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By Bonifacio Degay, Mike Lovitt

PT Freeport Indonesia is a block cave mine that now utilizes an advanced undercut method to set up the min in the Deep Ore Zone (DOZ). In this method a slice of rock (undercut) is broken such that it sits on top of the drawbell level. The drawbells are developed to channel the broken ore into the extraction level and to enable the caving orebody to be drawn out in an even and controlled manner. These drawbells are difficult to form due to the small amount of void that can be developed in the low strength rock before firing. Starting with two rises of 2m square, the void ratio for the entire drawbell around 6%, which would normally result in a frozen and unproductive blast. Orica -Mining Services have worked with PT Freeport in a collaborative effort to find a solution to the mining problem. With excellent control of timing of the blasting it is possible to get fluid flow of blasted rock out of the draw points such that more void can be made available for blasting the remaining parts of the drawbell. The i-konTM electronic blasting system gives the exacting control of timing within the blast to achieve this Dynamic Void Generation (DVG). The solution stops the need to charge close to brows in the drawbells and reduces the cost and time related to developing initial blast voidage. This paper identifies the results of the trials including design, photographic evidence and vibration analysis. The flexibility and accurate timing of this electronic blasting system has enabled single hole initiation rather than 4 or more holes being initiated together, thereby reducing the damaging vibrations to the extraction level.

Jan 1, 2004

By Larry R. Fletcher

The Bureau of Mines obtained blasting accident data from the Mine Safety ant Health Administration (MSHA), U. S. Department of Labor. These data were analyzed to determine the most frequent causes of accidents in mine blasting. Accident totals for 1971 through 1981 are tabulated for metal-nonmetal and coal mines both surface and underground. In the past 11 years (1971-1981, inclusive) there has been an annual average of 9 fatal and 121 nonfatal blasting accident victims. Underground mining averaged 6 fatal and 93 nonfatal injuries each year.

Jan 1, 1983

By Paul N. Worsey

Disturbed zones of rock have been measured for blasted highway rock cuttings by Matheson and Swindells of the Transport and Road Research Laboratory (TRRL) of Great Britain. These zones have been shown to be directly attributable to the blasting process and accordingly vary in depth depending on blasting technique. Perimeter blasting such as smoothwalling and pre-splitting has been shown to be effective in reducing the depth of disturbed rock. Although extensive work has been carried out on surface excavations for medium diameter (l00mm) blast holes, none has been undertaken for underground excavations.

Jan 1, 1985

By R Yang, D B. Kay

"Blast vibration control is of vital importance for tunnel blasting in urban environments. A vibration model with multiple seed waveforms (MSW) as input for a point of interest was developed in recent years by one of its authors. The MSW blast vibration model has been applied successfully in open cut and quarry blasting situations. From the literature, it appears that there may not be any seed wave-based vibration modelling work for tunnel blasting.A project was conducted to test the MSW model for tunnel blast vibration. A series of tunnel blast rounds were fired and tri-axial vibration waveforms from the blasts were recorded with several seismographs at distances ranging from 10 to 100 metres from the blasts. Seed waveforms were collected and the charge weight scaling law for the signature hole PPV were established.The MSW model is applied to tunnel blasting and specific issues associated with tunnel blast vibration addressed, such as variable effects of confinement and screening to vibration during a blast round. The capability of the model in terms of the PPV and frequency prediction is demonstrated in the paper. The paper demonstrates that the MSW blast vibration model is a useful tool for managing tunnel blast vibration with the potential to optimise round by round design in terms of managing the vibration below the limit while maximising tunnel advance rate."

Jan 1, 2011

By Ulrich Leiste

If the iron ore loss is 15% in the process of mining, the total iron ore loss in the world will be about 461 million tons, this is equal to the total production of 230 iron ore mines each of which produces 2 million-tons of iron ore per year. Based on a series of blast tests in the Malmberget mine, this paper shows that ore recovery can be markedly increased by improving blasting technology such as choosing a correct primer position and making use of shock wave collision. The paper further suggests that a high ore recovery can not only reduce natural resource loss and mining cost but also prolong the life of a mine. In addition, the paper shows an example of reducing blast-caused rock damage in the roofs and walls of underground drifts (tunnels) by using new blasting methods in the Malmberget mine. Finally, the paper shows how the Malmberget mine has successfully reduced the ground vibrations, without adversely affecting fragmentation and ore recovery in sublevel caving mining.

