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By Catherine T. Aimone

A series of experiments have been performed to characterize fragmentation and microcracking in quartz monzonite copper porphyry. The flyer plate impact method was used to generate plane shock waves in rock specimens for impact pressures between 1.6 and 7.3 GPa and impact pulse durations between 1.1 and 7.0 µs. The effects of pressures up to 4.8 GPa and pulse duration on fragment size distributions and microcrack densities were studied. The results show that pressures effect particle sizes to a greater extent at higher pulse durations. However, changes in pressure and pulse duration show little influence on the density of microcracks induced during explosive loading. These results indicate that the nucleation and growth of microcracks in rock subjected to shock waves occur uniformly throughout. A substantial decrease in particle sizes for high pulse durations is attributed to more time allowed for microcracks to grow and coalesce, forming individual particles.

Jan 1, 1985

This paper is written in response to a request from the UTRC Committee on Perimeter Control Blasting. That Committee is conducting "follow-on" research on the selection of appropriate blasting designs and products for perimeter control of rock excavations. This paper will deal with the rock mechanics principles which affect the outcome of such blasting, and explain to the reader how to apply techniques which will modify the typical site response one would expect for conventional blasting methods. For convenience of reference, and to emphasize the important concept that the application of this technique is site specific, that is it must be custom-designed for each site, the technique is being called "Modified Site Response Blasting".

Jan 1, 1984

By Sandor Nagy

The Explosive and Blasting Department of the Hungarian Mining Research Institute is responsible for the research and development of industrial applications of explosives. Appropriate explosives technology is developed for each application, including the explosive demolition of structures, which belongs within our charge.

Jan 1, 1977

By Claude Cunningham

Late in 1982 a fire began in the shallow, abandoned workings of the Uitkyk Colliery near Witbank, South Africa. Urgent measures had to be taken to quench the fire, before the surface caving it caused could put an important railroad connection out of action. This paper outlines the way in which the job was tackled.

Jan 1, 1984

By Ray Heater, Qian Liu, Alan Bauer

The channel effect is a phenomenon that takes place with decoupling explosive charges; an air shock wave propagating ahead of the detonation wave in the annular space around the explosive charge compresses the charge so that the process of detonation is modified and even stopped. For commercial explosives, such as AN/FO slurries and emulsions, the channel effect causes partial detonation under certain conditions. To simulate and evaluate the phenomenon, a hydrodynamic model was developed based on the assumption that the pre-shock wave is produced by Mach reflection at the tube walls. Based on instrumented experimental studies with the above explosives in diameters ranging from 25 to 90 mm in pipe sizes ranging from 35 to 127 mm, it has been possible to demonstrate that a criterion for failure based on a critical impulse concept fits the experimental data well. Critical impulse values for the various explosives tested are presented along with the necessary correlations between charge and borehole diameter required to produce this.

Jan 1, 1988

By Douglas R. Burns

Complying with SARA-Title III and the Emergency Planning and Community Right-To-Know Act as a Non-Manufacturing Facility. As of August 23, 1988 non-manufacturing facilities storing end using chemicals which require MSDS (Materia1 Safety Data Sheets) must fi1e with SERC (State Emergency Response Commission), the LEPC (Loca1 Emergency Planning Commission), and the loca1 Fire Department a list or copies of all MSDS sheets with the Tier I and Tier II forms completed.

Jan 1, 1989

By Brian Stump, Rong-Mao Zhou

A series of single-fired (simultaneously detonated) explosions were conducted in an Arizona copper mine. The explosions spanned yields from 1700 to 13600 lbs (773 to 6169 kg) and were all detonated in an approximate 100 m by 100 m area. In order to quantify the effect of the mine free-face, the individual explosions were also detonated under three different emplacement conditions including at the free-face of the mine under normal burden, twice normal burden and fully contained. The purposes of these experiments were to investigate: (1) Generation of in-mine and regional phases such as Pg, Pn, and Lg from mining explosions; (2) Quantification of the relationship between yield and seismic amplitudes; (3) Quantification of the effect of confinement; and (4) Similarities and differences between single-fired waveforms and those from delay-fired explosions. Instrumentation was deployed at near-source (100-700 m) and in mine (1-5km) distances. Empirical scaling relations for the different shots in this test series were developed in order to quantify the effects of yield and confinement.

