Workbook 1 - Introduction to Blasting and Explosives Safety

Note: Please DO NOT WRITE in workbooks. Answer on separate piece of paper.

Table of Contents

Introduction

While the evolution of explosives and their use was a painfully slow process for much of the history of mankind, a great deal has happened in recent years - especially during this century. Many improvements have been effected to make explosives less sensitive to unintended detonation...and, therefore, much safer to use in today's mining operations.

However, before you can thoroughly appreciate how explosives apply to mining, there are certain terms you must understand. In the upcoming frames of programmed instruction, we'll teach you what some of these definitions are and how they apply to your situation as a miner.

Our objective is not to teach you to "spit back" definitions to us. Those just might be meaningless words that would have very little bearing on your conduct with and around explosives. Just keep in mind that there's a definite relationship between these terms and the safe, efficient use of explosives in your mining environment.

Explosives and Blasting Agents

Frame 1. The term "explosives" means any chemical compound, mixture, or device, the primary or common purpose of which is to function by explosion - that is, the almost instantaneous release of heat and gas - except for those materials which are so insensitive as to minimize accidental detonation, which are called blasting agents. In other words, when a chemical compound is activated by an explosion - such as a blasting cap - it is an _____________. But if the compound is such that it cannot easily be detonated accidentally, it is called a _____________.

Frame 2. "Blasting agent" is defined as any material or mixture consisting of fuel and oxidizer, intended for blasting, not otherwise defined as an explosive, provided that the finished product, as mixed for use or shipment, cannot be detonated by means of an instantaneous detonator when unconfined. In other words, if the compound intended for blasting is:

• A. non-cap sensitive, it is classified as a _____________
• B. if the compound is cap-sensitive, it is called an _____________

Frame 3. Throughout this workbook and the entire series of workbooks concerning blasting, we'll often make reference to explosives and blasting agents. The brief definitions just discussed should help differentiate between the two. Explosives include, but are not limited to, dynamite, black powder, detonators, safety fuses, and detonating cord. So you know that these items are _____________-sensitive.

Frame 4. One of the more common ingredients in both dynamite and blasting agents is ammonium nitrate. Under the right circumstances and in combinations with a fuel such as fuel oil this mixture (will / will not - which?) _____________ explode.

Frame 5. So ammonium nitrate, mixed with the right substances and under the right circumstances, will explode. That's why ammonium nitrate is:

• A. an ingredient in _____________; and,
• B. a major ingredient in _____________ agents.

Detonators

Frame 6. Explosives of the type we use today in mining generally require both heat and impact for initiation. Since the items or materials which provide both elements can be used to detonate today's explosives, we call these materials _____________.

Here are illustrations of some of the most commonly used detonators.

Frame 7. A detonator is itself explosive and must be handled carefully. Many accidents have occurred with various types of detonators. Remember, from a blasting standpoint, detonators are used to initiate explosives. By definition, the most common types are the _____________ shown here.

ANFO

Frame 8. To become a blasting agent, ammonium nitrate must be combined with another substance. This substance is usually fuel oil. And that's where the name, "ANFO" comes from: the combination of _____________ and _____________.

Frame 9. You'll better understand how ANFO is produced once you know what "prills" are. When it's manufactured, ammonium nitrate is actually a hot liquid. It can be processed in any of several ways, two of which are shown here:

• It can be poured onto a conveyor belt, then carried along until it hardens into a thin sheet. This sheet can then be crumbled into a powder.
• Or, liquid ammonium nitrate can be sprayed into the top of a tower, or silo-shaped cylinder...and as the droplets fall to the bottom, they cool to form small balls of ammonium nitrate called _____________.

Frame 10. The longer the droplets of ammonium nitrate remain in the air, the more they coagulate - and the larger the _____________ they form.

Frame 11. If we install fans in the silo and blow warm air upward, we can control the size of the ammonium nitrate prills we get. Remember, the longer we keep the droplets suspended (CHECK THE CORRECT ANSWER):

• A. the smaller the prills become.
• B. the larger the prills become.

Frame 12. Prills used in making ANFO are relatively porous. They'll soak up water readily. In other words, these porous ammonium nitrate prills are hygroscopic. And if these hygroscopic prills soak up too much water, they become ineffective - they won't _____________.

Frame 13. As a part of the explosive prill manufacturing process, a light coating of clay is sprayed on the prills. The objectives of doing this are partly to combat the hygroscopic nature of the prills - that is, to help prevent their soaking up too much _____________ so readily - and partly to help keep the prills separate, instead of letting them stick together in a mass.

