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By Catherine Johnson, Kelly Williams

The ability to measure the overpressure of a shock wave is necessary for explosives research such as shockwave focusing and field testing of blast-resistant designs for buildings and vehicles. To record the peak overpressure of the nearly instantaneous pressure rise at the shock front, pressure transducers with a fast response rate and streamline pencil design are needed. Time spent setting up sensors coupled with the expense of high-frequency data acquisition systems, and the inconvenience of low impedance cables can make the process challenging. Additionally, only small inaccuracies in sensor position can drastically change the measurement recorded. Advances in high-speed video imaging make it possible to see the refraction of light due to the high-density gradient at the shock front without the need for parabolic mirrors or additional light sources necessary for Schlieren or shadowgraph imaging. The average shock front velocity between two points can be calculated by dividing the change in position by the elapsed time between the images. Using the Rankine-Hugoniot relationship demonstrated by Swisdak the peak overpressure of the shock wave can be calculated from its velocity eliminating the interference of the gage and mount. This paper investigates the accuracy of this method by setting dual transducer pencil probesat0and180 degrees perpendicular to the central axis of a285-gram(0.63-pound)cylindrical charge to record pressure versus time for comparison to the high-speed video. The axis of the camera lens is aligned with the central axis of the charge with both pencil probes in view. The pencil probes have two pressuretransducersset100millimeters (3.9 inches)apart to measure the time of arrival and are used to validate the velocities calculated from the high-speed images. This method can be used to evaluate the shock wave propagation from more complex prismatic charges with different cross-sectional shapes where precise placement of cumbersome pencil transducers in the near field is almost impossible.

By Harry Verakis, Thomas Lobb

Widespread use of ammonium nitrate compositions for mine blasting operations has led to various bulk transport vehicles designed especially for the explosives industry over the past half century or more. The advancements in explosives technology and continuing developments in bulk transportation have resulted in a variety of blasting agents and, more recently, oxidizers being transported and used from specially designed bulk transport vehicles. It is estimated that about 2000 bulk transport vehicles are used in mining operations. Many of the bulk vehicles carry about 15,000 to 33,000 pounds (6808 to 14,968 kilograms) of payload and some can carry up to 50,000 pounds (22,679 kilograms) for large open cast mines. Thus, it is imperative that detailed knowledge and safety instructions are available from the blasting personnel and mine management should an unplanned incident such as a fire occur with a bulk transport vehicle at a mine site.

Jan 1, 2008

By Richard J. Mainiero, Marcia L. Harris, James H. Rowland

In the past several years, there have been a number of blasting-related carbon monoxide migration incidents. In each case, there have been some common factors that appear to be related to carbon monoxide migration. Geology, heavy confinement of the blast, close proximity to the affected structure, and open pathways into the affected structure are just a few. Prince William County, VA is an area undergoing a boom in suburban development. In the year 2001, more than 4,050 new homes were constructed within the county.1 In the new housing development located in Bristow, VA, trench blasting was utilized to excavate proposed sewage and utility lines. On November 8, 2002, a trench blast was conducted for the installation of utility lines. Later that evening a carbon monoxide detector alarmed in a nearby house. The gas company and fire department sampled for carbon monoxide and measured 100 ppm and more than 200 ppm on the first floor and in the basement respectively. Subsequent efforts to prevent migration of CO into the nearby homes met with mixed results. The only reliable technique for protecting neighbors from CO appears to be the placement of CO monitors in the homes. The events are presented and discussed.

Jan 1, 2004

By J Lyall Workman, Peter N. Calder

Large hole rotary drilling is one of the most common methods of producing blastholes in open pit mining. Large hole drilling generally refers to diameters from 9 to 17 inch (229 to 432 mm), however a considerable amount of rotary drilling is done in diameters from 6½ to 9 inch (165 to 229 mm). These smaller diameters are especially prevalent in gold mining and quarrying.

