Search Documents

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 Janice Reed

The first seismograph was developed around 132 AD. Much has happened since then. The “modern” seismograph (> 1920) has seen a lot of changes. From falling pin seismographs to magnetic tape units to today’s Z-curve analysis models, the blasting seismograph remains a necessary and useful tool to the blasting community. But why so many changes? What forces drive the advancement of the seismograph? There are many answers and aspects to this question. Research, regulation, and technological advances are the primary forces behind innovation in our industry. But these three forces also drive each other. Research drove our industry from displacement seismographs to particle velocity seismographs. Technology took us from 80 pound seismographs to units weighing less than 5 pounds. Regulation (and litigation) - the driving forces behind the Z-curve analysis units. How have these innovations helped today’s blaster? Have there been any negatives? It is important for today’s blaster to understand how we got here and why.

Jan 1, 2005

By J Edmund Hay, Harry C. Verakisl, Richard J. Mainiero, John J. Mulhern

As the first stage in the rulemaking process, MSHA prepared requirements for the approval and use of permissible explosives and blasting items in underground coal mines. These draft requirements known as "preproposals" were announced in the Federal Register in mid-1984. The draft requirements on the use of explosives were written as a revision to Title 30, Code of Federal Regulations, Part 75, Subpart N. The draft requirements for approval of permissible explosives including sheathed explosives for unconfined applications, approval of water stemming bags, approval of detonators and approval of blasting machines were prepared as Parts 15, 16, 17 and 25 respectively.

Jan 1, 1985

By D T. Froedge

To preface these remarks, it is not intended that this paper be a criticism of anyone or any organization involved in drafting the current regulations, for it appears that everyone involved in the process has made an extreme effort to be safe. We wish to show that in this case by making huge safety margins, we have created an unsafe condition in another area. That is by creating vast safety margins in the area of mobile transmitter intensity versus distance scales we have caused a severe handicap in the use of the mobile transmitter in securing blasting areas. The use of these mobile transmitters, which are absolutely essential in clearing areas where there are woods, mountains, or urban structures is virtually eliminated because of the safety factors prescribed in the regulations. We wish to show that these mobile transmitter safety factors are much too great, and can be traded off to increase the margin of safety in the ability to clear blasting areas.

Jan 1, 1975

By Gungor Tuncer, Erhan Bakirci, Ali Kahriman, Atilla Ozmen, O. Nuri Ucan, Savas Gorgun

There are several methods for demolition of structures but most of them depend mostly on conventional ways of using machines for breaking and crushing structural elements. However the need for lots of work force, expense and extreme amount of time for demolition, made most of these methods non-popular nowadays. Therefore, trials to accomplish a more economic and less time taking method lasted with the use of blasting. By applying controlled blasting on a suitable structure, the structure can collapse and break down to pieces in very short period of time, with no extra work force and cost. In spite of advantages of explosive demolition, the potential danger of explosives and the damage that the blasting may cause to surrondings, if not controlled properly, made people timid to the method especially in urban areas. Therefore, the pre-assumption by computational analysis has become an essential matter in the process.

Jan 1, 2002

By G J. Kulbieda

The Empire Mine initiated production in 1963. Since then the unit operations of drilling and blasting have evolved continually in order to meet the increased mining requirements demanded by plant expansions in 1968, 1973 and 1980. Additionally, advance mine planning has become an integral part of proper pit development and is necessary to insure uniform blending of the distinct ore horizons contained within the mine area. Blasting practices have been modified to facilitate the autogenous grinding system utilized at Empire and pioneered in the Iron Ore Industry. Technical innovations in the explosives industry, as well as, progress regarding on site blast engineering methods have substantially increased the use of ammonium nitrate explosives and helped to establish efficient charging procedures. In addition, the recent introduction and use of ammonium nitrate fueled with nitropropane and methanol indicates that it is a viable substitute for aluminized ANFO.

Jan 1, 1981

By D Larson, M Finger

Chemical explosives may become a key element in many of the in situ energy and mineral recovery methods under development. This paper discusses the potential role of explosives in deep rock mining for resource recovery. Several energy and mineral recovery programs described are an outgrowth of the Plowshare Program and Explosives R&D conducted as part of the AEC/ERDA mission at Lawrence Livermore Laboratory. Several important aspects of the use of explosives in deep rock mining are reviewed. First, the status of knowledge of deep rock fracturing to create permeability underground is discussed. Completely contained blasting has not been a widely applied tool used in the mining industry. We conclude that data available on deep rock fracture is minimal and that the mechanisms that control the processes must be understood before technical and economic feasibility can be established. We also discuss the unusual problems in the selection of an explosive or blasting agent for deep rock applications including emphasis on the functioning at depth and safety aspects. Finally, a brief review of similar activities within the U.S. is given.