Frame 14. Of course, only the exact amount of clay must be applied to the ammonium nitrate prills. Too little, and they soak up water too readily or stick together in "clumps"; too much and the prills won't be able to absorb enough of the other important ingredient in ANFO - _____________.

Frame 15. Now, here's the importance of the fuel oil element: For a blasting agent such as ANFO to detonate, it must contain oxygen which is in the ammonium nitrate and a fuel. The fuel oil which is sprayed onto the ammonium nitrate prills provides the fuel to complete this chemical process. For an explosion to occur, then, we need both oxygen and a fuel which is provided by the _____________ and the _____________.

Frame 16. The finished blasting agent, ANFO, must have a certain percentage of fuel oil in it. Ideally, a combination of _____% ammonium nitrate and _____% fuel oil attains optimum results.

Frame 17. Blasting agents often have other combustible materials mixed into them - wood, meal, rice hulls, nut shells, etc. These items act to provide the same thing the fuel oil does in ANFO: a source of _____________ which is needed in the completion of the chemical process.

Frame 18. The combustible fillers just mentioned also perform other functions in some explosives - especially dynamite. For example, they can be used in just the right combinations to help control the density of the explosives... and they can serve to reduce the amount of fumes produced by the explosion. But the primary function of combustible fillers - called "pulps", or "dopes" - in blasting agents of various kinds is to provide (CHECK THE CORRECT ANSWER):

• A. the fuel to complete the chemical process.
• B. even more explosive material.
• C. inert material to offset the force of the explosion occurs.

Frame 19. Since we've mentioned ammonium nitrate in dynamite, let's look briefly at the manufacturing process involved here. When ammonium nitrate is to be used in dynamite, it's not sprayed into a "silo" or tower. Instead, it's mixed in large vats, stirred until it cools and reaches just the desired consistency - with other ingredients, such as dopes or pulps added - for dynamite. So the rounded _____________ are not used in dynamite manufacture, but are used in making the blasting agent we refer to as _____________.

Frame 20. Ammonium nitrate is used - in somewhat different form - for making both dynamite and ANFO. This tells us that ammonium nitrate is (CHECK THE CORRECT ANSWER):

• A. never used in making explosives.
• B. only used to manufacture blasting agents.
• C. essential to the manufacture of blasting agents and useful in explosives such as dynamite.

Frame 21. With ANFO, the prills make up the blasting agent - but only when they contain the right amount of fuel oil.

• A. The optimum mixture is _____% ammonium nitrate, _____% fuel oil.
• B. While they're used in many commercial dynamites, pulps or dopes (are / are not - which?) _____________ necessary in ANFO.

Frame 22. Now, don't get the idea that ANFO is the only type of blasting agent or explosive used in the mining industry. The chart on the following page presents further information concerning different explosives and blasting agents. Study this chart briefly - don't try to memorize it; you can always refer to it when necessary - then go on to the next frame. NO WRITTEN RESPONSE REQUIRED.

Ingredients of Explosives and Blasting Agents

Frame 23. You'll probably hear the term "powder" used in most mining operations. Don't be confused; this is a slang term that's generally applied to both blasting _____________ and explosives... almost any of the items shown in the preceding chart.

Frame 24. So if you're working with bulk ANFO and someone calls for more "powder" in the hole, all that's meant is that more _____________ is needed for that particular drill hole.

Frame 25. Finally, while dynamite is still used in some applications, the trend in recent years has been toward blasting agents, with ANFO being the most widely used. And as you'll recall:

• A. ANFO is the combination of _____________ and _____________.
• B. The proper combination is (WHAT)? _____% / _____%
• C. Even with its clay coating, ANFO (is / is not - which?) _____________ completely waterproof and must be kept dry.

Slurry

Frame 26. One last term you'll hear frequently is slurry. Most slurries are non-cap-sensitive, although some of them are. In other words, most - but not all - slurries are (explosives / blasting agents - which?) _____________.

Frame 27. Those slurries which are cap-sensitive are, of course, considered explosives. Slurries are water-resistant, which makes them usable in wet holes. A major use of slurries is to provide added "boost" to help detonate ANFO. And remember, slurry is (CHECK THE CORRECT ANSWER):

• A. a dry, powdery substance.
• B. available only in solid form.
• C. a gelatinous, jelly-like substance.

