Blasting Reviewer.docx

BLASTING TERMINOLOGIES - an airborne shock wave resulting from the detonation of explosive. - a system that uses 10,000 lb/in2 compressed air to break undercut coal. It will not ignite a gassy or dusty atmosphere. - a system for priming blasting agents where a core of priming materi...

BLASTING TERMINOLOGIES - an airborne shock wave resulting from the detonation of explosive. - a system that uses 10,000 lb/in2 compressed air to break undercut coal. It will not ignite a gassy or dusty atmosphere. - a system for priming blasting agents where a core of priming materials extends through most or all of the blasting agent charge depth. - most commonly used oxidizer in explosive and blasting agents. - an explosive material consisting of a mixture of ammonium nitrate and fuel oil. It is commonly used blasting agent. - rock broken beyond the limits of the last row of holes. - the top holes in tunnel/drift round. - the main explosive charge in a detonator. - the detonation of explosives to break rock. - the area near a blast within the influence of flying rock or concussion. - a hole drilled in rock or other material for the placement of explosives. - a detonator initiated by safety fuse. - the circuit used to fire one or more blasting caps. - a crew whose job is to load explosive charge. - any machine built expressly for the purpose of energizing blasting caps or other types of initiators. - a method of breaking a boulder with explosives placed in a small borehole. - a hole drilled into a boulder to allow the placement of a small charge to break a boulder. - a unit of explosive or blasting agent used for perpetuating or intensifying an explosive reaction. - portion of a borehole that remains relatively intact after having been charged with explosive and fired. It may contain unfired explosive & hazardous. - a property of explosive roughly equivalent to detonation velocity. An explosive with a high detonation velocity has high brisance. - strength of explosive per unit volume. - the distance to the nearest free or open face from an explosive charge. - length of safety fuse w/ an attached blasting cap - a cartridge of cap-sensitive explosive specifically designed to transmit detonation to other explosives & which contains a detonator. - a rigid or semi-rigid container of explosive or blasting agent of a specified length or diameter. - a cast unit of explosive, usually pentolite or composition B, commonly used to nitiate detonation in a blasting agent. - the process of enlarging a portion of blasthole (usually the bottom) by firing a series of small explosive charge. - the distance from the top of the powder column to the collar of the blasthole, usually filled with stemming. - a long, continuous charge of explosive or blasting agent in a borehole. - techniques used to control overbreak & produce competent final excavation wall. - the practice of driving tunnels horizontally into a rock face at the foot of the shot. Explosives are loaded into these tunnels and used where it is impractical to drill vertically. - a blasting technique used to produce competent slopes where holes, are fired after the main charge, have a reduced spacing and employ decouple charges. - an arrangement of holes used in U/G mining and tunnel blasting providing a free face for the remainder of the round to break. - a portion of a column of explosives that has failed to detonate owing to bridging or a shifting of the rock formation, often due to an improper delay system. - small charge/portion of a hole loaded with explosives & separated from other charges by stemming or an air cushion. - the use of cartridged products significantly smaller in diameter than the borehole. Decoupled charges are normally not used except in cushion blasting, smooth blasting, pre-splitting, and other situations where crushing is undesirable. - a subsonic but extremely rapid explosive reaction accompanied by gas formation and borehole pressure but w/o shock. - the use of delay detonators or connectors that cause separate charges to detonate at different times rather than simultaneously. - a non-electric, short-interval delay device for use in delaying blasts that are initiated by detonating cord. - an electric or non-electric detonator with a built-in element that creates a delay between the input of energy and the explosion of the detonator. - the weight per unit volume of explosive expressed as cartridge count or g/cm3. - a plastic covered core of high-velocity explosive, usually PETN, used to detonate explosives. The plastic covering is covered with various combinations of textiles and waterproofing. - a supersonic explosive reaction where a shock wave propagates through the explosive accompanied by chemical reaction that furnishes energy to sustain stable shock wave propagation. - the head-on pressure created by the detonation proceeding down the explosive column. - a device containing a detonating charge that is used to initiate an explosive. It includes blasting caps, electric blasting caps and non-electric instantaneous or delay blasting caps. - the line of detonating cord in the borehole that transmit energy from the trunkline down the hole to the primer. - also known as "headache ball". An iron or steel weight held on a wire rope that is dropped from a height into large boulders to break them into smaller fragments. - the high explosive invented by Alfred Nobel. Any high explosive where the sensitizer is nitroglycerin or a similar explosive oil. - an atmospheric disturbance of intense electrical activity presenting a hazard in all blasting activities. - an explosive material containing substantial amounts of oxidizers dissolved in water droplets surrounded by an immiscible fuel. - a thermochemical process where mixtures of gases, solids or liquids react with the almost instantaneous formation of gas pressure and sudden heat release. - any chemical mixture that reacts at high velocity to liberate gas and heat causing a very high pressure. It is a solid or liquid substance or mixture of substances which, on the application of a suitable stimulus to a small portion of the mass, is converted in a very short interval of time into other more stable substances, largely or entirely gaseous, with the development of heat and high pressure. - this includes dynamite and other high explosives, slurries, water gels, emulsions, blasting agents, black powder, pellet powder, initiating explosives, detonators, safety fuses, squibs, detonating cord, igniter cord, and igniter. - also called "ammonia dynamite that derives the major portion of its energy from ammonium nitrate. - a rock surface exposed to air. Also called as "free face" which provides the rock with room to expand upon fragmentation. - a line, often permanent, extending from the firing location to the electric blasting cap circuit. Also called as "lead wire". - rock that is propelled through the air from a blast. Excessive fly rock may be caused by poor blast design or unexpected weak zones in the rock. - the breaking of rock with or without movement of the broken pieces. - the extent that a rock is broken into pieces by blasting. - an explosive or blasting agent that has a gelatinous consistency. - a highly water-resistant dynamite with a