DDEPATMENT OF MINING ENGINEERING

INTRODUCTION:- What are explosives? An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An explosive charge is a measured quantity of explosive material, which may either be composed solely of one ingredient or be a mixture containing at least two substances. The potential energy stored in an explosive material may, for example, be

 chemical energy, such as nitro glycerine or grain dust

DDEPATMENT OF MINING ENGINEERING  pressurized gas, such as a gas cylinder or aerosol can

 nuclear energy, such as in the fissile isotopes uranium-235 and plutonium-239

Explosive materials may be categorized by the speed at which they expand. Materials that detonate (the front of the chemical reaction moves faster through the material than the speed of sound) are said to be "high explosives" and materials that deflagrate are said to be "low explosives". Explosives may also be categorized by their sensitivity. Sensitive materials that can be initiated by a relatively small amount of heat or pressure are primary explosives and materials that are relatively insensitive are secondary or tertiary explosives. A wide variety of chemicals can explode; a smaller number are manufactured specifically for the purpose of being used as explosives. The remainder are too dangerous, sensitive, toxic, expensive,

DDEPATMENT OF MINING ENGINEERING unstable, or prone to decomposition or degradation over short time spans.

DDEPATMENT OF MINING ENGINEERING HISTORY:- The use of explosives in mining goes back to the year 1627, when gunpowder was first used in place of mechanical tools in the Hungarian (now Slovak) town of Banská Štiavnica. The innovation spread quickly throughout Europe and the Americas. The standard method for blasting rocks was to drill a hole to a considerable depth and deposit a charge of gunpowder at the further end of the hole and then fill the remainder of the hole with clay or some other soft mineral substance, well rammed, to make it as tight as possible. A wire laid in the hole during this process was then removed and replaced with a train of gunpowder. This train was ignited by a slow match, often consisting simply of brown paper smeared with grease, intended to burn long enough to allow the person who fires it enough time to reach a place of safety. The uncertainty of this method led to many accidents and various measures were introduced to

DDEPATMENT OF MINING ENGINEERING improve safety for those involved. One was replacing the iron wire, by which the passage for the gunpowder is formed, with one of copper. Another was the use of a safety fuse. This consisted of small train of gunpowder inserted in a water- proof cord, which burns at a steady and uniform rate. This in turn was later replaced by a long piece of wire that was used to deliver an electric charge to ignite the explosive. The first to use this method for underwater blasting was Charles Pasley who employed it in 1839 to break up the wreck of the British warship HMS Royal George which had become a shipping hazard at Spithead. An early major use of blasting to remove rock occurred in 1843 when the British civil engineer William Cubitt used 18,000 lbs of gunpowder to remove a 400 foot high chalk cliff near Dover as part of the construction of the South Eastern Railway. About 400,000 cubic yards of chalk was displaced in an exercise that it was estimated

DDEPATMENT OF MINING ENGINEERING saved the company six month time and £7,000 in expense. While drilling and blasting saw limited use in pre- industrial times using gunpowder (such as with the Blue Ridge Tunnel in the United States, built in the 1850s), it was not until more powerful (and safer) explosives, such as dynamite (patented 1867), as well as powered drills were developed, that its potential was fully realised. Drilling and blasting was successfully used to construct tunnels throughout the world, notably the Fréjus Rail Tunnel, the Gotthard Rail Tunnel, the Simplon Tunnel, the Jungfraubahn and even the longest road tunnel in the world, Lærdalstunnelen, are constructed using this method. In 1990, 2.1 billion kg of commercial explosives were consumed in the United States (12 m3 per capita), representing an estimated expenditure of 3.5 to 4 billion 1993 dollars on blasting. In this year the Soviet Union was the leader in total volume with 2.7 billion kg of explosives consumed (13

DDEPATMENT OF MINING ENGINEERING m3 per capita), and Australia had the highest per capita explosives consumption that year with 45 m3 per capita.

