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By John Turner, James Lamb

The Minnesota Department of Transportation (MNDOT) has an extensive project to improve driving conditions and reduce hazards to motorists on US Highway 61 between Duluth, MN, and Canada along the north shore of Lake Superior. In 1991, the Lafayette Bluff Tunnel was completed just north of Two Harbors, MN, through a joint venture of Johnson Brothers Corporation of Litchfield, MN, and Obayashi Corporation of San Francisco, CA.

Jan 1, 1994

By Raymond M. Dixon, Dale L. Ramsey

Upon being introduced to the MAGNETIC COUPLING concept,Balsinger,Inc. wanted to conduct field trials to explore the potential of Magnetic Coupling in the U.S.. Although the Magnetic Coupling Concept has been widely used, the U.S. proposed blasting criterion not previously addressed by the system. Modification to the system assembly and blasting accessories had to be made to make the system adaptable to our specific requirements. The field trials and system modifications are the basis of this paper.

Jan 1, 1990

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 D. Scott Scovira, Rick Webber

The Iron Ore Company of Canada [IOC] is a global leader in Arctic mining applications, and the blasting crew have something to be very proud of. On Wednesday 21 Dec 2005 at 3:28 PM the largest single bench blast in the company history was detonated. The successful firing of this 5.0 million tonne [5.5 million ton] blast surpassed the previous company record of 3.8 million tonnes [4.18 million ton].

Jan 1, 2008

By Ken Fiorentino, Gordon F. Revey

H3 Tunnelers recently excavated two conventional 48 foot diameter highway tunnels through the Halawa side of the Tran-Koolau Mountains on Oahu. The primary blast design challenge on this Job was minimizing overbreak In the alternating layers of pahoehoe and aa lava, clinker, end tuff. Two different excavation techniques were evaluated in the Halawa tunnels. The first method used drilling and blasting to excavate the tunnels to within one foot of their final perimeter. A roadheader, mounted on a backhoe, was then used to excavate the remaining foot of ground. The second method used conventional smoothwall blasting techniques, without any mechanical excavation. This paper describes the details and relative success of the two excavation methods tried in the Halawa tunnels.

Jan 1, 1993

By George E. Jackson

ANFO, as a blasting agent, is used in large quantities in coal surface mines. It can be purchased on the open market or through reliable suppliers. The blaster in the field must assume that his ANFO is homogeneous, consistent, and nearly identical on a daily basis. A quality control program will enable him to be assured of the correct product. Therefore, the material cost and operational efficiency can be better controlled.

Jan 1, 1978

By Quian Liu

The problem of cross-hole explosive malfunctioning in rock blasting (including sympathetic detonation, desensitization and cut-offs) is a function of delay and spacing in a blast which should be designed to avoid such occurrences. On a delay-spacing chart, the phenomenon of explosive malfunctioning is explained by dividing the chart into different regions, while the shape and size of each region could vary from one explosive to the other. Over seventy blasts have been carried out at the CANMET Experimental Mine to identify the malfunctioning characteristics of specific emulsion, water-gel and dynamite explosives. In each experiment, two parallel blastholes, 32 mm in diameter and 1.7 m deep, were drilled downwards in an underground drift.

Jan 1, 1994

By J R. "Dick" Daniel

In the fall of 1988, The Cannon mine decided to investigate a central blasting system based on conventional electric blasting detonators being used to initiate rounds primed with Nonel detonators. The advantages of this hybrid detonator system were viewed as being safety and cost effectiveness. A study was done reviewing the safety aspects of utilizing a permanent blasting line installed throughout the main haulage drifts to a central blasting station located at the mine portal. The study addressed the following potential safety hazards: radio frequency induced current, stray current from both electrical utilities and transmission lines, galvanic and electrostatic sources of extraneous current.

Jan 1, 1989

By Michael S. Wieland

This report discusses the U.S. Bureau of Mines research regarding the desensitization and malfunction of cap-sensitive explosives deployed in underground coal mines. Delay blasting in underground coal generates severe shock waves and rifting forces that fracture and heave coal. These dynamic interactions can damage other charges still remaining in the delay pattern. The debilitating impacts precipitate degrees of reduced charge performance ranging from misfires to weak detonations or out-of-sequence firings. Damaged charges react poorly, perform less useful work, and/or generate atypical fumes with higher toxicity.

Jan 1, 1993

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 J Edmund Hay, T S. Bajpayee

The Bureau of Mines is developing a test to determine the initiating strength of commercial detonators. Various tests of "detonator strength" are in use, but many of them do not correlate well with each other, and so far, there is little evidence that any of them correlates well with the ability of detonators to initiate detonation in an explosive. Therefore, the Bureau decided to attempt a measurement of the ability of detonators to initiate detonation. To this end, an explosive mixture of adjustable sensitivity was developed. This mixture was nitromethane sensitized with ethylene diamine, the sensitivity being "fine-tuned" by the addition of nitropropane.