gelatinous consistency. Gun powder, blasting powder (BP) -- a low explosive consisting of potassium or sodium nitrate, charcoal, and sulfur. It has low energy, poor fume quality, and extreme sensitivity to sparks. - the detonation of an explosive charge after the designed firing time. - a term used to express the frequency of ground vibrations and airblast. One hertz is one cycle per second - the bench or ledge on edge of a surface excavation. - a cordlike fuse that burns progressively along its length with an external flame at the zone of burning and is used for lighting a series of safety fuses in sequence. - the act of detonating a high explosive by means of a cap, mechanical device, or other means. - a system of loading ANFO into small blastholes where the ANFO is sucked from a container and blown into the hole at high velocity through a loading hose. - a slot cut in a coal or soft rock face by a mechanical cutter to provide a free face for blasting. - the wire connecting the electrical power source with the leg wires or connecting wires of a blasting circuit. - the bottom holes in a tunnel or drift round. - an overbreak control method where a series of closely spaced holes are drilled at the perimeter of the excavation and the holes are not loaded with explosive. - an explosive where the speed of reaction is slower than the speed of sound, such as black powder. - a building, structure or container specially constructed for storing explosives, blasting agents, detonators, or other explosive materials. - a covering placed over a shot to hold down flying material usually made of woven wire cable, rope or scrap tires. - a charge that has failed to fire as planned and still contain explosives. - a pile of broken rock or dirt that is to be loaded for removal. - a charge of explosive fired in contact with surface of a rock usually covered with a quantity of mud, wet earth or similar substance with no borehole is drilled. - the explosive oil originally used as the sensitizer in dynamites, C3H5(ONO2)3 - a liquid compound used as a fuel in two-component (binary) explosives and as rocket and dragster fuel. - a liquid fuel that can be combined with pulverized ammonium nitrate prills to make a dense blasting mixture. - a solid explosive similar to nitroglycerin used as the base of "nonheadache" powders. - excessive breakage of rock beyond the desired excavation limit. - inducing a velocity higher than the steady state velocity in a powder column by the use of a power primer. It is a temporary phenomenon, and the powder quickly assumes its steady state velocity. - an ingredient in a explosive or blasting agent that supplies oxygen to combine with the fuel to form gaseous or solid detonation products. - a drillhole plan laid out on a face or bench to be drilled for blasting. - black powder pressed into 2-inch long, 1 ¼ - to 2-inch diameter cylindrical pellets. - a military explosive compound used as the core load of detonating cord and base charge of blasting caps. - a mixture of PETN and TNT used as a cast primer. - those explosives that been approved by MGB for use in U/G coal mines. - one of a variety of machine powered by compressed air used to load bulk blasting agents or cartridged water gels. - a strong, nonconductive portable container equipped with a lid used at blasting sites for temporary explosive storage. - a ratio between the amount of powder loaded and the amount of rock broken. - a survey used to determine whether subsequent blasting causes damage to the structures. - charge that detonates before intended. - controlled blasting where decoupled charges are fired in closely spaced holes at the perimeter of excavation & holes are fired before the main blast. - a small porous sphere of ammonium nitrate capable of absorbing more than 6% by weight of fuel oil. - the main blast executed to sustain. - an explosive mixture sensitive to spark, flame, impact, or friction used in a detonator to initiate the explosion. - a cartridge of cap-sensitive explosive used to initiate other explosives or blasting agents and that contains a detonator. - the detonation of explosive charges by an impulse from a nearby explosive charge. - the use of closely spaced, sensitive charges. The shock from the first charge propagates through the ground, setting off the adjacent charge and so on. - an explosive that normally deflagrates and is used for propulsion. - a cartridge of HE incorporating a detonating device. This is the key element of a charge of explosive. - the quantity of rock or length of advance excavated by a blast round. - holes adjacent to the cut holes used to expand the opening made by the cut holes. - the holes at the sides of a tunnel or drift round that determine the width of the opening. - a group or set of blast holes used to produce a unit of advance in U/G headings. - a core of potassium nitrate black powder, enclosed in a covering of textile and waterproofing, used to initiate a blasting cap or black powder charge. - an ingredient used in explosive compounds to promote greater ease in initiation or propagation of the detonation reaction. - a pressure pulse that propagates at supersonic velocity. - a piece of metal or metal foil that short circuits the ends of cap leg wires to prevent stray currents from causing accidental detonation of the cap. - an aqueous solution of ammonium nitrate sensitized with a fuel, thickened, and crosslinked to provide a gelatinous consistency. - controlled blasting where a series of closely spaced holes are drilled at the perimeter, loaded with decoupled charges and fired on the highest delay period of the blast round. - a hole drilled slightly downward from horizontal into the floor of the quarry. - the distance between holes or charges in a row measured perpendicular to the burden distance. - a firing device that burns with a flash. - a blasthole pattern where the holes in each row are drilled between the holes in the preceding row. - the inert material such as drill cuttings, used in the collar portion of a blasthole to confine the gaseous products of detonation. - loading cartridges end-to-end in a borehole w/o deforming them and used mainly in controlled and permissible blasting. - the extended hole depth of blasthole beyond the planned grade lines or below floor level to ensure breakage to the planned grade or floor level. - the ration of the volume of materials in an undisturbed state to that when broken. - slower than the speed of sound. - faster than the speed of sound. - an aqueous solution of AN sensitized with a combustible fuel (and thickened with gelling agent at the point of charging). - compressing the stemming or explosive in a blasthole. - the burden or distance between the bottom of a hole and the vertical free face of a bench in an excavation. - a military explosive compound used industrially as a sensitizer for slurries and as ingredients in pentolite and composition B. - a detonating cord line used to connect the downlines of other detonating cord lines in a blast pattern and usually runs along each row of blast holes. BLASTING PRINCIPLE - Explosive are used chiefly for breaking or fracturing of ores and rocks to facilitate excavation and loading operations in mining. (both open pit and UG) - It is done when or