Frame 28. Later in your study, you'll find that slurry has a great many uses in blasting operations. For now, remember that:

• A. Most slurries are non-_____________-sensitive, so they're considered _____________.
• B. Slurry is a (solid / liquid / gelatinous - which?) _____________ substance.
• C. While it can't remain effective when submersed in water indefinitely, slurry is considered water-_____________, adding to its usefulness.

Frame 29. All right... we've provided you with some terms that are commonly used in relation to blasting, explosives, and blasting agents. Time now to return to the tape/slide presentation.

Review Questions - Set 1

Answer each one as indicated; then check your answer by looking at the one provided on the next page. If you've made a mistake, cross out your wrong answer and write in (check, etc.) the correct one.

1. With a blasting agent such as ANFO, the fuel is provided by _____________ and the impact is provided by a _____________ which is detonated in the ANFO.

2. Cast primers are pre-packaged _____________ which can be detonated to provide the impact needed to set off a _____________ agent.

3. In a non-electrical blasting system, a primer is detonated by (CHECK THE CORRECT ANSWER):

• A. a series of blasting caps.
• B. an electrical charge.
• C. a detonating cord of appropriate size or other non-electrical initiator.

4. In an electrical blasting system, primers are detonated by (CHECK THE CORRECT ANSWER):

• A. blasting caps which are set off by electrical charges.
• B. detonating cord.
• C. heat generated by the fuel oil or other chemical in the blasting agent.

5. The primer should be put into the hole so that it (is / is not - which?) _____________ in direct contact with the blasting agent.

6. When a hole with a single charge in it is shot, there are three explosions:

• A. the blasting _____________ or detonating _____________ which in turn...
• B. detonates the _____________ which then detonates...
• C. the blasting _____________, the major explosion in the hole.

Answers to Review Questions - Set 1

1. Fuel oil, primer
2. explosives, blasting (agent)
3. C is correct
4. A is correct
5. is
6. A. cap, cord; B. primer; C. agent

Review Questions - Set 2

Answer each question, then check your answer by looking at those provided on the next page.

1. With an electric blasting (EB) cap, the legwires are connected to lead wires which, in turn, are connected to an electrical blasting _____________.

2. When the switch on the blasting machine is thrown, the _____________ is closed, or completed, and the EB caps wired to it _____________.

3. A single EB cap may detonate when (CHECK THE CORRECT ANSWER):

• A. no voltage flows through the wires.
• B. a current of just 1/4 amp flows through the wires.
• C. the legwires are joined.

4. When the legwires of an EB cap are tied together, a shunt, or a _____________ is formed, thereby preventing current flow.

5. When an EB cap is detonated:

• A. the current flowing through the _____________ wire heats it.
• B. this, in turn, ignites either a _____________ element, or the (primary / base - which?) _____________ charge.
• C. finally, the charge is detonated when the _____________ charge explodes.

6. List at least two sources of extraneous current that must be guarded against.

• A. _____________
• B. _____________

7. Delays in blasting applications may be measured in (CHECK ANY CORRECT ANSWERS):

• A. ms.
• B. milliseconds.
• C. minutes

Answers to Review Questions - Set 2

1. machine
2. circuit, detonate (explode, etc.)
3. B is correct
4. short
5. A. bridge; B. delay, primary; C. base, primary
6. ANY TWO: lightning, stray current from electrical devices and equipment, incorrect (not blasting) testing devices or instruments, static electricity, radio frequency hazards
7. A and B are correct

Review Questions - Set 3

1. The non-electrical detonation system that is especially dangerous is the black powder and blasting _____________ system, which has been outlawed in surface coal mines.

2. One of the more commonly used systems has been detonating _____________ and _____________ connectors.

3. Still another non-electrical system is detonating cord and Primadets, with the Primadets offering either fast delays measured in _____________ and _____________ connectors.

4. In this list of detonating cord sizes, indicate those which will consistently initiate primers.

• A. 4.5 grain
• B. 7.5 grain
• C. 40 grain
• D. 50 grain

5. The various sizes of detonating cord refer to the number of grains of _____________ contained per linear _____________ of cord.

6. One problem with using detonating cord is that it (CHECK THE CORRECT ANSWER):

• A. isn't reliable - often stops before reaching the holes.
• B. may or may not initiate primers, even when the larger sizes are used.
• C. is very noisy, since it contains explosives which explode loudly.

