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By Claude Cunningham

Simple bulk energy rating of explosives obscures the realities of how these deliver their energy, and diverts attention from the key question of controlling blasting results. Explosive performance is directly related to the pressure pulse impacting on the blasthole wall. This is helpfully visualised by comparing the adiabatic expansion plots for explosives of interest on the right scales and axes. The simple comparison of a pure emulsion with pure ANFO illustrates the practical significance of the intrinsic behaviour of these opposed formulations, showing that the emulsion can be expected to work more by softening rock, while ANFO will tend more to crack it. The explanation for these differences lies in the high shock, low sustained pressure of the former relative to the latter. The technique is readily applied, if a good detonation code is available and able to swap data into a spreadsheet. Any differences between codes will emerge most strongly in comparing the gamma plots.

Jan 1, 2002

By S Lukovic, Robert Briton, Calvin J. Konya

Investigators have reported that charges which are decoupled from the borehole wall produce different fragmentation then those which are fully coupled. The difference in effect could be as a result of energy doss during transmission across the air gap or it could be due to the change in detonation characteristics of the explosive as a result of the change in confinement on the charge during detonation. In order to better understand the phenomena of decoupling, a research project was conducted at the United States Bureau of Mines Station, near Pittsburgh, Pennsylvania. It was decided to use shock and bubble energy tests along with simultaneous velocity measurement to determine the mechanics of decoupling and energy transmission. Two explosives were selected for the test, one dynamite and one water gel. Test results indicated that decoupling could both boost the total energy output of the explosive and that further decoupling would drop the energy output.

Jan 1, 1987

By William Everett, Jack Eloranta

United Taconite is an iron ore mine operated by Cleveland-Cliffs Inc (Cliffs) located near Eveleth, Minnesota. The mine, originally known as Eveleth Taconite Mines, was purchased in December 2003 by Cliffs (70%) and Laiwu Steel (30%). The mine site, known as the Thunderbird Mine, produces taconite ore for delivery by rail to the company’s Fairlane plant, located approximately 10 miles to the south near Forbes, Minnesota. At the plant, the crude ore is ground, concentrated and processed into pellets for steel industry customers. Total pellet production capacity is about 5.4 million long tons (Ltons) per year.

Jan 1, 2006

By Rene A. "Moose" Morin, Craig Copping

Innovative concepts in drilling and blast design have been used to remove deteriorated concrete and have enabled contractors to reduce costs and time on St. Lawrence Seaway rehabilitation projects. Time is of the essence on these contracts since the Seaway system is only available for this work during the winter freeze up. Unique electrical sequential initiation systems and specially modified drilling equipment have been used to accurately remove a narrow slice from the 83 foot high lock walls. These new methods successfully reduced demolition time, minimized overbreak and adhered to strict vibration limits.

Jan 1, 1986

By Harry Verakis, Thomas Lobb

This paper is a summary and an update of the underground mine blasting accident investigations and studies previously conducted by the Mine Safety and Health Administration (MSHA) and the former US. Bureau of Mines. Blasting accidents are usually a small percentage of the total number of mining accidents. However, blasting accidents continue to occur and the severity of these accidents is disproportionately high with respect to other types of mining accidents. In 2000, about 5.7 billion pounds of explosives were produced in the USA. The mining industry consumed the greatest portion of explosives manufactured for blasting with about 67 percent used for coal mining. Metal and nonmetal mining operations account for about 23 percent of the use of explosives. The use of permissible explosives in underground coal mines continues to decline (3,373,069 pounds for 2000).

Jan 1, 2002

By R W. Givens

This paper presents blast casting design variables that have been developed and are currently being used at the High Power Energy mine in West Virginia. The shot specifications are summarized in Table I. The two active casting pits were designed with casting in mind and as a result are better designed and more efficient. About 55% of the overburden material is effectively cast and clean up is done by a bulldozer, front-end-loader, and trucks. This results in a 15X decrease in the cost of coal production.

Jan 1, 1988

By Thomas F. Mechtenberg, Michael S. Powell

In the past several years many coal operators and stone producers have reduced drilling and blasting cost by utilizing Bulk Emulsion/ANFO blends. For many operators the cost of equipment to handle blend products has been a major consideration in evaluating overall cost effectiveness of changing from packaged products or bulk ANFO to blends. This is especially true when the project length is short term or is uncertain.

Jan 1, 1990

By Alain Blanchier

Because in Europe and in many other countries as well every new project (quarry, mine, public work) needs a risk estimation to prove its feasibility, a model to estimate flyrock risks became necessary. This paper presents the basic hypothesis which should underlay such a model to estimate statistical flyrocks range for not only some single blasts but a whole project and in particular the way to take into account rockmass or blast pattern parameters variability. It describes a first usable quantitative flyrock model based on the characteristics of the blasting plan and of the generic laws utilised in casting and selective blasting operations and on a statistical approach of rockmass. In a second step, this paper discuss an approach of risks estimation compared to the classical one used in pyrotechnics studies for explosive magazine risks assessment.