ore is too hard for mechanical or hydraulic excavation methods; - Explosives function best when there is a free face approximately parallel to the explosive column at the time of detonation. - There must be adequate space for the broken rock to move and expand. Excessive confinement of explosives is the leading cause of poor blasting results such as backbreak, ground vibrations, airblast, unbroken toe, flyrock and poor fragmentation. THEORY OF ROCK BLASTING - In blasting, the following conditions have an effect on the performance of the operations: -- -- -- -- Blasthole - is drilled hole for placement of explosives. Round - is the series of blastholes required to produce a unit of advance to a development heading or other face. COMPONENTS INSIDE A BLASTHOLE 1\. Blasthole 5\. Detonating Cord ------------------------ ---------------------- 2\. Explosives 6\. Igniter Cord 3\. Stemming Materials 7\. Blasting Machine 4\. Blasting Cap 8\. Subdrill COMPONENTS OF BLASTING ROUND 1\. Series of Blastholes 6\. Blasting Cap --------------------------------------- ------------------------------ 2\. Free Faces 7\. Detonating Cord 3\. Burden Distance 8\. Igniter Cord/safety fuse 4\. Explosives Charge (light & heavy) 9\. Blasting Machine 5\. Stemming Materials 10\. Subdrill hole A close-up of a text Description automatically generated APPLICATION OF EXPLOSIVES 1. Military Purposes - gun ammunition - agent in bombs, torpedoes, and grenades - demolition - pseudo-civil purposes such as excavating, quarrying, road-making, etc 2. Industrial Purpose - Mining - to facilitate ease of excavation and loading of ore or rock materials - recovery of minerals - blasting of limestone quarries, etc. - geophysical shotfiring. CHARACTER OF AN EXPLOSIVES 1. It should contain a substance, or mixture of substances, which is insensitive to be the safe under all conditions of handling and storage, but is sensitive enough to initiate readily when required; 2. Upon initiation it must rapidly undergo chemical change, yielding gaseous products whose volume 3. under normal pressure and at the high temperature resulting from exothermic reaction; The reaction must be exothermic in order to increase the pressure; PROPERTIES OF AN EXPLOSIVE 1\. Strength -- is related to its energy content as a measure of its ability to do useful work. 2\. Weight Strength -- is determined by comparing the deflection of a ballistic mortar with that caused by an equivalent weight of blasting gelatin-the strongest industrial explosive. It is also influenced by ammonium nitrate content. 3\. Bulk Strength -- its relative density. 4\. Velocity of Detonation -- refers to the speed at which a one-dimensional detonation wave representing a shock front, travels through a charge of explosives confined in a borehole. - Detonation Pressure -- is a measure of the pressure in the detonation wave front. It is an important property especially when very hard rock is to be blasted. The borehole pressure reaches its peak value at point where the detonation wave had just completed its passage through the explosive column and the gases have expanded to fill the borehole. 6\. Initiation Sensitivity -- the ease at which an explosive charge can be detonated. 7\. Water resistant -- can prolong exposure to water 8\. Fume Characteristic -- are extreme importance when used in confined spaces as in U/G mines. All explosives produces noxious fumes on explosion, however, the types designed for underground use have the ingredients carefully formulated to control toxic fumes and keep them to a minimum. CLASSES OF EXPLOSIVES - Class A Explosive -- those that possesses detonating or maximum hazard; such as dynamite, nitroglycerin, lead azide, black powder, blasting caps and detonating primers. - Class B Explosive -- those possesses flammable hazard such as propellant explosives, photographic flash powders and some special fireworks. - Class C Explosive -- those explosive that contains Class A and Class B explosive or both, as components but in restricted quantities like blasting caps or electric blasting caps in lots of less than 1,000. TYPES OF EXPLOSIVES 1. High Explosives - detonator sensitive explosive (cartridge)3,000-9000 m/s - An explosive material that can be caused to detonate with a No. 8 blasting cap when unconfined. 2. Low Explosives (blasting powder) - An explosive material that can be caused to deflagrate when unconfined 3. Blasting Agent (detonator insensitive explosives) - Explosives and blasting agents detonate properly when initiated, whereas low explosives (black powder) to deflagrate (combustion/subsonic). Few cm to 400 m/s. - A mixture consisting of a fuel and oxidizer, intended for blasting but otherwise not an explosive (cannot be detonated with a No. 8 blasting cap) Detonation - Occurs when the rate of chemical decomposition is greater than the speed of sound - High Explosives detonate Deflagration - Occurs when the reaction rate is slower than the speed of sound - Low explosives deflagrate HIGH EXPLOSIVE : - detonate at velocities of 1,500 to 7,500 m/s & produce large volumes of gases and considerable heat at extreme high pressure. - The performance of such an explosive depends chiefly on the volume & temperature of gases produced and on the velocity of detonation. Ex. Water gel & Emulsion explosive, dynamite and cast pentolite boosters LOW EXPLOSIVE: - the type of explosion is really a rapid form of combustion in which the particles burn at their surfaces and expose more of the bulk until all has been consumed. Ex. Black blasting powder \- is a mechanical mixture of potassium or sodium nitrate with sulfur and finely ground charcoal. This type of explosive are characterized by a "push" rather than a "blow" or a "lift" rather than a "shatter". BLASTING AGENTS (NitroCarboNitrate-NCN): - are chemical mixture of a fuel and an oxidizer, intended for blasting: - it consist primarily of inorganic nitrates and carbonaceous fuels, and may contain additional non explosive sensitizers such as powdered aluminum or ferrosilicon. It will detonate at a velocity of 3,000 to 4,000 meters/second. - Basically its ANFO (94 AN + 6 FO ) LOW COST BUT WATER SOLUBLE 1. Choosing an Explosive +-----------------------------------+-----------------------------------+ | l. High detonating velocity | m. Density | +===================================+===================================+ | a. Cost/price | b. Sensitivity | +-----------------------------------+-----------------------------------+ | c. Type of rock to be blasted | d. Fumes | +-----------------------------------+-----------------------------------+ | e. Chemical composition | f. Storage & Handling | | | Requirements | +-----------------------------------+-----------------------------------+ | g. Purpose and usage | h. Physical characteristics | +-----------------------------------+-----------------------------------+ | i. Water resistance | j. Flammability | +-----------------------------------+-----------------------------------+ | k. Strength | | +-----------------------------------+-----------------------------------+ 2. Mechanics of Detonation - Explosives - either react slowly, or deflagrate or they detonate. A distinguishing characteristic of high explosive is that it detonates when it is properly