Answers to Review Questions - Set 3

1. fuse, cap
2. cord, ms
3. milliseconds, 1/2
4. C and D are correct
5. explosive, foot
6. C is correct

Review Questions - Set 4: Flash-Thru Non-Electrical Detonating Systems

1. The systems we've been discussing are appropriately called "flash-thru" systems because (CHECK THE CORRECT ANSWER):

• A. they burn up completely as they ignite.
• B. only substances inside them burn, not the tubes themselves.
• C. they can only be ignited with a flame.

2. Of the two major types of non-electrical detonation systems:

• A. Hercudet uses a system of carefully metered _____________ which is pumped into the plastic tubing and Hercudet caps.
• B. Shock Tube works by jarring loose, then igniting, reactive _____________ with which the interior of the plastic _____________ is coated.

3. Flash-thru systems are quiet when they ignite, leading to the name, "_____________" detonators.

4. TRUE OR FALSE: While delays can be used above ground, there are no delays that can be used in the hole with flash-thru systems.

• A. True
• B. False

5. Flash-thru systems (must / need not - which?) _____________ be handled with the same precautions as other detonating systems.

Answers to Review Questions - Set 4

1. B is correct
2. A. gas (OR) gaseous mixture, tubing; B. dust, tubing
3. noiseless
4. B - False - there are in-hole delays for these systems
5. must

Review Questions - Set 5: Explosives

1. Place the letter of the appropriate velocity beside each of the items listed.

2. When using a blasting agent such as ANFO, the primer must be powerful enough to enable the agent to reach its _____________ as quickly as possible to derive the most power from the blasting agent.

3. Whether or not a substance is considered an "explosive" depends upon its _____________ to detonation, not the _____________ at which it detonates.

4. If the primer is not powerful enough (CHECK ANY CORRECT ANSWERS):

• A. the explosion will be too great in the hole.
• B. the blasting agent may not reach its steady state velocity soon enough to provide maximum energy.
• C. the blasting agent may burn instead of detonating.
• D. there will be too much explosive power in the bottom of the hole, not enough toward the top.
• E. it won't set off the cap that's attached to it.

5. Substances which are used to boost the energy of the primer to detonate a column of blasting agent in hole are called boosters, and that's how _____________ are often used.

Answers to Review Questions - Set 5

1. D (1); B (2); B (3); C (4); A (5)
2. steady state velocity (SSV)
3. sensitivity, velocity (IN THIS ORDER)
4. B and C are correct
5. slurries or water gels

Instructions for Remainder of Workbook

The remainder of this workbook is presented in programmed instruction. Remember, answer on your own before you look at the answer provided in the text. This will help you learn faster and remember the material longer.

Ready? Then start with Frame 1, which follows.

The Borehole

Frame 1. The borehole is also called the blast hole or drill hole. Regardless of what it's called in your operation, the borehole is simply the hole that's drilled into overburden (or the coal, when necessary to blast it for removal) for the placement of explosives for _____________.

Frame 2. In this element of our workbook, we'll be using several drawings of a mining pit, overburden, boreholes, and other items pertinent to blasting operations. One such drawing will be standardized as follows:

• The pit is always to the left
• The highwall is the vertical line at the edge of the pit
• Our representations of _____________ will be similar to the one shown here - simple cylinders in the overburden, usually reaching down to the top of the _____________ to be mined.

Frame 3. We'll also use drawings that depict boreholes as if we were above them in a helicopter, looking down upon the area to be blasted. Again, we'll keep the pit to the left. Drawings like these will be standardized throughout this, and the following, workbooks, so you never have to wonder, "where you are." Just remember that, in every instance, the actual _____________ will be to the left of the drawing.

Frame 4. Now, about boreholes: when blasting overburden, boreholes usually extend to the top of the product... or would shatter the coal itself, which is undesirable. In addition, if the borehole doesn't extend to the top of the product. So in our drawings and our discussions, you can assume that the boreholes we discuss will extend from the top of the _____________ to the top of the _____________.

Frame 5. Borehole diameters can range from as small as 1", to as large as 15", or even larger. However, with the types of blasting agents now being used most commonly - ANFO, in particular - a hole that's 6", 10-5/8", 12", or 15" is most practical. In later workbooks, you'll find that the diameter of the hole is important in determining how many pounds or kg of explosives to put into the _____________ for best results.

Frame 6. The diameter of the hole in relation to the amount of explosives to put in... distance of the holes... the exact pattern... these are all subjects that will be covered in later workbooks. For now, remember that:

• A. boreholes generally cut through the _____________ to the top of the _____________.
• B. the usual diameters for boreholes are from _____ to _____ inches.

