Search Documents

By J. A. Rodgers, K. C. Whitaker

The time domain during which an explosive detonates and causes rock to fragment and displace is on the order of tens of milliseconds. Because of this, the dynamic processes that occur during this time frame often become a source of confusion when trying to analyze the performance of explosive products in decked blast designs. As an illustration, the authors have experimentally examined explosives malfunction in decked blasts through state-of-the-art measurement techniques. The interaction of explosive products and blast geometry was examined in detail using the analysis of a series of decked blastholes. Explosive and initiator malfunction in decked blasts is often considered to be entirely the result of insufficient inert decking material, however, it is shown that rock properties and dynamic burden conditions may have a significant impact on decking performance. The successful application of deck-blasting technique for control of ground vibration amplitude relies on an understanding of the true dynamic performance of the blasthole.

Jan 1, 2000

By B Mohanty

Several parameters such as, Energy, Strength, Brisance, Impulse, and Bubble Energy, are in common use in the explosives industry today to rate commercial explosives in terms of blasting performance. However, this multiplicity of terms, their frequent interchange and their purported one-to-one correlation with expected performance have given rise to a considerable amount of confusion, and have often resulted in unrealistic rating of explosives. In this paper, various theoretical and experimental methods of estimating energy and performance of explosives are discussed and their relative merits examined. These methods include, Computer Code Calculations, Cylinder Test, Trauzl Test, Ballistic Mortar Test, Underwater Test and Model-scale blasting. It is shown, in the light of actual blasting process, that such measures cannot be considered accurate indicators of expected blasting performance as the properties of rock to be blasted are either totally ignored or only partially accounted for in these methods. It is also shown that no single technique alone among those currently employed by the explosives industry can lead to realistic rating of explosives in terms of expected blast results. The need for the adoption of a two-tier rating system, one based on chemical potential "energy", and the other based on blasting "performance" is proposed, and specific approaches to achieve this objective are outlined.

Jan 1, 1981

By B R. Spencer

Using bulk repumpable water gel explosives in underwater shooting results in even more benefits to the user than a "dryland" customer. It is nearly impossible to reshoot underwater, so a bad shot causes tremendous problems. The huge expense of operating drill boats, dredging buckets and clamshells makes shot loading, hookup and digging cycle times critically important.

Jan 1, 1990

By Alan Minchinton, Ian Kirby, Jim Chan

It has long been known that successful blasting in soft and hard rock can require the use of different explosives. While choosing an explosive of the right energy density is important, the dynamics associated with non-ideal detonation behaviour play an equally major role. Tuning the energy release rate of an explosive to optimise its blast efficiency can be likened to tuning an internal combustion engine to improve its performance.

Jan 1, 2014

By James T. Ludwiczak

Drilling and blasting in a Karst (sinkholes and mud seams) environment has long been a problem for blasters, miners, quarry operators, contractors, and developers. While one cannot change the geological conditions, one can take some measures during the bidding process and the initial preparation of the blasting program to help reduce some of the problems. During the geotechnical investigation and developing the test/core drilling grid, the owner/developer needs to take some additional measures that will provide important data to the blaster to help reduce the problems associated with blasting this type of geology. The owner/developer must also understand that, due to the geologic conditions, the results of the blasting will not be ideal and there may be additional blast-related costs. If provided the proper geologic data, the blaster can develop drilling patterns and blast designs that will help reduce some of the more problematic areas.

Jan 1, 2005

By P A. Gibson, J R. Brinkmann

The South African gold mining industry fires approximately 800 000 sloping blastholes daily. A programme aimed at characterizing the stope blasting process is underway in order to identify areas for improvement and to provide blasting related information for the design of mechanized sloping systems.

Jan 1, 1985

By Salah A. Taqieddin

Blast casting or trajectory blasting, as it is sometimes called, is an innovative mining technique that has been receiving increasing acceptance among operations of surface coal mines and quarries as a means of offsetting the rising cost of mechanical excavation of overburden with a high overburden-to-ore ratio. Many similarities exist between geological characteristics of overburden formations of phosphate beds and the formations that conceal coal seams. Both are sedimentary origin and are removed for mining in an identical manner (i.e. use of a dragline or shovel to strip or cast the overburden aside).

Jan 1, 1997

By Yu Yalun, Meng Chuyan, Wang Lin, Wang Deshang

Based on the analysis of problems with wall control blasts in open pits, the essential theoretical basis and technological design of the damping presplit blasts are put forward. After practical application of this method in Nanfen Open Pit China, very good results have been achieved: 1) The rate of decreased vibration is up to 40%; and 2) The damage area of slope is reduced about 60%.

Jan 1, 1998

By Pierre-Alexandre Abeel, Charles Dowding, Justin Lueker

When blasting is eliminated as a cause of cosmetic cracking, often someone will ask, “If blasting didn’t cause the crack, then what did?” This paper describes detection by remotely operated instrumentation of the new cosmetic crack that was climatologically-induced. The measurement was obtained as a part of the development of Autonomous Crack Measurement (ACM) instruments to measure micro-inch response of cracks to both long-term, climatological, and dynamic, blast vibration effects. The crack occurred in the wall of a structure that was monitored for over 29 months and as such represents one of the longest periods of ACM observation.

