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By Bob de Raadt

After a review of the general principles for blasting stacks, the stagnations of two stack demolitions are investigated. The author concludes and demonstrates that MS-delay blasting can be risky under certain circumstances. How this initiation device can still be applied safely to the demolition of stacks is shown in an account of a blasting operation, in which two 106-m (350 ft) -high concrete stacks were involved. The recent discovery of a possible hazard of MS initiation in this field of blasting is an essential contribution to increased safety in blasting tall structures.

Jan 1, 1982

By Harry L. Siebert, Thomas Gelormino

Rock excavation in urban areas occurs with maximum public exposure and, with the aid of explosives, is one of the challenges facing this industry today. Such excavation is also a hidden factor in areas of new growth, revitalization or upgrading existing facilities in or near urban areas.

Jan 1, 1985

By Sharon K. Reamer, Yvan Sifre, Klaus-Gunter Hinzen

"Three case studies are presented that illustrate the successful application of firing timeoptimization (hybrid modeling) in the quarry environment and for a construction site. In allcases, the method requires the measurement of at least one in situ, single hole explosion asa representative model of the desired blast design."

Jan 1, 1993

By Bradley C. Paul

Similar rock formations exhibit great variability in resistance to fragmentation during crater blasting. This observation was made during an attempt to calibrate the Kuz-Ram blast fragmentation model for crater blast geometries used in a modified in situ mining method for copper. The KuzRam equation is used to predict the fragment size distribution from blasting and includes a term called the "rock factor" to account for the fragmentation characteristics of the material. A data base of field scale crater shots in oil shale was available to supplement more limited data on copper ores. First, the blast geometry terms of the Kuz-Ram formula were modified to fit field data with various crater blast geometries. Rock factors were chosen to center the predicted curve on the curve representing observed fragmentation. Next, five possible sources of variability in rock factor were investigated: the grade of the oil shale, the aspect ratio of the charge, the type of explosive, the charge depth, and the rock itself.

Jan 1, 1989

By Catherine T. Aimone

A series of experiments have been performed to characterize fragmentation and microcracking in quartz monzonite copper porphyry. The flyer plate impact method was used to generate plane shock waves in rock specimens for impact pressures between 1.6 and 7.3 GPa and impact pulse durations between 1.1 and 7.0 µs. The effects of pressures up to 4.8 GPa and pulse duration on fragment size distributions and microcrack densities were studied. The results show that pressures effect particle sizes to a greater extent at higher pulse durations. However, changes in pressure and pulse duration show little influence on the density of microcracks induced during explosive loading. These results indicate that the nucleation and growth of microcracks in rock subjected to shock waves occur uniformly throughout. A substantial decrease in particle sizes for high pulse durations is attributed to more time allowed for microcracks to grow and coalesce, forming individual particles.

Jan 1, 1985

By F. Malek

An extensive blast monitoring program has been carried out to study explosive performance and the effectiveness of blast designs in production blasts in a deep underground mine. Comprehensive monitoring of blasting vibrations through multi-station high-capacity high-frequency accelerometers, and borehole deformation history have been the main tools of such analysis. The mining activity involves relatively unstressed stopes as well as highly stressed stopes. More than 30 production blasts have been monitored, and the respective vibrations from close-range as well as distant seismic stations have been analyzed, and the vibration parameters (amplitude and frequency) have been correlated with explosive charge weight in the holes. It is found that the correlation between blasting rounds and the corresponding vibration amplitudes often have poor correlation for a very significant portion of the blasts. These point to either explosive charge malfunction in those specific blast holes, or inadequate blast design, or the effect of high in-situ stresses, or any combination thereof. This paper analyzes these variables and their effect on the overall blasting operation at the mine.

Jan 1, 2013

By M-C. Lee, Shomaker, R. Turcotte, B. Short

This research program was undertaken to better understand the factors causing abnormal NOx fumes generation from blasting operations in surface coal mining. More specifically, unusual quantities of nitrogen dioxide and nitric oxide have been observed at several surface coal mines in the Powder River Basin, Wyoming. All these mining operations have several points in common: (i) Blasting is performed using gravity loaded emulsions or emulsion/ANFO blends (ii) Unusual NOx (Oxides of Nitrogen) emissions are observed mostly when blasting is conducted in the overburden as opposed to the coal seam itself (iii) The overburden consists of very weakly consolidated ground strata, providing relatively weak confinement conditions for the explosives, and (iv) Significant ground water is observed.

