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By John C. Didlinger

How do you measure the highwall? Why do you even need to know the highwall measurement? Why is it important? The importance of this measurement is to help keep a level floor and to help control vibration. Nevertheless, since most of us are not mountain climbers, there must be a safe and easy way to make an accurate highwall measurement. So with these factors in mind, how do you make your measurement?

Jan 1, 1997

By Gimtong Teowee

SDI has launched the Electronic Detonator Blasting System containing a set of robust serial protocol and hardware exhibiting great ease in field usability and deployment. Programmable delay time with increments of 1 ms up to 10s is possible with excellent timing accuracy. Bus length of up to 2 km containing 1600 EIMs can be employed. A key feature of the SDI Electronic Blasting System has been its high tolerance towards current leakage in the bus line.

Jan 1, 2007

By Larry R. Fletcher

The Bureau of Mines obtained blasting accident data from the Mine Safety ant Health Administration (MSHA), U. S. Department of Labor. These data were analyzed to determine the most frequent causes of accidents in mine blasting. Accident totals for 1971 through 1981 are tabulated for metal-nonmetal and coal mines both surface and underground. In the past 11 years (1971-1981, inclusive) there has been an annual average of 9 fatal and 121 nonfatal blasting accident victims. Underground mining averaged 6 fatal and 93 nonfatal injuries each year.

Jan 1, 1983

By N L. Thomas

Hole size affects many factors which directly influence fragmentation in the muckpile and hence, the cost effectiveness of the entire operation. These factors include production capability, explosives and accessories efficiency and usage and drilling accuracy. In addition, hole size should be chosen to suit the geological conditions. The paper concludes that the optimum hole size is generally the largest that can be used commensurate with production and environmental considerations.

Jan 1, 1986

There is an intuitive tendency to equate rock strength with rock stability, yet the two must be evaluated separately. A slope in strong hard rock is not necessarily stable, nor is a slope in weathered weak rock necessarily unstable. In some cases the reverse is true, depending on the geometry of joints and weak planes. The time element is a matter of special concern, that is how suddenly the failure begins and how rapidly it progresses. Sudden failures can be catastrophic, whereas creep usually is not. In soils and weathered rock, the process is usually incremental and is more likely to give some warning of impending failure. With careful observation, the failure process in these materials can be detected and monitored instrumentally or visually. In some cases, the slope may be stabilized, reinforced or modified. When that is not possible, there is usually enough time on this type of slope to remove men and equipment from the area before complete failure occurs.

Jan 1, 1996

By Stephen John Brace

Increasingly, electronic blast initiation systems are being made available to the mining and construction community, both in South Africa and internationally. Indeed, in some parts of the world, perhaps half a dozen electronic products are being used, with a choice also of shock tube, electric and fuse and igniter cord systems. As these developments have taken place, improvements have been made in safety, reliability and accuracy, so much so that high performances in all these areas are now expected. However, disadvantages often seen by customers, other than : higher price, are decreased user-friendliness and loss of flexibility.

Jan 1, 1998

By Robert Hopler

Complying with our request in the February issue of the AGRICULTURAL BLASTER for items that would be of interest to other blasters, Mr. Thomas H. Benton of Tennessee sends us an article in which his methods of securing contracts are explained:

Jan 1, 2013

By Peter N. Calder, John N. Tuomi

The development of a successful control blasting program for an open pit iron mine in hard jointed rock is described. The objectives and mechanics of control blasting are discussed. Design and implementation procedures, which should have wide application, are given. Small diameter angle hole pre-split blasting, buffer blasting with production holes in front of pre-split lines and in front of strongly defined rock structures, and vibration control of production blasts are dealt with.

