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By Stephen Chung, John Carpenter, Scott Gosch, James Breedlove

While controlling fly rock and ground vibration in quarrying in the neighborhood of a residential area, producing good fragmentation and keeping different grades of material separated in a muckpile are important in maintaining the productivity of quality aggregates. This paper describes a single row production blast for the study of fragmentation and displacement in the grade control carried out at a quarry of Barrett Paving Materials Inc. in Sylvania, Ohio. Digital video imaging was used to monitor the blast-induced motion of the bench face as input to the DMC_Blast (Distinct Motion Code), for the analysis of the formation of the muckpile. The actual digitized blast video and the DMC_Blast simulation are compared. The displacement and mixing of all the inter-bedded limestone layers are made visible in the simulated cross-section of the muckpile. The apparent fragmentation analysed with PowerSieve is also discussed.

Jan 1, 2001

By Paul Worsey

A strong inverse relationship between rock face movement and stemming ejection is presented. Previously unpublished data from blast control plug research and development involving high speed video analysis, which was conducted between 1986 and 1988, is presented. Face and stemming ejection velocities were calculated for tests utilizing the same bench blasting configuration comprising; a 4 ft high bench in dolomite, 3 ft burden and single 1.75 in. holes loaded with 2 ft of small diameter cartridge emulsion. The singular difference between these tests was the stemming configuration. Varying lengths of stemming were used with the presence or absence of differing experimental configurations of blast control plug. The effectiveness of this plug has been published previously.

Jan 1, 1990

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 U. Prasad

This paper summarizes the investigation carried out on a wide range of rock types, subjected to high velocity impact to simulate explosive action. A Split- Hopkinson Bar apparatus was used to generate the high velocity impact. The rock samples included both homogeneous and isotropic, and anisotropic types. The strain rate achieved was between 600 and 12OO/sec, The respective measured dynamic compressive strengths were compared with their low strain-rate or static values. It was found that the ratio of the dynamic to static values ranged between 2.5 and 4.6. It was also determined that the high strain-rate loading produced finer fragment size distribution than the static loading. The fragment size distribution from the two strain-rate regimes has been further analyzed to establish correlation with rock types and the strength characteristics. The results also confirm that high strain-rate loading (i.e. high detonation pressure and high velocity of detonation in an explosive column) would significantly affect the degree of fineness in a blast.

Jan 1, 2001

By R W. Givens

This paper presents blast casting design variables that have been developed and are currently being used at the High Power Energy mine in West Virginia. The shot specifications are summarized in Table I. The two active casting pits were designed with casting in mind and as a result are better designed and more efficient. About 55% of the overburden material is effectively cast and clean up is done by a bulldozer, front-end-loader, and trucks. This results in a 15X decrease in the cost of coal production.

Jan 1, 1988

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 Roy McKinstry, Mark Rantapaa, Thomas Bolles

In March of 2001 Barrick Goldstrike Mines, Inc. began evaluating the potential benefits of electronic detonators at the Betze Post open pit gold mine. The original evaluation focused on increased fragmentation, and excavator productivity. During the original evaluation there was an attempt to quantify mill throughput. Early tests indicated that there would be a benefit to mill throughput, however management was hesitant to take on the added cost of electronic detonators based on the initial evaluation. In early 2002 a decrease in mill throughput was being forecast as a result of harder ore being encountered. As a result of the initial electronic detonator evaluation a team of individuals from the Open Pit and Process areas worked closely on the Drill-to-Mill (D2M) Continuous Improvement initiative. This initiative was targeted at improving mill throughput as the harder ores were encountered. Batch tests were conducted to determine if adjustments to drilling and blasting in the open pit could increase mill throughput and justify a 50% increase in drilling and blasting costs for the harder ore material.

Jan 1, 2004

By Michael Noy

Current image based systems used to measure fragmentation are measuring the two dimensional presentation of a set of three dimensional objects. A two dimensional measurement of fragmentation restricts both sampling and particle size classification and hence provides a different evaluation of the fragmentation to that of a conventional sieve analysis of the same sampled material. Many modern image based fragmentation measurement systems attempt to convert this two dimensional analysis to a three dimensional analysis in order to deliver a "real" measurement of the fragmentation distribution. This paper questions the necessity and validity of this transformation and lays down the framework for the establishment of a standard in fragmentation measurement based on a two dimensional analysis. The results of image based measurements of laboratory prepared samples indicate that differences in mass distributions (3D distribution) can be mapped by an appropriate image based analysis which provides area versus particle size information.