Jan 1, 2014

By Abraham Lindo

Taboguilla is a small island located 10 miles outside the Panama Canal Pacific Entrance. In 2002 a fuel distribution facility was installed in order to supply fuel to vessels passing thru the canal. The current capacity of the tank farm is equivalent to 1,100,000 barrels. The demand for marine diesel at this location still exceeds the current capacity, thus an expansion project is currently underway to increase the available space for diesel tanks. There is a total of 800,000 cubic meters to be excavated in order to create the new space. 400,000 cubic meters of that total is basalt rock which will need to be blasted

Jan 1, 2011

By Charles W. Trettel

Confined explosives upon detonation produce a chemical reaction generating expanding gases that result in fragmentation of matrix a chemical to mechanical transition. A 100% energy conversion during transition is difficult, if not impossible, to achieve. There are numerous variables that affect energy transition. Although fragmentation is the most often used criteria to determine shot efficiency, the escaping energy profile provides additional data as to the efficiency of a blast. Escaping energy can also have deleterious effects in the form of ground motion.

Jan 1, 1975

By Karl Christopherson, Vanessa de Viterbo

Trim blasting is an integral part of the mining processes at the Morenci Mine, a Freeport-McMoRan Copper & Gold Inc. property. Trim blasting near high-walls or Finals blasting requires a tighter distribution of energy but a reduction in total energy factor near the wall. Recent Finals blasting in Morenci Mine was allowing the shovel to dig to the final design limit, but causing high-wall instability due to excessive energy or production of energy (blast design and timing). Slope instability events reduced production in two of the three operating pits in Morenci over 2009. In order to avoid high-wall instability from Finals blasting, a new method was required. The new method utilizes air-decks, unconventional row timing, and blast design based on the geology predicted. Many different geologic structures and rock types exist in Morenci, and different strategies were needed for the many predicted geologies. Drill penetration rate and core mapping were the primary tools for determining the blast design. Patterns were designed within a consistent geology; with weaker rock types receiving a lighter load than the stronger rock types. Penetration rate returned by the drill would be the determining factor on the actual rock hardness. Maintaining the pattern geometry on Finals designs should not be an issue as long as the lb/hole is adjusted to reduce powder factor close to the high-wall. One requirement of Finals blasting should be that the powder factor matches the geology as closely as possible. A softer, fractured zone should use approximately one-half to two-thirds the explosive charge of a competent, sound geological zone. This has been incorporated into the final Trim blast design. It is impossible to protect every high-wall from close-in blasting, especially those with crossing prominent joint sets inclined toward wedge failure, but this new design has provided protection on walls where the mine was encountering problems.

Jan 1, 2011

By Z X. Zhang

In sublevel caving mines, eyebrow break usually gives rise to lower ore recovery and worse safety in the field. Eyebrow break is caused mainly by two tensile stress waves: one from the front surface of a blasting ring, and the other from the roof of the drift. In order to reduce the two waves and finally to reduce eyebrow break at Malmberget mine, we employed two methods: (1) cartridge charge, and (2) double-primers in each blasthole. The two methods were tested in one ore body called ViRi. A total of 10 rings with the cartridge charge and 25 rings with the double-primers were blasted. At the same time a total of 34 ordinary rings were blasted in the same ore body. The result shows that the eyebrow break is 3.0 m for the ordinary rings, 2.3 m for the cartridge charge rings, and 2.1 m for the double-primer rings, respectively. In addition, the ore recovery for the double-primer rings is increased by 3% on the level of ViRi930, compared with that for the ordinary rings.

