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By LaRay Collyer

San Juan Mine began pre-splitting the highwall prior to cast blasting in August 1986. The first pre-split shot used six inch PVC (polyvinylcloride) pipe inside a 10 5/8 inch hole, drilled at a 74 degree angle. The powder factor was about .90 pounds per cubic yard.

Jan 1, 1990

By Thomas Palangio, Lyall Workman, Jack Eloranta, Tom C. Palangio

The fragmentation distribution of the blasted ore is an important descriptor of blasting results. Traditionally it has been hard to measure quantitatively. Developments in image analysis over several years makes it more feasible to measure fragmentation before crushing on a continuous basis. Post crushing, mill feed distributions can also be measured.

Jan 1, 2007

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 Mark S. Stagg, Rolfe E. Otterness, Stephen A. Rholl

The Bureau of Mines fired seven test blasts in a 22-ft bench of limestone, screening the material to investigate the influence of explosive type and between row delays on fragmentation. Four 4-hole, single-row test shots were conducted evaluating dynamite, ANFO, emulsion, and a 60-40 emulsion-ANFO mix. Three 12-hole shots, with three rows of 4-holes, evaluated delays between rows of 24, 36, and 120 ms. Accurate in-hole electronic delays were used, firing within 1.5-ms of the nominal delay. All seven shots had a 6- to 7-ft burden, 10-ft spacing, with a hole diameter of 3-1/2 in fired on a 12-ms delay between holes in the row. The tests were instrumented with strain gauges grouted in the burden region examining stress wave and gas pressure effects. Fiber optic probes were used to confirm timing and to obtain detonation velocities.

Jan 1, 1989

By Corry Goumans

The job location is at Bear Lake Hydro Project located north of the town of Sechelt, British Columbia, Canada

Jan 1, 2013

By W. Fourney

In the late 70’s and early 80’s in conjunction with other oil and gas well stimulation studies, personnel from the Dynamic Effects Lab performed model testing to demonstrate the effectiveness of utilizing an open section of borehole just before a plug. We called the process stem induced fracturing. The open section beneath the stem was used to increase the pressure magnitude and spread out the duration of the pressure pulse. This technique was later utilized to by Frank Chiapetta (1) in the fracture and fragmentation of rock in quarry blasting situations. He called his technique air deck blasting. In fact, Frank found that the Russians had previously discovered the same technique. There is currently interest in utilizing air deck blasting with an open section of hole beneath the explosive at the bottom of the bore hole to better remove the toe in a fragmentation shot. This paper reviews the development of stem induced fracturing and then describes a series of model tests conducted to measure borehole pressure at points along a borehole when an explosive charge is detonated at the midpoint of the borehole. Tests were conducted in both stiff boreholes (aluminum) and less rigid boreholes (PMMA-Plexiglas). Pressure time profiles were measured at the charge site, midway between the charge and the bottom of the hole, at the stemming at the top of the borehole, and at the bottom of the borehole. Crack initiation sites and crack propagation were also determined in the PMMA models. Some high speed pictures were taken of the event in the PMMA.

Jan 1, 2006

By A. S. Tawadrous

The stress field around a detonating charge in a borehole was calculated using AUTODYN for a variety of in-situ stress conditions. Calculations were conducted for zero in-situ stress, hydrostatic conditions at 100MPa, uniaxial stress conditions of 100MPa, and bi-axial state of stress with amplitudes of 200MPa and 100MPa along the axes. Two different explosives, ANFO and emulsion, were used for the calculations. It was shown that in-situ stress fields had an effect on the tensile and compressional damage zones around the blasthole, calculated on the basis of the maximum amplitude of the stress pulses in the rock after the detonation of the explosive in the blasthole. The extent of compressional damage increased around the borehole, whereas, the extent of the tensile damage decreased. The damage zones are of elliptical nature with their axes parallel to the direction of the principal stresses. The difference between the major and minor axis of the elliptical damage was not very significant in the case of the compressional damage; however it was significant in the case of the tensile damage.