Jan 1, 1997

By Pierre Allard, Wilfrid Comeau

Near-field and close-in blasting can be safe and efficient, near engineered structures, if the dynamic reaction of structural members to blasting vibrations are considered. Safe particle velocity criteria can be derived from allowable safe static flexural deflections and critical frequencies. Control of close-in blasting can be accomplished using low-pass filtering of the particle velocity signal at the critical frequency. The CETE Mediterranee laboratory at Aix-en-Provence, France, a branch of the Ministry of Roads and Bridges has -pioneered this approach and successfully applied it to major road cuts and tunnels in built-up areas, as well as a major powerhouse expansion project in Africa. This approach is presently being used for a spillway rehabilitation project in Quebec, Canada. This paper exposes- the theoretical aspects and gives case histories of its use. The SCS-15 an automated, peak reading, data acquisition device is described.

Jan 1, 1991

By Jaime Huidobro, Mervin Austin

The effect on an explosive column of the sharp transient stress waves generated during the earlier detonation of adjacent blastholes is of paramount importance to explosives users. Some explosives will sympathetically detonate under these stresses. Others may suffer a transient desensitization, arising from a temporary increase in the density of an explosive beyond certain limits and persisting until the explosive mass relaxes back to the original density. Some explosives are so adversely affected by these stresses that the product suffers immediate and permanent loss of sensitivity. These effects can be clearly seen while blasting in tough conditions such as burn cuts or wedge cuts and in materials, such as coals, that propagate shock waves well.

Jan 1, 1992

By Tapan Goswami, Geoff Keith

"At Bulga Coal, the objectives of drilling and blasting are to maximise safety and to minimise the totalcost of mining. A recent audit of two overburden blasts established that the standard of drilling and blasting is excellent. No apparent hazards were identified. Laser profiling showed that highwall free faces are reasonably planar with some exceptions, thereby promoting uniform burden distances along front-row charges. However, in three isolated areas along one face, small burden distances existed. The mean and the standard deviation of errors in the collar positions of front-row blastholes was found to be 0.3 + 0.03 m. A borehole video camera was used to show that blastholes did not feature open bedding plane partings, cavities or damage produced by the blast in front of them."

Jan 1, 1999

By Dale S. Preece, Lee M. Taylor

Computer simulation of the physics involved in conventional rock blasting can be split into two phases; transient stress wave propagation and rock motion. Because the two phases involve totally different mechanisms and time scales, they must be numerically modeled with two different computer programs. The first phase is usually modeled with a finite element or finite difference code which treats the rock as a continuum and simulates the transient stress wave and subsequent fragmentation of the rock. The second phase is usually modeled with a distinct element technique where the rock mass after fragmentation is no longer treated as a continuum but as a finite number of distinct particles that interact with each other through collision mechanics.

Jan 1, 1989

By Paul Worsey, Gerald Rupert, Mark Kirkbride

The realignment of Highway H in the proximity of Crystal Cave (Springfield MO.) required the development of a blasting program that was both economical and efficient for construction, yet ecologically safe for the cave. Three component seismographs were strategically placed underground near prominent and sensitive cave features and the vibration levels from the construction blasting continuously monitored. Peak particle velocity (PPV) values were found to obey the square root scaling law and a peak particle velocity value of 0.3 in/sec was chosen as the safe maximum limit. This value proved adequate in preserving the integrity of the cave and its features. Scaled distances for the maximum and lower values enabled blasting personnel to select explosive charge weights per delay for given distance to the cave. Delays were determined from the dominant frequencies recorded underground.

Jan 1, 1997

By Mark D. Kirkbride

This paper outlines the process for designing a hard rock blast in an underground coal mine. The coal mine is located in Western Kentucky and operates four continuous miner units at 7 unit-shifts per day. The mine operates in the Western Kentucky No. 11 Seam with local variations from 4.5 - 5.5 feet seam thickness. The seam has sporadic siderite deposits. Usually these deposits do not significantly interfere with the mining process. When previous siderite deposits were encountered they were small enough to drop an entry for a couple of crosscuts. The blasting plan was called for after a siderite deposit was encountered in the belt entry at about one third of the panel length. The other sides of the panel had been previously mined and sealed so the decision was made to mine through the siderite deposit with the continuous miner instead of abandoning the panel. The deposit was approximately 300 feet in length down the belt entry. Mining through the deposit with the continuous miner was expensive in both terms of production and of wear and tear on the continuous miner. A blasting plan for the siderite deposits was designed to minimize damage to the continuous miner should a similar situation occur.

