. .. .. .. .. .. .. . .. . .. . .. 71 89. Crack generated by a pre split blast. 72 90. Three typical blasthole loads for presplitting.. .. . . .. .. . .. .. .. . .. .. .. .. .. .. 73 91. Typical smooth blasting pattern. 73 92. Mining near a residential structure .. .. .. . .. .. . .. . . .. . . . .. . .. .. .. .. .. .. .. .. .. .. . . . 75 93. Example of a blasting record . . . . . . .. . . .. . . . . . . . . .. . . . . . .. . .. . . .. . . . .. . .. . .. .. . 76 94. Seismograph for measuring ground vibrations from blasting.. 78 95. Effects of confinement on vibration levels . . . .. . . . . .. .. . .. . .. . .. .. .. . . . .. .. 79 96. Effect of delay sequence on particle velocity.. 79 97. Blasting seismograph with microphone for measuring airblast.. 81 98. Causes of airblast. 81 99. Proper stacking of explosives. 86 1 00. AN-FO bulk storage facility.. 87
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vi Page ILLUSTRATIONs-Continued 101. Checking the rise of the AN-FO column with a weighted tape .. , 89 102. Blasting shelter.. 91 TABLES 1. Properties of nitroglycerin-based explosives .. . . . . .. .. . .. . . . . . . . .. .. .. . . .. . . . .. . . .. . .. . . . . .. . . .Ł 5 2. Fume classes designated by the Institute of Makers of Explosives 15 3. Characteristics of pneumatically loaded AN-FO in small-diameter blastholes.. 52 4. Approximate B/0 ratios for bench blasting .. .. . .. 62 5. Approximate J/B ratios for bench blasting .. . . . .. . 62 6. Typical powder factors for surface blasting . . . 65 7. Average specifications for line drilling 71 8. Average specifications for presplitting .. .. . .. . 73 9. Average specifications for smooth blasting 73 10. Average specifications for cushion blasting 74 11. Maximum recommended airblast levels . . 82 A-1. Federal regulatory agency responsibility.. 96 UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT amp ampere ft foot min minute em centimeter g gram ms millisecond cucm cubic centimeter gr grain pet percent cu ft cubic foot Hz hertz ppm parts per million cu yd cubic yard in inch psi pound per square inch dB decibel kb kilobar sec second 0 degree kcal kilocalorie sq ft square foot OF degree Fahrenheit lb pound sqin square inch fps foot per second mi mile yd yard
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2 ;, INTRODUC1″10N The need for better and more widely available blasters’ training has long been recognized in the blasting community. The Mine Safety and Health Administration (MSHA) of the Department of Labor requires health and safety training for blasters. In 1980, the Office of Surface Mining Reclamation and Enforcement (OSM), Department of the Interior, promulgated regulations for the certification of blasters in the area of environmental protection. These regulations are certain to have a positive influence on the level of training and competence of blasters. They will, however, present a problem to the mining industry. That problem is a scarcity of appropriate training material. Although numerous handbooks and textbooks are available (9, 24, 27, 29-30, 32, 46)4 none are geared for use in training the broad spectrum of people involved in practical blasting. This manual is designed to fulfill that need. It is appropriate that the Bureau of Mines prepare such a manual. Sinc-e its inception, the Bureau has been involved in all aspects of explosives and blasting research including productivity, health and safety, and environment, and has provided extensive technical assistance to industry and regulatory a_gE!ncies in the promotion of good blasting practices. This manual serves two basic functions. The first is to provide a source of individual study for the blaster. There are literally tens of thousands of people involved in blasting at mines in the country and there are not enough formal training courses available to reach the majority of them. The second function is to provide guidance to industry, consultants, and academic institutions in the preparation of practical training courses on blasting. The manual has been broken down into a series of discrete topics to facilitate self·study and the preparation of training modules. Each section stands on its own. Each student or instructor can utilize only those sections that suit his or her needs. An attempt has been made to provide concise, yet comprehensive coverage of the broad field of blasting technology. Although liberal use has been made of both Bureau and non-Bureau literature in preparation ofthis manual, none of the topics are dealt with in the depth that would be provided by a textbook or by a publication dealing with a specific topic. Each section is supplemented by references that can be used to pursue a more in-depth study. These references are limited to practical items that are of direct value to the blaster in the field. Theory is included only where it is essential to the understanding of a concept. Where methods of accomplishing specific tasks are recommended, these should not be considered the only satisfactory methods. In many instances there is more than one safe, effective way to accomplish a specific blasting task. None of the material in this manual is intended to replace manufacturers’ recommendations on the use of the products involved. It is strongly recommended that the individual manufacturer be consulted on the proper use of specific products. 41taliclzed numbers in parentheses refer to items In the bibliography preceding the appendixes.
