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By Peter Moser, Frank Chiapetta, Sacha Diaj, Florian Bauer

Good toe breakage and a flat working bench after blasting are important parameters to achieve a high productivity during material loading and reduce the necessity for secondary blasting. Good toe breakage requires a proper burden – side spacing design and a suitable sub-drilling. With unfavourable jointed rock mass conditions the use of horizontal bottom holes still can be found as common work practice even that this is associated to high risks.

Jan 1, 2009

By Tristan Worsey, Nathan Rouse

The Florida legislature allocated funding for the Florida State Fire Marshal (FSFM) to review the applicability of the United States Bureau of Mines (USBM) Report of Investigations (RI) 8507 blast vibration limits with respect to Florida and its soils. The study also discusses whether the current blasting vibration limits set by statute are still appropriate, including a review of measured vibration amplitudes and frequencies, structure responses, and theoretical analyses of material strength and strains.

Jan 1, 2019

By Chris Breeds, Larry Leone, Jerry Wallace

Project Owners typically require General and Detailed Blast Plans when blasting close to important structures and specify the maximum allowable peak particle velocity for each potentially affected structure. Low, residential level PPV limits may be specified which significantly restricts the potential for blasting to be effectively used. Contractor’s responding to these contract conditions typically cite historic case studies which may, or may not, apply to the specific situation and/or types of structures for which limits have been set. A long submittal cycle typically follows.

Jan 1, 2010

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 Michael S. Stern, Gordon P. McDonald

The increasing costs and problems associated with transporting and safely disposing of used engine oils from remote mine sites have caused mining companies to consider other ways to consume their used oil. One practical method of disposing of these used oils is to blend them with the diesel component of ANFO and Heavy ANFO type explosives.

Jan 1, 1993

By Stuart Brashear, Lee Schettler

"The effect of water on several ANFO/emulsion blend ratios is documented by both physicalobservations and analytical testing to demonstrate the effect even small quantities of water canhave on water resistant blends."

Jan 1, 1996

By J R. "Dick" Daniel

Over the past several years, the Hercules Technical Service Group for the Explosives Department has produced a series of programs for the TI59 programmable calculator dealing with explosive application problems. These programs have been made available to both our internal staff and to the Hercules explosives distributor organization. Several of these programs have found good acceptance and wide usage.

Jan 1, 1984

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 C. Feliciano, M. Cavalcante

A large iron ore open pit mine in Brazil operates with reduced blast sizes, due to the imminence of red alerts in the rainy season and the proximity of plant and dam structures that demand control of the maximum load of fired explosives. Blasts are currently not allowed to remain loaded with explosives due to the risk of red alerts, limiting mine operations close to them. There is a need to increase the blast sizes, reducing the number of events required to obtain the planned mass and, consequently, the unproductive operating hours lost with mine evacuations. The WebGen™ wireless electronic initiation system is a technology for firing detonators via lowfrequency magnetic induction that propagates through the medium, without physical connection. A blast was carried out with 406 holes divided into 4 panels, aiming to validate the preloading technique with wireless detonators and its performance in safety and productivity. The absence of lead wires in the system eliminates the risk of interaction between vehicles and detonator cables in stemming and loading operations, which can result in unplanned detonation or misfire. By eliminating the need for a spotter, it reduces people's exposure to dust and the risk of human-machine interaction. Furthermore, it eliminates the risk of unplanned detonation caused by lightning strikes. The pre-loading technique with wireless detonators enables flexibility and efficiency in planning through temporary accesses over loaded areas. In the demonstration, driving over the loaded area was essential to avoid jams and excessive wear on equipment due to the narrow berm and very friable material. Another gain in productivity was optimizing operational stages, since detonators were programmed in parallel with loading, anticipating process stages, in addition to eliminating the need to connect detonators. Considering the average handling and savings in downtime due to the reduction of blasting events, a potential increase in movement of 49,000t (54,013 short tons) in 3 months was estimated, keeping the vibration results within the required limit. The trial with wireless detonators demonstrated the feasibility of carrying out blasts with preloaded panels, without restrictions on the number of panels or detonators, enabling vibration control, innovating mine planning and increasing safety and productivity