Jan 1, 2007

By H Russell

An account of an experimental blast at the Sullivan Mine involving a small pillar drilled with 4 1/2" diameter up-holes, and loaded with emulsion explosives from a truck-mounted tank/pump unit.

Jan 1, 1984

By Fumihiko Sumiya, Koichi Kurokawa, Yukio Kato, Tetsuya Sawada

In some metal mines, it is a serious problem the decomposition of explosives which occurs suddenly by contact with ore containing pyrites under high temperature conditions. In the present paper, we investigated heat resistant properties of emulsion explosives and other industrial explosives by contact with ore containing pyrites under high temperature conditions.

Jan 1, 1992

By John C. Adams, Robin Irwin

In early 1993 a test program was designed to determine if mining costs could be reduced by using a high density ammonium nitrate mini-prill blasting agent. The goal was to reduce mining costs by expanding blast hole patterns while maintaining or improving dig-ability of the shot material. The program was conducted at Santa Fe Pacific Gold's Lone Tree gold mine near Valmy, Nevada.

Jan 1, 1994

By Steven V. Crum, David E. Siskind

In response to its own concerns and those of the public, industry and regulatory agencies, the Bureau of Mines is studying the impacts of low-frequency blast vibrations on structures. Previous research has identified potential problems associated with low-frequency ground vibrations and also found that their existence was not particularly rare, given large surface mine blasts and certain geologic conditions. Only a limited amount of data existed in the blast vibration literature on structure response to ground-vibration frequencies below 6 Hz.

Jan 1, 1993

By Pierre Auger, Benoit Levesque, Richard Martel, Guy Sanfacon, Louis-Charles Boutin, Marc-Andre Lavigne, Patrick Brousseau, Luc Trepanier, Louise Galarneau

Explosives used for blasting operations in civil engineering works, like construction of piping systems under roads, of pools, of houses and buildings can generate large volumes of carbon monoxide (CO). Carbon monoxide can represent between 1 to 3% of the gases produced by usual explosives. The production of 10 to 24 1 of CO by kg of explosives blasted is theoretically anticipated. CO is a gas that has no characteristic colour, smell or taste. It can migrate in the fractured rock of the blasted areas on fair distances, and then infiltrate in closed spaces like sewage systems, manholes, but also in basements of houses. In Quebec, in the last 10 years, 7 people were poisoned by CO in their houses to the point that they had to be treated in hyperbaric chambers. In the USA, many accidents have occurred and one worker died in a manhole. From the review of intoxication cases, the distance of migration of CO may reach 55 m if a conduit is present underground. Underground conduits broken by blast, tilling around underground conduits in road or house trenches, or fractured rock created by blasts between houses or between a house and a road, are the different pathways identified in the Quebec incidents. Field tests were performed at sites close to CO intoxication locations in order to evaluate the behaviour of CO in fractured rock following blasting operations. From these tests, the following conclusions may be drawn. The structural geology of the rock formation (schistosity, family of joints, fractures) plays a role in the direction and extent of gas migration in fractures generated when rock is blasted with explosives. The confinement of the rock can affect the quantity of gas migrating in the fractured rock. Significant concentrations of CO may persist in the fractured rock even 7 days after a blast. Advection is the initial mechanism of CO migration in fractured rock generated by the blasts or naturally occurring before the blast. The distance of migration with this mechanism is short (5 to 8 m). In trenches of muck (equivalent to tills under roads) the distance of CO migration by advection is 12 to 20 m. In the 2 to 3 days following the blasts, further CO migration up to 15 m is made by diffusion in the induced fractures, or up to 30 m in the trenches. To minimise CO production and migration in the fractured rock during blasting, special procedures can be applied by the blasting contractors: (1) do the complete excavation of the overburden before drilling and put mats for each blast; (2) do the complete excavation of the muck after each blast; (3) the last blasting should be the one for the private services entrance of the house and the excavation of the muck should begin at the junction between the road trench and the services entrance trench. Another technique consists in the pumping of interstitial air in the muck with a vacuum truck immediately after each blast.