DDEPATMENT OF MINING ENGINEERING MODERN EXPLOSIVES USED IN MINING INDUSTRY 1. NONEL Nonel is a shock tube detonator designed to initiate explosions, generally for the purpose of demolition of buildings and for use in the blasting of rock in mines and quarries. Instead of electric wires, a hollow plastic tube delivers the firing impulse to the detonator, making it immune to most of the hazards associated with stray electric current. It consists of a small diameter, three-layer plastic tube coated on the innermost wall with a reactive explosive compound, which, when ignited, propagates a low energy signal, similar to a dust explosion. The reaction travels at approximately 6,500 feet/s (2,000 m/s) along the length of the tubing with minimal disturbance outside of the tube. The design of nonel detonators incorporates patented technology, including the Cushion Disk

DDEPATMENT OF MINING ENGINEERING (CD) and Delay Ignition Buffer (DIB) to provide reliability and accuracy in all blasting applications. Nonel was invented by the Swedish company Nitro Nobel in the 1960s and 1970s, under the leadership of Per-Anders Persson, and launched to the demolitions market in 1973. (Nitro Nobel became a part of Dyno Nobel after being sold to Norwegian Dyno Industries AS in 1986.) Nonel is a contraction of "non-electric". The hookup of the Nonel (also called the shock tube) system is similar in some respects to the detonating cord system. The cap used in the system is higher strength than most electric blasting caps. Instead of leg wires, a single hollow tube protrudes from the cap (fig. 43). The Nonel tube has a thin coating of reactive material on its inside surface, which detol'!ates at a speed of 6,000 fps. This is a very mild dust explosion that has insufficient energy to damage the tube. Several varia· tions of the Nonel system can be used, depending on the blasting situation. In addition to the Nonel tube-cap

DDEPATMENT OF MINING ENGINEERING assembly, system accessories include noiseless trunklines with built-in delays, noiseless lead-in lines, and millisecond delay connectors for detonating cord trunklines. One Nonel system for surface blasting uses a None I Primadet in each blasthole with 25- to 60-gr/ft detonating cord as a trunkline. The Nonel cap used in this system is factory crimped to a 24-in length of shock tube with a loop in the end (fig. 44). The caps are available in a variety of millisecond delay periods. A 7 .5-gr detonating cord down line is attached to the loop with a double-wrapped square knot. The 7.5-gr detonating cord extends out of the borehole. This downline will not disrupt a column charge of blasting agent but it may initiate dynamite and other cap-sensitive products. As a precaution, 7.5-gr to 7.5-gr con· nections should never be made, because propagation from one cord to the other is not dependable. Since the force of the shock tube detonation is not strong enough to disrupt the tube, it will not initiate high explosives. A 25· to 60-gr

DDEPATMENT OF MINING ENGINEERING trunkline is used in this system with a double clove hitch used for downline· to-trunkline connections. The delay systems used with this method of initiation are the same as those discussed in the "Detonating Cord Initiation" section. They include in-hole cap delays and surface delay connectors. In some cases this system creates an exCessive amount of airblast and noise. To prevent this, the detonating cord trunkline can be replaced by an electric blasting cap circuit with a cap connected to each downline, or a noiseless Nonel trunkline can be used. The noiseless Nonel trunkline is employed as follows. First, each hole is primed and loaded. The downline should be an 18-gr or larger detonating cord. A 7 .5-gr downline can be used if a 25-gr pigtail is used at the top end, tied into the connector block. The noiseless trunkline delay unit consists of a length of shock tube, 20 to 60ft in length, with a quick connecting sleeve on one end and a plastic block containing a millisecond delay blasting cap (delay assembly) on the other end, and

DDEPATMENT OF MINING ENGINEERING a tag denoting the delay period (fig. 45). The delay may be from 5 to 200ms. The sleeve is attached to the initial hole to be fired and the shock tube is extended to the next hole in sequence. The downline from this next hole is connected to the plastic block containing the delay cap, using abo.uHTirKlf cord at the end of the down line. Another delay unit is selected and the sleeve is attached to the downline below the plastic block. The shock tube is extended to the next hole, where the delay assembly is connected to the downline. The process is repeated until all the holes are connected.

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2. Detonating Cord Detonating cord (also called detonation cord, detacord, det. cord, detcord, primer cord or sun cord) is a thin, flexible plastic tube usually filled with pentaerythritol tetranitrate (PETN, pentrite). With the PETN exploding at a rate of approximately 6400 m/s, any common length of detonation cord appears to explode instantaneously. It is a high- speed fuse which explodes, rather than burns, and is suitable for detonating high explosives. The velocity of detonation is sufficient to use it for synchronizing multiple charges to detonate almost simultaneously even if the charges are placed at different distances from the point of initiation. It is used to reliably and inexpensively chain together multiple explosive charges. Typical uses include mining, drilling, demolitions, and warfare."Cordtex" and "Primacord" are two of