Overburden & Burden

Frame 7. You're aware that overburden is the amount of material - topsoil, sand, gravel, rock, shale, whatever - that lies on top of the _____________.

Frame 8. But "burden" may be a new term to you. Note that the line representing the highwall, if you were standing in the pit, is also the free face. And the distance from the free face to the first row of boreholes is the _____________.

Frame 9. Now, we can take this one step further, because the area indicated by the arrows is also considered _____________ and it is the distance between the rows of _____________.

Frame 10. So now you know that:

• A. the material that lies on top of the coal in a surface mine is called the _____________ and it must be removed to reach the coal.
• B. the distance from the free _____________ to the first row of holes, as well as the distance between rows of holes, is called the _____________.

Frame 11. Actually, there are three areas, or types of burden, depending upon the point from which it's measured. You'll note that the bottom part of the free face often projects out into the pit, and this part of the face is called the _____________, while the top edge of the free face is called the _____________.

Frame 12. Looking at this situation from the top again, we see that there are three ways to measure and express burden:

• Crest Burden: measured from the top of the face
• Toe Burden: measured from the bottom of the face
• Burden: the distance between rows of holes

And these are the _____________ burden, when measured from the top of the face, the _____________ when measured from the bottom of the face; and, simply, the _____________ when referring to the distance between rows of holes.

Frame 13. Most of the time, we'll refer to burden in general terms, stating "toe" or "crest" burden only when such information is critical. And in those general terms, burden is either the distance from the _____________ to the first row of holes, or the distance between (WHAT?) _____________.

Frame 14. Okay...based on what we've said, label each of the areas indicated in the illustration.

Spacing & Patterns

Frame 15. Spacing is the term applied, quite simply, to the distance between individual holes in a row. In these illustrations, we see two different (and very common) borehole patterns... "square" and "staggered".

Common Borehole Patterns

In each instance, the distances indicated by the arrows and the letter "S" represent the _____________.

Frame 16. With a square pattern, the holes are necessarily (CHECK THE LOGICAL ANSWER):

• A. different distances apart.
• B. the same distances apart, or the pattern wouldn't form squares.

Frame 17. In a later workbook, we'll discuss patterns and spacing in detail. At that time, you'll learn that you don't always shoot toward the free face represented by the pit - it may be toward an area which has already been shot, called "shot ground," but which is not yet removed. This area is called an internal free face in the same sense as the open pit.

How you accomplish these types of shots, and which ones you make, will be covered later, as noted. But remember, the open area into the pit is the free face, and an area that's already shot, but not removed, is called an _____________.

Frame 18. Shooting into an internal free face is sometimes called "shooting in the tight," or "shooting into a buffer." There are often very good reasons for shooting in this manner, and it can effectively shatter the overburden sufficiently for removal. So the areas toward which you may be shooting are called (CHECK ANY CORRECT ANSWERS):

• A. free faces (usually the pit).
• B. internal free faces (shot, but not yet removed, overburden).
• C. shooting in the tight.
• D. shooting into a buffer.

Frame 19. Keep these definitions in mind:

• A. the distance from the free face to the first row of holes is called the _____________.
• B. measured from the top of the pit edge, this is known as the _____________ burden.
• C. measured from the bottom of the highwall to the first row of holes, this distance is known as the _____________ burden.
• D. the distance between rows of holes is also known as the _____________.
• E. the distance between individual holes in a row is called _____________.
• F. two common types of patterns are _____________ and _____________.
• G. and in one of these patterns, both the burden and the spacing are the same - the _____________ pattern.

Buffer Shooting

Frame 20. Look again at the drawing in Frame 17. We've mentioned several terms applied to shooting into shot ground without first digging the previous shot. One of these is buffer shooting. In effect, the area of shot, but not yet dug, ground forms a _____________ between the new blast and the open area beyond the previously shot ground.

Frame 21. This is another, less commonly used, example of the same kind of situation. In this instance, _____________ shooting would occur, and the buffer lies between _____________ and the new area to be shot.

Frame 22. Up to now, all of our discussion has centered around shooting areas in which there's an open pit, or at least a free face in the form of a buffer, into or towards which shooting occurs. Obviously, however, every blasting operation must start somewhere... an initial opening must be blasted so that excavation of the pit can be started. Since such an operation cuts into virgin ground, it's referred to as an opening _____________.

