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By Shao Li, Chen Zhiming, Wu Jihong

In this paper,powder emulsion explosives,which have high sensitivity and strong detonation force,have been studied by applying emulsion technology to the production of the present powder ones.Under the condition of #8 industrial detonator initiation,the distance of air gap propagation is 110~180mm,brisance !3.5mm, lead block test value 325ml and detonation velocity 3000~4000m/s for small diameter (35mm) explosive cartridges.In addition to these,the factors effect on are investigated by experimental study and theoretical analysis.

Jan 1, 1991

By Lewis L. Oriard

The purpose of this paper is to provide an overview of close-in blasting effects on various types of structures and building materials, as encountered in this writer's professional practice. Structures range from old, deteriorated historical monuments to new, heavily reinforced buildings. Materials range from clay adobe to concrete and steel. Site locations range from tropical to arctic. Blasting ranges from sculpture blasting inside buildings to "coyote" blasting and large surface blasting operations. Space limitations permit a brief discussion of only 25-30 specific cases, but they have been selected to be typical of conditions found on hundreds of similar cases. The writer was asked to present a discussion of representative cases where relatively high vibration intensities were experienced. Virtually all of these cases were free of damage, but the few damage cases provide valuable insight to the mechanisms involved. Observations of such damage and non-damage cases have served as the basis of this writer's criteria for various structures and materials, as well as the technology to conduct blasting operations within those criteria. A sampling of these experiences is gladly shared with the reader.

Jan 1, 1991

By Douglas R. Burns

During the summer of 1989, Maine Drilling and Blasting of Gardiner, Maine was contracted by Cayer Corporation of Harvard, Massachusetts to drill and blast an interceptor trench at the Nyanza Chemical Superfund Site in Ashland, Massachusetts.

Jan 1, 1991

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

Blast design parameters were studied in an attempt to quantify their relationship to rock fragmentation. The Bureau of Mines conducted a series of 29 reduced-scale shots at the University of Missouri-Rolla's experimental mine with bench size from 40 to 80 inches. Design parameters varied were burden, spacing, explosive diameter and stemming-explosive length. The shots had 3 or 4 blastholes fired at delays of 1-4 ms per foot of burden, based on previous tests that showed hole interaction could improve fragmentation by 12 to 20 percent over single-hole shots or simultaneous firing. All rock, 2000 to 23,000 pounds per shot, was screened and weighed to determine the fragmentation size-weight distribution.

Jan 1, 1991

By Thomas L. Barkley, Michael A. Indihar

The new Cyprus Northshore Mining Co. has taken the previous blasting methods of Reserve Mining Co.'s mine in northern Minnesota and adapted them to a new competative Iron Ore Industry. Cyprus was challenged to develop new blasting methods to reduce costs and improve results over the previous mining operation. Many of the older procedures have been kept, but others have been changed in ways that bring the mine operation up to state of the art technology. In addition, unique ideas not previously tried in the North American Iron Ore Industry have been instituted. So far, this has reduced Cyprus's blasting costs by 70 percent.

Jan 1, 1991

By R D. Skaggs

A good blast is dependent on a well engineered design. However, a good design's performance depends on the control of the drilling and loading of the blast holes. The key stone to good blasting is the drilling of straight holes of the correct orientation in the required positions.

Jan 1, 1991

By Andre Pinsonnault, Francois Lefebvre, Yves Newman

In 1989, Les Entreprises Kiewit Ltee signed a C$32 million contract with the Societe d'energie de la Baie James, on behalf of HydroQuebec, to excavate the intake and tailrace channels for a second powerhouse at the LO-2A James Bay hydroelectric project. The multistage contract included removing three marine rock plugs. The first plug was blasted in April 1990. It was a 43 yards wide, triangular shaped wedge that projected into 18 yards of water. Located at the mouth of the intake channel, it contained over 72,000 yd3 of rock, more than twice the 30,000 yd3 found in most rock plugs.

Jan 1, 1991

By M Scoble, J Szymans

During the past year, the Canadian Centre for Automation and Robotics in Mining (CCARM), McGill University, Montreal, has been involved with INCO Ltd.'s Manitoba Division in investigating the extent and mechanisms of blasthole deviation. Drilling accuracy can well be regarded as perhaps the single greatest "controllable" factor influencing dilution in INCO's open sloping operations. As INCO and other underground mines seek to minimize dilution, while attempting to maximize productivity, issues of drilling accuracy become increasingly significant. It is important therefore, that means exist by which true blasthole trajectories can be determined, so that if needed, modifications to hole loading instructions or redrilling of holes can be ordered, thus avoiding poor blast results.

Jan 1, 1991

By Jonathan Peck, Doug Pollitt, Malcolm Scoble

Over the past 5 years the Department of Mining and Metallurgical Engineering, McGill University, has been involved in the performance monitoring of both percussive and rotary drills. Studies conducted in open pit coal and iron ore mines using microprocessor-based research and commercially available instrumentation resulted in the monitoring of at least 6 performance parameters while drilling vertical production blastholes.

Jan 1, 1991

By Jackson R. Pressley, M L. Hopkins, R E. Danell, N T. Moxon, Andrew Bowman

Efficient and cost effective blasting is achieved by closely matching the explosive energy to the strength of the material in which it is being used. Although there are many empirical relationships wich approximate this situation complete the blast optimization can only be achieved by quantitatively assessing explosive/rock interactions and explosive performance. The performance of an explosive is essentially governed by its velocity of detonation or the rate at which the detonation wave travels through the explosive column.