Jan 1, 2015

By Zhang Shixun, Wang Xuguang, Wang Guoli

A massive millisecond blast at an open-pit mine of large scale can be realized by using the blasting technology of pre-loaded explosives, which can enlarge production scale, reduce the frequency of blasting and of large production equipment movement, and raise the production efficiency. The reason why application of this technology is restricted at high sulfide ore deposits of variable and complex geological conditions is that an exothermic reaction will take place when explosives contact sulfide ores, which could lead to accidents such as spontaneous burning and detonation of explosives pre-loaded in boreholes, influencing blasting and production safety. The thermal decomposition reactions of emulsion explosives of different prescriptions in contact with pyrite have been studied by differential thermal analysis (DTA), kinetics parameters calculation and accelerating rate calorimetry (ARC), and on the basis of the above studies, the safety of emulsion explosives used in sulfide mines has been evaluated with the safe contact time of different emulsion explosives with pyrite determined.

Jan 1, 1998

By Joseph W. Hejny, Marlyn G. King

Coal mining in the Powder River Basin has changed in recent years to accommodate the large quantity of coal produced. With strip ratios of one to one and up to three to one, extensive amounts of overburden have to be removed to get to the large thick seams of coal. Larger shovels and trucks have been implemented in the removal of this overburden. The addition of draglines and continuous miners have been added to increase the production of coal. Drills used today are capable of drilling up to 13.5 inch blast holes.

Jan 1, 1994

By R Vuolio, B A. Jonsson

In the center of Helsinki - capital of Finland - extensive blasting operations were carried out during the years 1982 - 84. At the corner of the streets Mannerheimintie and Simonkatu - in the Forum block - about 125,000 cu.m. of rock were blasted to give place for a new modern shopping centre (Fig. 1). Added to this amount of rock another 10,000 cu.m. were blasted for a transport tunnel to an adjacent underground bombshelter (Fig.2) which is to be used as a parking place in peace-time. The blasting work was demanding and difficult to carry out due to old buildings surrounding the work-site as well as computers and other sensitive equipment installed in some of them.

Jan 1, 1985

By Stuart Brashear, Lee Schettler

"The effect of water on several ANFO/emulsion blend ratios is documented by both physicalobservations and analytical testing to demonstrate the effect even small quantities of water canhave on water resistant blends."

Jan 1, 1996

By RR Vandebeek, A W. Bauer

The Canadian Explosives Research Laboratory regularly evaluates the properties of commercial explosives for authorization under the Canada Explosives Act. Propagation sensitivity is normally measured using small scale tests. Relating the results in actual mining practice is difficult. In the mining industry, the propagation sensitivity is a measure of the ability of one cartridge to propagate to an adjacent cartridge in a borehole. They may be separated by a gap of in-filling material. As well the propagation sensitivity will be affected by the explosive type, temperature, degree of coupling, cartridge diameter and other factors.

Jan 1, 1987

By Deane Tunaley, Paul Tidman, Qian Liu, John Mullay

Laboratory studies have indicated that the crystallization and desensitization of microballoon sensitized emulsion explosives start immediately after shocking or pre-compression. However, the question of whether or not the shocked emulsion could be worsened by the growth of crystallization or recovered by rebounding back to lower densities has been rarely examined under actual rock blasting conditions. This study was primarily intended to investigate the desensitization characteristics of two commonly used emulsion products in terms of blasthole spacing and delay duration. In the experiment, two parallel blastholes, 32 mm in diameter and 1.7 m deep, were drilled downwards in an underground drift.

Jan 1, 1995

By Reynold N. Hoover, Davis S. Shatzer

The Bureau of Alcohol, Tobacco and Firearms (ATF) is responsible for the regulation and enforcement of the explosives laws codified in the Organized Crime Control Act of 1970, Title XI. To meet its responsibilities ATF has special agents, inspectors and specialists who regularly interact with the explosives industry. However, with just over 2,000 special agents and 800 inspectors and specialists, it is difficult to visit the almost 10,000 explosives licensees and permittees in the United States.

Jan 1, 1995

By Charles M. Curtin

A significant advance in nonelectric delay blast initiation has been achieved by Nonel shock tube, an invention patented by Nitro Nobel AB of Gyttorp, Sweden. Ensign Bickford has been licensed by Nitro Nobel to manufacture Nonel in the United States.

Jan 1, 1976

This paper describes experience in designing and implementing casting blasts over the past fifteen years. Important design parameters such as powder factor, burden and spacing, blast pattern geometry, front row burden and toe distance, pit width versus height, blast length, explosive selection, millisecond delay timing and tie-in types are discussed.

Jan 1, 1995

By Jaki Wilson, Les Armstrong, Neville T. Moxon

Low shock energy ANFO (ANFO) mixtures have been developed for use in fragmenting weak overburden materials and reducing damage.outside the blast zone in dry conditions. These mixtures can be readily produced on a minesite using conventional equipment and are formed by mixing low density additives such as polystyrene, bagasse and sawdust with ANFO.

Jan 1, 1990

By P Cotton, N Cox

The Brisbane City Council has implemented a program of continual improvement at its Mount Coot-tha Quarry in the heart of Brisbane, Australia. The program has been underway for the past 6 years, and has resulted in very significant improvements in terms of both the cost effectiveness of its operation, and in terms of its environmental impact on nearby residents. The work has included a focus, amongst other things, on blasting efficiency, and has challenged conventional thinking in terms of the size of blasts fired, the frequency of firing, the diameter of blastholes, and the use of bulk emulsion or slurry explosives.

Jan 1, 1995