Frame 23. Just how an opening cut is made depends upon the placement and timing of boreholes and the shots in them. These activities will be covered in another module. One such operation involves proper timing of the blasts in the indicated holes to form a sort of "V" of shot ground. Logically, this type of shooting would result in a _____________.

Frame 24. There are other patterns, and other ways to stagger the shots, to form initial openings for a new pit in "virgin" ground. Remember, the objective of an opening "cut" is to (CHECK THE CORRECT ANSWER):

• A. completely fragment an entire field.
• B. provide "relief", in a sense, for a later hole to break toward.

Frame 25. Most of the time, there will be a free face which will provide the necessary relief for ground to be shot. There will already be some place for the overburden to move when it's shot. When a new hole (pit) must be opened, however, a _____________ is made and this must provide the necessary _____________ for subsequent blasts, until the pit is actually opened.

More About Boreholes

Frame 26. In the opening of this part of the text, we noted several facts about drill holes, or blast holes. You learned that they can range widely in size, but are frequently 6" to 15" in diameter, in surface mine operations. For this discussion, we'll refer to blast or drill holes as _____________ or simply "holes."

Frame 27. With especially hard or thick seams of coal, it's sometimes necessary to blast the coal itself (even though just slightly) to loosen it for removal. Coal shooting is done after the overburden - that is, the top of the ground above the coal - to the (CHECK THE CORRECT ANSWER):

• A. bottom of the coal deposit.
• B. top of the coal deposit or seam.

Frame 28. Here are the typical elements of a borehole that is loaded and ready for shooting:

Elements of a Loaded Borehole

Note that an electrical system would call for two wires coming out of the hole, since a complete circuit would have to be made. But with detonating cord or Nonel - a flash-thru detonator, remember - just one line would run into the hole.

• A. Near the bottom of the hole are located the cast _____________ and the _____________; objectives are to initiate the blasting agent to its steady state velocity.
• B. The blasting agent shown in this hole is _____________ and it's indicated in the drawing by a series of dots.
• C. Above the blasting agent is the earth - usually drill cuttings from the hole - that fills the hole, and the term for this material is _____________.
• D. At the very bottom of the hole is dirt and rock that has fallen into the hole after it was drilled, or which was put into the hole on purpose, and this is called _____________.

Frame 29. Keep these factors in mind concerning boreholes:

• A. When the hole is drilled, it must be deep enough - and it may be, until too much dirt and other material, called _____________, fall into it.
• B. To make certain the drilled hole is as deep as it should be, blasting crews usually (CHECK THE BEST ANSWER):
  • (1) measure each hole.
  • (2) assume that the backfill is insignificant, so the hole is deep enough.
• C. Without material on top of the blasting agent, the noise of the explosion will be much greater, so sufficient _____________ must be placed on top of the explosives.

Frame 30. Now look at this hole - it includes information concerning the strata in the area of the blast, with "strata" referring to the layers of material that comprise the overburden.

Decked Borehole Example

Note that there are actually two "shots" to be made in this hole, each intended to fragment a given part of the overburden. These layers of explosives are called _____________ and this method of filling a hole is called _____________.

Frame 31. Whether there are one or more layers of explosives in a hole depends upon the fragmentation desired, the distance from any buildings, and the actual layers, or _____________ of different materials, that comprise the _____________ above the coal.

Frame 32. Now, think about the material used for stemming for a moment. When the blast occurs, the idea is to cause the overburden to fragment or shatter. If the hole is filled with material that is too large, such as frozen chunks or rocks:

• A. those larger items can be blown out of the hole, thereby causing a _____________ hazard.
• B. the shot causes too much _____________.
• C. therefore, material such as crushed stone and drill cuttings are the kinds of material that should be used as _____________ above the blasting agent, and between the _____________ of blasting agent if the hole is decked.

Frame 33. When a hole is shot (the explosives are detonated), one problem that may occur is "backbreak". This is evidenced by cracks in the ground between the last row of holes and the unshot ground. Assume the hole in the drawing has just been shot.

Which area of this illustration would be considered backbreak? _____________

Frame 34. The amount of backbreak generated by a blast depends on many factors. One factor that is under the control of the blaster and has a great effect on backbreak is _____________.

Frame 35. Finally, when the blasting agent (ANFO) is placed in the hole, it must make good contact with the borehole wall. This is called "coupling". The entire column created by the hole should become a column of _____________.