Jan 1, 1991

By Calvin J. Konya

Precision Blasting has designed easy to use, yet, highly powerful databases for storage and retrieval of blasting data. Three different Databases are available for blasting data management. The Vibration Data Management is a complete vibration record keeping system. The Blasting Data Management will record the information from the blasting report as well as the vibration data. The Explosives Inventory Control makes the control of explosives and initiators quick and easy.

Jan 1, 1991

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

The Bureau of Mines is conducting research on blasting methods that reduce highwall overbreak and the associated rockfall hazards. This paper presents the results of a series of tests to improve presplitting at a western surface coal mine. Reductions in overbreak were achieved by decoupling and/or repositioning the main explosive charge in the 10-5/8 inch presplit blastholes that formed the highwall. Blast designs are presented by the authors for 1) repositioning the explosive charge from a weak rock layer to a stronger rock layer, 2) decoupling with cardboard tubes in the toe region, and 3) suspending bagged powder at intervals along the length of the blasthole. About the same total quantity of explosives was used in all three test designs. It was readily apparent from periodic visual examination and photographic surveys of the highwalls that the amount of rockfall was reduced, and with a longer delay before rockfalls began, in all test areas.

Jan 1, 1991

By Larry R. Fletcher, John W. Kopp

The safety record for explosives in U. S. mining is excellent considering that over 4 billion pounds of explosives are now being used each year. However, blasting accidents remain one of the most serious concerns based on the number of injuries, the injury severity rate and the disaster potential. The Bureau of Mines has been analyzing blasting accident data obtained from the Mine Health and Safety Administration (MSHA) to determine the most frequent causes of mine blasting accidents and to examine trends in blasting accidents. This accident analysis is an update of two previous blasting accident studies conducted by the Bureau and published in 1983 and 1987.

Jan 1, 1991

By Sharon K. Reamer, Klaus G. Hinzen, Brian W. Stump

"This study investigates seismic wave propagation from two production shots in a limestone quarry. Our motivation is to investigate the efficiency of two superpositioning techniques. The production shots consisted of an 18 and 20 hole explosive array detonated in a single row with constant delay times of 32 and 20 ms, respectively. A single shot was fired on a neighboring part of the quarry bench. The experiments were instrumented with 20 three component seismometers (35-120 m range). The computer-controlled electronic firing system resulted in firing time deviations of less than 1.4% of desired fired times. Linear superpositioning with the observed single shot data produces seismograms which adequately reproduce temporal effects of the multiple explosions; however, spatial effects due to the extended source length (68-76 m) are not modeled with this method. Linear superpositioning with individual half-space Green's functions for each explosion in thearray convolved with a calculated Mueller-Murphy source produces seismograms which match the time duration of the observed production shot seismograms and differ in absolute peak amplitude by less than a factor of three. Parameter estimation for the source is taken from chemical explosion study results. The single source model differs in amplitude from the observed single source seismograms by a factor of 2.3."

Jan 1, 1991

By R H. Stevenson

This paper deals with a new variation of the cast blasting technique, where-in the object is to cast the economic deposit out front under the overburden, while avoiding dilution from the floor material. To date, the technique has been successfully applied at two cement quarries in Iowa and at a granite quarry in Minnesota.

Jan 1, 1991

By Carl Hendricks, Malcolm Scoble

There currently exists no viable means of obtaining continuous, quantified feedback on blast efficiency. This paper describes the adaptation of a loading shovel to serve as a diagnostic tool in evaluating the success of ground preparation practices. Work undertaken in a large western Canadian open pit involved microprocessor-based instrumentation for the performance monitoring of an electric mining shovel. The monitored shovel responses proved to be reliable indicators of variations in muckpile d&ability. This approach is considered to provide a very comprehensive survey of post blast conditions since the shovel must physically interact which every cubic yard of blast fragmentation.

Jan 1, 1991

By Richard H. Granhom

Detonation pressure, or Chapman-Jouguet pressure, is an intrinsic property of an explosive, and like detonation velocity, is an indicator of explosive performance. Pressure and velocity are also important for calibrating computer codes and for other calculations such as the stress imparted to rock or metal by an explosive. The detonation pressures, P~cj, of many "ideal" explosives have been measured indirectly by recording some hydrodynamic flow variable other than pressure, with P~cj being inferred from hydrodynamics and the assumed Chapman-Jouguet equations. One such method is the difficult and expensive "aquarium technique''.] Commercial explosive manufacturers generally rely on estimates of P~cj generated by computer codes not explicitly designed for non-ideal explosives typically used in commercial applications. Over the last decade, U.S. national and government laboratories have developed in-situ gauge techniques such as the manganin gauge, for direct measurement of detonation pressure. Manganin is an alloy of copper, manganese and nickel, and is ideally suited for use as a pressure transducer because its electrical resistance changes with pressure, but is nearly constant with changes in temperature. A simplified manganin gauge technique adapted for use at a commercial test site is described and some initial results from measurements on commercial emulsion explosives are presented.

Jan 1, 1991

By O E. Crenwelge

Seismograph measurements are usually made near blasting operations solely for the purpose of monitoring compliance with governmental regulations. However, recordings of seismograph signals have far greater potential than this, if the proper procedures are used for analyzing the transient data.

Jan 1, 1991

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 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