Jan 1, 2024

By K. Hausmann, P. A. Sashin, G. J. Prejean

Misfires caused by unreliable shock tube constructions can have significant cost implications and place field workers at serious risk during remediation. Ionomer materials, used as a subtube in shock tube constructions, provide superior hot tack strength, oil resistance, impact resistance at cold temperatures and excellent thermoformability properties. These are important features for resisting blast-throughs and ensuring blasting reliability in demanding environments, such as open pit mining in harsh environments. Superior hot tack strength, strain hardening, and excellent thermoformability properties of the ionomer materials ensure uniform powder distribution along the shock tube during construction and avoid undesired powder accumulation due to deformation or vibration during use. Oil or chemical resistance is another feature of Ionomers. This allows improved property retention in contact with oils and hence longer sleep times of the shock tube. Another feature of these highly engineered ionomers is superior impact strength at low temperatures. This plays an important role considering the resistance to fly rock impact in open pit mining operations in particular in cold climates.

Jan 1, 2011

By Barend Botha, Trevor Davids

The presence of an extensive soft siltstone layer in the middle of the inter-burden sequence of rocks at Syferfontein Colliery in the Republic of South Africa prompted tests to determine the effect of different mid-column decks of inert material in the siltstone layer. The objective was to achieve significant cost savings in explosives use whilst not degrading dragline productivity. An important factor that had to be considered was that the initiation systems available in South Africa are not accurate enough to ensure simultaneous initiation of explosives decks in a blasthole. A number of inert materials were tested including ash, drill cuttings, river sand and crushed stone. It was found that the ash, drill cuttings and river sand did not effectively attenuate the shock wave and that the risks of sympathetic detonation or partial disruption of one or the other explosives deck in a blasthole was high. This became much worse when the inert material was saturated with water. Crushed rock was the most effective in attenuating the shock wave, but this material was very expensive to use because it had to be imported onto the mine.

Jan 1, 2000

By K Taylor

Small scale tests have been conducted in blasting vessels in the laboratory, where the effects of explosive composition, charge diameter, explosive confinement as well as additives to the explosive were examined on NO, NO2, CO and CO2 production. Fumes were analyzed continuously using a flue analyzer, providing analysis every 15 seconds. The results were compared to previous work conducted in the laboratory and to literature findings. It was found that the type of the explosive was the most dominant factor with emulsion explosives producing significantly less amounts of toxic gases. ANFO was shown to always produce nitrogen oxides, even when fuel rich. Tests were also conducted by detonating explosives in broken rock, simulating the release of products of detonation during the formation of a muckpile. Products of detonation were affected by the presence of atmospheric air or rock around the charge. Gaseous products of detonation migrated through the rock piles at different rates, resulting in a change of toxicity values over time. In the small scale experiments, CO appeared to travel faster than CO2 while NOX was not identified. Analysis of the gases that were released during digging, several hours after the blast, resulted in high temporary concentrations of toxic fumes.

Jan 1, 2014

By Virgil J. Stachura, Calvin L. Cumerlato

The Bureau of Mines conducted a series of tests to develop a blasting method that would reduce overbreak and rockfall hazards at a limestone quarry in northeastern Wisconsin. Reductions in overbreak were achieved by shortening the main explosive column and reducing the explosive load in shortened stemming zones in shotholes which were to form the highwalls. Two blasthole diameters, 3 and 4 inches, were used with 7 by 7 foot and 9 by 12 foot burdens and spacings respectively. ANFO, Comsol 300, or PowerAN were used in the body of the shots and Gelmax or 40 pct extra dynamite cartridges were used in the reduced load zones. Smoother highwalls were visually apparent, however further analysis by seismic refraction techniques were performed as an aid to studying overbreak within the rock mass.

Jan 1, 1989

By L D. Santis, L Wardrip

This paper begins with a summary of the development of the sheathed explosive charge from it's conception by the Bureau of Mines in 1981 through the evaluation of its safety, culminating in revisions to the Code of Federal Regulations (CFR), Title 30, Parts 15 and 75 which provide for its approval as a permissible explosive and safe use in underground coal mines. In 1989, Austin Powder Company decided to market a sheathed charge and proceeded to develop a commercial version which they call the Rock*Buster. The Rock*Buster was tested by the Bureau of Mines and subsequently approved as a permissible sheathed explosive unit by the Mine Safety and Health Administration (MSHA). Marketing of the Rock*Buster began in the Spring of 1990. In May 1990, the Rock*Buster was first used in an underground coal mine, Jim Walter Resources' (JWR) No. 4 Mine in Brookwood, AL. Trials with Austin's units were impressive. Representatives from MSHA, the State of Alabama, JWR, the United Mine Workers, and other local mining companies observed the charge break large boulders on the surface. Later, the charges were used underground to break large rocks from a roof fall that were obstructing ventilation. During its first week on the job, the Rock*Buster reduced the downtime experienced on JWR's longwall sections by quickly taking care of problem roof falls which halt operations.

