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By Larry R. Fletcher, John W. Kopp

The safety record for explosives in U. S. mining is excellent considering that over 4 billion pounds of explosives are now being used each year. However, blasting accidents remain one of the most serious concerns based on the number of injuries, the injury severity rate and the disaster potential. The Bureau of Mines has been analyzing blasting accident data obtained from the Mine Health and Safety Administration (MSHA) to determine the most frequent causes of mine blasting accidents and to examine trends in blasting accidents. This accident analysis is an update of two previous blasting accident studies conducted by the Bureau and published in 1983 and 1987.

Jan 1, 1991

By Henry P. Van Ormer

This paper is written to outline the capabilities and flexibility of the electric motor driven oil cooled rotary screw air compressor in construction and mining applications. With the changing economics between fuel and electric power all over the world, the viability of the electric motor is a choice all construction and mining people should be aware of. The advent of large efficient electric motor driven rotary screw compressors have given a great deal of flexibility to the use of these units on many applications not considered before. Examples are given for rotary and percussion drilling, fennels, and underground, sandblasting and "uniting, general uses - shows wheel mounted and skid mounted units.

Jan 1, 1976

By Dave I. McGregor

The Multiple Raise Round Blasting Technique (MRRBT) is a safe, efficient, cost effective method of blasting thee will use existing mine personnel. The MRRBT, developed from the conventional 'drop raise method' style of blasting, can be used for most raise mining applications. Current results using MRRBT indicate no upper limit for the maximum length that a raise can be blasted.

Jan 1, 1994

In situ, most Taconite is heavily pre-fractured; because of the high cost of comminution of taconite, maximum fracture of pre-existing blocks is desirable. Sustained borehole pressure plays a significant role in fragmentation, especially by penetrating pre-existing fractures. The distribution of explosive-induced energy in the burden in three dimensions was calculated. Data on the comminution of single particles was used, with the distribution of energies and the distribution of pre-existing block sizes, to calculate fragmentation for a case study. The calculation agreed well with the measured fragmentation. Sequential comminution events are much more efficient than single ones, and enhanced fragmentation may be possible with alternative blasting practices. Some important factors in the dependence of comminution on energy input are discussed.

Jan 1, 1995

By Douglas Lindsey, Glenn Hazen, Shad Sargand

"With the innovation of computational equipment, an exact analysis of structures as dynamic systems is more approachable. Accordingly, the dynamic system can be established, if the natural characteristics such as the natural frequency and the damping fraction of a system are known. Through dynamic analysis, the response of a structure can be predicted from ground vibration, and it becomes possible to forecast the damage potential to the structure with reasonable accuracy. Most vibration will appear as single harmonic or superposition of waves that consists of several harmonics with different frequencies. A vibration signal can be expressed, therefore, as the function of sine waves. If a signal is periodic, the particular harmonic with the smallest frequency will befundamental and frequency of the others will be multiples of the fundamental frequency."

Jan 1, 1993

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 Brian W. Stump

The cessation of testing of any nuclear explosive devices in all environments is the goal of the Comprehensive Test Ban Treaty. In order to assure compliance with such a treaty, an international monitoring system has been proposed. This system will include seismic, infrasound, hydroacoustic and radionucleide monitors located throughout the world. The goal of this system is the detection of any nuclear test. In preparation for this treaty, a series of monitoring system tests, focusing primarily on seismic observations, have been undertaken. The most recent of these tests, Group of Scientific Experts Technical Test Three (GSETT-3), provides valuable data for assessing future monitoring systems. During the course of this experiment, seismic events associated with earthquakes, nuclear explosions and mining explosions have been recorded. This presentation will discuss the numbers and types of mining explosions triggering the system, in a particular area. Possible implications for the mining industry will be explored.

Jan 1, 1997

By B Mohanty, R Deshaies

Initiation of small diameter explosives by sympathetic shock pressure in water has been investigated under controlled laboratory conditions. Changes either in the geometry of the donor explosive or its point of initiation can alter the essential characteristics (amplitude and duration) of the resulting shock pressure pulse. The pressure signatures from both spherical and cylindrical explosives donors have been studied, in water as well as in various explosive matrices. This paper summarizes the investigations carried out with both 'primed' and 'non-primed' slurry and emulsion explosive matrices with various types of voids. These measurements serve the basis for predicting distances in water for sympathetic initiation for both spherical and linear charges. It is shown that the explosive-detonator system in combination has a far greater probability of initiation due to sympathetic shock pressure than either the explosive or the detonator alone. Various explosive matrices with air bubbles and glass microballoons have been examined and the differing sensitivities to shock pressure explained on the basis of these measurements. It is also concluded that explosives containing air bubbles instead of microballoons would be significantly more prone to sympathetic initiation.

