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By J Mensah, G C. Sen

Often large boulders of rock have to be fragmented in civil or mining engineering operations. These oversize boulders are encountered after primary blasts in both surface and underground excavations of minerals. Various methods are employed to break large boulders into a manageable size for loading and crushing. These methods range from mechanical breaking (such as drop-ball and hydraulic impactor) to the use of explosives. Apart from these, static agents (such as expanding chemicals) are used in special circumstances.

Jan 1, 1989

By Valerie A. Rhodes, Catherine T. Aimone

Often blast damage litigation involves structural damage which clearly is not blast related. The fact that structures are observed to be damaged when blasting has taken place in the near vicinity of these structures does not necessarily mean that the damage was caused by blasting. If careful blasting and seismograph records were kept by the blaster which decisively indicate damage is not blast related, then other causes of structural damage need to be assessed. These include problematic soil characteristics and long-term changes in climate or subsurface soil moisture. This paper presents the evaluation process required to investigate soil problems leading to damage often attributed to blasting.

Jan 1, 1991

Introduce self – thanks for having me.Indiana program – spent first 15 years of program telling folks how smart we are and to trust us. “We are from the government and we are here to help you.” How well would that go over with you if the IRS invited you in for an audit and that was their openning? Our audience was the same way – not thrilled or inspired. We decided we were the problem – being nice guys just was not enough. We had to learn to communicate with people who did not know us. I am here to share a few things we have learned – and are still learning.

Jan 1, 2007

By Sally Lynn Zadra

"In May, 1994, Echo Bay Minerals - McCoy/Cove Mine petitioned for approval to recycle used oil formanufacturing ANFO. Recycling oil in this way will result in a cost savings for the minesite as well ashaving a positive environmental effect The petition has met the approval of the Bureau of LandManagement, the Nevada Department of Environmental Protection, and has received tentative approval from the Mine Safety and Health Administration."

Jan 1, 1996

By D Linn Coursen

Detonation propagates in the subject blasting agent at about 2.7 km/sec when it is heavily primed but explosion propagates in it at only about 0.43 km/sec when it is lightly primed. When propagating at 0.43 km/sec, it produces a borehole pressure that is slightly less than 1 kb, but no yellow fumes or other sign of incomplete reaction. It is a pumped AN/emulsion blend to which additional water is added by circumferential injection at the inlet of the hose through which it is pumped.

Jan 1, 1994

By Gordon Revey

In construction and mining work, situations occasionally occur where hard rock or concrete must be excavated at locations near critical structures or utilities. Fearing damage from blasting, contractors and engineers often explore the viability of using mechanical methods or expansive concrete to facilitate the excavation work. However, for moderate to large excavations, the prolonged duration and high cost of using these methods is often impractical. In these situations, under the right conditions, controlled blasting and blast-management methods can be used to speed up the work and lessen costs. The process of determining whether or not blasting is practical is ofien complex, particularly when risks are high.

Jan 1, 2001

By William H. Snyer, Victor A. Sterner

A cache of buried explosives was discovered by ICI Explosives, USA Inc. at one of their sites near Gillette, Wyoming. An intensive investigation conducted by ICI management indicated that nitroglycerin sensitized dynamite might be present. Information also indicated that up to 20,000 pounds of explosives may have been buried.

Jan 1, 1997

By Paul Worsey, Delbert Da, Eric Achelpohl

The University of Missouri-Rolla is currently researching the concept of using glass microspheres in explosives as taggants as part of a 3-year technical project funded by the Bureau of Alcohol, Tobacco, and Firearms. These taggants are intended to provide two functions, first explosive detection and second post explosive event identification. The key priority is being able to detect explosives used in terrorist acts prior to detonation. The research on the use of microspheres includes the development of indicator taggants for the purpose of revealing the presence of hidden explosives, by either emitting radiation when bombarded with neutrons or emitting selective vapors, such as DMNB which may be readily “sniffed”. Of secondary importance, after an illegal explosion, the tags serve to identify the lot number, etc of the explosive. This information is to aid in the tracking, arrest, conviction and imprisonment of the perpetrators.

Jan 1, 2001

By Mike McGill, Stephen Chung, Dale S. Preece

Cast blasting can be designed to utilize explosive energy effectively and economically for coal mining operations to remove overburden material. The more overburden removed by explosives, the less blasted material there is left to be transported with mechanical equipment, such as draglines and trucks. In order to optimize the percentage of rock that is cast, a higher powder factor than normal is required plus an initiation technique designed to produce a much greater degree of horizontal muck movement. This is a significant change from normal blasting practice where fine fragmentation and sufficient muck movement were the prime requirements to permit efficient excavation.

Jan 1, 1994

By K Uenishi, H P. Rossmanith, N Kouzniak, A Daehnke

This contribution presents an introduction into that part of the field of elastic wave propagation which is relevant to blasting of boreholes and addresses briefly borehole breakdown and the formation of the fracture network around a borehole which ultimately leads to the disintegration of the rock mass. Phenomena of this kind are encountered in mining and quarrying. Numerical as well as experimental work referring to stress wave expansion from a detonating borehole is addressed.

Jan 1, 1998

By Thomas R. Scotese, John L. Ackerman

The Hanging Lake Tunnel Project represents a major portion of the Glenwood Canyon Project, the last piece of Interstate 70 to be constructed. The project features twin bore, large span rock tunnels and six open cut portal excavations, all excavated by drilling and blasting. This paper presents descriptions of the methods used by the Owner and Engineer to control and monitor the drilling and blasting practices in the tunnels and in the portal areas.