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3 Chapter 1.-EXPLOSIVES PRODUCTS CHEMISTRY AND PHYSICS OF EXPLOSIVES It is not essential that a blaster have a strong knowledge of chemistry and physics. However, a brief discussion of the reactions of explosives will be helpful in understanding how the energy required to break rock is developed. An explosive is a chemical compound or mixtureofcompounds that undergoes a very rapid decomposition when initiated by energy in the form of heat, impact, friction, or shock (4)1Ł This decomposition produces more stable substances, mostly gases, and a large amount of heat. The very hot gases produce extremely high pressures within the borehole, and it is these pressures that cause the rock to be fragmented. If the speed of reaction of the explosive is faster than the speed of sound in the explosive (detonation), the product is called a high explosive. If the reaction of the explosive is slower than the speed of sound in the explosive (deflagration), the product is called a low explosive. The principal reacting ingredients in an explosive are fuels and oxidizers. Common fuels in commercial products include fuel oil, carbon, aluminum, TNT, smokeless powder, monomethylamine nitrate, and monoethanol amine nitrate. Fuels often perform a sensitizing function. Common explosive sensitizers are nitroglycerin, nitrostarch, aluminum, TNT, smokeless powder, monomethylamine nitrate, and amine nitrate. Microballoons and aerating agents are sometimes added to enhance sensitivity. The most common oxidizer is ammonium nitrate, although sodium nitrate and calcium nitrate may also be used. Other ingredients of explosives include water, gums, thickeners and cross-linking agents used in slunies (11), gelatinizers, densifiers, antacids, stabilizers, absorbents, and flame retardants. In molecular explosives such as nitroglycerin, TNT, and PETN, the fuel and oxidizer are combined in the same compound. Most ingredients of explosives are composed of the elements oxygen, nitrogen, hydrogen, and carbon. In addition, metallic elements such as aluminum are sometimes used. For explosive mixtures, energy release is optimized at zero oxygen balance (5 ). Zero oxygen balance is defined as the point at which a mixture has sufficient oxygen to completely oxidize all the fuels it contains but there is no excess oxygen to react with the nitrogen in the mixture to form nitrogen oxides. Theoretically, at zero oxygen balance the gaseous products of detonation are H20, C02, and N2, although in reality small amounts of NO, CO, NH2, CH4, and other gases are generated. Figure 1 shows the energy released by some of the common products of detonation. Partial oxidation of carbon to carbon monoxide, which results from an oxygen deficiency, releases less heat than complete oxidation to carbon dioxide. The oxides of nitrogen, which are produced when there is excess oxygen, are “heat robbers;” that is, they absorb heat when generated. Free nitrogen, being an element, neither absorbs nor releases heat upon liberation. It should be noted that the gases resulting from improper oxygen balance are not only inefficient in terms of heat energy released but are also poisonous. Although the oxidation of aluminum yields a solid, rather than a gaseous. product the ‘Italicized numbers in parentheses refer IP items in the list of references at the end of this chapter. ŁŁŁ.———————-20 STANOAA’O MEAlS OF FORMATION, M,o -144 4120] -399 w,o .,. co, -.. co _,. ., 0 NO, .. . , NO ‘” Figure 1.-Energy released by common products of detonation. large amount of heat released adds significantly to the explosive’s energy. Magnesium is even better from the standpoint of heat release, but is too sensitive to use in commercial explosives. The principle of oxygen balance is best illustrated by the reaction of ammonium nitrate-fuel oil [(NH4N03)-(CH2)J mixtures. Commonly called AN-FO, these mixtures are the most widely used blasting agents. From the reaction equations for AN-FO, one can readily see the relationship between oxygen balance, detonation products, and heat release. The equations assume an ideal detonation reaction, whiph in turn assumes thorough mixing of ingredients, proper particle sizing, adequate confinement, charge diameter and priming, and protection from water. Fuel oil is actually a variable mixture of hydrocarbons and is not precisely CH2, but this identification simplifies the equations. and is accurate enough for the purposes of this manual. In reviewing these equations, keep in mind that the amount of heat produced is a measure of the energy released. (94.5 pet AN)-(5.5 pet FO): 3NH4N03 + + + + 0.93 kcal/g. (92.0 pet AN)-(8.0 pet fO): 2NH4NOa + + CO + 2N2 + 0.81 kcaVg. (96.6 pet AN)-(3.4 pet FO): 5NH4NOa + 11 H20 + C02 + 4N2 + 2NO + 0.60 kcal/g. (1) (2) (3) Equation 1 represents the reaction of an oxygen-balanced mixture containing 94.5 pet AN and 5.5 pet FO. None of the detonation gases are poisonous and 0.93 kcal of heat is released for each gram of AN-FO detonated. In equation 2, representing a mixture of 92.0 pet AN and 8.0 pet FO, the excess fuel creates an oxygen deficiency. As a result, the
