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By Salah A. Taqieddin

Blast casting or trajectory blasting, as it is sometimes called, is an innovative mining technique that has been receiving increasing acceptance among operations of surface coal mines and quarries as a means of offsetting the rising cost of mechanical excavation of overburden with a high overburden-to-ore ratio. Many similarities exist between geological characteristics of overburden formations of phosphate beds and the formations that conceal coal seams. Both are sedimentary origin and are removed for mining in an identical manner (i.e. use of a dragline or shovel to strip or cast the overburden aside).

Jan 1, 1997

By P A. Gibson, J R. Brinkmann

The South African gold mining industry fires approximately 800 000 sloping blastholes daily. A programme aimed at characterizing the stope blasting process is underway in order to identify areas for improvement and to provide blasting related information for the design of mechanized sloping systems.

Jan 1, 1985

By Richard Dooley

This paper is one sided because it presents the problem, but not the solution. The problem of blisters (bubbles) and occasional tears in caisson liners occurred when blasting and we have not found a conclusive cause nor a preventive solution. (For back ground information, consult Techniques of Precision Blasting in the Excavation of Drilled Piers, by George Mosteller at the Sixth Conference on Explosives & Blasting Technique in Tampa, Florida 1980).

Jan 1, 1983

By Donald J. Moore

It has become more important today than ever before to reduce costs and improve equipment utilization. One area where such improvement can he achieved is in the use of explosives. Effective blast design for efficient use of explosives as well as optimum fragmentation can achieve this. Towards this end we must have available to us a practical design method in which experience and observation can be translated to engineering concepts. We must he able to communicate the design data to field blasting personnel as well as management in an understandable way.

Jan 1, 1975

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 Lon Santis

Although unproven, it is suspected that there have been eleven locations since 1988 where explosive generated carbon monoxide (CO) gas moved through the earth and accumulated in nearby underground enclosed spaces. This paper summarizes the incidents, which involved about 30 suspected or medically verified CO poisonings and 1 fatality. Ten incidents occurred in residences and one occurred in a manhole. Although practically nothing is known about the mechanism behind the suspected gas migration, review of the incidents and available information indicates there are certain warning signs and a successful remediation technique available. In each case, overburden heavily confined the explosive in the blasts, preventing release of explosive-generated gases to the atmosphere. All the blasts were in residential areas, and none were excavated immediately. Where the distance from the blast was recorded, 5 of the blasts were within 20 to 50 feet (ft) (6 to 15 meters [m]) of the underground enclosed spaces, 3 were 100 to 150 ft (30 to 46 m) away, and 1 was 400 to 500 ft (120 to 150 m) away. Investigators often identified suspected pathways from the blast site into the underground enclosed spaces. One technique appeared successful at quickly correcting an existing condition. This technique involved applying negative pressure to the earth and removing the CO from the ground surrounding the underground enclosed space.

Jan 1, 2001

By J. Sigler

A series of small scale tests have been performed to establish the effect of powder factor and initiation timing on the grindability of rocks. The blasts were performed in high quality granite blocks, which were cut from stone prepared by dimensional stone quarry operations. Three different types of granite were tested. The charge configurations included detonating cord placed in five holes with water as a coupling medium or concentrated charges of equal mass, placed in the same number of holes, fully stemmed or air decked. The powder factor was varied from 0.4 to 1.2 kg/m3. Typically all charges were detonated simultaneously; however, in some experiments, detonation waves collided in the middle of each borehole and in others a small delay was used between charges. All fragments were collected and screened, and drop weight impact tests were performed on selected size fractions, using different impact energy, to calculate the resistance of the rock to impact breakage. The work index of some of the blasted samples was measured using a standard Bond mill arrangement. The experiments generally showed increased softening of the rock with powder factor, which appeared to be the dominant factor. Charge configuration as well as in-hole collisions of detonation waves affected the initial fragmentation but had little effect on the impact breakage of the samples.

Jan 1, 2008

By Jared Redyke

Thursday, October 14, 1999 marked another important milestone for America’s space program. At exactly 10:05 AM EST on a beautiful, sunny Florida morning, Dykon, Inc. of Tulsa, Oklahoma detonated approximately 300 pounds of explosives to fell the seven million pound Umbilical and Mobile Service Towers at Space Launch Complex 41 (SLC-41) at NASA’s Cape Canaveral Space Station. Completed in 1965 at the height of the Space Race to the moon, the Mobile Service Tower/Umbilical Towers (MST/UT) were part of the Titan rocket launch facilities. The MST was 265 feet high and weighed over five million pounds. The UT was 175 feet high and weighed over 2 million pounds.

Jan 1, 2001

By Mark S. Stagg, Stephen A. Rholl, Steven G. Grannes

A method of determining the fragment size distribution of rock quarry muckpiles using photographic and digital-image processing techniques has been developed by the Bureau of Mines. To assess the fragmentation, photographs and video tapes were taken in both the laboratory and in the field and then digitized for analysis. The fully-automated process uses specially written image-interpretation software which had been developed previously by Bureau researchers to measure irregular taconite ore shapes. The advantages of photographic assessment in comparison with other methods include speed and cost.

Jan 1, 1993

By Lars Osen

Both fragmentation and safety can be improved by following proper procedures in loading boreholes. Proper loading procedures such as primer location, borehole sealing, decking, and stemming along with the hazards of dropping on primers are presented. Discussions follow on the reason for the use of each procedure along with the possible consequences such as hazards, misfires, or poor fragmentation.

Jan 1, 1985

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 Jack Eloranta

This paper describes a method of evaluating shot performance through the use of available mine- data. The mine had already been monitoring the following parameters for other purposes: drill penetration rates, shovel loading rates, crusher throughput, crusher power and crusher hangups. By assigning pit coordinates to these factors, maps showing the location of difficult and favorable blasting are as are identified. Products and techniques are compared by the same method.