Jan 1, 1996

By Krishna Nand

For assessing the safety of structures during underground explosions, ground particle velocity gives the best damage criteria, and 100 mm/see of ground particle velocity has been internationally accepted as the threshold value of safety (no damage). Results of extensive controlled underground explosion experiments conducted by the author to study the effects of ground vibrations on specially prepared concrete blocks, and also on low rise buildings and dams showed that no damage normally occurred when ground particle velocities were less than 100 mm/sec. Analysis of a large number of accelerograms from a dam site in India also indicated that no damage occurred to normal structures when integrated ground particle velocities were less than 100 mm/sec. Major damage in well built structures like a dam was noticed for ground particle velocity as high as about 350 mm/sec. These results are also generally substantiated from damage data obtained for various structures during other earthquakes, including Elcentro (1940), Taft (1952), Parkfield (1965), and San Fernando (1971). These studies, therefore, suggest that the damage criteria during underground explosions and earthquakes are similar; and 100 mm/see of ground particle velocity seems to be the general threshold value of safety (no damage) against ground vibrations.

Jan 1, 1988

By Luan Monteiro, Francisco Biulchi

The AngloGold Ashanti - Cuiaba mine sought innovative approaches to minimize lateral development and stope extraction time while maintaining optimal gold recovery and minimizing dilution. The stope 8GAL EXT 30 was selected as a case study. Traditionally, conventional blasting methods in such a scenario would necessitate either a single mass blast or slot development at each end of the stope. These methods typically compromise recovery and dilution or increase development time and risk. Additionally, conventional wired detonators require workers to re-enter the stope between blasts to load blastholes and connect detonators. The wireless initiation system offers a solution by initiating blastholes using magnetic induction signals that can penetrate rock, air, and water. This technology allows a pre-charged stope to be mined without requiring workers to re-enter the area between blasts to charge and connect blastholes. Engineers from Orica and AngloGold Ashanti designed a new extraction sequence utilizing the wireless initiation system. The process began with the opening of one end of the stope using a conventional slot and wired electronic detonators. Subsequently, pre-loaded rings were fired in three blasts to extract the opposite end and the intersection. The 8GAL EXT 30 stope was successfully mined using this technology enabled method. Each blast was meticulously monitored, and the stope void was scanned to assess blast performance. The results demonstrated a 4.6% improvement in recovery and a 16% reduction in dilution compared to the initial plan, and reduced exposure of people to hazardous locations in the stope. These results represent an additional value of USD 200k, gained from implementing wireless initiation to enable this particular blasting schedule.

Jan 21, 2025

By Jesús V. Saccsa, Kenji B. Loayza, Erick M. Condori, Jorge A. Velásquez

This research investigates how to reduce manufacturing costs of a safety fuse composed of black powder, replacing its ingredient NO3K by NO3Na for processing, and contributing to minimize costs per blasting.

Jan 1, 2017

By Finn Ouchterlony, José A. Sanchidrián

"A model for fragmentation in bench blasting that originates from dimensional analysis of fragmentation in asteroid collisions is presented. Percentiles of the size distribution are obtained in the basic model as the product of a rock strength-to-explosive energy ratio, a bench shape factor, a scale factor or characteristic size and a percentage passing-related factor. The parameters of the model are fitted to 169 bench blasts in different sites and rock types, bench geometries and delay times, for which thefragmentation of the muckpile was obtained by sieving. The basic model is found to significantlyimprove with an additional factor describing the rock mass structure in terms of the spacing and orientation of discontinuities, and another one describing the delay between successive contiguous shots; the latter is conveniently formulated as a function of the P-wave velocity and the holes spacing. The rock strength property chosen is the strain energy at rupture that, together with the explosive energy density in the rock (or energy powder factor), forms a combined rock strength/explosive energy nondimensionalfactor. The model, called xP-frag, is applicable from 5 to 100 percentile fragment sizes, with all parameters determined from the fits significant to a 0.05 level. The expected error of the prediction is below 25 % at any percentile. These errors are half to one third of the errors expected with the best prediction models available to date."

Jan 1, 2017

Explosive manufacture, handling and transportation is hazardous and special precautions should be taken while manufacture, handling and transportation. Various regulations and rules defined in explosive act and factories act of India are discussed in this communication. General process control measures during the manufacturing of different types of explosives are also dealt in detail. Various processes hazardous in manufacture of various explosives like slurry explosives, PETN, detonators, styphnic acid, lead azide and lead styphnate and special precautions to be taken during the manufacture of the above explosives are also discussed.