Testing ANFO

Frame 36. Okay...since we've touched, here, upon getting the most out of the blasting agents used in a mine, let's look briefly at a few of the testing methods employed to assure that the explosives (using the term generally, here - "blasting agent" is more accurate) are manufactured properly. As you'll recall from our earlier discussions, there must be just the right combination being _____% ammonium nitrate, and _____% fuel oil.

Frame 37. While ANFO testing is a laboratory process in which you probably won't be involved, you should be aware that the blasting agents you're to use have been tested - at least on a spot-check basis - to be sure they'll do what you expect them to. Here are some of the tests that are commonly run:

Common ANFO Tests

The screen analysis is just what it sounds like - sifting ANFO particles through a screen to check on the size of the individual grains, or _____________ of the blasting agent.

Frame 38. You're aware that the fuel oil content should be about 6% (it can range from 5.7 to 6.3%, by weight). The fuel oil percentage includes other moisture (water) in the ANFO, so subtracting the _____________ content from the fuel oil percent gives a more accurate indication of the percentage of _____________ oil in the blasting agent.

Frame 39. Bulk density, expressed in terms of pounds per cubic foot of ANFO, is another important factor... mainly because the tables you'll use later in determining how many pounds of blasting agent per cubic foot of column, or hole. Forty-eight to fifty-one pounds per cubic foot is the range for industrial grade ANFO - that is, this is the range of the acceptable bulk _____________ of this blasting agent.

Frame 40. Finally, the percent of insoluble matter is tested. You'll recall that, to help keep the prills of ANFO separate, they're sprayed with a light coating of _____________ and this is the _____________ matter to which we're referring here.

Frame 41. So there are relatively simple, inexpensive tests which can be run to check on the blasting agents used in mines - tests which many companies choose not to make, although some do. We've mentioned several of them in this discussion. Name three such tests: _____________, _____________, _____________.

Frame 42. As noted, the tests we're discussing are simple and inexpensive to conduct - especially in light of the alternatives, including waste caused by ineffective blasting agent. Most of the samples that are pulled out for analysis and testing are taken from the point at which the product will be used - that is, right at the _____________ site at the mine.

Frame 43. Other samples are taken as the products are delivered to the mine. If there's a difference in the analysis when these two tests are compared - those taken when the blasting agent arrives from the manufacturer, as compared to samples taken at the blasting site - then, assuming that the ANFO was right when it arrived, there is probably some problem in (CHECK THE LOGICAL ANSWER):

• A. storing and/or transporting the ANFO to the blasting site.
• B. the manufacturing process.
• C. loading the holes.

Frame 44. If the ANFO doesn't arrive at the mine site in proper form (CHECK THE CORRECT ANSWER):

• A. nothing can be done with it.
• B. the mine operator will probably refuse it or send it back.
• C. it doesn't matter, since you can use it anyway.

Frame 45. And, obviously, if the ANFO or other blasting agent was received in good order from the manufacturer, but samples at the blasting site show some sort of problem (too much moisture, coagulation of particles, too little fuel oil, etc.), then action will be taken at the mine to improve or correct any problems that exist in _____________ or handling the blasting agent.

Frame 46. The point of this section has been to indicate to you some of the precautions taken to assure the efficiency and safety of the products you use in blasting operations. The ultimate responsibility for safety rests, of course, with those of us who are directly involved in the drilling and blasting process. Use explosives as they're intended, and they'll do the job for us; use them improperly - and they can really do a job on us!

Conclusion

In the remaining workbooks in this series, you'll learn a great deal more about blasting and explosives - how they're detonated, how to determine appropriate loads, decks, patterns, etc., for specific applications, and so on.

Throughout the entire series, we'll be stressing safety, as well as efficiency, in using the various explosives commonly found at mine sites. You'll soon discover that there's no one way that's always the best... different types of explosives, detonating systems, drilling equipment, etc., might be best suited to specific situations. But the one thing that always pertains is safety...and while we won't overdo it, please remember that drilling and blasting operations require even greater efforts than usual to prevent accidents and avoid errors.

We hope you've enjoyed this method of study. Good luck in applying what you've learned - and in your efforts towards performing blasting in a safe, efficient manner!

Test - Workbook 1

Introduction to Blasting and Explosives

1. A detonator is used for what purpose?

• A. To cut down on noise and protect the environment.
• B. To initiate or detonate explosives and blasting agents.
• C. As a safety device.

2. What are prills?

• A. Small spheres of ammonium nitrate.
• B. Types of blasting caps.
• C. A mixture of blasting caps.