DDEPATMENT OF MINING ENGINEERING many trademarks which have slipped into use as a generic term for this material. As a transmission medium, it can act as a downline between the initiator (usually a trigger) and the blast area, and as a trunkline connecting several different explosive charges. As a timing mechanism, detonation cord detonates at a very reliable rate (about 7,000–8,000 m/s), enabling engineers to control the pattern in which charges are detonated. This is particularly useful for demolitions, when structural elements need to be destroyed in a specific order to control the collapse of a building. While it looks like nylon cord, the core is a compressed powdered explosive, usually PETN (pentrite), and it is initiated by the use of a blasting cap. Detonation cord will initiate most commercial high explosives (dynamite, gelignite, sensitised gels, etc.) but will not initiate less sensitive blasting agents like ANFO on its own. 25 to 50 grain/foot (5.3 to 10.6 g/m) detonation cord has approximately the same initiating power as a #8

DDEPATMENT OF MINING ENGINEERING blasting cap in every 2 to 4 inches (5 to 10 cm) along its entire length. A small charge of PETN, TNT, or other explosive booster is required to bridge between the cord and a charge of insensitive blasting agent like ANFO or most water gels. Low-yield detonating cord can be used as a precision cutting charge to remove cables, pipes, wiring, fiber optics, and other utility bundles by placing one or more complete wraps around the target. Detonation cord is used in commercial boilers to break up clinkers (solidified coal ash slag) adhering to tube structures. Also a vertical centered cord being lowered into the water of a drilled well can remove any clogging that obstructs water flow. Higher-yield detonating cord can be used to cut down small trees, although the process is very uneconomical compared to using bulk explosive, or even a chainsaw. High-yield detonating cord placed by divers has been used to remove old dock pilings

DDEPATMENT OF MINING ENGINEERING and other underwater obstructions. Creating a slipknot from detonating cord yields a field- improvised device that can be quickly employed to cut a locked doorknob off a door. Detonation cord can be taped in several rings to the outline of a military man-sized target and detonated, breaching a man-sized hole into wooden doors or light interior walls. Detonating cord is also employed directly in building demolition where thin concrete slabs need be broken via channels drilled parallel to the surface, an advantage over dynamite since a lower minimum of explosive force may be used and smaller diameter holes are sufficient to contain the explosive. Anything much more substantial than these uses requires the use of additional explosives.

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DDEPATMENT OF MINING ENGINEERING

DDEPATMENT OF MINING ENGINEERING 3. Emulsion Explosive EMULITE is an emulsion explosive. It consists of small droplets of ammonium nitrate solution, tightly packed in a mixture of oil and wax. Looked at through a microscope, its structure resembles that of a honeycomb. The thickness of the oil and wax membranes separating the droplets is less than one tenthousandth of a millimetre. This involves an extremely large contact area between the fuel-oil and wax and the oxidizer-ammonium nitrate. As a result very rapid and complete explosive combustion is obtained. The oil and wax membrane also protects every droplet of ammonium nitrate and makes the explosive highly water resistant. By adding "hot spots" in the form of small hollow glass spheres (microspheres) or air bubbles the sensitivity of the emulsion can be varied. The hot spots, which are only one tenth of a millimetre m diameter, act

DDEPATMENT OF MINING ENGINEERING as density gradients in the explosive and effectively transfer shock wave energy to heat and enhance the rapid explosive combustion of the emulsion. EMULITE contains no raw materials classified as explosives and becomes itself an explosive only in the final stage of production. EMULITE is extremely insensitive to accidental initiation through friction, fire or other mechanical stimuli. It is therefore extremely safe to manufacture and handle than any other commercial explosive. Production of EMULITE can be either centralized or decentralized depending on for instance consumption volumes, regulations etc. Centralized production comprises besides manufacturing of tailor-made explosives, also a possibility to produce a non-explosive emulsion matrix, which can be sensitized on site by chemical gassing or by microspheres. Since production of EMULITE is very