primed and an explosion is initiated in it. - Detonation - a supersonic explosive reaction where a shock wave propagates through the explosive accompanied by chemical reaction that furnishes energy to sustain stable shock wave propagation. PRINCIPLE OF DETONATION (Duvan & Atchision) Detonation of explosive charge creates a high gas pressure in the charge hole, which generates a compressive strain pulse in the surrounding rock and travels outward in all directions from the charge hole. Near the charge hole the amplitude of the strain pulse is sufficient to cause crushing of the rock. However, as the strain pulse travels outwards, it amplitude decays until no further crushing of the rock is possible. The compressive strain pulse continues to travel outward until it is reflected by a free surface. Upon reflection, the compressive strain pulse becomes a tensile strain pulse. As the strength of the rock in tension is much less than in compression, the reflected tensile strain pulse will break the rock in tension, progressing from the free surface back towards the shot point. This means that rock is pulled apart, not pushed apart. The high gas pressure generated by detonation of charge produces the stress waves, but the expanding gases are not directly responsible for much of the fracturing that occurs. Detonation Pressure - It is a borehole pressure at the beginning of explosive detonation front. It is responsible for the fracturing and crushing the rock around the borehole which is referred to as "Brisance". The detonation pressure can be calculated using the formula: P = 0.25 ρ x D^2^ x 10^-6^ Where: P = detonation pressure ρ = explosive density (g/cc) D = velocity of detonation (m/s) A blue rectangular box with white text Description automatically generated TYPES OF HIGH EXPLOSIVES - Nitroglycerin (NG) \- sp gr. 1.6, detonation velocity over 25,000 fps - Dynamite \- consist of nitroglycerin, sodium nitrate, antacid, carbonaceous fuel, sulfur & weight strength of 20-60%. - Blasting Gelatin \- tough rubber-textured composition made by adding nitrocellulose, also called as gun-cotton to nitroglycerin. It emits large volume of noxious fumes upon detonation and very expensive and excellent water resistant. - Straight Gelatin \- like blasting gelatin w/ sodium nitrate, carbonaceous fuel. TYPE OF HIGH EXPLOSIVES FOR PARTICULAR APPLICATIONS I. Permitted Explosive -- these are explosive that passed special and standard test. 1. Ajax - gelatinous high strength/density permitted explosive used for blasting hardest coal & sedimentary rocks under wet conditions. This includes shaft sinking and stone drifting. 2. Morcol - semi-gelatinous permitted explosive with high weight strength & medium density. Ideal for mechanized coal mines with thick seams. 3. Dynagex - specifically designed and officially approved for "grunching" coal or "shooting off the solid" in conjunction with Carrick short-delay detonators and the ME12 exploder. Provides superior blasting results & good water resistance and fume characteristics; 4. A3 Monobel - non-gelatinous, high strength, low density, low VOD explosive w/ very little water resistance but good fume characteristics. A slow explosive that gives low shattering effect thus it is suitable for dry coal seams where lump coal is required. II. Practical Usage of Explosives - This in turn sets up in the rock a compressive strain pulse which travels in all directions from the borehole until it is reflected from the free face as a tensile strain pulse. The rock is thus broken in tension and is displaced, aided by the high gas pressure (bubble energy).  III. Conventional Placement of Explosive Charges 1. The hole is first cleaned out with compressed air by means of a blowpipe; 2. The cartridges of explosive are inserted into the borehole one by one & firmly squeezed into position (to occupy the full section of the hole) by means of wooden tamping stick; 3. The primer cartridge (if conventional safety fuse-plain detonator type) is placed last. 4. The hole is then sealed by stemming with a cartridge of sandy clay material squeezed against the primer. Care is taken to see that no damage is caused to the safety fuse, the free end of which is now protruding from the mouth of the hole; 5. When the charge is fired electrically, the electric primer is the first cartridge to be inserted (inversely) in the hole. The lead wires are then held taut to one side of the hole with the ordinary cartridges are tamped into position; 6. With either type of primer, the live-end of the detonator should face the bulk of the charge, (i.e. with the ordinary primer-inwards, with the electric primer-- outwards); 7. No metal tipped or metal tamping rod (e.g. drill steel) shall be used; 8. The primer charge itself should not be tamped or squeezed with the tamping stick. WAYS TO USE OF AN/FO ON MINE SURFACE - AN/FO is the cheapest explosive material for blasting wherever the circumstances are compatible with its use. It can be used at the watery surface mines by placement it in polythene sleeves. TWO (2) MAIN DISADVANTAGES: 1. its low loading density when gravity- loaded into "down" holes; 2. its inherent low water resistance. TREATMENT OF MISFIRES - Misfires are charges that has not exploded. - Allow a safe interval of time between report of misfires and an approach to the face; - Before commencing and while removing the broken rock from the face, extreme care should be taken to identify unexploded cartridges or detonators, and to remove them to a safe place; - The face should be carefully examined for remaining "butts" of holes which may contain remnants of a charge. All such explosive remnants should be carefully removed before drilling commences; - Holes should never be drilled into old butts; - Defective explosives (due to deterioration in storage); - Damage to components while charging; - Water entering the detonator; - Discontinuity of the electrical circuit; - Insufficient current in the circuit; - By "cut-offs" (i.e. the explosion of a previous hole breaking out the collar of a hole and dislodging the primer). In case of AN/FO, its less dangerous to resolve due AN is soluble and may be sluiced out of a butt with water hose. - Delaying too long in lighting fuse; - Drilling into explosive; - Premature firing of electric blasts; - Returning too soon after blasting; - Inadequate guarding; - Unsafe practice during transport, handling and storage; - Improper handling of misfires; - Using fuse too short in length; - Improper tamping procedure; - Smoking during handling of explosives. INITIATING DEVICES 1. DETONATORS -- metal tube (aluminum or copper) closed at one end, and into which is pressed a base charge of "penta-erythritol-tetra-nitrate (PETN). The base charge is super-impressed a mixture of heat sensitive explosives, usually containing lead azide, to prime the base charge. - Type of Detonators 1. Plain Detonators - is the simplest and is used for all general purposes under relatively dry non-gaseous conditions and particularly where single independent charges are fired. 2. Electric Detonators -- same as general construction as electric fusehead is plain detonators except that an provided, and the mouth of the detonator tube is plug through which pass the plastic covered leading wires. 