Jan 1, 2013

By Brendan O'Reilly, Outokumpu Zinc, Geoff J. Johnston, S Durucan

Historically vibration monitoring has dealt primarily with surface blasting or "near field" monitoring of underground blasts. The Situation at Tara Mines is different, blasting occurs up to 400m underground, with a number of blasts occurring daily and occasionally with residential properties directly above the blasting site. Tara Mines, due to both its location (1.5 km from the rural town of Navan) and stringent planning conditions have always had to monitor, carefully plan and control the levels of vibration from blasting. The statutory vibration limit at Tara allows a maximum peak particle velocity of 7.62 mm/s with no frequency limitations. Levels of vibration have been monitored continuously since mining operations began in 1972.

Jan 1, 1994

By Jaime Huidobro, Mervin Austin

The effect on an explosive column of the sharp transient stress waves generated during the earlier detonation of adjacent blastholes is of paramount importance to explosives users. Some explosives will sympathetically detonate under these stresses. Others may suffer a transient desensitization, arising from a temporary increase in the density of an explosive beyond certain limits and persisting until the explosive mass relaxes back to the original density. Some explosives are so adversely affected by these stresses that the product suffers immediate and permanent loss of sensitivity. These effects can be clearly seen while blasting in tough conditions such as burn cuts or wedge cuts and in materials, such as coals, that propagate shock waves well.

Jan 1, 1992

By Lewis L. Oriard

Near the village of Villarino de los Aires, in the province of Salamanca, Spain, was an existing underground hydroelectric power plant. A major enlargement was undertaken to increase the electrical generating capacity, under a contract awarded to a joint venture of Dragados y Construcciones, S. A. (Spain), Entrecanales y Tavora, S. A. (Spain), and S. A. Conrad Zschokke (Switzerland). The enlargement required the excavation of a large and complex underground system of tunnels, shafts and chambers adjacent to existing facilities and interconnected with these facilities. The existing machine hall and transformer chamber were both extended, requiring the blasting of the existing end walls. The drilling, blasting and excavating of the underground system had to be done without damage to existing underground chambers and tunnels, or any of the existing structures, equipment or instrumentation facilities, often within just a few feet of the blasting. This required careful control of vibrations, airblast overpressures and dust.

Jan 1, 1997

By D Linn Coursen

In the proposed method, the charges are elongated and arranged in one or more arrays. The orientation of each charge in an array, its velocity of propagation of explosion, and the velocity of propagation of vibration in the formation are such that, at an outlying location where vibration is to be reduced, the onset of vibration from explosion of the first negligibly small increment of each charge arrives a finite time before that from explosion of the last negligibly small increment of that charge. The charges of each array are fired in accurately-timed sequence, with the times between initiations chosen so that, at the outlying location, the onset of vibration from explosion of the last small increment of each charge, except the last charge, arrives a negligibly small increment of time before the onset of vibration from explosion of the first negligibly small increment of the succeeding charge. With such timing, vibration may be reduced at the widest range of locations by tilting the boreholes so that the terminal end of each charge is directly above or below the terminal end of the succeeding charge.

Jan 1, 1995

By P Wapner, C Lo Edwards, S CO Schmidt, J N. Johnson, R Oliver

Shale oil recovery rates that can be achieved in underground in situ retorts can be strongly influenced by the shale breakage and fragment-size distribution achieved during rubblization. Since the fragmentation pattern in the retort is a direct result of the blast design used for rubblization, the characterizing blast parameters should be carefully selected. Explosives should be matched to the host material and blast geometries properly chosen so that the required fragmentation results are achieved at optimum costs. Special attention must be directed to selecting blast parameters that produce uniform bed permeability, suppression of fines, proper fragment size distribution, and minimal damage to the retort walls and ceiling. The influence of joints and natural fractures should also be known. In instances where the requisite blasting parameters are unknown, they should be determined from test blasts.

Jan 1, 1979

By Mark D. Kirkbride

This paper outlines the process for designing a hard rock blast in an underground coal mine. The coal mine is located in Western Kentucky and operates four continuous miner units at 7 unit-shifts per day. The mine operates in the Western Kentucky No. 11 Seam with local variations from 4.5 - 5.5 feet seam thickness. The seam has sporadic siderite deposits. Usually these deposits do not significantly interfere with the mining process. When previous siderite deposits were encountered they were small enough to drop an entry for a couple of crosscuts. The blasting plan was called for after a siderite deposit was encountered in the belt entry at about one third of the panel length. The other sides of the panel had been previously mined and sealed so the decision was made to mine through the siderite deposit with the continuous miner instead of abandoning the panel. The deposit was approximately 300 feet in length down the belt entry. Mining through the deposit with the continuous miner was expensive in both terms of production and of wear and tear on the continuous miner. A blasting plan for the siderite deposits was designed to minimize damage to the continuous miner should a similar situation occur.