Jan 1, 1980

By R R. Dimock

A goal of all mine operators is to optimize the breakage of the inplace rock to achieve maximum excavating efficiency. The use of the seismograph at Kennecott Copper Corporation's Nevada Mines Division, open pit mine in Ely, Nevada, has demonstrated that optimum blastability can be predicted by knowing the seismic velocity of the inplace rock. The relationship of seismic velocity to the quantity of the explosive required to achieve adequate breakage of the material can be determined. Once quantified, this relationship can be used by the mine operator to obtain the optimum drill pattern and powder factor for breaking the material to be excavated. A substantial savings in primary and secondary drilling and blasting costs can result from using the seismograph for blastability determination.

Jan 1, 1976

By Daniel B. Conn, John L. Floyd

PhotoSeis™ is a blast analysis method that combines the advanced technologies of high speed motion picture photography and digital seismology. When fracturing rock with the use of explosive energy, the human eye cannot detect the details of the process due to its short duration. An extended time base is required to accurately quantify the response of the rock mass to the detonation process. This time base is provided by the use of high speed motion picture cameras. The control of ground vibrations and airblast is an important consideration when developing efficient blast designs. High vibration and airblast levels can be an indication of improper design, inaccurate detonators, or adverse geology. Since many factors can elevate airblast and ground vibration, a greater understanding of the site specific response to the blast design is needed that is beyond the scope of simple seismographic recordings. By synchronizing the photographic record provided by the high speed motion picture cameras with the airblast and vibration information from digital seismological monitoring, the Photoseis™ technique can be of great assistance in controlling airblast and vibration and optimizing the use of explosive energy for rock fragmentation.

Jan 1, 1990

By Ali Kahriman

This paper presents the results of ground vibration and air blast measurements from tunnel blasting activities during the construction of the Beylerbeyi-Kucuksu waste water tunnel under a residential area in Istanbul, Turkey. Within the scope of the study, the blasting pattern of the tunnel was engineered using Tunnel2000 design software and field studies and measurements for evaluating the productivity and safety of shots were realized for 136 rounds. During the study, the advance of the tunnel, face condition, ground vibration, air blast and neighbours’ complains and comments after every round were observed and the tunnel pattern was improved. Finally, an empirical relation for this tunnel route was developed between scaled distance and maximum amount of explosives, to continue activities in a safe and productive manner.

Jan 1, 2006

By Lina Lopez, Jose Sanchidrian, Manuel Lopez, Pablo Segarra

Previous work in which rock properties and blasting parameters (geometry, charging and timing) were reported together with truck filling times, is taken as a starting point for a thorough analysis of the influence of the former on the mucking velocity. The experimental set was composed by 11 blasts made in an open pit mine. Non-parametric, distribution-free statistics is applied. The mucking rates (in bank cubic meters per unit of bucket volume and per hour) appear to be clearly dependent on the explosive energy and powder factor, both magnitudes combined as energetic powder factor (energy per unit of rock volume). The mucking rate is a non-monotonic function of such factor in the range of the blasts analyzed. The determination of the function is optimum when the fraction of the explosive below grade is not considered and when the explosive energy is qualified as that delivered at a partial detonation regime. Different types of loaders seem appropriate for different energy levels. At low levels both front loaders and rope shovels obtain small productivities without a statistically significant difference in their performance. At high energy levels, front loaders qualify higher than rope shovels. Mucking velocities can be equally small at low energy powder factors and at high ones if rope shovels are involved.

Jan 1, 2008

By George Young Mosteller

This paper is summary of the practical solutions developed in the excavation of drilled piers (caissons) at GPCo's Plant Scherer, Juliette, GA. Plant Scherer is a 3,245 Megawatt Fossil Fuel Powerhouse and, when completed, will be one of the largest fossil fuel plants in the Southeast.

Jan 1, 1980

By Michael K. Phang, Thomas A. Simpson

Field studies at an underground mine site were conducted to evaluate and monitor blast-induced vibrations on an underground coal mine roof. The vibration data were evaluated so that a suitable damage criteria or guidelines from which a safe operating distance between surface blasting and underground mine operations can be established.

