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By B Mohanty, R Yang

Blasting vibration information is now commonly used to diagnose blast malfunctions. These range from limiting vibration levels to protect normal dwellings to determining scatter in detonator firing times, and even to rating of explosives in the borehole. Although blasting vibrations have the potential to yield reliable information in all these issues, there are key restrictions on their specific use, which are often ignored. These include all aspects of instrumentation, and sensor layout, as well as methods of analysis. This paper highlights these limitations. It emphasizes the distinction between near-field and far-field seismic recording in terms of borehole dimensions and blast geometry. Several case studies from both underground and open-pit blasting operations are discussed to illustrate and emphasize the essential characteristics of blasting vibrations and their optimal use in diagnosing blast malfunctions.

Jan 1, 1997

By P Wapner, C Lo Edwards, S CO Schmidt, J N. Johnson, R Oliver

Shale oil recovery rates that can be achieved in underground in situ retorts can be strongly influenced by the shale breakage and fragment-size distribution achieved during rubblization. Since the fragmentation pattern in the retort is a direct result of the blast design used for rubblization, the characterizing blast parameters should be carefully selected. Explosives should be matched to the host material and blast geometries properly chosen so that the required fragmentation results are achieved at optimum costs. Special attention must be directed to selecting blast parameters that produce uniform bed permeability, suppression of fines, proper fragment size distribution, and minimal damage to the retort walls and ceiling. The influence of joints and natural fractures should also be known. In instances where the requisite blasting parameters are unknown, they should be determined from test blasts.

Jan 1, 1979

By N. Paley

An engineering project was undertaken at the Cominco Alaska Red Dog Mine to determine the extent that Semi-Autogenous Grinding (SAG) mill throughput could be increased by blasting differently. The Julius Kruttschnitt Mineral Research Center (JKMRC) blast fragmentation, jaw crusher, and SAG mill breakage models were used to relate changes in the blast design to the SAG mill performance. For optimum performance a SAG mill requires a particular size distribution; a number of large rocks to facilitate breakage by impact, as few as possible middle size rocks that become critical size, and the maximum fines which will pass quickly through an open-circuit mill. Physical constraints of drill and charging equipment size limit the extent that pattern geometry can be changed and the powder factor increased to maximize fines. However, JKMRC research had shown that it appeared possible to increase primary breakage by blasting to such an extent that SAG mill throughput could reach a plateau or even begin to decrease. Modeling was carried out on a range of blast pattern geometries and emulsion explosive blends to determine if a plateau existed and at what powder factor it would be reached. It was found that the relationship between powder factor and grinding throughput was nonlinear. Modeling was also used to compare the SAG mill throughput which could be expected from different emulsion explosive blends to determine which blends should be used in dry and wet holes to provide similar fragmentation. For heavy-ANFO mixtures, the highest modeled throughput was at a ratio of 30/70, with ratios on either side indicating lower throughput. For emulsion blends, the highest modeled throughput was at a ratio of 80/20; however, ratios from 80/20 to lOO/O were similar. Crusher product size distributions were obtained from belt cuts early in the analysis to confirm model predictions. At later stages, actual SAG mill throughput was compared to predicted. The economic benetit from the different blast designs was calculated by accounting for the reduction in recovery due to the higher throughput and the additional drilling and blasting costs. Increasing the powder factor by 150% from the 0.29kg/t {0.58lb/st] being used to 0.72kg/t { 1.44lb/st}, the maximum feasible with mine equipment, could provide a sign&ant net benefit of $3OWyr due to the increased concentrate production. However, because the relationship between throughput and recovery is affected by other factors which were not modeled, a more conservative approach was taken. The powder factor was instead increased by 50°h, providing 45% of the gain. This was possible because the relationship between powder factor and grinding throughput was nonlinear.

Jan 1, 2001

By Lawrence C. K Hu

The release of load mechanism during rock breakage by explosives was founded by Dr. T. N. Hagan & published at the Sixth International Colloquium on Gasdynamics of Explosions and Reactive Systems Stockholm, Sweden, 1977.

Jan 1, 1995

By Ralph King

Blasting has been completed when the lawyer calls to say that a landowner has filed a suit alleging damages to the roof of his home. Mitigation talks fail to produce an adequate resolution and the case goes to court. The blaster has pictures of the area made after the blasting was done showing the good condition of the roof. However the judge fails to allow the photographs to be entered as evidence and the homeowner wins the case.

Jan 1, 2008

By Dale S. Preece, J Paul Tidman, Stephen H. Chung

A discrete element computer program named DMC_BLAST (Distinct Motion Code) has been under development since 1987 for modeling rock blasting (Preece & Taylor, 1989). This program employs explicit time integration and uses spherical or cylindrical elements that are represented as circles in two dimensions (2-D). DMC_BLAST calculations compare favorably with data from actual bench blasts (Preece et al, 1993).

Jan 1, 1998

By Paul Worsey, Gillian Worsey

Description of Project:The basic blasting class underground lab at the Missouri S&T experimental mine in Rolla, o., shows the students how to drill, set up, load, and shoot a shot underground. In this case the shot was part of a new ramp to a second level.

Jan 1, 2014

By Dennis Dobson, Keith M. Henderson

Lone Star Industries, Inc. in Cape Girardeau, Missouri operates an open pit mine to produce limestone for its portland cement manufacturing plant. The present mining method, for safety and legal reasons, requires a set back from the property line, a berm, sloped overburden, and vertical rock walls with catch benches.