3. A combustible additive is included in blasting agents for the purpose of:

• A. Providing more bulk.
• B. Adding energy in the form of heat.
• C. Preventing premature explosion.

4. What provides the impact to initiate the blasting agent?

• A. A primer.
• B. A detonator.
• C. Slurry.

5. For optimum results ANFO should contain:

• A. 94% AN and 6% FO.
• B. 50% AN and 50% FO.
• C. 4% AN and 96% FO.

6. A single EB cap detonates when:

• A. The legwires are joined.
• B. A current as low as 1/4 amp flows through the wires.
• C. It strikes a hard surface.

7. Tying the legwires of an EB cap together prevents detonation, because:

• A. A short is formed in the circuit.
• B. The circuit is delayed.
• C. The current is shunted back to the blasting machine.

8. An EB cap can be detonated by which of the following:

• A. Lightning or stray current from electrical equipment.
• B. Incorrect testing devices or instruments.
• C. Both of the above.

9. Legally, how many milliseconds (ms) are required between shots for them to be considered separate shots?

• A. 1 ms.
• B. 8 ms.
• C. 10 ms.

10. Various sizes of detonating cord refer to what?

• A. Grains of explosives per linear foot of cord.
• B. Diameters of the cord in inches.
• C. Grains of explosives per linear inch of cord.

11. What is one problem with using detonating cord?

• A. It often stops burning before reaching the hole.
• B. It will not initiate primers of large sizes.
• C. Because it contains explosives, it is very noisy.

12. A hole is considered ready for blasting when:

• A. The blasting agent is in place.
• B. Detonating cord is attached to the blasting agent.
• C. The blasting agent, primer, and cap or cord are in position.

13. The two types of electric detonation systems are:

• A. Instant and delay.
• B. Cap and cord.
• C. Mechanical and hand-operated.

14. The heat and impact needed to ignite a flash-thru detonator are supplied by:

• A. A large explosion, such as that provided by a blasting cap.
• B. Appropriate lengths of detonating cord.
• C. A small explosion, such as that provided by a primer from a shotgun shell.

15. Lightning and static electricity are important to blasting operations because they are:

• A. Sources of extraneous current.
• B. A constant "shock" hazard.
• C. Excellent sources of energy, when properly channelled.

16. The borehole is usually drilled into the overburden down to the:

• A. Pit wall.
• B. Strata.
• C. Coal.

17. In relation to the coal, the overburden is actually located:

• A. All around.
• B. In the second and third strata.
• C. On top.

18. Two types of burden are:

• A. Toe and pit.
• B. Square and diamond.
• C. Toe and crest.

19. Two common types of borehole patterns are:

• A. Diamond and diagonal.
• B. Square and diamond.
• C. Square and staggered.

20. Burden - the distance from the free face to the first row of boreholes - also refers to the distance:

• A. To the next free face.
• B. To the coal.
• C. Between rows of holes.

21. The function of a relief is to provide:

• A. A V-cut into the coal.
• B. A place for overburden to go.
• C. A deeper borehole.

22. Shot material that ends up lying on the pit floor is sometimes called:

• A. Burden.
• B. A pile of slag.
• C. A muck pile.

23. Above the blasting agent in a hole is an important material usually made up of earth, clay and gravel. It is called:

• A. Muck.
• B. Backfill.
• C. Stemming.

24. The layers of material in the overburden are called:

• A. Strata.
• B. Decks.
• C. Columns.

25. The practice of placing layers of explosives in the hole for each layer of overburden is called:

• A. Layering.
• B. Decking.
• C. Stemming.

26. An important factor that affects backbreak is:

• A. Amount of stemming.
• B. Consistency of the slurry.
• C. Diameter of the borehole.

27. "Hole coupling" refers to:

• A. Connecting holes together by a horizontal bore through the burden.
• B. Filling the entire borehole diameter with explosives or blasting agent.
• C. Drilling holes in pairs to assure even depth.

28. If the primer is not powerful enough:

• A. There will be too much explosive power in the bottom of the hole.
• B. It may not have enough power to initiate the ANFO.
• C. It won't set off the cap that is attached to it.

29. Which of the following elements is not necessarily needed for a hole to be ready to shoot?

• A. Daylight.
• B. Stemming.
• C. Blasting agent.

30. Hercudet and Nonel are:

• A. Two major non-electrical detonation systems.
• B. Two types of prills used to ignite ANFO.
• C. The two major electrical detonation systems.

Answer Key