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By Don Thompson

The Minntac Mine drills and blasts approximately 75 million long tons of taconite per year. This requires drilling one million feet of 1 6-inch diameter holes. We are in the process of replacing our old generation rotary blasthole drills (Gardner-Denver 120's and Bucyrus-Erie 61R's) with new generation rotary blasthole drills (Bucyrus-Erie 59R's and P&H 120A's).

Jan 1, 1998

By M Lemieux, R Mason

The SABREX blast modeling program was introduced to I.O.C.C.'s Carol Lake Iron Ore Project in December 1987. As part of CIL's Technical Services, SABREX was used to implement an optimization program designed to analyze and introduce various grades of MAGNAFRAC at a constant pattern while maintaining acceptable blast results.

Jan 1, 1989

By Glenn Ludwig, Stephen H. Chung

Fragmentation has a direct impact on mine costs and productivity. Computer programs have been developed to calculate fragmentation using data on the properties of the explosive, the characteristics of the rock, the rock mass and the blast pattern. While computer models can yield good data, conclusions must be verified. Fragmentation assessment, muckpile surveys or high speed film analysis of rock mass movement are some of the techniques that have been used to confirm blast results. Digitizing photos of the muckpile is now the most common method to assess fragmentation. But it has some drawbacks. Although automatic electronic imaging equipment speeds up the process, the results depend on the photographs. Shadows will distort results. High resolution, black-and-white prints are essential.

Jan 1, 1992

By Max Pena Woolcott, Winfried Rosenstock, Maria Chappuis, Walther Hennig

"In a Peruvian-German Technical Cooperation project for the Mining Sector the ""Milpo-cut"" along with the electric initiation system has been successfully implemented in a Peruvian metal-ore mine.Specific savings in drill work and explosives consumption up to 50 % have been achieved in headings and slopes. The positive results have motivated further Peruvian mining companies to introduce the new technique."

Jan 1, 1994

By Sam Oaks, David A. Smith

The new Corridor "G" Federal Highway Project in Logan County, West Virginia is the largest mass excavation highway project currently being built in the United States. Seven sections covering 14 miles of four lane highway and two connector roads will require over 30 million cubic yards of excavation. Construction is on a fast track schedule requiring the contractors to complete excavation and pavement placement in a little over 19 months. The two different general contractors have implemented several innovative Blasting and Excavation Programs to complete this project within the tight completion schedule. The paper expands on some of these unique programs that made the project a reality.

Jan 1, 1994

By Alday B. Andrews

A computer program called Seiswise that predicts the character and intensity of ground vibration generated by surface blasting operations was developed and field tested. The program uses the time histories of one or more pilot shots in combination with various initiation sequences to construct synthetic seismograms which are examined to select designs that will produce low levels of ground vibration.

Jan 1, 1990

By Larry R. Fletcher, John W. Kopp

The safety record for explosives in U. S. mining is excellent considering that over 4 billion pounds of explosives are now being used each year. However, blasting accidents remain one of the most serious concerns based on the number of injuries, the injury severity rate and the disaster potential. The Bureau of Mines has been analyzing blasting accident data obtained from the Mine Health and Safety Administration (MSHA) to determine the most frequent causes of mine blasting accidents and to examine trends in blasting accidents. This accident analysis is an update of two previous blasting accident studies conducted by the Bureau and published in 1983 and 1987.

Jan 1, 1991

By Jack Eloranta

This paper describes a method of evaluating shot performance through the use of available mine- data. The mine had already been monitoring the following parameters for other purposes: drill penetration rates, shovel loading rates, crusher throughput, crusher power and crusher hangups. By assigning pit coordinates to these factors, maps showing the location of difficult and favorable blasting are as are identified. Products and techniques are compared by the same method.

Jan 1, 1993

By P. D. Katsabanish

Air decking applications are examined using numerical modelling and the AutodynTM code. The mechanism of damage is illustrated and discussed. Air decking is shown to provide advantages over stemming when powder factor is maintained. The current effort does not support reduction of the explosives column in favour of air decking. In a similar fashion, bottom hole air decking increases fracturing in the area of the air deck, compared to when the same volume is occupied by inert materials; however air decking does not appear to reduce the requirement for subdrilling. The apparent discrepancy between the numerical results and some field observations reported in the literature is discussed.

Jan 1, 2005

By Clarence Zink

Aside from the mechanical properties and process of actual rock breakage, rotary drill bit performance is affected by several “post breakage” items: cuttings size, flushing air pressure, flushing air volume, cuttings load, drill hole geometry, etc. We all recognize that more efficient drilling creates bigger cuttings, more air pressure cleans the hole bottom better, more air clears the cuttings from the hole, and a better hole geometry allows cuttings to escape with a minimum of “regrind”.