Jan 1, 2011

By Alejandro Ferrada Vergara, María Jesús Barros Godoy

Reducing costs while maintaining productivity and achieving good results is a constant challenge in mining operations, especially in the drilling and blasting stage, since a bad blast can affect production plans, increase costs, affect safety and jeopardizing the pit stability. Examples of undesirable blasting effects are: flyrocks, boulders, loading equipment damages, lower production rates, etc. In some of the biggest open pit mines using conventional blasting patterns visited by the authors, the pattern does not adjust properly to the rock mass, in most cases blasting polygons are large and the rock mass condition is variable within the designed blasting pattern. On the other hand, conventional blasting patterns with stemming columns use 40-50% of the blast hole with inert material (the stemming). Moreover, blasting engineers spend efforts to improve fragmentation results by increasing explosive charge in spite of having the negative effect of ground vibrations, with little or no success. The classic approach is "the more explosive in, the better the fragmentation is", furthermore it is assumed this relation is direct and infinite, but it is definitely wrong. This work challenges the notion of a limitless direct relationship between explosive charge and fragmentation, this means this is partially true but just up to a certain limit. In other words, there is still room to improve energy distribution among the classical blasting techniques without increasing the explosive energy by using air decks. In the work to be presented air decks are built using conical shaped stemming plugs called Paraplug®. The results obtained suggests a wedge effect acts in the bottom of the stemming column that cushions the shock wave and the air deck to reduce the detonation pressure (this is due to the decoupling factor resulted from the air deck). The demonstration shows improvements in fragmentation results, reduced vibration records accompanied with lower dust column and costs savings in explosive charge.

Jan 21, 2025

By A. S. Tawadrous

Fines are produced in any blasting application. Depending on the application, fines may or may not be a desirable product of the blast. In most quarry and construction applications, fines are considered an undesirable product since it does not constitute a sellable product and there are costs to the operation for disposal. On the other hand, in most open pits fines do not represent as much of a problem since the ore has to be crushed and ground after being blasted. Therefore, fines in such operations may reduce the energy consumed in the downstream operations.

Jan 1, 2012

By E. Líder, J. Pavez, J. Rivera

The application of new technologies, methodologies, and the use of new products in mining operations is a practice that is becoming more common in the industry every day, added to the new challenges and restrictions found in the operation. In the city of Tierra Amarilla, the interaction between mining operations and the community presents a constant challenge given the proximity to the community and the limitations that this presents. Explosive charge mass, in conventional blasting using traditional explosives (ANFOs, packaged explosives for example) limits the explosive charge lengths (they are reduced), impacting the explosive charge productivity. To improve the productivity of explosive charge and fragmentation, the use of low-density explosives was proposed, allowing the increase of the explosive charge length, trying to maintain the vibration levels within the established limits (2mm/s), preserving the fragmentation of the rock in the required sizes. The present study shows the results obtained from the application of low-density bulk emulsion for production blasting charges using upward and downward fan drillings. During this process, 18 blasting events were carried out, of which 8 were Up-hole loading (average density of 0.75 gr/cc) and 10 with Down-Hole loading (average density of 0.95 gr/cc). In summary, a total of 110,760 tons of ore have been broken, using low density emulsion, meeting the proposed objectives such as: 33% reduction of vibrations, 12% overbreak (within the theoretical design), P80 of 11in and 4.6% in fines.

Jan 1, 2024

By Tuan Nguyen, Dirk Hummel, Ruilin Yang

In a tunnelling site in Japan, it was found that detonators failed to initiate with their shells and primary explosive intact. Their capacitors, however, were discharged due to some damage on the application-specific integrated circuits (ASICs). These detonators are distinctly different from other commonly observed failures, where the shells are rather crashed due to excessive dynamic pressure received from neighbouring blastholes which fired earlier. Such incident has not been reported elsewhere. Detonator failures during a blast are deemed not safe and can cause disruption on the project productivity. It is therefore desirable to understand the origin of such event. Various measurements were conducted to diagnose the problem, but the root cause had yet to be identified. This paper applies a discovery from a 60-year-prior-laboratory experiment and formulates a theory that could explain the observed detonator failure and predicts the measurements and observations.