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4 carbon in the fuel oil is oxidized only to CO, a poisonous gas, rather than relatively harmless C02. Because of the lower heat of formation of CO, only 0.81 kcal of heat is released for each gram of AN·FO detonated. In equation 3, the mixture of 96.6 pet AN and 3.4 pet FO has a fuel shortage that creates an excess oxygen condition. Some of the nitrogen from the ammonium nitrate combines with this excess oxygen to form NO, which will react with oxygen in the atmosphere to form extremely toxic N02. The heat absorbed by the formation of NO reduces the heat of reaction to only 0.60 kcal, which is considerably lower than that of an overfueled mixture. Also the ·CO produced by an overfueled mixture is less toxic than NO and N02. For these reasons a slight oxygen deficiency is preferable and the common AN·FO mixture for field use is 94 pet AN and 6 pet FO. Although the simple AN-FO mixture is optimum for highest energy release per unit cost of ingredients, products with higher energies and densities are often desired. The common high-energy producing additives, which may be used in both dry blasting agents and slurries, fall into two basic categories: explosives, such as TNT, and metals, such as aluminum. Equations 4 and 5 illustrate the reaction of TNT and aluminum as fuel-sensitizers with ammonium nitrate. The reaction products, again, assume ideal detonation, which is never actually attained in the field. In practice, aluminum is never the only fuel in the mixture, some carbonaceous fuel is always used. (78.7 pet ANH21.3 pet TNT): 21 NH4N03 + 2C6H2CH3(N02)3-Ł47H20 + 14C02 + 24N2 + 1.01 kcal!g. (81.6 pet AN)-(18.4 pet AI): 3NH4N03 + 2AI-Ł6H20 + Al203 + 3N2 + 1.62 kcal/g. (4) (5} Both of these mixtures release more energy, based on weight, than ammonium nitrate-carbonaceous fuel mixtures and have the added benefit of higher densities. These advantages must be weighed against the higher cost of such high-energy additives. The energy of aluminized products continues to increase with larger percentages of metal, even though this “overfueling·· causes an oxygen deficiency. Increasing energy by overfueling with metals, however, is uneconomical except for such specialty products as energy boosters. The chemical reaction of an explosive creates extremely high pressures. It is these pressures which cause rock to be broken and displaced. To illustrate the pressures created in the borehole, a brief look will be taken at the detonation process as pictured by Dr. Richard Ash of the University of Missouri-Rolla. Figure 2, adapted from Ash’s work shows (top) a column of explosive or blasting agent that has been initiated. Detonation has proceeded to the center of the column. The I Lofirtif’!OhOn Oitection oi detonat1on movement -Shock froM EJplos1on . . IJnreocted product CO:l, N2 / NH,.N03,CHt prone Primoty reoe1ion tone F\t-slurry IJil!pk)Stve Pd slurry blotllraq oqel’! KEY pd oerortohol”‘ pressure Pe Explosion pressvte Figure 2.-Pressure profiles created by detonation In a borehole. primary reaction occurs between a shock front at the leading edge and a rear boundary known as the Chapman-Jouguet (C·J) plane. Part of the reaction may occur behind the C·J plane, particularly if some of the explosive’s ingredients are coarse. The length of the reaction zone, which depends on the explosive’s ingredients, particle size, density, and confinement, determines the minimum diameter at which the explosive will function dependably (critical diameter). High explosives, which have short reaction zones, have smaller critical diameters than blasting agents. . · The pressure profiles in figure 2 (bottom) show the explosive forces applied to the rock being blasted. A general comparison is given between an explosive and a blasting agent, although it should be understood that each explosive or blasting agent has its own particular pressure profile depending on its ingredients, particle size, density, and confinement. The initial pressure, called the detonation pressure (P.), is created by the supersonic shock front moving out from the detonation zone. The detonation pressure gives the explosive its shattering action in the vicinity of the borehole. If the explosive reacts slower than the speed of sound, which is normally the case with black powder, there is no detonation pressure. The detonation pressure is followed by a sustained pressure called