Jan 1, 2006

By David R. Holberg

In the Kansas City metropolitan area, mineable Bethany Falls Limestone occurs 80 ft below river level under the 700 acre Park College Campus on the north bank of the Missouri River at Parkville. For 20 years prior to this project various firms passed over this opportunity to mine this property for construction aggregate because of uncertain costs, financial risk, and the difficulty of constructing an entry tunnel. This paper describes the drill and blast construction, rock bolting, and shotcrete lining of a 750 ft. long, 15% declining grade, truck tunnel through several Pennsylvanian limestones and shales.

Jan 1, 1997

By P Albert

A wedge-shaped underwater rock plug has to be blasted in order to tap the reservoir and furnish water to a new underground powerhouse at Manicouagan-5. The paper deals with the design and engineering aspects of drilling and blasting of this plug where the topographical configuration is extremely difficult. In this study small diameter vertical holes are considered with the OD-method and a fixed platform is recommended for drilling and loading operations.

Jan 1, 1984

By Finn Ouchterlony, Gert Bjarnholt, Robert Holmberg

A system for contour blasting with a linear shape charge principle has been studied /10/. In one operation the charge creates two notches along the bore hole wall and breaks the rock mass. The built in notching capability makes it possible to reduce the specific charge and the bore hole pressure to 1/3 of what is used in conventional contour blasting and to ensure that cracks are initiated and propagated only at the notches and nowhere else. The notching capability of linear shape charges has been studied experimentally and the bore hole pressure calculated to aid in optimization of a charge for future field experiments in bore holes with a diameter of about 50 mm.

Jan 1, 1983

An explosive's velocity of detonation (VOD), can be used to indicate a number of important characteristics regarding the product's performance under specific field and test conditions. A number of new characteristic and transient VOD curves have been identified in the field, which can be used to evaluate explosive performance, control ground vibration amplitudes and frequencies, select the correct amount and type of stemming for use at the collar and in stem decks, eliminate explosive desensitization, evaluate primer performance, design air deck based blasts, evaluate contaminated explosives and to overcome post blast noxious fumes.

Jan 1, 1994

By Young-Dong Cho, Han-uk Lim, Bok-Ki Park, Sang-Eun Lee

Many methods and techniques have been developed to reduce ground vibrations. Some of them are an adoption of electric millisecond detonators with a sequential blasting machine and an improvement of initiating system with an adequate number of delay intevals.

Jan 1, 1995

By Dennis J. Viscusi, James H. III Rowland, Lon D. Santis, Mark H. Weslowski

This paper describes the procedure for analysis of toxic fumes from the detonation of high explosives using the Large Chamber at the U.S. Bureau of Mines (USBM), Pittsburgh Research Center (PRC). This test is specified in 30 Code of Federal Regulations (CFR) Part 15.20 (g) as a requirement for the Mine Safety and Health Administration's (MSHA) approval of an explosive as permissible for use in underground coal mines. The Large Chamber replaced the Bichel gauge and CrawshawJones (C-J) apparatus in the 1989 revision of these regulations. To determine the safety of an explosive in terms of toxic gas production, the Large Chamber Test attempts to simulate mine conditions and miners' exposure to toxic gases from explosives.

Jan 1, 1995

By Lee Julian

Ground vibrations generated by mine blasting must be controlled to comply with legislation and to protect sensitive local or site infrastructure. The consequences of exceeding imposed limits can range from negative publicity to structural damage to infrastructure. It is imperative that vibrations are controlled without compromising fragmentation and delivery of blasted inventory. General practice is to reduce the charge weight and the blast size as blasting approaches the sensitive structures; however such an approach results in blasting smaller volumes more frequently which places greater pressure on production to meet their targets.

Jan 1, 2014

By Paul Worsey

A strong inverse relationship between rock face movement and stemming ejection is presented. Previously unpublished data from blast control plug research and development involving high speed video analysis, which was conducted between 1986 and 1988, is presented. Face and stemming ejection velocities were calculated for tests utilizing the same bench blasting configuration comprising; a 4 ft high bench in dolomite, 3 ft burden and single 1.75 in. holes loaded with 2 ft of small diameter cartridge emulsion. The singular difference between these tests was the stemming configuration. Varying lengths of stemming were used with the presence or absence of differing experimental configurations of blast control plug. The effectiveness of this plug has been published previously.

Jan 1, 1990

By Peter Bellairs, Anthony Bubb

The Porgera Gold Mine is located at an altitude of 3000m in the central highlands of Papua New Guinea some 600 km Northwest of Port Moresby the capital city. Access to the mine is via a five hour trip on an unsealed road from Mount Hagen the nearest regional centre or 40 minutes via air. The mine operates on a fly in - fly out basis and currently produces ore from both opencut and underground operations with the former providing the bulk of the mill feed. Opencut mining utilises conventional truck / shovel, drill and blast methods on both 10 metre and 14 metre bench heights with the larger benches being restricted to the stripping areas. This paper presents the strategy used and the results of a blast optimisation process in the opencut that was a joint effort between the mine personnel and the explosives manufacturer/supplier.

Jan 1, 1997

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