Jan 1, 1997

By Jaak J. K Daemen, Clayton R. Morlock

A study was performed to evaluate the predictability of airblast overpressures induces by production mine blasting. Thirty-seven production blasts were monitored using 3 blasting seismographs giving over 100 blast overpressure records. Blasts were monitored at 5 coal highwall operations and at a limestone quarry, all in the midwest. Blasts consisting of small surface charges were monitored to permit an assessment of prediction methods under controlled conditions, as well as to observe actual delay intervals and their influence on the overpressure.

Jan 1, 1983

By Hu Wenjun

This paper changes the section of copper of copper to aluminum adapter bar into aluminum plate covered one face or double face with copper coat, and changes the conductor material of knife switch, fuse box, plug and socket into steel plate covered one face or double face with copper plate, and manufactures the composite (two layers or three layers) metal plates by means of explosion welding with the plates installed horizontally. Introduced in this paper are the blasting designing technique, manufacturing process and the electrical performances of the explosion bonded products. Besides, this paper presents the designing and manufacturing technique of cumulative charges and their time detonating units for cutting off the retired nuclear submarine pipes. Experiments on cutting off the stainless steel pipes by cumulative flow and on the time detonation are made. Keywords: explosive welding, electric, explosion bonded products, retired nuclear installation; pipe; blasting cutting; cumulative charge; time detonation

Jan 1, 2000

By V Krishna Mohan, J Edmund Hay

This paper discusses the results of the gap sensitivity measurements made on water-gel explosives, sensitized by monomethylamine nitrate (MMAN) and flake aluminium, and one emulsion explosive. This study specifically deals with the effect of the mode of initiation, end or center, on the measured L50 values with air gap and coal dust gap for the above explosives. Similar measurements have also been carried out on a nitroglycerine (NG) - based explosive. The results show that the mode of initiation plays an important role in determining the air-gap sensitivity of these explosives. However, in tests carried out with the coal dust gap, the L50 ( grams of coal dust ) values for these explosives are close in both the types of initiation. The results indicate that the sensitivities of these explosives may be ordered in the following manner: NG-explosive>> Aluminized explosive ~ MMAN-explosive > Emulsion explosive

Jan 1, 1982

By Michael McDougall

"Suncor Inc. Oilsands Group, Mining Operation in Northern Alberta, Canada, has beenblasting to loosen the oilsands to increase production and decrease maintenance of the hugebucketwheel excavators for over twenty years. In 1991 an area of the mine wasencountered which had a working face in excess of 130 feet. In order to maintain theproduction objective, the blasting department took on the task of providing as much of ablasted face to work with as possible. In doing this Suncor has exceeded several knownrecords in production blasting."

Jan 1, 1993

By G Dean Barrett, Ed Jr Smith, Calvin J. Konya

The purpose of the project was two fold: 1. To determine whether Pyrodex, a propellant, manufactured by the Hodgdon Powder Company, could be used as a substitute for high explosives for presplitting in granite and other materials. 2. To determine if Pyrodex, a slow reacting propellant which produces no stress waves in rock because it reacts subsonically, could cause the rock to crack similar to the results achieved with high explosives.

Jan 1, 1986

By Michael Wieland

Three laboratory tests were developed for rating the wave-impact ruggedness of cap-sensitive explosives that are used for blasting in underground coal mines. Destructible pipe fixtures, called simulators, reproduce the shock wave or rift compression registered during the cross-hole wave interactions. The rift-compression fixture was modified to render quasi-static desensitization, when utilized with a remote air supply. Waves that were recorded near charge explosions show narrow pulses resembling underwater shock waves, followed by wide, weak humps, called rift compressions.

Jan 1, 1996

By James Ludwiczak

We are coming to an end of an era in Midwest surface coal mining. For many years, large tracts of coal lands were readily available for sale or lease to surface mine operators.

Jan 1, 1980

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 E Emery Gray, Gary Ard

Each year when hundreds of Engineers and Specialists in the explosives industry meet for the SEE Annual Conference, new ideas are exchanged and new business relationships formed. Harbert Construction Corp. and EGA, Inc., a company specializing in drilling and bIasting, formed such a relationship through mutual interest in such a manner.

Jan 1, 1981

By J J. F Smith

The application of pneumatically loaded ANFO for underground mining has continued to increase year by year since the technique was first developed and introduced underground during the early 1960's. Improvements in the manufacturing process for explosives grade prills, the design and construction of more efficient AN prill-fuel oil blending equipment, and the introduction of more durable and reliable pneumatic loaders have promoted the wide application of the relatively low cost blasting agent, ANFO.

Jan 1, 1982

By J R. Brinkmann, S G. Giltner

Nearly all of the South African gold mining industry still uses fuse and igniter-cord initiation systems. Over the past 30 years numerous attempts at developing new initiation systems have not yielded a viable alternative. New initiation systems for narrow stopes are currently being developed by various concerns and the likelihood of these efforts producing feasible alternatives is greatly improved due to the recent advances in electronics technology. The greatest potential benefit of alternative initiation systems is increased production rates through improvements in accuracy and reliability of firing over that of fuse/igniter-cord. Another important feature is the capability of millisecond delay firing as this can lead to reduced stope cleaning times by way of enhanced rock throw and improved fragmentation characteristics.

Jan 1, 1989

By B Mohanty, R Yang, M Leblanc

A total of 33 blasts in the pillar recovery program at INCO-Crean Hill has been investigated by means of an extensive set of diagnostic techniques. These included, borehole deviation measurements, stope cavity survey, near-field seismics in both rock and backfill, in-hole VOD and fragment size analysis. The 200 mm diameter VCR blasts employed a variety of explosives types (ANFO, slurry and ANFO/Polystyrene) and deck sizes. The objective of the investigation was to control dilution and backbreak through optimal choice of explosive type and charge weight, without exceeding vibration limits in the adjacent backfill or causing significant degradation in fragmentation.

Jan 1, 1995