Jan 1, 1991

By Romel Villanueva, Juan Vasquez

We present the results of our field research on the variation of the density of the gassed explosives and their influence on the blasting results in the Peruvian mines: Yanacocha, Toquepala and Antamina. Currently, 90% of Peruvian mines uses gassed explosives, for their economic and technical benefits. But new practices and design criteria have had to be adopted, and the most important a careful control of the in-hole density, whose variation in the depth of the hole strongly affects the detonation process. For gassed explosives the density varies gradually according to the depth in the hole, due to the pressure on the bubbles by its own weight. The density at the bottom of the hole can reach critical values, which directly affects the start of the detonation in the booster zone with a high probability of nitrous fumes formation. On the other hand, density translates into the amount of explosive and energy available. Therefore, for the optimum performance of the explosive, the minimum and maximum values of the in-hole density must be determined. For the cases studied, the maximum in-hole density and the maximum charge length have been determined. When the charge length is greater than 7.0 m [ 23 ft.] special care must be taken with the cup density, which as a general rule should not exceed the value of 1.15 g/cm3 [71.8 lb/ft3] at the risk of losing the sensitivity at the bottom, also increasing the probability of nitrous fumes, bad fragmentation and finding intact explosive after blasting. In the large holes in Toquepala and Antamina mines, where the charge length can be greater than 9.0 m [29.53 ft]. If the cup density is greater than 1.15 g/cm3 [71.8 lb/ft3] the in-hole density can easily reach a high value of 1.30 g/cm3 [81.16 lb/ft3].

By Tom Short, Paul Kunze

In this paper, the authors describe major changes in drilling and blasting methods instituted at the Zortman And Landusky Mining Company Properties to maintain the viability of these north central Montana surface mines in the present period of depressed precious metal prices. The authors explain how improved drilling procedures minimized problems due to uneven benches and floors. They also describe changes in explosives loading and delay blasting techniques which improved fragmentation, thus increasing metal recovery from heap leaching. Quantities were increased substantially and a new bulk explosives loading system was placed in service with a special down-the-hole bulk loading truck and storage facilities for bulk ANFO and bulk emulsion. At the same time, drill patterns were expanded by nearly 40%. The authors also describe a new technique of using explosives to selectively cast waste and ore in different directions so as to reduce the cost of separating the ore.

Jan 1, 1986

By John R. Jr Tripi, Paul N. Worsey

Split round blasting is commonly practiced in underground uranium mining in the Big Indian ore belt located in Southeast Utah. The technique is used to prevent ore dilution by separately blasting the ore from the face.

Jan 1, 1985

By Robert B. Hopler

The Hercudet ? Nonelectric Delay Blasting Cap System has undergone significant changes since the last paper on the subject was presented at the 1978 S.E.E. Conference. The changes have been made to improve reliability of the blasting machine at low temperatures, and to improve efficiency and economy in usage in surface mining. The paper includes examples of the blast design process, details of use of the new in-hole connected cap, and delay patterns which have found use in quarrying and coal stripping.

Jan 1, 1980

By Billy J. Thorne

The damage model in PRONTO simulates the dynamic fracture behavior of brittle rock. It is based on work started by Kipp and Grady, [lg] continued by Taylor, Chcn and Kuszmaul [I91 [20] and recently.modified by B. J. Thorne (first documented here). The essential feature of this model is the treatment of the dynamic fracture process in rock as a continuous accrual of damage in tension, where the damage mechanism is attributed to microcracking in the rock medium. The fundamental assumption of the damage model is that the material is permeated by an array of randomly distributed microcracks which grow and interact with one another under tensile loading.

Jan 1, 1989

By Grant Small, Deon Pieterse

Reactive ground conditions at an open pit manganese mine in the Northern Cape of South Africa resulted in an unexpected detonation.

Feb 1, 2020