Jan 1, 1992

By Elaine Gorham-Bergeron

CAROM is a distinct element, dynamic code developed at Sandia National Laboratories to calculate the motion of rock fragments during blasting.[1] It has recently been improved to incorporate a mechanism for its elements to mimic non-circular rock fragments. With this option, elements stack and move in ways that are characteristic of irregular boulders of blasted rock. In bench geometry, CAROM has been used to examine the possibility of producing variations in muckpile shape due to variations in detonation-time delays between rows. Surprisingly, the shape of the muckpile was predicted to be insensitive to time delays between detonation of rows of explosive, except where the rock fracturing was affected by the time delays.

Jan 1, 1987

In situ, most Taconite is heavily pre-fractured; because of the high cost of comminution of taconite, maximum fracture of pre-existing blocks is desirable. Sustained borehole pressure plays a significant role in fragmentation, especially by penetrating pre-existing fractures. The distribution of explosive-induced energy in the burden in three dimensions was calculated. Data on the comminution of single particles was used, with the distribution of energies and the distribution of pre-existing block sizes, to calculate fragmentation for a case study. The calculation agreed well with the measured fragmentation. Sequential comminution events are much more efficient than single ones, and enhanced fragmentation may be possible with alternative blasting practices. Some important factors in the dependence of comminution on energy input are discussed.

Jan 1, 1995

By William McFerren, Pragasen Moodley

In contrast to global trends, African, especially South African, surface mining operations have shown a significant rate of adoption of Electronic Detonators (ED’s) over the last few years. Proven benefits of converting to ED’s from pyrotechnic initiation systems have aided this market conversion. These benefits are experienced throughout the mining operation. Benchmarking exercises, prior to the introduction of ED’s, form part of the conversion process and allow for quantifying improvements. Extensive work has been done on quantifying the benefits of converting to ED’s and have shown that results can be reproducible. Improvements have been experienced in many applications and include environmental impact control, improved mining efficiencies, increased cast benefit and improved size distribution. These step changes in blasting results, in conjunction with the adoption of ED technology have aided the rapid conversion of the African surface market.

Jan 1, 2004

By Ray Jambakhsh, Craig Copping

The St. Lawrence Seaway's Welland Canal has been undergoing a rehabilitation program that requires the removal of deteriorated concrete from the 25 meter high lock walls. Multi million dollar contracts must be completed during the three month winter freeze up. New blast designs have drastically cut the time required for concrete demolition. All blast results including vibration, noise, underbreak, overbreak, scaling and flyrock have been improved and at a lower cost.

Jan 1, 1994

By Virgil J. Stachura, Larry R. Fletcher, Matthew N. Plis

Falls of ground remain a leading cause of fatalities and injuries in underground mines. In response to this situation, the Bureau of Mines conducted a series of experiments in the White Pine room-and-pillar copper mine which resulted in smoother, safer ribs due to a reduction in the amount of overbreak caused by blasting. The tests evaluated the effects of changes in the loading of the rib holes of the mine's 20- by 28-ft drift round driven in shale and sandstone. The relative integrity of the ribs remaining after the blasts was measured using both photographic and seismic refraction techniques.

Jan 1, 1989

By Richard W. Watson, Julius Roth

The Bureau of Mines has recently completed a contract study of the hazards associated with surface mining.! Part of this effort involved an analysis of surface mining accidents associated with blasting activities. For this purpose, 71 reports of accidents investigated by the Bureau of Mines or the Mining Enforcement and Safety Administration (MESA), covering the period from 1962 to 1976, were collected and analyzed. In addition, blasting accident frequencies for the period 1973-1976 were extracted from the central computer files maintained by the Health and Safety Analysis Center (HSAC) in Denver, Colorado. This paper presents a preview of the findings, which are treated in more detail in the final report.

Jan 1, 1978

By Calvin Konya, Janos Foldesi

A bridge over a main line railroad system was scheduled for demolition. The bridge was made of reinforced concrete and spanned three mainline railroad tracks which could not be shut down due to blasting or demolition. To further complicate matters, the mainline tracks had high tension power lines running above the tracks, but below the bridge. These high tension wires provided the electricity for electrically powered trains. The tracks could not be damaged or disrupted, nor could the power line be broken.

Jan 1, 1992

By Clarence Zink

Aside from the mechanical properties and process of actual rock breakage, rotary drill bit performance is affected by several “post breakage” items: cuttings size, flushing air pressure, flushing air volume, cuttings load, drill hole geometry, etc. We all recognize that more efficient drilling creates bigger cuttings, more air pressure cleans the hole bottom better, more air clears the cuttings from the hole, and a better hole geometry allows cuttings to escape with a minimum of “regrind”.

Jan 1, 2006

By P. Katsabanis

Numerical modelling was used to examine damage in wall control operations. Decoupled charges appear to create larger damage zones than fully coupled low density charges with similar charge distributions: Air was shown to be a very efficient coupling medium, while water coupling resulted in significant damage. However, Mach stems are formed when air is used as a decoupling medium, leading to compression of the charge ahead of the detonation wave. Air decked charges generate two damage zones, one close to the charge and another close to the air-deck/stemming interface, where pressure pulses are reflected. The extent of the latter depends on the length of the air-deck.

Jan 1, 2001