DDEPATMENT OF MINING ENGINEERING safe, the manufacturing unit can be located close to worksite. No explosive needs to be stored as loading of the truck is integrated with production of the explosive. This implies storing and transport of non-explosive raw materials only. Manufacturing units are available with production capacities from 1,200 tonnes per annum. They are built up by container modules adaptable for a wide variety of applications. Nitro Nobel has designed two basic types of bulk truck bodies for transport and charging of emulsion explosives. The EMULITE Pump Truck body is suitable for straight EMULITE or plant-mixed EMULAN®. The EMULITE Multi Truck body is designed for: - Pumping of straight EMULITE; Mixing and pumping of EMULAN; Mixing and augering of EMULAN and ANFO. Both types can pump explosive into even water-filled drillholes. Pumping starts

DDEPATMENT OF MINING ENGINEERING with the charging hose at the bottom of the hole and the water, if any, is displaced. The bodies are available with different load capacities to fit demands of explosive per shift etc. EMULAN is a bulk explosive produced by mixing PRILLIT (ANFO) with an emulsion. The addition of emulsion will give a more powerful explosive than PRILLIT itself with higher bulk strength and improved water resistance. The proportions of emulsion and ANFO can be varied to produce a range of products to meet different blasting conditions. A mixture of 75 per cent EMULITE and 25 per cent PRILLIT is named EMULAN 7500, a mixture of 40/60 EMULITE/PRILLIT is named EMULAN 4 000 etc. Generally the following is valid for EMULAN: a) EMULAN with up to 40 per cent EMULITE matrix can be augered into dry holes. Poor water .resistance. b) EMULAN 4000-6000 can be

DDEPATMENT OF MINING ENGINEERING augered into wet holes but dewatering is necessary before loading. Average to good water resistance. c) EMULAN with more than 60 per cent EMULITE matrix is pump able and can be loaded into water filled holes. Excellent water resistance. Velocity of detonation measurements have been used to control the water resistance of EMULAN 7500. VOD measurements in the hole diameter 9 7/8" shows that the VOD is stable 5,300 - 5,500 m/s, even when the explosive has slept for one month in wet holes.

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DDEPATMENT OF MINING ENGINEERING

4. HERCUDET The hookup of the Hercudet (also called gas detonation) blasting system resembles a plumbing system. The cap is higher strength than most electric blasting caps. Both millisecond and long delays are available. Instead of leg wires, two hollow tubes protrude from the cap. The cap may be used in a primer in the hole or at the collar of the hole for initiating detonating cord downlines. In

DDEPATMENT OF MINING ENGINEERING addition to the Hercudet cap, system accessories include duplex trunkline tubing, single trunkline tubing; various types of tees, connectors, ells, and manifolds for hooking up the system; circuit testers; a gas supply unit containing nitrogen, oxygen, and fuel cylinders; and a blasting machine. The system functions by means of the low-energy detonation of an explosive gas mixture introduced into the hollow tubes. This low-energy detonation does not burst or otherwise affect the tubing. For surface blasting, a cap with 4-in leads is used (fig. 37). For surface initiation of detonating cord downlines this cap is connected directly to the trunkline tubing by means of the reducing connector that is factory-attached to the cap. The reducing connector is needed because the trunkline tubing is larger than the capline tubing. A special plastic connector is used to attach the cap to the

DDEPATMENT OF MINING ENGINEERING detonating cord downline. When in-hole initiation is desired, the 4-in cap leads are extended by connecting them to an appropriate length of larger diameter duplex trunkline tubing (fig. 38). This trunkline tubing is cut squarely, leaving 2 to 3ft of tubing extending from the borehole collar, and a plastic double ell fitting is inserted. Trunkline tubing is later connected hole to hole. Figure 39 shows typical Hercudet connections for surface blasting with in-hole delays. Not all cast primers have tunnels large enough to accept the Hercudet duplex tubing. This should be checked before purchasing cast primers. When using cartridge primers with Hercudet, the tubing is taped to the primer, not half-hitched to Jt. For undergrouna otasting, millisecond and long period delay caps are available with 16· to 24-ft lengths oftubing. The tubes are cut to the appropriate length by the blaster. The tubes are then connected in series or series-in-parallel,

DDEPATMENT OF MINING ENGINEERING similar to electric cap circuits, using capline connectors and manifolds instead of the wire splices used in electric blasting. In all Hercudet blasting circuits, the tubing at the end of each series is vented to the atmosphere. The tubing network should be kept free of kinks. When the circuit has been hooked up, a length of trunkline tubing is strung out to the firing position, similar to the firing line in an electric system. Atthis time nitrogen from the gas supply unit is tumed on and the pressure test module is used to check the integrity of the tube circuit (fig. 40). The tester uses flow and/or pressure checks to locate blockages or leaks in the circuit. As with a galvanometer in electric blasting. Each series should be checked individually, followed by a check of the entire system. The Hercudet tester is a smaller unit than the pressure test module and uses a hand air pump to test single boreholes or small hookups. If a plug or a leak is detected when

DDEPATMENT OF MINING ENGINEERING checking the completed circuit, the circuit is broken into segments and checked with the Hercudet tester or pressure test module.