2. PRIMERS (Boosters) -- provide adequate initiation of the charge. The charge is made one of the cartridges and a detonator. For lower strength high explosives, a from cartridges of AN Gelignite "60" with a no. 6 detonator is a recommended as a primer. 3. DETONATING CORD -- consist of a core of PETN contained within a wrapping of textile yarns and sheathed in plastic. Ex. Cordex -- regarded as a continuous detonator with a VOD of about 7000 m/sec, when initiated with a detonator strapped to the free end. FIRING WITH CONVENTIONAL SAFETY FUSE - Initiation of a high explosive charge by a plain detonator which has been ignited by safety fuse. A safety fuse is used because of built-in safety feature where the device burns at a closely controlled regulated rate, so that a given length represents an equivalent interval of time. In other words, a fuse of certain length can be selected to provide adequate time for the shotfirer to retreat to a place of safety. It is used nowadays when "capped" with a plain detonator, for initiating detonating cord and primers in charges of high explosives and blasting agents. - Primer -- a cartridge of HE incorporating a detonating device. This is the key element of a charge of explosive. - Round -- a group or set of blast holes used to produce a unit of advance in U/G headings. - Safety fuse -- a core of potassium nitrate black powder, enclosed in a covering of textile and waterproofing, used to initiate a blasting cap or black powder charge. Speed 30 s/ft. - Preparation of Capped Fuse - Capping of Fuse - can be performed either with a bench-mounted Detonator Crimper or with an approved type of hand crimping pliers. The prescribed safe series of operations for hand crimping is as follows: 1. Cut squarely across the fuse to the standard length required; 2. Remove detonator carefully from cardboard box 3. Insert freshly and squarely cut end of fuse into detonator as far as possible w/o using force; avoid using a screwing action; 4. Crimp mouth of detonator over fuse evenly, about 10mm from the end; 5. Dip in waterproofing compound so that the whole of the detonator and about 25mm of the fuse is submerged; 6. Avoid squeezing or pressing (or applying heat to) the closed end of the detonator. - By lighting the safety fuse (with a hot flame) a jet of flame known as **"IGNITION SPIT"** is observed by the shotfirer, giving him positive evidence that the fuse is alight and functioning normally. The burning powder then travels slowly along the length of the fuse until it reaches the other end, which has been "crimped" into the detonator. The **JET OF FLAME** ignites the priming charge in the detonator and the main explosive charge is thereby safely initiated. - Speed is 0.3 m/min - Detonating cord (Cordtex) - It is a cord consisting of a core of initiating explosive (PETN) contained w/n various combinations of textile yarns and plastic sheating. It is used for the simultaneous (& delay) firing of widely distributed charges & for the mass initiation of very large charges, as in quarry and chamber blasting. One of the chief advantages of detonating cord (DC) is that, when initiated, it is capable of transmitting the energy of a detonator to and at all points along its length. It is capable of increasing the effectiveness of a blast as it explodes with extreme violence the high explosives (other than blasting agents & slurries). It detonates all connecting charges simultaneously from one point of initiation. - In Quarry Blasting - it is usual to lay out a trunk line of detonating cord extending along each line of holes, connecting to branch or "downlines" into each hole. BLASTING PLAN - Consists of the following: - Method & equipment for transport of explosives and detonators; - Type and location of storage facilities; - Type & quantity of explosives & detonators - Primer assembly procedure and location; - Employees training program; - Provision for protecting people, structures, private and public property; - Provision for developing & distributing a daily blasting plan covering hole diameter, spacing, loading and delay patterns; - Provision for disposal of explosives, blasting agents, and associated materials. SURFACE BLASTING FACTORS: 1\. Blasthole Diameter 7\. Subdrilling ---------------------------- -------------------------------- 2\. Choice of Explosive 8\. Collar Distance (Stemming) 3\. Quantity of Explosives 9\. Spacing 4\. Fragmentation 10\. Hole Depth 5\. Blast Pattern 11\. Delays 6\. Burden Distance 12\. Powder Factor BLASTHOLE DIAMETER - Blasthole diameter along with the type of explosive and rocks determines the burden distance; Practical blasthole diameter for surface construction excavations range from 3-15 inches; - As a general rule, large diameter blastholes, 6-15 inches have limited applications due to fine fragmentations; - the choice of borehole diameter in quarry blasting is critical due to following: - Drill equipment specification; - Burden distance - Spacing distance - Explosive distribution - Efficiency and economics of the complete operation - Geologic structure is a major factor in determining the blasthole diameter. Joints, shears, or zone of soft rock tend to isolate large blocks of rock in the burden. The larger the blast pattern, the more likely these blocks are to be thrown unbroken into the muckpile; - Airblast and flyrock often occur because of an insufficient collar distance (stemming column) above the explosive charge. As the blast hole diameter increases, the collar distance required to prevent violence increases; - The ratio of collar distance to blasthole diameter required to prevent violence varies from 14:1 to 28:1 depending on the following: - Relative densities and velocities of the explosive and rock; - The physical condition of the rock; - The type of stemming used; - The point of initiation - Larger collar distance is required where the sonic velocity of rock exceeds the detonation velocity of the explosive or where the rock is heavily fractured, or low density; - As collar distance increases, the powder distribution becomes poorer, resulting in poorer fragmentation of the rock in the upper part of the bench; - Ground vibrations are controlled by reducing the weight of explosive fired per delay interval. This is done more easily with small blast holes than with large blastholes. Where large diameter blastholes are used near populated areas, several delays, along with decking, must be used within each hole to control vibrations; - Large holes with large blast patterns are best suited to an operation with: - A Large volume of material to be moved; - Large loading, hauling and crushing equipment; - No requirement for fine, uniform fragmentation; - Easily broken toe; - Few ground vibrations or airblast problems (few nearby buildings); - Relatively homogeneous, easily fragmented rock without many plane of weakness or voids; Factors to Consider in Determining Blasthole Diameter: 1. Rock Parameters - density, propagation velocity, characteristic impedance, energy absorption; strength (compressive & tensile), texture, lack of homogeneity. 