Jan 1, 2006

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 G. F. Revey

When rock blasting occurs near new concrete of varying age, engineers representing project owners often express concern that vibration from the blasting will crack nearby concrete. Regulations and/or specifications for civil construction projects usually include particle velocity vibration limits intended to protect concrete. In some cases specified limits are unreasonably low and needlessly restrict and increase the cost of excavation work. This paper discusses how methods of predicting resulting flexural strains caused by blast-motion can be used to develop safe and reasonable PPV limits to protect new concrete. Three case histories demonstrating how these evaluation techniques were used to establish higher PPV limits designed to protect concrete of various structural condition are also presented.

Jan 1, 2006

By Jared Redyke

Thursday, October 14, 1999 marked another important milestone for America’s space program. At exactly 10:05 AM EST on a beautiful, sunny Florida morning, Dykon, Inc. of Tulsa, Oklahoma detonated approximately 300 pounds of explosives to fell the seven million pound Umbilical and Mobile Service Towers at Space Launch Complex 41 (SLC-41) at NASA’s Cape Canaveral Space Station. Completed in 1965 at the height of the Space Race to the moon, the Mobile Service Tower/Umbilical Towers (MST/UT) were part of the Titan rocket launch facilities. The MST was 265 feet high and weighed over five million pounds. The UT was 175 feet high and weighed over 2 million pounds.

Jan 1, 2001

By Otto E. Jr Crenwelge, Timothy A. Peterson

We have developed a site-specific method for analysis, prediction, and control of ground vibrations induced by overburden blasting operations in surface coal mines. Field tests conducted at R&F Coal Company have verified our approach for obtaining signatures of the overburden vibration characteristics at locations of interest near the mine, selecting the optimum excitation frequency for minimizing vibrations, measuring and synthesizing multiple-charge excitation signals for minimizing vibration amplitude and duration and controlling frequency, accurately predicting the multiple-charge vibration response in both the time and frequency domains, and accurately controlling the blast detonation to achieve the predicted vibration control. Initial field studies also indicate that by minimizing the vibrational energy radiated from the blast zone, and by optimizing the number of charges detonated per delay period as allowed by this technique, more effective use of the explosive energy is obtained within the blast zone itself for improving overburden fragmentation, swell, and cast. In all of the phases of this technique, including actual blast detonation, personal computer hardware and software have been verified for use in either field or office environments.

Jan 1, 1986

By B R. Spencer

Using bulk repumpable water gel explosives in underwater shooting results in even more benefits to the user than a "dryland" customer. It is nearly impossible to reshoot underwater, so a bad shot causes tremendous problems. The huge expense of operating drill boats, dredging buckets and clamshells makes shot loading, hookup and digging cycle times critically important.

Jan 1, 1990

By Claude Cunningham, Szendrei

The partitioning of blasting energy into “Shock” and “Heave” components is a popular concept for attempting to match explosives to particular ground conditions and blasting results. The issue is complex, as it affects both the detonation process and the immediate response of the rock skin. However, the fundamental process of energy transfer from the explosive to the rock through the blasthole wall is not well defined. Clues to the “Shock” phase of blasthole expansion are given by cratering behaviour of materials subject to high velocity penetrators. The final cavity volume defines both the energy used to achieve this and the resistance of the confining material. Attention is being given to the link between penetration of a solid target and expansion of a readymade hole, both producing the same outcome. The benefit of this work is that it leads to clearer understanding of how explosives will impact upon the blasting results and helps to explain the energy consumption in blasting.

Jan 1, 2004

By P. Katsabanis

Researchers in the field of blasting have been trying to develop ways of predicting fragmentation in the last few decades. The Kuznetsov equation estimates the average fragment size, XJ~, based on explosive energy and powder factors. Cunningham calculates the uniformity of a fragment size distribution using drilling accuracy, blast geometry and a rock factor A associated with a “blastability index”, which can be estimated from the jointing, density and hardness of the blasted rock mass. Knowing the mean size and the uniformity index, a Rosin-Rammler distribution equation can then be derived for calculating the fragment size distribution in a blasted muckpile. Analysis of existing data has revealed serious discrepancies between actual and calculated uniformity indices. The current integrated approach combines the Kuznetsov or similar equation and a comminution concept like the Bond Index equation to enable the estimation of both the 50% and SOoh passing sizes (X& and X& ). By substituting these two passing sizes into the Rosin-Rammler equation, the characteristic size (Xc ) and the uniformity index (n) can be obtained to allow the calculation of various fragment sizes in a given blast. The effectiveness of this new fragmentation prediction approach has been tested using sieved data from small-scale bench blasts, available in the literature. This paper will cover all tested results and a discussion on the discrepancy between measurement and prediction due to possible energy loss during blasting.