Jan 1, 1976

By Bruce B. Redpath, Thomas E. Ricketts

Scaling laws commonly used for describing or predicting blast motions generated by conventional arrays of blastholes are dimensionally incorrect. The scaling of distance by the cube root of charge weight is correct only for spherical charges, and scaling by the square root of charge weight is incorrect for any charge configuration, although both approaches may result in empirically useful formulas for a limited range of charge sizes. Analysis of motions generated by a large set of underground blasts shows that scaling distance by the square root of the linear charge density, which is dimensionally correct for a cylindrical borehole, yields much more consistent results than the traditional scaling rules. Further, this scaling law is valid right up to the free face of the burden. A significant result of this work is that the peak particle velocity for an array of blastholes is primarily dependent on blasthole diameter and not on total charge weight or maximum explosive weight per delay, which are the commonly used parameters for scaling seismic amplitudes generated by conventional blasting arrays.

Jan 1, 1987

By John S. Manka

Of the various methods used to reduce the density of emulsion explosives prior to detonation; ammonium nitrate prill addition, glass micro-balloon addition and chemical gassing, chemical gassing is the method most often selected by emulsion explosive end users. Chemically gassing emulsions costs less than adding micro-balloons and chemically gassed emulsions have better water resistance than emulsions that add ammonium nitrate prills to reduce the bulk density. Unfortunately, the chemical gassing of emulsion explosives can be intricate and is often more art than a science. To gain a better understanding of chemical gassing, we investigated the factors that may affect the chemical gassing of emulsion explosives. Variables investigated as having an effect on gassing were the pH of the oxidizer phase, the amount and type of nitrogen in the emulsifier, the composition of the oxidizer phase, the use of pH buffers in the oxidizer phase, and how the gassing reagents are added to the emulsion.

Jan 1, 2004

By Claude Cunningham

AEL’s Electronic Delay Detonators are in routine use and growing in both volume and breadth of application in Africa. This trend will continue and grow internationally owing to increasing pressure on rockbreaking operations to conform to sustainable development principles. A fundamental breakthrough has been achieved, bringing production blasting into line with technologies, which leverage performance through tight monitoring and control. When moving from pyrotechnic systems, benefits are normally realized without having to adopt different timing patterns, but significant additional benefits are realisable by using the flexibility and precision of the electronic units to enter windows of timing previously closed. The higher price and increased care needed are a worthwhile investment, enabling operations to cross the chasm to stronger revenues, but the system must be robust and suited to the application and personnel. Economic models are vital for keeping track of the potential and achieved benefits of these systems. Some resistance can be expected from those who stand to lose income as a result of the improved efficiencies.

Jan 1, 2004

By D Frantzos

Pressure time histories were recorded for low density ammonium nitrate/fuel oil, detonated in long heavy walled steel cannons of various bores. These were shell used in a finite element model of a horizontally layered limestone rock mass to predict the crack propagation limits in presplit blasting for a range of borehole diameters. Apart from showing very good agreement with field results, the model clearly demonstrated the strong dependence of the results on the pressure-time curve. The important elements were the peak pressure, the rise time to it and its duration. Control of these characteristics offers the possible future production of more ideally suited pressure-time profiles for the optimization of crack propagation distances and borehole spacings for various ground conditions. Also the results to date provide the basis for investigating the characteristics of the explosives presently used in presplit blasting, and finding ways to modify them with the purpose of optimizing the field results.