Jan 1, 1999

By A. Spathis, I. Yacob, A. Labriola, G. Smith

Wall control is a significant issue for many mines. Improvements to the design process for blasts adjacent to temporary or final walls will require better measurement tools and predictive models. Orica Explosives has developed capability in both these areas and uses them to guide better wall control blasting practices. Vibration and gas pressure were monitored behind a series of production blasts and single hole blasts at the Freeport Grasberg Operations Opencut Mine. The blasts used ANFO in both 3 11 mm and 35 1 mm blastholes in a blast design which reduced the charge weight by between 30 to 50% in the final row of the production blasts. Single hole blast data were obtained by delaying the last hole in the production blast. Vibration levels were within the range often associated with vibration induced damage: 178 to 1080 mm/s at distances between 14-75 metres from the blast.

Jan 1, 2001

By Michael Wieland

Delay blasting in underground coal generates shock waves and rifting forces that damage charges remaining in the blast pattern. Damaged charges detonate poorly, raise fume toxicity and reduce coal breakage. Such circumstances could be prevented by using explosives resistant to cross-hole interaction damage. The design of rugged explosives is fraught with contradictory requirements, but tradeoffs related to hard-particle size characteristics prove useful. Hard particles, related voids or trapped bubbles represent reaction nucleation centers which strongly influence the performance of coal mine explosives.

Jan 1, 1992

By John C. Brulia

PowerAN is a tradename of Atlas Powder Company for a new line of explosive products comprising blends of emulsion and ANFO in a variety of bulk and packaged grades. The bulk PowerAN grades are either augered or pumped depending upon emulsion content. Augered PowerAN blends contain up to 60% emulsion. Pumped PowerAN grades have an emulsion content of 75% or higher. The blending of PowerAN is usually accomplished at the borehole to satisfy specific borehole conditions. Packaged PowerAN grades are produced in several types of mix plants in diameters of 4" and greater. PowerAN 300 (30% emulsion) and PowerAN 500 (50% emulsion) are the two most popular grades and their chief application is as an economical, high energy replacement for ANFO HD in wet holes. PowerAN combines the cost effectiveness of ANFO with the high performance of emulsions, permitting the blasting engineer to strike an optimum balance between drill pattern expansion and increased productivity according to need.

Jan 1, 1985

By J Edmund Hay, Harry C. Verakisl, Richard J. Mainiero, John J. Mulhern

As the first stage in the rulemaking process, MSHA prepared requirements for the approval and use of permissible explosives and blasting items in underground coal mines. These draft requirements known as "preproposals" were announced in the Federal Register in mid-1984. The draft requirements on the use of explosives were written as a revision to Title 30, Code of Federal Regulations, Part 75, Subpart N. The draft requirements for approval of permissible explosives including sheathed explosives for unconfined applications, approval of water stemming bags, approval of detonators and approval of blasting machines were prepared as Parts 15, 16, 17 and 25 respectively.

Jan 1, 1985

By Joshua Hoffman, Catherine Johnson, Braden Lusk

The practice of dual initiation using precise timing from electronic detonators in boreholes is thought to be beneficial for increasing fragmentation at a desired location in the rock strata. This increased capacity for fragmentation is understood to be a product of both the collision of detonation waves in the explosive column and an increased energy liberation rate, each resulting from dual initiation. In addition, the collision of shock waves from two adjacent blast holes is suggested to improve fragmentation at the location the two shock waves meet, which can be controlled with precise timing. This paper presents the results from scaled laboratory experiments where converging detonation waves and shock waves were studied.

Jan 1, 2014

By Fumihiko Sumiya, Kunihisa Katsuyama, Yuji Ogata, Yukio Kato, Yuji Wada, Yoshikazu Hirosaki

Smooth blasting technique is widely applied for tunneling road or railway construction in Japan. However, smooth blasting technique often causes problem related to detonation failure in explosive column due to channel effect. Channel effect is attributed to the precursor air shock wave (PAS), which propagates ahead of detonation front in an air channel of borehole. PAS precompresses and desensitizes the unreacted explosive column. The failure of detonation propagation occurs as a result. It was concluded in our previous work that reducing PAS velocity was one of the effective methods for the prevention of channel effect.

Jan 1, 2003