Jan 1, 1999

By A. Spathis, I. Yacob, A. Labriola, G. Smith

Wall control is a significant issue for many mines. Improvements to the design process for blasts adjacent to temporary or final walls will require better measurement tools and predictive models. Orica Explosives has developed capability in both these areas and uses them to guide better wall control blasting practices. Vibration and gas pressure were monitored behind a series of production blasts and single hole blasts at the Freeport Grasberg Operations Opencut Mine. The blasts used ANFO in both 3 11 mm and 35 1 mm blastholes in a blast design which reduced the charge weight by between 30 to 50% in the final row of the production blasts. Single hole blast data were obtained by delaying the last hole in the production blast. Vibration levels were within the range often associated with vibration induced damage: 178 to 1080 mm/s at distances between 14-75 metres from the blast.

Jan 1, 2001

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 John C. Brulia

PowerAN is a tradename of Atlas Powder Company for a new line of explosive products comprising blends of emulsion and ANFO in a variety of bulk and packaged grades. The bulk PowerAN grades are either augered or pumped depending upon emulsion content. Augered PowerAN blends contain up to 60% emulsion. Pumped PowerAN grades have an emulsion content of 75% or higher. The blending of PowerAN is usually accomplished at the borehole to satisfy specific borehole conditions. Packaged PowerAN grades are produced in several types of mix plants in diameters of 4" and greater. PowerAN 300 (30% emulsion) and PowerAN 500 (50% emulsion) are the two most popular grades and their chief application is as an economical, high energy replacement for ANFO HD in wet holes. PowerAN combines the cost effectiveness of ANFO with the high performance of emulsions, permitting the blasting engineer to strike an optimum balance between drill pattern expansion and increased productivity according to need.

Jan 1, 1985

By Farshad Rashidi Nejad, Ali Asgari, Sanaz Norouzi

Blasting is known as the first step of rock breakage in mines. An indication of the importance of blasting is that more than 1 billion kg (2.2 billion lb) of explosives are used annually in Australia and 3 billion kg (6.6 billion lb) in the United States for rock breakage, more than 85% of which is used in the mining industry. The notion that blasting, as the first step of comminution, plays a significant role in crushing and grinding energy consumption is not an unfounded thinking. It can be noted that the comminution electrical energy consumption decreases in these ways: First, if the feed size to the primary crusher is decreased, less energy will be required to crush the ore to the same product size. Second, a decrease in work index (Wi) related to additional macro fracturing and micro fracturing within individual fragments.

Jan 1, 2015

By F O. Otuonye

Full-face blasts were fired in a 12 x 8 ft drift of an underground hardrock mine in a basalt formation with porphyry copper to study the effects of drill pattern and explosive type on the size distribution of the resulting muckpile. Each muckpile produced by five full-face blasts was sampled four times with a scooptram equipped with a 5-cu yd bucket and the size distribution of the broken rock in each bucket was determined by screen analysis. Results show a strong dependence of the fragment size distribution of muckpile on the blast pattern and explosive type for a given rock type. The mean fragment size of the broken rock was compared with the predictive equations of other investigators. Random sampling of the muckpile from full-scale blasts and screen analyses of the samples are recommended in assessing the size distribution of the broken rock because of scaling errors that are inherent in full-scale blasts when designed from results of small-scale tests.

Jan 1, 1985

By Sean Paterson

The purpose of this paper is to demonstrate a method of delaying and loading a shot. Since entering the construction industry, I have learned that cover is needed on a lot of blasts. When in close having to cover shots was new to me and it seemed time consuming and wastefull. Until I really needed it and didn’t have it. So What To Do??? Remember that safety comes first, if you have concerns cover it. Even if you have to sit on your shot all night to wait for cover. This method is not a replacement for cover, but it will help keep your rock down. Do not bet your life, others lives or your career on it.

Jan 1, 2001