explosion pressure (P.), or borehole pressure. Borehole pressure is created by the rapid expansion of the hot gases within the borehole. The detonation pressure of high explosives is often several times that of blasting agents, but the borehole pressures of the two types of products are of the same general magnitude. The relative importance of detonation pressure and borehole pressure in breaking rock will be discussed in the “Properties of Explosives” section of this chapter. TYPES OF EXPLOSIVES AND BLASTING AGENTS This section will cover all explosive products that are used for industrial rock blasting, with the exception of initiators. Products used as the main borehole charge can be divided into three categories: nitroglycerin-(or nitrostarch-} based high explosives, dry blasting agents, and slurries, which may also be referred to as water gels or emulsions. These products can also be broadly categorized as explosives and blasting agents. For ease of expression, the term explosives will often be used in this manual to collectively cover both explosives and blasting agents. The difference between an explosive and a blasting agent is as follows. A high explosive is any product used in blasting that is sensitive to a No. 8 cap and that reacts at a speed faster than the speed of sound in the explosive medium. A low explosive
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is a product in which the reaction is slower than the speed of sound. Low explosives are seldom used in blasting today. A blasting agent is any material or mixture consisting of a fuel and an oxidizer, intended for blasting, not otherwise classified as an explosive, provided that the finished product, as mixed and packaged for shipment, cannot be detonated by a No. 8 blasting cap in a specific test prescribed by the Bureau of Mines. Slurries containing TNT, smokeless powder, or other explosive ingredients, are classed as blasting agents if they are insensitive to a No. 8 blasting cap. AN-FO, which in normal form is a blasting agent, can be made cap sensitive by pulverizing it to a fine particle size, and a slurry can be made cap sensitive by including a sufficient amount offinely flaked paint-grade aluminum. Although neither of these products contains an explosive ingredient, their cap sensitivity requires their being classified as explosives. The term nitrocarbonitrate, or NCN, was once used synonymously with blasting agent under U.S. Department of Transportation (DOT} regulations for packaging and shipping blasting agents. DOT no longer uses this term. NITROGL YCERIN·BASED HIGH EXPLOSIVES Nitroglycerin-based explosives can be categorized as to their nitroglycerin content (4}. Figure 3 shows this breakdown 5 Ingredients Nongelntinous , 81osting gelat 1 n i Nit rog 0 , ‘e-o Q :i? n :i? , . Straiqhl dynamite Stralqht gelatin < -· "" ; .. ' , O:&l ' .. .. -· Q "' "" , , High-dens1ty 1 .. ("j ;· Ammonia gelatin :::ro ! ammonia dynamite '"'o , " r <> 0 0 , , 3 I Low-density ” ;;3 Semlqe!otin 0 , 0 9mmooia dynamite , 3 I Dty blasting agents Slurries I Inc-reasing wolef resistance Figure 3.-Relatlve iogredients and properties of nitroglyceriri·based high explosives. along with some relative properties and ingredients of these products. Table 1 shows some properties of based explosives. Property values are averages of turers’ published figures. As a group, nitroglycerin-based explosives are the most sensitive commercial products used today (excluding detonators). Because of this sensitivity they offer an extra margin of dependability in the blasthole but are somewhat more susceptible to accidental detonation. This is a tradeoff that many operators using small-diameter boreholes Table 1. ·Properties of nitroglycerin-based explosives Weight Bulk Specific Detonation Water Fume strength, strength. gravity velocity, resistance class pet pet Ips STRAIGHT DYNAMITE 50 50 1.4 17,000 Good Poor. HIGH-DENSITY AMMONIA DYNAMITE 60 50 1.3 12,500 Fair .. Good. 40 35 1.3 10,500 do . Do . 20 15 1.3 6,000 do . Do . LOW-DENSITY AMMONIA DYNAMITE, HIGH VELOCITY 65 50 1.2 11,000 Fair .. Fair. 65 40 1.0 10,000 do . Do . 65 30 . 9 9,500 Poor . Do. 65 -20 . 8 6,500 do . Do . LOW-DENSITY AMMONIA DYNAMITE, LOW VELOCITY 65 50 1.2 6,000 Fair .. Fair 65 40 1.0 7,500 Poor . Do. 65 30 . 9 7,000 do . Do . 65 20 .a 6,500 do . Do. BLASTING GELATIN 100 90 1.3 25,000 Excellent Poor. STRAIGHT GELATIN 90 80 1.3 23,000 Excellent Poor. 60 60 1.4 20,000 . do Good. 40 45 1.5 16,500 . do Do. 20 30 1.7 11,000 . do Do. AMMONIA GELATIN 80 70 1.3 20,000 Very good . Good. 60 60 1.4 17,500 do . Very good. 40 45 1.5 16,000 do . Do. SEMIGELATIN 65 60 1.3 12,000 Very good . Very good. 65 50 1.2 12,000 do . Do. 65 40 1.1 11,500 Good Do. 65 30 .9 10,500 Fair .. Do.
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