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By J Lyall Workman, Peter N. Calder

The Manassas Quarry is a large industrial stone quarry in Northern Virginia owned and operated by Vulcan Materials Company. The quarry experienced instability in a portion of the north wall, which included toppling failure in a metasediment and movement on a major fault zone. It was necessary to take remedial measures to stabilize the wall and create good quality final pit walls.

Jan 1, 1992

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 Floyd W. Crump

New technology in video equipment, such as Super Video Tapes, Super Video Camera Recorders equipped with high speed electronic shutters, and VCR's with editing capabilities make it possible to resolve high speed events to still frames with an event elapsed time of 17 milliseconds (ms). This is far from the 2 ms resolution available with a High Speed 16 mm Film Camera such as the LOCAM at its maximum 500 frame persecond speed, but is adequate for many field blast evaluations.

Jan 1, 1991

By Robert E. Miller

Mass blasting of open stopes and pillars is a normal operating practice at Isa Mine. Three main parameters are used to classify the types of mass blasts. These are type of explosive used, blasthole diameter and system of initiation. Both electric and non-electric initiating systems are currently employed. The advantages gained by large firings are many. More efficient utilization of manpower, due to the concentrated and continuous charging, is achieved. There is no requirement for men to re-enter areas where localised ground conditions may have deteriorated and exposure of ringfirers to stope voids is reduced.

Jan 1, 1980

By D K. Joyce, B Mohanty

In a previous paper, it was shown that a lack of clear understanding of the role of initiation mode on detonation characteristics often leads to under-utilization of the explosive system in blasting. This is of particular significance since the very large number of explosive initiation practices currently in use implicitly assumes that the blasting performance of an explosive is largely independent of the exact mode of initiation. This paper deals specifically with bulk-loaded and pneumatically-loaded ANFO under various initiation modes in small diameters. These include initiation by booster and detonating cords of various strengths, and combination of cords and boosters. The nature of energy release and energy partitioning between shock and gas energy have been studied in the underwater test as a function of charge diameter. The paper describes the relative merits of various initiation modes for specific charge geometries and confinement, under end- and side-initiated conditions. Guidelines have also been formulated for use in the field to match initiation practice with blasting requirements.

Jan 1, 1994

By Pharis E. Williams

The ability of voids, microballoons, and even solids to sensitize explosives has been known and used for many years. This phenomenon has generally been studied and reported under the terminology of "hot spots" because of the increase in local pressure and temperature when a shock wave encounters such sensitizers. A method for treating this phenomenon in detonation theory or in a detonation model has been studied for almost the same length of time. Perhaps because of the complexity and non-linearity of the void, or microballoon collapse, several of these studies have used the expediency of including additional terms in the burn rate law to account for the influence of hot spots. The detonation model proposed here considers the sensitization due to discontinuities in the shock impedance to be a mechanical phenomenon to be accounted for in the mechanical equations governing the detonation and not in the burn rate law. While this is not a new contention, the method for handling this non-linear phenomenon within the proposed model is new. The model also includes a method which accounts for the manufacturing variables of emulsion matrix cell size, microballoon size and type, as well as energetic additives.

Jan 1, 1992

By Josephine Bones, Robb Larson, Daniel Miler

Avalanches are commonly mitigated through the use of explosives at ski resorts and above transportation corridors. Surprisingly, very little research has been conducted on snowpack response to explosive inputs, and efforts to model this response have been limited. The purpose of this ongoing research project is to ascertain an understanding of the dynamic snowpack response in relation to explosive size and height above the snowpack, coupled with snow conditions, to enhance avalanche control. A system of sensors and computer-controlled data acquisition components has been created to record the movement of snow resulting from the charge detonation. The system records acceleration vertically and radially within the snowpack at two distances from the point of detonation as well as blast air pressure at one location during explosive events. The data at two locations allows inferences to be made about the transmittance and attenuation of shock waves through the snowpack radially as well as vertically. The data shows that raising charges above the surface results in increased snowpack dynamic response when compared to surface detonations. Applying power function regression to accelerations for individual charge elevations, it was determined that both radial and vertical rates of attenuation were not dependant on charge elevation. Additionally, raising the charge also resulted in increased dynamic response at depth within the snowpack

Jan 1, 2012

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 Jesús V. Saccsa, Kenji B. Loayza, Erick M. Condori, Jorge A. Velásquez

This research investigates how to reduce manufacturing costs of a safety fuse composed of black powder, replacing its ingredient NO3K by NO3Na for processing, and contributing to minimize costs per blasting.

Jan 1, 2017

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 Thomas A. Gelormino, Ulrich La Fosse

"Deep blasting was used to densify foundation soils for a large manufacturing facility inChicopee,Massachusetts. A 360,000 square foot building, whose construction began inthe summer of 1990, is founded on alluvial deposits up to 90 feet in depth. These deposits are comprised of saturated very loose to loose fine to medium grained sands with traces of silt and gravel. During the building foundation design it was found that to withstand earthquake forces without soil liquefaction, it would be necessary to improve portions of the alluvial deposits by densification. The zone in need of densification extended from approximate depths of 20 to 50 feet. Several conventional densification methods, including vibrocompaction and deep dynamic compaction, were evaluated along with deep blasting. Detonation of 1-3/4 inch diameter charges of 65 percent gelatin dynamite (Atlas Power Primer) installed inside 2-inch diameter PVC casings to a depth of up to 40 feet, was used to achieve the desired densification. This method was selected over others due to its lower cost and decreased construction time. Although used in New England once in1940 for a dam and once in 1960 for a transmission line tower to improve foundation soils, there is no precedent found in the literature for densification by blasting to improve liquefiable soils below a proposed building. Details of a test program and the production blasting, including vibration data are presented. Pre-and post-blasting data conclusely shows an increase in the density of the sand deposit after blasting."