Jan 1, 2001

By Malcolm Mellor

Practical procedures that have been developed for pre-split blasting and smooth blasting in common rocks are reviewed systematically. Topics covered include shothole spacing, charge weight per unit length of shothole, decoupling ratio, adjustments for explosive type and rock type, and weight of explosive per unit face area. Relevant properties of frozen rocks, frozen soils, and ice are compared with those of common unfrozen rocks, and appropriate adjustment of blast design is discussed. Interim relationships for the design of controlled perimeter blasting in frozen soils and massive ice are put forward, recognizing that additional experimentation is required. Special problems in controlled blasting of ice are discussed. These include effects of wet holes, delayed removal of burden, and submerged burden. Special attention is given to the cutting of ice islands and icebergs. An Appendix describes an operation in which the face of an ice wharf at McMurdo Sound was trimmed by pre-split blasting.

Jan 1, 1976

By Tom Hale

Developers and blasters are faced with increasing public demand and regulatory restrictions to maintain the lowest possible levels of noise and vibration from blasting operations in populated urban areas. Pyrotechnic products have proven to be a low noise, low vibration alternative to conventional blasting for close-in rock excavation and concrete demolition applications. Pyrotechnic breaking charges often yield 1/10th the vibration and noise compared to traditional explosives, and have been demonstrated to increase public confidence and decreased damage potential where they have replaced explosives, thus allowing new opportunities for work and greater job profitability. This paper presents a practical approach to utilizing pyrotechnic products in various applications including trenching, mass excavation, demolition, and dimension stone production, providing methodology for pattern design, vibration probability and loading calculations. Field research data is reviewed and compared to conventional explosives.

Jan 1, 2008

By Robert L. Martin, Brian W. Stump, David P. Anderson, David Gross

In an attempt to better understand the impact that large mining shots will have on verifying compliance with the international, worldwide, Comprehensive Test Ban Treaty (CTBT, no nuclear explosion tests), a series of seismic and videographic experiments has been conducted during the past two years at the Black Thunder Coal Mine. Personnel from the mine and Los Alamos National Laboratory have cooperated closely to design and perform experiments to produce results with mutual benefit to both organizations. This paper will summarize our activities, highlighting the unique results of each.

Jan 1, 1997

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 O E. Jr Crenwelge

Recently promulgated regulations governing blast induced ground vibrations in the mining industry contain a frequency criterion as one option for verifying compliance. This criterion is based upon an oversimplified method which assigns the entire peak particle velocity amplitude to one frequency. Depending upon the nature of the vibration time history, it is possible that this frequency may not even be one of the predominant frequencies of the signal. In addition, the criterion does not specifically define the data analysis approach to be used by the industry for obtaining either the amplitudes or the frequencies of the vibration components. And because personnel in this industry generally have little understanding of vibration phenomena, a number of different approaches are currently being used for satisfying the criterion. This paper presents a method for obtaining both the Fourier amplitude-frequency spectrum and the integrated predominant amplitude-frequency components for the vibration record. The method is both physically and mathematically correct and is in common use in a number of other industries. Therefore, it should be of help to regulators, blasters, and consultants charged with developing, enforcing, or implementing ground vibration criteria.

Jan 1, 1988

By Diane F. Baker, Cathy Aimone-Martin

A series of small-scale explosive experiments were conducted in a perlite mine near Socorro, New Mexico. These experiments were a joint effort between Los Alamos National Laboratory, New Mexico Institute Of Mining and Technology, Southern Methodist University, and Defense Nuclear Agency. The purpose of these tests was to measure the changes in the shock wave and seismic coupling as a function of depth of burial and structural setting. The size of the explosive charges ranged from 1 to 68 kg. Over 1150 measurements of velocity and acceleration were made on thirteen experiments using three component sensors. The sensors were placed to maximize the azimuthal coverage as well as to provide data at a variety of ranges from ~1 to 130 m A few far field measurements were made at ranges of ~2Êkm. While the bulk of the measurements were made on the surface, high g accelerometers were placed in one instrumentation borehole to provide some free-field measurements. Preliminary results indicate that significant differences in the amplitudes of signals can occur when the location of the explosive charges are changed by only meters. Part of the observed difference is attributed to variations in the rock immediately adjacent to the charge affecting the shock coupling; and part to the effects of the site characteristics.

Jan 1, 1994