2. Explosive Parameters - (density & detonation velocity \[detonation pressure\] detonation impedance, gas volume, and available energy - related to charge diameter; 3. Local restrictions connected with the proximity of built areas; 4. Production factors related to size of loading, haulage, crushing, screening equipment and scale of production. CHOICE OF EXPLOSIVE - Depends on the tenacity and physical character of rock to be broken like presence of bedding planes, joint planes, and plane of weakness. There are four main types of explosive used in surface mining: **slurries, dry mixes, emulsions** and **hybrid heavy ANFO.** - Dynamite - It is an explosive used for blasting. Dynamite consist of 25% of sandy earth saturated with 75% of nitro-glycerin. It is in the form of thick paste and it is sold in cartridge. It is very poisonous in nature and develops violent headaches through touch with skin. Dynamite cartridge is placed in the bore hole and tamped with wooden bar. The charge is fired by a fuse - Slurries - An aqueous solution of ammonium nitrate sensitized with a fuel, thickened and cross-linked to provide gelatinous consistency, sometimes called "water gel". - Ammonium Nitrate Dry Mix - Consist of 94.4% AN and 5.6% FO - Emulsions - An explosive material containing substantial amount of oxidizers dissolved in water droplets surrounded by an immiscible fuel - Hybrid Heavy ANFO - The use of polyethylene liners with slits in the wall are used to successfully load Heavy ANFO in water-filled holes. QUANTITY OF EXPLOSIVE - Is a function of hole diameter, hole spacing, hole depth, burden distance for any particular advance, after the type, strength and density of the explosive has been determined for particular conditions. - To determine the type, strength, quantity and cartridge diameter of explosive considers the following: 1. Applicability to the particular job; 2. Safety of life and property; 3. Efficiency ( i.e. explosive consumption in kg/ton ore) 4. Economy (i.e. cost of drilling, charging, firing including cost of explosive and accessories) FRAGMENTATION - it describes the size distribution of rocks boulders, chunks, and particles produced when a solid rock mass is blasted. - Improvement of Fragmentation: 1. Shallower holes, or better distribution of the explosive charge over the length of the hole; 2. Shorter spacing distance between holes in a row; 3. Short burden distance 4. Use of an explosive that yields less brisance and greater gas production; 5. Use of short-delay detonation. DRILL HOLE PATTERNS - For 3 m by 3 m tunnel: **31 holes** - For 2.7 m by 2.7 m: **28 holes** (called XC or AR pattern) - For 2.5 m by 2.5 m: **24 holes** - For 2 m by 2 m breasthole: **11 holes** - Wedge Cut - Blastholes drilled at an angle to the face in a uniform wedge formation so that the axis of symmetry is at the center line of face. - Cut used for large size drifts which have well laminated or fissured rocks A diagram of a structure Description automatically generated - Pyramid Cut / Diamond Cut / Cone Cut - Variation of wedge cut - Blast holes have horizontal and vertical axes symmetries - 4 or 6 blast holes driven at middle of the face which are inclined and will form a cone or pyramid shape - Cut used for blasting hard rock mass A diagram of a square with numbers and symbols Description automatically generated - Drag Cut - Suitable for small sectional drifts  - Fan Cut - ½ wedge cut - Applicable where only one machine is employed in a narrow drive, as well as to soft ground  - Burn Cut - Series of // holes drilled closely spaced at right angles to the face - ≥ 1 hole at the center of the face is uncharged - Uncharged holes are often larger in diameter than the charged ones - Effective in hard, brittle, homogenous ground which breaks evenly - Coromant Cut - Drilling 2 overlapping holes in the center and left uncharged, and then 6 outer cut holes - Serves as 1 big burn cut A black and white drawing of a column Description automatically generated BLASTING PATTERN 1. Square pattern -- has equal burdens and spacing; 2. Rectangular pattern -- has a larger spacing than burden; 3. Staggered pattern - The holes in each are positioned in the middle of the spacing of the holes in the preceding row and the spacing should be larger than the burden. - Staggered drilling pattern is used for row-on-row firing where the holes of one row are fired before the holes in the row immediately behind them; - Both square and rectangular, the holes of each row are lined up directly behind the holes in the preceding row; - Square and rectangular drilling pattern are used for firing V-cut or echelon rounds; BURDEN DISTANCE - It is distance from a blasthole to the nearest free face at the instant of detonation. It is measured perpendicular between rows. The true burden on most holes is measured at an angle of 45 degrees from the original free face; - An insufficient burden will cause excessive airblast and fly rock; - Too large a burden will produce inadequate fragmentation, toe problems and excessive ground vibrations; - If it is necessary to drill a round before previous round has been excavated, it is important to stake out the first row of the second round before the first round is fired to ensure proper burden on the first row of blast holes in the second blast round; - For bulk loaded charges, the charge diameter is equal to the blasthole diameter; - For tamped cartridges, the charge diameter will be between the cartridge diameter and the blasthole diameter depending on the degree of tamping; - For untamped cartridges, the charge diameter is equal to charge diameter; - When blasting with ANFO, or other low density blasting agents with densities near 53 lb/ft3 (0.85g/cm3) in typical rock with densities near 170 lb/ft3 (2.7g/cm3), the normal burden is approximately 25 times the charge diameter; - When using denser products such as slurries or dynamites with densities near 75 lb/ft3 (1.2g/cm3), the normal burden is approx 30 times the charge diameter; - The burden-to-charge-diameter ratio is seldom less than 20 or seldom more than 40, even in extreme cases. - When using low density blasting agent such as ANFO in a dense formation such as basalt, the desired burden maybe about 20 times the charge diameter; - When blasting using denser slurries or dynamites in low density formation such as sandstone, the burden may approach to 40 times the charge diameter.  - Subdrilling -- is the distance drilled below the floor level to avoid hard toe. - When there is a pronounced parting at floor level for the explosive charge to conveniently break, subdrilling may not be required. - In surface blasting, it is necessary to make sure the shot pulls to grade. A diagram of a structure Description automatically generated COLLAR DISTANCE (Stemming) - Collar distance is the distance from the top of the explosive charge to the collar of blasthole; - The zone is usually filled with inert material called "stemming" to confine explosive gases and to reduce airblast. - A well-graded, crushed gravel works best as stemming, but it is common practice to use drill cuttings because of availability and economics; - Too short stemming, result in excessive violence in the form of airblast and flyrock and may cause backbreak; - Selection of collar distance is often a tradeoff between fragmentation and amount of airblast and flyrock that can be tolerated; Collar distance equal to 70% of the burden is a good first approximation.  