Jan 1, 1993

By Fumihiko Sumiya, Kunihisa Katsuyama, Yuji Ogata, Yukio Kato, Yuji Wada, Yoshikazu Hirosaki

Smooth blasting technique is widely applied for tunneling road or railway construction in Japan. However, smooth blasting technique often causes problem related to detonation failure in explosive column due to channel effect. Channel effect is attributed to the precursor air shock wave (PAS), which propagates ahead of detonation front in an air channel of borehole. PAS precompresses and desensitizes the unreacted explosive column. The failure of detonation propagation occurs as a result. It was concluded in our previous work that reducing PAS velocity was one of the effective methods for the prevention of channel effect.

Jan 1, 2003

By Andrew Ritter, Victor I. Montenyohl, Stephen R. Winzer

Thirty-seven open pit production blasting operations have been monitored using high-speed cameras running between 500 and 7000 frames per second. Analysis of the resulting films reveals irregularities in timing including sequencing errors and crowding (holes firing less than 8 ms apart), confirming results of laboratory testing of ms delay blasting caps (Winzer, 1978). Where blasting parameters are otherwise constant and within recommended guidelines (stemming, spacing, burden, etc.), timing problems dominate the overall performance of the blasting operation. Model tests in layered Homalite 100, designed to simulate joint or bedding planes in rock, indicate the importance of the stress waves generated by the explosive in developing the crack network which is ultimately responsible for the fragmentation seen in the resulting muckpile. These mechanisms are strongly supported by high-speed film studies at Pinesburg, Maryland. Experiments in controlling relief in deep shots (where depth approaches the lateral extent of the bench blasted) using borehole geometry and hybrid initiation systems (electronic timer and pyrotechnic delays) were carried out. The results suggest that the 1 me/ft. of burden guideline developed by Bergmann et aI., 1974 is too short, and that much longer times are necessary to optimize fragmentation and muck digability. Longer times are found to reduce noise, vibration, and flyrock.

Jan 1, 1979

By H Fukui, K Ichikawa, K Aikou, E Suzuki

An electronic delay detonator (EDD) consisting of a digital-base electronic delay module and a conventional instantaneous detonator module, designed for series connections with a special adjustable-output blasting machine, is described and shown to provide a delay time accuracy some four to twelve times higher than that of pyrotechnic millisecond and decisecond delay detonators, together with the other performance characteristics necessary for practical use. Also described is a blasting design system which allows effective reduction of ground and air vibration, through the use of EDDs with optimum delay times as determined by accurate computer simulation based on wave form and other data obtained from an on-site single-shot test blast.

Jan 1, 1989

By R Holmberg, C Sjoberg, B Larsson

This paper describes the excavation of an underground naphta storage facility at Stenungsund in Sweden. The main purpose with this paper is to give an overall view of how the excavation was carried out and in what type of bedrock the storage was built. Emphasis has been done to highlight the importance of using cautious blasting to avoid blast damage in the remaining rock. Attempts has also been done in order to evaluate what the degree of Swedish cautious blasting has meant for the rock support costs during the construction period.

Jan 1, 1984

By R Malo, A Yetter

The use of large diameter blastholes for underground mining began approximately twelve years ago and are now routinely employed in a variety of ore types and stope designs. These large boreholes, ranging in size from 4 1/2 inch to 8 inch diameter, were first utilized in the same fashion as in open pit bench drilling. However, a variety of changes quickly followed in order to accommodate the unique conditions encountered while using a blasthole sloping method.

Jan 1, 1984

By D. C. Valdemeri, Oppermann J. P. Z., R. G. Schaarschmidt, C. S. Mendonca

This case study was conducted in an aggregate company, located at Estância Velha town, RS, Brazil. The study was based on the results of vibration monitoring mainly in terms of PPV (peak particle velocity) and frequency. Changes in the blasting design were performed to adjust the limits determined by the Brazilian standard NBR 9653:2005. Understanding the seismic wave attenuation for the site, changes in the blasting design were tested to fit the limits, such as reduction of maximum charge per delay, initiation orientation and sequencing and finally the replacement of accessories like "shock tube" by electronic initiation system. The results are shown below.

Jan 1, 2015

By Jennifer P. Harrell, D. Joseph Hagerty

In many areas of the eastern United States, especially in the Midwest, past mining activities have left large and extensive underground openings. Now, renewed mining is occurring in such areas in surface pits. Also, construction blasting often occurs in rock over such old openings. Within the last fifteen years, some attention has been given to the interaction between surface blasting and underground cavities; concern has been expressed about the possible changes in vibrations transmitted through areas underlain by old mine workings (Siskind, Stachura and Nutting 1987). Previous studies also had indicated that underground openings could influence transmission of surface mine blast vibrations (see, for example, Woodward-Clyde Consultants 1977). The principal concern is that underground openings under surface blasting may intensify low-frequency vibrations. If such intensification occurs, use of available equations to predict peak particle velocities and to design blasting patterns and select blasting parameters could lead to possibly damaging ground shaking.

Jan 1, 2002

By Charles E. Joachim

Railroad and blast induced vibrations were measured in the vicinity of the proposed Big Bend Cutoff. Peak horizontal and vertical particle velocity relations were developed using least squares regression analysis. The dominant frequencies of these data are in the range of 30 to 50 hz. Therefore, allowable charge weight per 30 msec delay curves were generated for buildings (2 in./sec) and unlined tunnels (8 in./sec). A blasting contour map is presented for this site.

Jan 1, 1984