Jan 1, 1992

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 John M. Bolger, Keith E. McMaster

Excessive salt fines are undesirable in underground salt mining as they are considered a costly waste by-product. This paper describes an extensive explosive application program conducted at The Canadian Salt Company Ltd, located in Pugwash, Nova Scotia, Canada. The prime objective of the program was to reduce the quantity of fines generated from this company's underground production blasts. The program was known as the "The Fines Reduction Program".

Jan 1, 1996

By Richard Scales, Giles Hellyer, Ian Travers, Dean French, Peter Bellairs

"The Mt Whaleback iron ore mine is located in the Hamersley Province situated about 1OOOkm to thenorth of Perth, the capital city of Western Australia. A small but significant portion of the waste in Mt Whaleback presents problems due to its ability to react with normal commercial bulk explosives resulting in premature detonations, two of which occurred at the mine in 1983 causing great consternation as well as disruption to the mining operation. The techniques and procedures developed to overcome this problem were based on the use of tough durable, acid and heat resistant liners to provide a physical barrier separating the explosive from the rock togetherwith the development of an accurate down the hole remote temperature logging technology. The liner technology was developed due to the inability to produce a reliable inhibited ANFO despite exhaustive mine based testwork."

Jan 1, 1999

By Koichi Kurokawa, Takeo Ueda, Masahi Nakano, Yoji Tasaki

A lightning strike generates several 10kA and several billion volts, and earth currents generated by lightning is dangerous to some underground and all surface blasting operations. In order to evaluate the safety against lightning in conventional electric firing method and electromagnetic induction blasting system, a test is conducted by connecting a wire with an impulse generator. Frequency of impulse current used in the test is 17kHz and the waveform is a vibration type and the duration time is 250 ~usec. The results of the test show that induced current increases with the increasing of impulse current. In the case of MBS connection, when maximum primary current is 1700A, Maximum secondary current is 11.8A and the electric detonator is fired at this condition.

Jan 1, 1988

By Courtney W. Shea, Dennis Clark

Reckless blasting can have tragic consequences: The death of an innocent traveler, the financial demise of a coal company, and even criminal prosecution. In June 1993, a Tennessee coal mining company was blasting to loosen overburden at its surface mine. The mine was located immediately adjacent to the right-of-way of the northbound lane of Interstate 75. The approved permit included special precautions to be taken when blasting in the area closest to the interstate, including monitoring traffic so as to blast when the northbound lane was clear.

Jan 1, 1998

By Donald H. Matthews

The usual method of dismantling massive concrete formations with explosives, is to totally demolish the entire concrete structure. If any portion of a concrete structure is required to remain in its original form and retain its structural integrity, the use of explosives is usually forbidden and the portion to be dismantled is demolished by mechanical means, using various techniques and equipment that are tedious and expensive.

Jan 1, 1978

By Frank Barker

Mining operations present a very different environment to the suppliers of explosives, initiating systems and services, both on surface and underground. Typical hazards include underground movement, air quality, ground stability, moving equipment, and the use of explosives. As contractors to the mining industry we do not have management control over the environment in which our people operate. The hazards and consequent level of risk that our people are exposed to in some mining operations are significantly higher by orders of magnitude than in a normal factory environment. Orica Explosives (and other Explosives suppliers) are continually and increasingly identifying opportunities to partner with customers by adding value through the provision of services leading to a reduction in total mining costs. These services include the provision of a bulk underground loading services, delivery of product into underground magazines, magazine management, value added blasting, conversions, rock-on-ground contracts, and blast management programs.

Jan 1, 2000

By Jack Eloranta

Transmission of sound through the atmosphere is affected by local conditions. Anecdotal accounts of the sound of cannon fire traveling great distances go back to the Civil War. The Royal Society published a paper near the turn of the century concerning the reports from the cannons fired in London at the funeral of Queen Victoria. Early computers were used by the U.S. Army at Aberdeen in Maryland in the 1950’s to model airblast problems during munitions demolition. Today’s blaster has to have access to weather information beyond a simple local forecast. Surface winds, winds aloft and temperature profiles have a dominant role in neighbors reaction to blasting. Many ground vibration complaints are really airblast complaints. Blasters who maintain ground velocities under . 1 inches/ second are often perplexed by complaints from distant neighbors, even when local monitoring shows airblast to be under 110 dB. This paper will help the blaster identify warning signs of high airblast conditions.

Jan 1, 2000

Several surface coal mining operations in North America are attempting to adapt microprocessor-based monitoring equipment as well as programmable logic controllers onto rotary blasthole drills, towards improving overall drill and blast productivity. These Monitoring While Drilling (MUD) systems permit the recording and processing of important drilling parameters such as rotary speed and torque, instantaneous penetration rate and weight on the bit, and enable the operator ultimately to optimize drill and bit performance. MWD systems on production drills in surface coal mines offer the potential to define mine bench geology in detail and in advance of explosives loading. Recent advance s in explosives and initiation technology will require such a detailed knowledge of ground conditions in order to be fully exploited. Additionally, the logic developed from drill monitoring technology will eventually enable full drill automation through feedback and control, once a more complete understanding of the influences of rock mass characteristics on machine performance is achieved.

Jan 1, 1988