SPACING - It is the distance between adjacent blastholes measured perpendicular to the burden; - It is calculated as a function of the burden and also depends on the timing between holes; - When there are rows are blasted one after the other, the spacing is measured between holes in a row; (Fig. 19-8) - When the blast progresses at an angle to the original free face (Fig. 19-9), the spacing is measured at an angle from the original free face; - Too close spacing causes crushing and cratering between holes and large blocks in the burden and toe problems; - Too wide spacing causes inadequate fracturing between holes, toe problems and accompanied by humps on the face (Fig. 19-12) - The true spacing is twice the true burden, even though the holes originally were drilled on a square pattern; - The use of millisecond (ms) delays between holes in a row results in better fragmentation and also reduces ground vibrations produced by the blast; - When ms delays are used between holes in a row, the spacing-to-burden ratio must be reduced to somewhere between 1.2 and 1.8 with 1.5 being a good approximationsl - Large diameter blastholes require lower spacing-to-burden ratios usually 1.2 to 1.5 with ms delays than small diameter blasthole usually 1.5 to 1.8. - When using controlled blasting, the spacing should never be less than the burden distance. - For bench blasting is that the hole depth-to-burden ratio should be between 1.5 to 4.0; - Hole depth less than 1.5 x burden causes excessive air blast and fly rock and because of short, thick shape of burden gives coarse and uneven fragmentation; - Where operational conditions require a ratio of less than 1.5, a primer should be placed at the toe of the bench to assure maximum confinement. Keep in mind that placing the primer in the subdrill can cause increased ground vibrations and unacceptably irregular final grades for engineering structures; - If the use of hole depth-to-burden ratio of less than 1.5 it is necessary, consideration should be given to increasing the bench height or using small drillhole diameters; - Hole depth greater than 4x burden are undesirable, the longer a hole to its diameter, the more error there will be in the hole location at the toe level; - High benches with short burdens can also create safety hazard such as small equipment having to drill the front row of holes near the edge of the high ledge or small shovel have to dig at the toe of high face; - Lower benches yield more efficient blasting results, lower drilling costs, less chance of cut-offs and are safer; - If it is impractical to reduce bench height, larger rock handling and drilling equipment should be used, effectively reducing the blast hole depth-to-burden ratio; - If it is necessary to use blast designs with large hole depth-to-burden ratios, multiple priming should be used as insurance against cut-offs; DELAYS - Millisecond delays are used between charges in a blast round to: - Ensure that proper free face is developed to enable the explosive charge to efficiently fragment and displace the rock. - enhance fragmentation between adjacent holes; - reduce the ground vibrations created by the blast A diagram of firing sequence Description automatically generated FOR SUCCESSFUL FIRING, KEEP IN MIND THE FOLLOWING: 1. The delay time between holes in a row should be between 1 and 5 ms/ft (0.3m) of burden. Delay times less than 1 ms/ft of burden cause premature shearing between holes, resulting in coarse fragmentation. If an excessive delay time is used between holes, rock movement from the first hole prevents the adjacent hole from creating additional fractures between the two holes. A delay of 3 ms/ft (0.3m) of burden gives good results in many tyoes of rock. 2. The delay time between rows should be 2-3 times the delay time between holes in a row. To obtain good fragmentation and control of fly rock, a sufficient delay is needed so that the burden from previously fired hole has enough time to move forward to accommodate moving of rock from subsequent rows. If the delay between rows is too short, movement in the back rows will be upward rather than outward. 3. Where airblast is a problem, the delay between holes in a row should be at least 2 ms/ft of spacing. This prevent airblasts from one charge from adding to that of subsequent charges as the blast proceeds down the row; 4. For controlling ground vibrations, most regulatory authorities consider two charges to be separate events if they are separated by a delay of 9 ms or more. 5. When using surface delay systems such as detonating cord connectors and sequential timers the chances of cut-offs will be increased. To solve this problem, in hole delays should be used in addition to the surface delays; 6. When using surface detonating cord connectors, the use of 100-ms delays in each hole is suggested. This will cause ignition of the in-hole delays well in advance of rock movement, thus minimizing cut-offs; - It is best if all the explosive in a blasthole is fired as single column charge. When firing large blastholes in populated areas, 2 or more delays within a blast hole can be used to reduce ground vibrations; - When it is essential that one charge fires before an adjacent charge, such as in a tight corner of a blast, it is a good idea to skip a delay period. POWDER FACTOR - It is the pounds of explosive per cubic meter (kg/m3) of rock; - Powder factor is a necessary calculation for cost accounting purposes; - Powder factors for surface blasting can vary from 0.25 to 2.5 lbs/yd3 (0.1 to 1.1kg/m3) with 0.5 to 1.0lb/yd3 (0.2 to 0.45kg/m3) being most typical. - Powder factor for a single blast hole is calculated by the following:  P. F. = Powder factor in pounds of explosive per cubic yard of rock L = Length of explosive charge, feet d = density of explosive charge, grams/cm3 D = charge diameter, inches B = burden, feet S = spacing, feet H = bench height, feet GENERAL REQUIREMENTS FOR SURFACE BLASTING OPERATION +-----------------------------------+-----------------------------------+ | 1\. Competent Supervision | 10. Thunderstorms | +===================================+===================================+ | 2\. Qualification | 5. Vibration and Damage Control | | | | | a\. Personnel | | | | | | b\. Blasters | | +-----------------------------------+-----------------------------------+ | 1. Blasting Plan | 6. Warning Signs | +-----------------------------------+-----------------------------------+ | 2. Security and Inventory | 7. Destruction of Explosives | +-----------------------------------+-----------------------------------+ | 3. Notifications | 8. Empty Explosive Containers | +-----------------------------------+-----------------------------------+ | 4. Smoking Restrictions | 9. Fire | +-----------------------------------+-----------------------------------+ QUARRY AND OPEN-CUT BLASTING PRACTICES - In quarry operation, a high face of rock or ore for quarry work is normally divided into several steps or benches for ease and safety of operation. - Width of bench should be sufficient to accommodate the spread of rock broken from the face and to provide space to deploy shovels, haulage units, and drilling equipment and also on the degree of