Jan 1, 2002

By Ronald R. Rollins

A continuous propagation velocity measurement probe has been utilized to determine velocities of slurry explosives, whole prills, crushed prills, aluminized crushed prills, in bulk and plastic screw tubes.

Jan 1, 1984

This paper examines the hypothesis that the fragment size distribution of blasted rock contains information about the changes in fragment sizes with distance from the borehole, and that this information can be interpreted and used to predict the effect of powder factor on fragmentation. A set of simple relationships between the fragment size distribution curve and the dependence of fragmentation on powder factor is proposed. The equations derived are compared with published data on fragmentation in small scale blasting. Two data sets were analyzed, and the results confirm the hypothesis.

Jan 1, 1997

By J Lyall Workman, Peter N. Calder

The Manassas Quarry is a large industrial stone quarry in Northern Virginia owned and operated by Vulcan Materials Company. The quarry experienced instability in a portion of the north wall, which included toppling failure in a metasediment and movement on a major fault zone. It was necessary to take remedial measures to stabilize the wall and create good quality final pit walls.

Jan 1, 1992

By E W. Kohler

Geophysical wireline logging of blastholes provides useful geological data and has considerable potential to improve overall blasting control and costs. This paper uses case histories to show how logging techniques have highlighted certain problems, and discusses the various in-hole tools available. In particular, the issue of the effects of hole diameter on explosive column height,and the importance of this when deck charging is addressed. The suitability and cost-effectiveness of currently available logging technology to the wide range of blasting applications is discussed.

Jan 1, 1988

By Pierre Mousset-Jones, Jaak Daemen, Songlin Zhang, Jon Hurley

Most western United States open pit gold mine ore bodies are disseminated deposits. The mineralization is so irregular that it is difficult to visually identify the ore/waste boundary. Blast hole samples are used to interpolate digging polygons based on the pre-blast position of the bench. Dilution caused by blasting is of major concern at these mines, since blast movement can mix and dilute the ore and move it beyond flagged digging polygons established on the blasted rock according to their pre-blast location. Typically, mines try to reach a compromise between blast fragmentation and movement.

Jan 1, 1994

By William H. Snyer, Victor A. Sterner

A cache of buried explosives was discovered by ICI Explosives, USA Inc. at one of their sites near Gillette, Wyoming. An intensive investigation conducted by ICI management indicated that nitroglycerin sensitized dynamite might be present. Information also indicated that up to 20,000 pounds of explosives may have been buried.

Jan 1, 1997

By John W. Kopp, David E. Siskind

Over 4 billion pounds of commercial explosives are used by the U.S. mining industry every year with an excellent and improving safety record. However, accidents involving explosives are seldom minor. They produce a disproportionate amount of fatalities compared to other mining activities, as reflected in the relatively high severity rates. The U.S. Bureau of Mines (USBM) has been analyzing blasting accident data obtained from the Mine Safety and Health Administration (MSHA) to determine the most frequent causes of mine blasting accidents, examining trends in these accidents, and identifying areas of needed research. This paper is an update of three previous blasting accident studies conducted on 4-year intervals by the USBM and published in 1983, 1987, and 1991, and is based on a total of 869 blasting accidents.

Jan 1, 1995

By Salah A. Taqieddin

The blast casting technique of removing overburden is an innovative technique which was successfully used in the mining of certain surface coal and quarries. This method was found to be efficient in minimizing the labor and equipment cost while accelerating mining operation with safety. This method was successfully applied to horizontal as well as to dipping coal seams. Also it was practically applied to single as well as to multiple ore bodies

Jan 1, 1992