Jan 1, 2002

By A Lance McAnuff, Marcus V. van Bers, Andrew Curic

During the summers of 1992 and 1993, blasting operations were carried out to effect the crossing of two of Canada's better known game rivers, the Nipigon and Winnipeg, in connection with the completion of a third natural gas utility across north-western Ontario. The Nipigon River, crossed in 1992, involved a single fast-flowing channel while the Winnipeg River, crossed in 1993, involved three separate channels.

Jan 1, 1994

By John J. Barnes

The advent of more powerful explosives, increased bench heights, and larger diameter blastholes has necessitated the use of presplitting techniques in sub-bituminous coal mines. The combination of these factors has increased the energy concentration during blasting, producing severe overbreak problems in the final pit walls. Presplitting with large diameter blastholes has proven to be the most viable method of reducing back break in sub-bituminous coal mines.

Jan 1, 1988

By Ismael Gottreux Vollet, Carlos A. Muñoz Lira, Alejandro Ferrada Vergara

Currently, underground mining of deeper massive deposits with lower grades, harder rock conditions in high strength environments, entails difficulties in caving, fragmentation and seismicity of the ore body. So far, the use of Pre-Conditioning (PC) with Hydraulic Fracturing (HF) has shown positive results in terms of seismic response and caving ability, while preconditioning combined with explosives aims to weaken the rock mass, causing an additional effect on fragmentation.

Jan 1, 2016

By Mark S. Stagg, Rolfe E. Otterness, Stephen Rholl

The Bureau of Mines is engaged in research to develop and test high explosive fracturing and rubblization techniques that will enhance ore body permeability and thus increase recovery during in situ mining. The natural permeability of many ore bodies is too low to allow successful in-place leaching. These deposits could be profitably mined if flow rates of leach solutions could be increased. Blasting represents a potentially low-cost and effective permeability enhancement technique.

Jan 1, 1991

By Cam Thomas

"Reflectorless laser survey equipment has made it much easier to take accurate measurements toinaccessible locations in quarries, open pit mines and rock slopes. Prior to the introduction of thereflectorless laser as a working tool, it was not possible to directly measure to inaccessible locations on rock faces. If a person could not occupy the point, only indirect measurements could be made. For blasting work, measuring the burden in front of the first row of holes could only be done approximately, using such techniques as holding a plumb line in over the crest, triangulating in on a few points or “eyeballing” the burden. This led to direct and significant problems with blasting, including flyrock and airblast (caused by insufficient front row burden), excessive vibrations, problems with oversize and tight digging (all of which may be caused by excessive front row burdens)."

Jan 1, 1999

By Daniel Vargas Quispe, Yorhinio León Robles, Marco Jauregui Vargas, Helen Espinoza Bailon, Oshin Quispe Luya

This project describes the methodology applied during the execution of tests to determine the multiple controls that mitigate damage to the final walls of the pit. The different tests were executed on production pattern, which considered: modification of the angle of pre-split drill line, damage evaluation in individual drills with different load designs, varied detonation sequences, capture and analysis of elementary waves. After the evaluation and analysis of the results obtained in the tests, we are in process to standardize various damage controls such as; the combination of pre-split drill line angles at 80° and 90°; charge design in buffer drills that reduce the angle of action of the explosive and a detonation sequence that involves the creation of a relief filter that is made up of the detonation of two rows next to the pre-split drill line, which will have the function of filtering the waves of vibrations produced by the detonation of the production drills and at the same time it modifies the direction of damage towards the blasted material. The analysis of the different controls, as well as their combination, will allow us to improve the compliance results of the formation of benches.

Jan 21, 2025

By Ed Jr Smith, Calvin J. Konya

The purpose of this paper is to describe the case history of a blasting project conducted jointly by Precision Blasting Services and Cherokee Explosives. It is the intent of the authors to show how blasting could be done in controlled fashion near very expensive computer controlled machinery. The job was done in minimal time with no complaints or allegations of damage in spite of the fact that blasting was conducted within five feet of the equipment and with the 32 acre plant fully operational, with machine operators working within 10 feet of the blasting site.

Jan 1, 1986

By Zhang Qi

For the most part, the flying piece is serious endangerment in the demolition blasting. To prevent the endangerment, a large number of materials are needed as the protection. Therefore, the determination and design way of the flying distance of piece in demolition blasting have been concerned extensively. Previously, the experienced or half experienced formula was adopted to calculate the distance of the flying pieces. The calculating values of the distances of flying pieces are not identical with the practice results. The problems concerning the design way of flying distance of pieces are researched in the paper.