Jan 1, 2007

By Jerome S. Brower

Quadrex-L is a two component liquid explosive which was developed by J. S. Brower & Associates, Inc. to facilitate handling and shipping, and use in unique applications, while emphasizing safety. It may be advantageously used for all explosive applications. Quadrex-L can be introduced into a preinstalled container configuration and may be easily drained or flushed from these containers when necessary to do so. This characteristic can be effectively utilized to reduce the hazard period during assembly or disassembly operations.

Jan 1, 1975

By L. Wilson, M. Kotzel, T. Pienaar

An empirical equation is presented for the maximum airblast from unconfined charges. This has been tested at a number of sites and with charges ranging from 0.1kg to 311kg. The equation is developed to predict community response to potential explosive test range sites and the testing has added to our knowledge of the effectiveness of mitigating measures. The first site had 10m to 15m high walls that were intended to ameliorate the airblast. These walls functioned to a limited extent and reduced the airblast levels by 2dB to 5dB. The airblast was affected somewhat by topography. Noise levels at the nearest residences exceeded 130dB for charges larger than 1kg, whereas the vibration levels were very small. Formal complaints were received where the airblast level exceeded 128dB as per conventional expectations. Pedestrians and pets in the suburbs were startled by the blasts, emphasizing that the community response is much more sensitive to noise and airblast than vibration levels. The maximum airblast levels were too high for this site to be used on a regular basis. At another site, the airblast levels were significantly increased downwind by up to 10dB due to a moderate wind. A third site, at a quarry, produced unconfined airblast levels beneath the derived limits, but are much higher than the normal quarry blasting. By involving community forums there were no complaints, possibly due to desensitization by the normal blasting activities. The study has highlighted new areas for research in understanding the effect of noise, air blast and vibration on the low cost and informal housing typical in South Africa

Jan 1, 2011

By Gary Kahn

In this document the VODR is discussed from a technical point of view and is intended to give the reader a feel for the design of the instrument, its technical specifications, and its limitations. It is not intended as a tutorial on the use of the instrument in the field.

Jan 1, 1989

By John W. Brown

"Adequate dust control in and around rock drills is a problem that must be solvedfor the health and safety of workers running the drill as well as those working around thedrilling operation This paper will discuss the designs available from most drill manufacturers todayand the effort ‘nvolved in keeping them effective on a productive basis."

Jan 1, 1999

By Doug Anderson

Two quantities, Peak Particle Velocity (PPV) and Scaled Distance (SD), have controlled aspects of many blasting projects and operations for a long time. Vibration criteria typically use both PPV and SD because they are simple to measure, and simple to calculate. Their use in regulations worldwide is fairly ubiquitous, in efforts to limit damage to structures in the neighborhood of a blasting operation. PPV and SD are also used to determine likely blast damage effects in mining operations.

Jan 1, 2018

By Bruce B. Redpath, Doug Crice, Rob Huggins

Over the last decade, instrumentation has been developed that allows the application of seismic reflection methods to groundwater and engineering problems. At the Geological Survey of Canada, we have been developing and testing shallow reflection techniques for mapping the bedrock topography and structure within the overburden. We have attempted to develop methods which can be implemented with a minimum investment in equipment and computing capabilities. The data are recorded on a l&channel engineering seismograph, using a single high-frequency geophone per channel, and a hammer or in-hole shotgun (“Buffalo gun”) as the seismic source. Processing and display of the data can be accomplished on an Apple II+ or IIe microcomputer and an Epson wide-track dot-matrix printer.

Jan 1, 1991

By Peter Moser, Finn Ouchterlony, José A. Sanchidrián

"Blast fragmentation data in the form of percentile fragment sizes as function of specific charge oftenform a set of straight lines in log(size)-log(energy) space that tend to converge on a common focal point.Single-hole shots in specimens of virgin material clearly show this and the phenomenon is called the fragmentation-energy fan. Field data from bench blasting in rock scatter much more but may be interpreted to form such fans. The slopes values of the fan lines depend primarily on the percentile level. This property can be derived from sieving functions of the form P[ln(x/xmax)/ln(xmax/x50)]. An example is the Swebrec function when the parameter b is constant."