Jan 1, 1991

By Mark S. Stagg, David E. Siskind

The Bureau of Mines arranged to have a wood-frame test house built in the pat of an advancing surface coal nine so it could investigate the effects of repeated blasting on a residential house. Structural fatigue and damage were assessed over a 2-yr period. The house was subjected to vibrations from 587 production blasts with particle velocities that varied from 0.10 to 6.94 in/s. Later, the entire house was mechanically shaken to produce fatigue cracking. Failure strain characteristics of construction materials were evaluated as a basis for comparing strains induced by blasting and shaker loading to those induced by weather and household activities. Cosmetic or hairline cracks 0.01 to 0.10 mm wide occurred during construction of the house and also during periods when no blasts were detonated. The formation of cosmetic cracks increased from 0.3 to 1.0 cracks per week when ground motions exceeded 1.0 in/s. Human activity and changes in temperature and humidity caused strains in walls that were equivalent to those produced by ground motions up to 1.2 in/s. When the entire structure was mechanically shaken, the first wallboard tape joint crack appeared after 56,000 cycles, the equivalent of 28 yr of shaking by blast-generated ground motions of 0.5 in/s twice a day.

Jan 1, 1985

By Joseph Meyers

Explosives techniques and technology are constantly evolving and improving, yet basic communication and business skills are not being used regularly. Many potential blasting projects never occur due to simplistic, basic factors, such as a lack of communication. Articulate communication is the key component in the blast approval process, which has changed remarkably from how business was conducted fifty years ago. Imperative to the approval process is communication outlining the safety and benefits of the blasting project. Information and transparency with the stakeholders and the Authority Having Jurisdiction (AHJ) will greatly improve the chances of having a blasting project approved. This open communication starts at the inception of the project when the memorandum of understanding (MOU) is obtained, and involves the AHJ through all steps of the approval process. The blasting industry and regulators must work collaboratively to improve safety, security, regulations and licensing. Implementing state of the art blasting techniques, security, safety measures, vibration monitoring and strict licensing allows the AHJ and all stakeholders to remain integrated and informed, contributing to process approval. Regulatory operators should strive to achieve success thru communication, cooperation and compliance which is accomplished thru continued education and transparency. These steps, combined with regular meetings, has proven to be a benefit to both industry and regulators. Relationships are built through trust, teamwork, transparency and communication –including the take holders and AHJ in the approval process from the inception solidifies these relationships and improves teamwork

By J. Eloranta

"Previous work indicated that the annual per-capita consumption of raw aggregate material averages about 10 tons; half of which is produced by blasting. Given a population of approximately 320 million in the United States alone, this amounts to 1.6 billion tons of blasted material annually. It was also estimated that up to 20% of the blasted material in aggregate operations is smaller than 6.35 mm (1/4inch) in size. Thus, about 320 million tons (i.e. 1 ton per capita) of byproduct is produced annually and sold at significantly lower prices or potentially discarded in waste dumps."

Jan 1, 2017

By Tristan Worsey, John Henchion, Nathan Rouse, Yannick Lauras

"This paper presents an approach used to plan and evaluate drill and blast trials for a mine that currently mechanically excavates in-situ rock. The document presents the approach used to plan the trials, the key performance indicators (KPIs) that were necessary to evaluate the mining methods, the test matrix used during the trials, and the results of the trials. The trials, which occurred as part of an overall drill to mill optimization project at this site, helped to evaluate various blast designs using fragmentation results,drilling and blasting costs, and downstream costs. This project was unique in that (1) drill and blast methods were trialed on multiple rock types and various bench heights using a range of blasthole diameters and powder factors and (2) the load and haul costs were evaluated using a range of loading equipment, from 66 tonne (73 ton) excavators up to 250 tonne (276 ton) excavators. A ten year net cost financial evaluation of the material extraction alternatives was also prepared for the site management. Ultimately, the process of evaluating the drill and blast trials helped the management decide whether to continue extracting using mechanical methods or to introduce drill and blast methods to extract the rock."

Jan 1, 2017

By S. Klerkx, R Battulwar, J Valencia, J Sattarvand, E Emami, M. Soleymani Shishvan

A new technology for energy distribution optimization, supported by NIOSH.

Feb 1, 2020

By Steven Townend, Don Wadden

In today's global economy the need to stay competitive is essential for commercial survival and growth. To this end Inco is committed to continuous improvement in its operations. Various aspects of the mining process have been examined to find ways of improvement.

Jan 1, 1994

Many North American coal strip operations are practicing trajectory control blasting with good results, often based on trial and error methods. This study summarizes the basic technical requirements for the design of bench-type casting with explosives to achieve further improvements.

Jan 1, 1987

By John R. Schuring, Walter Konon

The 2.0 in./sec. peak particle velocity criterion traditionally used to protect structures from blast induced vibration damage is non-conservative for landmark structures. Various factors which must be considered in establishing vibration criteria for landmark structures are discussed. Existing criteria by past investigators for this class of structure are presented.

Jan 1, 1984

By J Edmund Hay, T S. Bajpayee

The Bureau of Mines is developing a test to determine the initiating strength of commercial detonators. Various tests of "detonator strength" are in use, but many of them do not correlate well with each other, and so far, there is little evidence that any of them correlates well with the ability of detonators to initiate detonation in an explosive. Therefore, the Bureau decided to attempt a measurement of the ability of detonators to initiate detonation. To this end, an explosive mixture of adjustable sensitivity was developed. This mixture was nitromethane sensitized with ethylene diamine, the sensitivity being "fine-tuned" by the addition of nitropropane.

Jan 1, 1992