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5. Delay Detonator In this type of detonator, the base charge detonates within a millisecond or two after the external energy enters the detonator. However, in most types of blasting, time intervals are required

DDEPATMENT OF MINING ENGINEERING between the detonation of various blastholes or even between decks within a blasthole. To accomplish this, a delay element containing a burning powder is placed immediately before the priming charge in the detonator. Figure 18 shows a delay detonator. There are three basic delay senes; slow or tunnel delays, fast or millisecond delays, and coal mine delays for use in underground coal mines. For all commercial delay detonators, the delay time is determined by the length and burning rate of the delay powder column. As a result, slow delay caps may be quite long in dimension whereas lower period millisecond delays are shorter. Although the timing of delay detonators is sufficiently accurate for most blasting needs, these delays are not precise, as indicated by recent research. Recently, however, manufacturers' tolerances for some delay caps have been tightened. It is important to use the manufacturer's

DDEPATMENT OF MINING ENGINEERING recommended current level to initiate electric blasting caps. Current levels above or below the recommended firing level can further increase the scatter in delay cap firing times. Extremely high currents can speed up delay firing times. Near the minimum firing current, delays can become extremely erratic. Slow delays are useful underground under tight shooting conditions where it is essential that the burden on one hole moves before a subsequent hole fires. This situation may occur In tunnels, shafts, underground metal- nonmetal mines, and in trenching. Slow delays are available with all initiation systems except surface detonating cord and delay cast primers. Delay intervals are typically 0.5 to 1 sec. Millisecond delays are the most commonly used delays and are useful wherever the tight conditions previously mentioned are not present. Millisecond delays provide improved fragmentation, controlled throw,

DDEPATMENT OF MINING ENGINEERING and reduced ground vibration and airblast, as compared with simultaneous firing. They are availablewith all initiation systems. In millisecond detonators, delay intervals are 25 to 50 ms in the lower periods and are longer in the higher periods. In detonating cord delay connectors, the delay may be as short as 5 ms. Coal mine delays are a special series of millisecond delays. Since only electric initiation systems are permissible in underground coal mines, coal mine delays are available only with electric initiators. Delay intervals are from 50 to 100 ms, with instantaneous caps being prohibited. Coal mine delay caps always utilize copper alloy shells and iron leg wires. Iron leg wires are also available optionally with ordinary electric detonators and are used primarily to facilitate magnetic removal of the wires from the muck pile, such as In trona and salt mines.

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DDEPATMENT OF MINING ENGINEERING

DDEPATMENT OF MINING ENGINEERING CONCLUSION:- From results that has obtained at Drainage Level, Truck Haulage Level, Extraction Level, and Undercut Level, can be concluded that emulsion application produced some under break and few of over break. However, ANFO application produced more over break than emulsion and some under break. The impact of over break is excessive usage of ground support and the impact of under break is doing blasting again that’s mean disadvantageous and also dangerous in geotechnical side. The advantages of ANFO are inexpensive or economic, easy to create, safe handling. However, ANFO also has disadvantages i.e. low density and density can’t be adjusted, not water resistance, so using cartridge emulsion at lifter hole, and usually leaving detonating cord at perimeter hole. Afterwards, the advantages of emulsion are water resistance, safe

DDEPATMENT OF MINING ENGINEERING handling, not using detonating cord at perimeter hole, and density can be adjusted depend the type of gasser used. However, the disadvantages of emulsion are expensive, emulsion consumption more than ANFO because have to do QA (Quality Assurance) and QC (Quality Control) before loading at blast hole, and not easy to create. Thereby, the explosives that effective to use in blasting development at underground Deep Mill Level Zone (DMLZ) PT. Freeport Indonesia is emulsion. However, it should be redesign drill pattern and blasting geometry for emulsion. To use emulsion in blasting development UG DMLZ PTFI, be recommended to redesign drill pattern and blasting geometry using radial crack method.