Jan 1, 2017

By Jeffrey Meissner, Charles Dowding

Cracking is one of the concerns cited by owners of structures adjacent to construction or mine blasting. During the past decade a large number of measurements have documented the low level of crack response produced by typical, ground motions compared to those produced by climatological effects. These data support the observation that there is a level below which ground motions do not cause even cosmetic cracking. As with all new findings, these crack response measurements need to be thoroughly investigated for all possible alternative interpretations. Among these alternatives is that uncracked locations are more affected than cracked locations. This paper presents measurements to shed light on the influence of existing cracks and the response of uncracked, but weak locations. Blast and weather induced responses of cracked and uncracked areas of gypsum wall board are compared in two structures: one near a surface coal mine in Indiana, the other near a limestone quarry in Florida. The ground motions that excited one of the structures were unusual in that the dominant excitation frequencies of 5 Hz were near the structure’s natural frequency and amplitudes exceeded 0.7 ips (18mm/s).

Jan 1, 2011

By Jim Hall, Denis Rickman, Jon Windham, John Ehrgott, Stephen Akers, Byron Armstrong

With the growing concerns about terrorism world-wide, numerous agencies conduct experiments to investigate the effects of terrorist vehicle bombs. In many cases, the vehicle bomb of interest utilizes some form of ammonium nitrate/fuel oil (ANFO) as the explosive source. Due to the high cost of fullscale testing, it is advantageous to conduct at least some vehicle bomb experiments at reduced scale. Extensive testing has shown that ANFO is a non-ideal explosive, and its explosive output does not scale reliably at explosive masses below approximately 400 lb (182 kg). Most scale-model testing requires explosive masses 1 to 5 orders of magnitude smaller. Thus, scale-model testing is typically conducted with “ideal” explosives, such as composition C-4, which perform in a scalable manner at virtually any charge mass. The utilization of an ideal explosive to model ANFO requires the existence of an accurate means of equating the performance of the two explosives. The airblast equivalence of C-4 and ANFO has been well established. However, the cratering equivalence of these explosives is not thoroughly quantified. This is especially true for the case of an above-ground detonation, which is precisely the scenario of interest in vehicle bomb studies. A study has been conducted to better define the cratering equivalence of C-4 and ANFO for above-ground detonations. This paper presents a discussion of results from this research.

Jan 1, 2008

By Dave Weymer

Falling timber in BC has always been a hazardous job. Huge, often rotting trees and steep, rugged terrain combine to create difficult and dangerous conditions. Death and injury rates are among the highest of any occupation in North America. In BC, the men that head out, saw in hand, are called fallers.

Jan 1, 2013

By Ajoy Singh

A study was conducted to investigate the damage potential to underground multi-seam openings caused due to vibration generated by open-pit coal mine blasting. The objective was to recommend optimal explosives weight per delay to be detonated in open-pit blasts to ensure the safety and stability of underground openings. Sixteen blasts with varying charge weights and initiation sequences were conducted at Samleshawari open-pit mine and eighty four blast vibration data were recorded in the Hingir Rampur underground colliery in India. Analysis of vibration data showed that roof of the underground openings vibrated with higher amplitude of vibration compared to pillars and floors. The amplifications of vibration in the roof at the junction were upto 4.3 times the pillar vibration. It was observed that coal chips detached from roof when the peak particle velocity reached 131 mm/s or high. The vibration magnitude recorded was higher in upper seams openings than in below seam openings. Rapid attenuation of vibration was recorded in below-seam openings at similar locations. Appropriate particle-charge weight-distance equations were established to calculate the safe explosive weight per delay to be detonated in open-pit mine for safety of multi-seams workings of underground mine. The support for the galleries and junctions were further modified for the working seams to ensure greater safety.erground Coal Mine

Jan 1, 2012