Jan 1, 1994

By P D. Katsabanis

The phenomenon of sympathetic detonations in blastholes is investigated by comparing experimental observations and numerical modelling results. Numerical modelling using the TDL computer code and Forest Fire decomposition rates for commercial explosives has shown the importance of blasthole diameter, impedance of stemming material and host rock. Comparison with experimental observations has also shown that sympathetic detonations cannot always be treated as shock to detonation transitions (SDT). Examination of previous results which have been obtained from calibrated low amplitude shock experiments reveal that there is an ignition threshold prior to the detonation threshold. The difference between the two thresholds is more pronounced in the case of air bubble sensitized products. The ignition threshold can be very important under the confinement provided by the blasthole and the conditions of application. It also correlates well with the pressures expected at the gap distances of interest in the practical application. It is suggested that critical energies are used as the criterion for cross initiation in blastholes. Practical suggestions based on the numerical calculations and experiments based on these calculations are also given and discussed.

Jan 1, 1992

By Peter Moser

The average annual consumption of raw minerals in Europe is 10 ton per person. About 50 % is produced by blasting. For a population of 450 million (including the population from the countries of the new member states) this makes 2.25 billion tons of blasted rock, 80 % being building industry aggregates and industrial minerals. In aggregate quarries 10-15 % of the rock blasted can’t be sold, as the material is too fine, i.e. smaller than 4 mm. This ‘fines problem’ is worse in the quarries of limestone and cement producers where up to 30 % of the material is useless. Thus about 450 million tons of useless rock fines are produced and put on waste dumps every year, i.e. 1 ton/person. This problem is addressed by the research project LESS FINES - “Less Fines production in aggregate and industrial minerals industry” which is funded by the European Union under the project contract G1RD-CT-2000-00438. The project consortium, formed of nine partners from 5 EU countries, works on the following two main research subjects: 1. The determination of the natural breakage behavior (NBC) of the rock mass, which is defined as the particle size distribution curve for a certain rock mass with the maximum uniformity and thus for a given maximum particle size that fragmentation curve which gives the minimum amount of unusable fine material. The comparison between the NBC and an actual blast fragmentation curve allows to quantify the fines reduction potential. 2. The adaptation of explosives properties, charging techniques and timing in order to produce only the minimum, inherently unavoidable percentage of fines. With about 15 full time working persons the project is estimated to be one of the largest blast related research activities in Europe at the time of the project period. The project is coordinated by the Department of Mining Engineering& Mineral Economics of the University of Leoben.

Jan 1, 2004

By Lewis L. Oriard

Ground vibrations associated with blasting are generally in a higher frequency range and of shorter duration than those generated by earthquakes, and the intensity scales for earthquakes cannot be applied directly to blasting vibrations without modification. Further, the profession does not need an intensity scale merely to estimate vibration intensity. If the blasting in question was not monitored instrumentally, it is a simple matter to estimate the range of intensities based on published prediction formulae or data from various sources such as Oriard (1), Nicholls et al (2), Hendron and Oriard (3), Siskind et al (4), and others. However, the profession has a serious need, for purposes of evaluating damage claims, to understand the relationships between vibration intensities and the levels of observed effects. The criteria for threshold damage do not apply to typical cases which usually involve structural damage. If the damage in question would have required ground vibration with a particle velocity of, say, 20-120 ips, damage is not verified by showing that the vibration merely approached a suggested limit to avoid threshold damage. That is not the question. This paper provides some guidelines for comparing severity of damage to intensity of vibration which would be required to cause such damage, much as is done when determining earthquake intensities. In addition, this paper includes a discussion of strain amplitudes induced by environmental forces, the predominant causes of damage to structures. Also, certain popular myths regarding blasting damage are discussed in the paper. Due to space limitations, the paper will not include a discussion of airblast effects.

Jan 1, 1989

By W. J. Birch, R. Farnfield, S. Hosein, C. Johnson

Modern smart phones include accelerometers based on MEMS (Micro Electro Mechanical System) technology giving the possibility to measure both acceleration and orientation. The widespread use of such phones has driven technological development to such a degree that it is now possible to obtain a triaxial accelerometer unit, that also include signal conditioning and analogue to digital conversion, in a package smaller than 1 cm2 (1/2 sq.in) for a relatively low cost.

Feb 6, 2023

By Eduardo Berger

This paper describes a mechanized loading system, the HYDRODOSE, which allows the use of pumpable emulsions in underground mining. It also describes a pumpable emulsion explosive for small diameter holes, HYDROMITE PDB. Included are test results carried out in two Chilean underground mines.

Jan 1, 1991