Jan 1, 1992

By Thomas A. Gelormino, Ulrich La Fosse

"Deep blasting was used to densify foundation soils for a large manufacturing facility inChicopee,Massachusetts. A 360,000 square foot building, whose construction began inthe summer of 1990, is founded on alluvial deposits up to 90 feet in depth. These deposits are comprised of saturated very loose to loose fine to medium grained sands with traces of silt and gravel. During the building foundation design it was found that to withstand earthquake forces without soil liquefaction, it would be necessary to improve portions of the alluvial deposits by densification. The zone in need of densification extended from approximate depths of 20 to 50 feet. Several conventional densification methods, including vibrocompaction and deep dynamic compaction, were evaluated along with deep blasting. Detonation of 1-3/4 inch diameter charges of 65 percent gelatin dynamite (Atlas Power Primer) installed inside 2-inch diameter PVC casings to a depth of up to 40 feet, was used to achieve the desired densification. This method was selected over others due to its lower cost and decreased construction time. Although used in New England once in1940 for a dam and once in 1960 for a transmission line tower to improve foundation soils, there is no precedent found in the literature for densification by blasting to improve liquefiable soils below a proposed building. Details of a test program and the production blasting, including vibration data are presented. Pre-and post-blasting data conclusely shows an increase in the density of the sand deposit after blasting."

Jan 1, 1991

By Midori Sakamoto, Nobuaki Sakuma, Tsuyoshi Murashita

Recently, tunnel blasting works near the residential area and existing building are increasing and environmental problems caused by vibration have become serious public concern. In order to solve these problems, blasting works have been conducted with segmented blasting and reduce advance per round. However, with these blasting, work efficiency is not obtained, and regrettably the cost and risk of accident tend to increase. We developed a new controlled tunnel blasting technique with electronic delay detonator. Electronic delay detonator can supply extremely large range of delay period which could not be achieved with conventional pyrotechnical delay detonators. We utilized advantages in initiating hole by hole over entire tunnel face at the same round. Much seismic data obtained from tunnel blasting with conventional detonator was statistically analyzed in order to find average duration time of vibration caused by a single hole initiation. Numerical simulation using sample waves from a single hole initiation was carried out in order to find an optimum delay time which can separate vibration in each hole initiation and without decreasing blast performance. Trial blasting was conducted to examine the correctness of optimum delay time obtained from numerical simulation. This blasting technique was applied to an actual tunnel construction. This tunnel is 2 lane automobile tunnel with a total length of 659 meters and internal cross section of 70 square meters. The purpose of the use of blasting technique on occasion, was the protection of fresh water reservoirs directly above the tunnel, and to keep the effect on local private houses to a minimum. The vibration level against this station was limited under 20 mm/see P.V.V. With this blasting, the tunnel construction was completed without exceeding the limited vibration level, with minimum cost and construction time.

Jan 1, 1998

By C Yeung, G Fitz, R Heater, P D. Katsabanis

Explosives malfunction due to shock waves is a serious concern for successful blasting results. Malfunction can range from sympathetic detonation to desensitization and modification of firing times of conventional pyrotechnic detonators.

Jan 1, 1994

By Roger N. Prescott

The Bureau of Alcohol, Tobacco and Firearms (BATF) is sponsoring legislation requiring the addition of identification taggants to commercial explosives. These are plastic particles with color coded layers that theoretically can be used to identify the explosive by date shift code.

Jan 1, 1980

By Donald J. Westmaas, Fred C. Drury

The Great Lakes Region, in the states of Illinois, Indiana, Michigan and Ohio, uses approximately 14% of the explosives annually consumed in the United States. While materials being blasted differ widely over this geographical area, a basis of comparing practices is proposed and evaluated.

Jan 1, 1979

By T N. Hagan

Where explosion energy moves rock from the in-situ to its desired location without considerable assistance from digging and/or hauling equipment, good fragmentation is of minor importance. Maximum displacement must remain uppermost in the mind of the blast design engineer.

Jan 1, 1979

By Beau Bryson, Tony Cooley

The following paper is a technical discussion depicting the type of blasting procedures used to control vibration levels. The blast vibration control criteria that was established and the type of monitoring program that was used. Also, the importance of good communication with the concerned neighbors.

Jan 1, 1985

By Jaime Huidobro, Michele Hall

The desensitization of an explosives column by the transmitted effects of the earlier detonations in nearby explosive charges is of vital concern to the explosives and blasting industries. Stress waves from detonations of borehole charges have the capacity to desensitize adjacent delayed borehole charges. This desensitization can be of a transient or a permanent nature.

Jan 1, 1994

By R DeLon Hunsaker

In the past, quarrying and other small operations have not been able to take advantage of the lower cost, convenience and better performance of bulk slurries. However, with the introduction of repumpable emulsion slurries and their ability to be stored in containers as blasting agents, bulk slurries are now available for small operations with small diameter boreholes and are producing excellent results. This same concept is being used successfully in larger underground operations.

Jan 1, 1984

By Patricia Mendoza Watson, Lundquist Robert G

The velocity with which the burden moves after blasting is of concern for safety and economic reasons. Models developed for motion velocity by various researchers were reviewed and likely model parameters were used to develop statistically significant models. Regression analysis and residual analysis were used to determine the model coefficients and the accuracy of the models.

Jan 1, 1990

By Charles A. Kliche

The Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA) established a national program for responding to releases of hazardous substances into the environment. The funding mechanism for this program is the Hazardous Substance Response Trust Fund (commonly referred to as Superfund), which provides funding for the implementation of removal and remedial response actions.

Jan 1, 1997

By Scott Giltner, Allan Koski

Blasting is one of the lowest cost yet most critical parts of the mining cycle. This paper discusses the findings of an audit conducted on the blasting operation at an iron ore mine. The purpose of the audit was to review current blasting practices in order to identify opportunities for production/cost improvements. The approach taken in the audit was to observe general blasting practices, their related downstream effects and to compare current procedures to established best practices.

Jan 1, 2009