Jan 1, 1984

By Kevin Cole, Dennis A. Clark, F William Laslow

Since 1976, the Metropolitan Sanitary District of Greater Chicago, (MSDGC), has commissioned the excavation of a tunnel system in the Chicago area, hundreds of feet below the surface in solid limestone. This paper outlines the blasting patterns, explosive selections, and monitoring techniques used to assure a satisfactory job completion, following the specifications.

Jan 1, 1982

By Z X. Zhang

In sublevel caving mines, eyebrow break usually gives rise to lower ore recovery and worse safety in the field. Eyebrow break is caused mainly by two tensile stress waves: one from the front surface of a blasting ring, and the other from the roof of the drift. In order to reduce the two waves and finally to reduce eyebrow break at Malmberget mine, we employed two methods: (1) cartridge charge, and (2) double-primers in each blasthole. The two methods were tested in one ore body called ViRi. A total of 10 rings with the cartridge charge and 25 rings with the double-primers were blasted. At the same time a total of 34 ordinary rings were blasted in the same ore body. The result shows that the eyebrow break is 3.0 m for the ordinary rings, 2.3 m for the cartridge charge rings, and 2.1 m for the double-primer rings, respectively. In addition, the ore recovery for the double-primer rings is increased by 3% on the level of ViRi930, compared with that for the ordinary rings.

Jan 1, 2011

By Pierre-Alexandre Abeel, Charles Dowding, Justin Lueker

When blasting is eliminated as a cause of cosmetic cracking, often someone will ask, “If blasting didn’t cause the crack, then what did?” This paper describes detection by remotely operated instrumentation of the new cosmetic crack that was climatologically-induced. The measurement was obtained as a part of the development of Autonomous Crack Measurement (ACM) instruments to measure micro-inch response of cracks to both long-term, climatological, and dynamic, blast vibration effects. The crack occurred in the wall of a structure that was monitored for over 29 months and as such represents one of the longest periods of ACM observation.

Jan 1, 2015

By Richard J. Mainiero, Harry C. Verakis, John J. Mulhern

There are application in coal mines where it would be advantageous from a safety stand point to fire unconfined shots. However, the firing of mud caps (adobes) or other unconfined explosive charges in underground coal mines is not permitted because of the explosion hazards associated with methane gas and coal dust. Present safety regulations in Title 30, Code of Federal Regulations prohibit such Practices. Recently, MSHA proposed revised coal mine regulations for the approval and use of sheathed explosives for Public comment.

Jan 1, 1987

By Virgil J. Stachura, Larry R. Fletcher

The Bureau of Mines conducted a series of delayed blasting experiments at a West Virginia contour coal mine which resulted in smoother highwalls. The highwalls were smoother due to reduced overbreak and inherently safer due to reduced likelihood of rockfall. Reduced overbreak was accomplished by an increase in the highwall hole delay intervals which changed the effective delay pattern geometry and the direction of burden movement. Three combinations of blast delay intervals in the highwall holes were tested: 1) 50 ms longer than the nominal design, 2) 50- and 100-ms longer delays in the nearest two rows that form the highwall, and 3) 100 ms longer than the nominal design. The mine's nominal blast design was a flat vee formed by 17-ms surface delays between holes and 42-ms surface delays between rows, with 200-ms in-the-hole delays. All three test designs produced highwall improvements over the nominal design with only occasional exceptions because of geologic variations.

Jan 1, 1985

By Shawn Kirkpatrick, Yang Ruilin, Tamara Whitaker

In order to manage blast vibration in soft ground containing large diameter holes and large charge weights, a number of issues must be considered. This paper describes techniques to control and reduce near-field blast vibrations absorbed by highwalls in soft ground. Sympathetic detonations need to be controlled. Sympathetic detonations can cause excessive vibration due to an unknown number of charge weights firing out of sequence. The excessive vibration can cause damage to the ground. Sympathetic detonations can be controlled through proper design of blast patterns and, in some cases, through the use of specialized electronic detonators.

Jan 1, 2009