Jan 1, 1987

By Greg Rappard, Francois Holowenczak, James Rickard

The King George V (KGV) Shaft forms part of MTR Corporation Limited (MTRCL) Works Contract 703 extension of the underground West Island Line on Hong Kong Island. The Shaft and the associated adit was the sole access to excavate the running tunnels. Originally during the Detailed Design stage, it was concluded that blasting was not feasible at the KGV Shaft due to the close proximity of sensitive receivers in the form of residential buildings, electrical cables and hospitals. As a result, the Contractor planned to excavate the Shaft using mechanical means with a programme time of seven months. The Contractor appointed a Sub-contractor to analyse the feasibility of excavating the Shaft by blasting. The Sub-contractor reviewed the proposal and recommended the use of an innovative blasting technique that had never been previously employed in Hong Kong. The Sub-contractor recommended the Shaft be blasted using DetNet electronic delay detonator technology, manufactured by AEL Mining Services in South Africa, with an initial 1.5m depth of water ballast covering the blast face. The electronic delay detonators provided initiation accuracy to ensure there would be no overlap between sequentially detonating blastholes. The water ballast makes use of the effect of energy lost through the shock front causing the water to break up into droplets creating a spray dome resulting in the attenuation of the energy imparted into the surrounding rock mass. Various tests have demonstrated that both the maximum overpressure and impulse density are significantly reduced when water of a minimum depth is in direct contact with detonating explosives. This innovative blasting technique reduced the excavation programme by three months, saved HK$5 million in direct costs and totally mitigated the impacts on the public and other stakeholders nearby the KGV Shaft. Peak Particle Velocities (vibrations) rarely exceeded 2-3mm/sec (0.08-0.12in/sec) at a distance of 30-40m (98-131ft) from the blast location and air overpressure levels were reduced below the Hong Kong target level of 120dBL. In total, 24 blasts were fired with an average advance of 1.6m (5.25ft) with an average powder factor of 2.03kg/m3 (0.127lb/ft3) to 1.84 kg/m3 (0.114lb/ft3). The initiation pattern had 5ms between sequentially detonating blastholes and 20ms between adjoining rings.

Jan 1, 2013

By John N. Jr Edl

Geokinetics, Inc. has pioneered an in-situ oil shale retorting production process that provides the requisite void space for producing a permeable rubble bed, within the retort zone, by using the explosive energy from vertical blastholes to lift the overburden. By installing suitable instrumentation on the surface of the overburden over an appropriate blasting pattern, it is possible to obtain estimates of the average radius of gas penetration around the blasthole and the average volume, per unit length of blasthole, that is actually occupied by the explosively produced gases (which includes both the volume of the cracks that are penetrated by the gas pressure and the deformed blasthole volume). It is expected that these estimates can be used to examine, and quantify, the effects of such blast design parameters as the type of explosive, the blasthole diameter, the geometry of the explosive charge (length to diameter ratio), and the relative timing of sets of charges.

Jan 1, 1983

By Dave I. McGregor

The Multiple Raise Round Blasting Technique (MRRBT) is a safe, efficient, cost effective method of blasting thee will use existing mine personnel. The MRRBT, developed from the conventional 'drop raise method' style of blasting, can be used for most raise mining applications. Current results using MRRBT indicate no upper limit for the maximum length that a raise can be blasted.

Jan 1, 1994

By A T. Spathis, J J. Felice, W Klass

Cast blasting has become one of the most efficient ways to move waste rock in open cut coal mining. It is used at Mount Thorley Mine in conjunction with a dragline to move some of the overburden onto the spoil dump.

Jan 1, 1992

By Roger N. Prescott

The Bureau of Alcohol, Tobacco and Firearms (BATF) is sponsoring legislation requiring the addition of identification taggants to commercial explosives. These are plastic particles with color coded layers that theoretically can be used to identify the explosive by date shift code.

Jan 1, 1980

By W. Reisz

Dealing with misfires can be one of the most difficult and serious issues that blasters must confront. Most of us will - at some point, have to deal with a misfire situation.

Jan 1, 2009

By Roger Holmberg, William Hustrulid

Swedish cautious blasting techniques were used to excavate a room at the CSM Experimental Mine in Idaho Springs, Colorado,as part of a ONWI/DOE sponsored nuclear waste disposal research program.

Jan 1, 1981

By John F. Vynne

This paper will discuss the application of available monitoring technology on blasthole drills with the goal being to reduce costs and increase productivity. Case studies from the monitoring of blasthole drills in North American open pit mines will be used to illustrate the ability to meet these objectives.

Jan 1, 1997

By Mark S. Stagg, Stephen A. Rholl

As part of its research program to evaluate efficient design criteria for improved blast fragmentation, the Bureau of Mines has developed two computer programs to facilitate data analysis. Results of these two programs are used to better understand the fundamental parameters of blasting for surface mine rock fragmentation.

Jan 1, 1990