fragmentation required for a particular rock. - Most large scale operation use a nominal bench height of 12 -- 15 meters. Higher benches (deeper holes) generally mean coarser fragmentation, reduced accuracy in locating the hole bottom, but fewer drill set-up. - Blastholes are normally drilled vertically, or at a steep angle, in rows parallel to the face. Alternate rows of holes may or may not be staggered. - Loading Explosives +-----------------------------------+-----------------------------------+ | 7. Planning | 8. Tamping | +===================================+===================================+ | 1. Drilling | 2. Priming | +-----------------------------------+-----------------------------------+ | 3. Loading Areas | 4. Stemming | +-----------------------------------+-----------------------------------+ | 5. Boreholes | 6. Shooting | +-----------------------------------+-----------------------------------+ - Firing +-----------------------------------+-----------------------------------+ | 3. Preparation | 5. Post Blasting Signals | +===================================+===================================+ | 1. Responsibility | 4. Disconnection | +-----------------------------------+-----------------------------------+ | 2. Blasting Signals | | +-----------------------------------+-----------------------------------+ Composition of Blasting Crew 1. Blasting Engineer/Foreman - a licensed mining engineer or any engineer tasked to plan and oversee the over-all implementation of blasting operation of the mine. 2. Chief Shotfirer - a licensed blaster and will oversee the whole drilling and blasting operations. He prepares the daily blasting plan and coordinate with main authorities regarding the schedule, and area of blasting for approval. He direct and supervise the shotfirer and his crew in the proper implementation of the approved blasting plan and oversee the imple-mentation of standard operating procedures in order to achieve a safe and productive operation. 3. Shotfirer - a licensed blaster who will conduct the actual handling of explosives and monitor its movement from the satellite magazine towards the blasting site. He implements the approved blasting proposal for the particular blast area & make revisions to suit the actual site configuration. Install primers, initiation lines/connectors, & column charges into the blasthole. He is responsible for the location of blasting barricades, traffic guards and clearing of the affected areas. 4. Asst. Blaster - minimum of 4 personnel to assist in the trans-portation of explosives to and from the blast site, prepares blast holes, application of stemming materials, installation of blasting mats and sand bags, and act as blasting guards. Conventional Blasting: - It consists of creating and blasting holes at any location without considering environmental and stability concerns. Pre-splitting: - It consists of creating a plane of shear in solid rock on the desired line of break. It is carried before any production blasting, and even in some cases before production drilling. It is applicable where walls of the excavation must be located within precise limits. It is done in which alternate holes only are loaded, and also in other cases short-delay firing has been used. Cleaner faces can be achieved if every hole in the pre-split line is loaded and the holes fired simultaneously, about 50 or more milliseconds before the main round is fired. Smoothwall Blasting: - When the rock is reasonably competent, this method is advantageous. Horizontal holes are charged with small diameter low-density decoupled cartridges strung together and by providing good stemming at the collar hole. Charges are fired simultaneously after the lifters. Line Drilling: - Regular drillholes about 38mm diameter are spaced 100-150mm apart from the perimeter and left uncharged. Large diameter holes could be placed at greater spacing intervals. The buffer zone between the perimeter holes and last row of main round holes shall be about 200-300mm wide (the buffer distance). The drilled unloaded holes along the periphery alone provide a place of weakness to which the rock will break readily and cleanly when the round is fired. Its disadvantages are: 1. Greater amount of drilling is involved; 2. Precise hole alignment is required to establish an effective plane of weakness; 3. The method is applicable only to massive homogenous rock. CALCULATION OF BURDEN DISTANCE - In using the different formulas, the burden distance alone was taken as the variable factor while the correction factor embraced the effects of type of explosive, bearing resistance of the rock, depth, and diameter of drill holes, and charging depth. Burden distance is the distance between the hole bottom to the free face. - To break a ground has main considerations like: a. the burden distance; b. the strength, quantity, and distribution of explosive charge. - But Fraenkel developed a formula for rock characteristic which he calls, **"resistance to blasting":**  Where: B=burden distance, m R=resistance to blasting (varying, 1-6 for all rock types) L=length of hole, m I= length of charge, m d= diameter of hole, mm CALCULATION OF CHARGE - A correct charge need for: 1. For successful blasting, the borehole must be drilled to give the correct burden distance; 2. It is essential to obtain a high loading density for the explosive in the bottom portion of the hole. - The quantity of explosive, Q, required per blasthole for a given powder factor (E kg/tonne) is derived as follows: where: B = burden distance, m S = spacing of distance, m D = hole depth below grade, m d = density factor, tonnes per m^3^ BURDEN DISTANCE: - The optimum fragmentation burden is that which allows the gasses to loss virtually all of their energies by the time they escape into the atmosphere w/o producing any air blast with minimum objectionable side effects like toe, air blast, ground vibration, etc.  SPACING: - Spacing must be large enough to prevent excessive overlap and over break zones behind adjacent holes but just small enough to give a relatively even distribution of explosive energy in the rock to be broken A close up of a number Description automatically generated SUB-DRILLING: (Blastholes beyond the planned grade lines or below floor level to ensure breakage)  STEMMING: - Stemming = 0.7 Burden DEPTH OF HOLE: - D = 2.1 to 2.25B (B is Burden) Flyrock Problems in O/P Blasting - Flyrock in open pit blasting usually means the unexpected/undesired outward projection of rock mass from blasting. Cause/Formation of Flyrock 1. Front Row Burden - Flyrock can be ejected from front row blast holes where insufficient burden exist either at collar or at the toe. 2. Stemming Depth/Stemming Material - As stemming depth decreases, larger proportion of explosion gases become available for premature ejection of pre-fractured rock. Stemming material acts to confine explosion of gases to perform useful work before venting. With insufficient stemming material, the gases stream up the blast hole prematurely resulting in fly rock formation. 3. Initiation Sequence - the degree of sequential blasting procedure. 4. Blast Pattern/Blast Shape - when explosive charge common is overburdened, vertical crate ring can take place causing fly rock.