Feb 6, 2023

By Adrian Moore, Dominic Hooton, Alan Richards

Significant factors affecting airblast overpressure (AOP) emissions include charge mass per delay, distance from the blast site, burden, stemming height, and delay timing, topographic shielding, and meteorology. The effect of charge mass on the frequency of the airblast produced, and the delay timing required to control the level of airblast overpressure is explained by two case history examples which were not affected by topographical shielding and meteorology. One is a cast blast with a charge mass per hole of 1000 kg (2200 lb), and the other is a quarry blast with a charge mass per hole of 64 kg (141 lb), These examples show that the delay interval necessary to prevent an increase in AOP levels must be increased with an increase in charge mass per hole. The effect of a ‘soft-start’ technique where a reduction in AOP levels is achieved by decking only the initial front-row holes is also illustrated.

Jan 21, 2025

By Ulrich Leiste, David M. Fox

This paper presents the results from small scale testing aimed at measuring the loads on a rigid target due to the detonation of a buried mine. The aim of this research is to find how the impulse delivered to the target varies as the air filled void volume fraction within the soil changes.

Jan 1, 2013

By Tapan Goswami, Stephen Jeric, Geoff Brent

Highwall failures in large deep open cut mines have very significant safety and commercial implications. There are many factors influencing the stability of highwalls. The major influence is the interaction of the local geology with the shape of the pit wall. This factor is in the realm of the geotechnical engineer and is beyond the control of the blasting engineer. However, a secondary influence is the blastinduced damage to the wall. In most open cut metal mines the blasting strategy to control this damage involves the use of separate production and trim blasts bounded by presplits at the final wall.

Jan 1, 2011

By C W. "Mickey" Bradley

Thunder strikes terror in the hearts of man and has since the advent of time. We all fear the unknown; even the Greeks created a god, THOR, to be responsible for the thunder and rain. Thunder, by itself, can't hurt anyone; it is simply hot air moving very fast. Thunder, however, is caused by lightning and lightning is what we need to fear and rightfully so. Annually, lightning kills hundreds of Americans, injures another 2,000, damages or destroys approximately 30,000 structures, 1 starts thousands of forest fires and strikes mine properties over 100,000 times.

Jan 1, 1992

By Gregory Hempen, Thomas Keevin, Russell Wilcox, William Wild

The Department of Defense Strategic Environmental Research & Development Program (SERDP) awarded funding for evaluation of procedures to mitigate peak pressures and energy flux density in the water column from ordnance being detonated on the ocean floor. The research purpose was to conduct scaled testing to resolve whether a theoretically-viable covering technology was operationally effective in reducing blast effects and the impacts of shrapnel. An additional objective was testing effectiveness of this method for hard-bottom units (rock or coral) and (unconsolidated) sediment substrate.

Jan 1, 2011

By James R. Kennedy

The recent drop in world gold prices is driving many northern Nevada underground gold mines to look for new ways to improve and enhance current mining operations. Continuous improvement programs at these mines are finding the means to increase mine productivity while reducing total production cost. This paper looks at developments in the drill and blast program at Independence Mining Company’s Murray mine.

Jan 1, 1999

By Harry Verakis

Flyrock is the second leading cause of all blasting related injuries in surface coal, metal and nonmetal mining operations. It is also a primary cause of property damage, monetary losses and “near misses.” For the period 1978 to 2008 flyrock accounted for 11.6 percent of all blasting-related injuries in surface coal, metal, and nonmetal mines. A large amount of published material has been published on the safety hazard of flyrock, on ways to predict how far rock will travel from a blast, as well as ways to protect mine personnel and neighbors from flyrock. However, flyrock incidents continue to occur resulting in fatalities and “near misses” that could have caused fatalities. It was only good fortune in some instances that no one was in the mine's parking lot or other unprotected area when flyrock rained down or in harm’s way when a large rock punched a hole in the roof of a building or other structure.

Jan 1, 2011