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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 X. Gumede

A model is being developed to quantify the benefits for mining houses resulting from the reduction in greenhouse gas and energy consumption by the application of innovative blast designs in addition to direct financial benefits throughout the mine to mill value chain. The conversion from shock tube initiation systems to electronics and some changes to powder factor measured on an open pit mine had previously been used to show significant improvement on blast outputs. Benefits were realised on drilling, blasting, loading, hauling and beneficiation. Quantification of the relationship between powder factor and reduced greenhouse gasses is investigated in this study. The study has highlighted new data that must be recorded and hence some assumptions were made as to fuel consumption and the energy in crushing was obtained from the Bond work equation. The mine to mill projects in an open pit platinum mine and a quarry produced energy savings and reduced greenhouse gas emissions associated with the careful application of explosives and blast innovations. The less fines project showed an increased carbon footprint. The model provides a new insight into how project feasibility should be decided based on economic and environmental viability.

Jan 1, 2012

By Lon Santis

In 1923, Ralph Assheton compiled a report for the Institute of Makers of Explosives (IME) on accidental explosions in manufacturing plants. The report chronicles the type and amount of explosive involved in the event and the effects and distances to nearby buildings and workers for over 100 events from 1880 to 1916. Apparently, this report was never published but served as the origin of the IME’s first intra-plant distance table published in Pamphlet No. 3 in 1926. The effort was a parallel effort to the IME’s development of the American Table of Distances. The intra-plant distance table has never been changed by the IME and follows the US Department of Defense (DoD) standard very closely. This paper freshly compiles the data from the 1923 report and analyzes it with modern methods not generally available in 1923. Interestingly, the analysis indicates that the original intra-plant distance tables were established primarily to protect workers from serious injury and that preventing propagation was a side benefit. The data shows that a strong relationship exists between the probability of injury and the traditional K-factor. The data indicate that people in the open are better protected than those inside structures and that barricades reduce risk close to an event. Individuals at the intra-plant distance had a 95 percent chance of receiving no worse than a minor injury. A comparison of the data to explosive event consequence models indicate the models are overly conservative in regards to risk inside inhabited building distances.

Jan 1, 2010

By Tom C. Palangio

Commercially available online particle size analyzers (OPSA) are in their third decade of development (Palangio, T.C., 1985), (Franklin, J. A., Maerz, N.H., 1987), (Maerz, N.H., Franklin, J.A., and Coursen, D.L., 1987). The installed base of operating analyzer numbers is in the hundreds. This paper takes a look at five critically important relationships that users have discovered through the use of OPSA systems. The two key attributes of these systems are: 1) consistency and, 2) historical context compared with traditional practices.

Jan 1, 2016

By Duncan Chalmers, Rob Nowell, Miguel Araos

Australian underground mines produce in excess of 60 mtpa of coal. Most of these use the longwall method, and they require the use permitted explosives (which are called “permissible” in other countries) for challenges that appear during the day-to-day activities. To obtain the approval for these explosives, they should pass Testing Memorandum #2 (TM-2), which sets out the test required for each category of permitted explosive. These categories are P1, P3, and P5. With P5 being unrestricted use and P3 and P1 have conditional use in underground mines. The TM-2 test was originally set up for NG-based permitted products around 1900. With the closing of NG plants around the world, ammonium nitrate explosives were the natural replacement, and therefore these explosives need to pass the TM2. Australia does have a P1-emulsion based explosive available. For high-risk scenarios (like blasting coal), no P5 explosives are available. The lack of P5 explosives has been prolonged for more than 25 years, since the phasing out of nitroglycerine-based permitted explosive products around the world. The main problem has been that when emulsion based permitted products are tested in the deflagration cannon, the results obtained were not considered in the TM2 criteria and therefore the tests were invalid. A research work on permitted explosives began in 2005 funded by the Australian Coal Association Research Program (ACARP). The aim of the project was to address the lack of P5-type permitted explosive (and, potentially develop them further, i.e., develop safer explosives) and understand the behaviour of emulsion explosive and the results they presented in the tests. Both bureaucratic and technical barriers appeared along the way. On the bureaucracy side, the facility was shut down, reopened, and shut down again. In view of these difficulties, assistance was sought overseas. On the technical side, from the very start the results of the tests when using emulsion-based permitted explosives were not established in the criteria, ignitions occurred for trial samples that were expected to be P5-type, etc. The aim of this document is to present the painful journey in the Australian industry to have a P5-type emulsion-based permitted explosive, for use in UG coal. Also, the technical learning acquired about emulsion explosives and the ignition path of mixtures methane / air will be shown.

Jan 21, 2025

By Jorge Flores, Benjamin Cebrian

Blast Optimization at a high altitude mine operation involves not only the selection of the right drilling designs and explosives but also the circumstances of operators working at low oxygen levels and low temperatures.

Jan 1, 2015

By Norm Disley, Kingsley Hortin, Gertjan Bekkers

As part of the expansion of the Kidd Creek Mine to 2,682 meters (8800 feet) below surface, two largediameter 3000kW (4000HP) booster fans were installed at the 6000 level. Shortly after commissioning the fans, significant damage to the fan bearings were observed, forcing several shutdowns for repairs, which were very disruptive to the mine’s production process.

Jan 1, 2008

By Keith Best

It has been said that when a person does something right no one remembers but when they do something wrong no one forgets. This statement, when applied to the explosives industry, has never been truer. Think about it.How many times have you seen a news crew reporting on how well a blaster is doing his/her job? Normally, all you will see is how bad things are going and how much “damage” is being done.

Jan 1, 2008

By Chick Kerkering, Stephen Iverson

Perimeter control blasting is common in civil construction projects but not as common in mining. A poorly designed and executed underground mine development blast design can result in unwanted wall rock damage. This damage increases the risk of rock falls and injury. With the availability of good drilling equipment, it is a simple matter to add the few extra holes needed to change conventional drifting into drifting with perimeter control.

Jan 1, 2008

By Tony Rorke, Tamara Wiseman

Due to the advancements in technology it becomes easier to obtain accurate measurements for mining, quarry, and construction operations even in the most remote places. The use of off-the-shelf photogrammetric imaging technology and unmanned aerial vehicles (UAVs) are becoming more common in the mining industry for blast design and surveying. Pattern optimization, face profiles, pre and post blast volumetric, stockpile measurements and mine mapping are all areas where these technologies can be used with ease.

Jan 1, 2015

By J Silva Castro, W C. Wedding, B T. Lusk, J Calnan, E G. Morris

The emergence of electronic detonators for use in production mine blasting has enabled mining professionals to rethink the traditional blast design methodologies that pertain to timing. In many ways, electronic detonators can allow great advances in productivity, cost effectiveness, fragmentation, and safety. This paper reports on an independent study quantifying the accuracy of two electronic and two non-electric systems in which 674 detonators were tested. This research aimed to determine the accuracy of commercially available electronic detonators as compared to non-electric shocktube systems. Each system was tested over the viable ranges of delays available. Statistical models were then applied to quantify the scatter present in each system. Suggestions for the use of electronic detonators are made from the findings of this work. This work was made possible through funding from the United States Department of the Interior Office of Surface Mining Reclamation and Enforcement.

Jan 1, 2012

By Catherine T. Aimone-Martin, Kristen Kolden

In August of 2013 the USDA Forest Service (USFS) blasted bedrock at the base of a waterfall in Kanalku Creek within the Kootznoowoo Wilderness Area on Admiralty Island in the Tongass National Forest located in Southeast Alaska. The purpose of the blasting was to widen and deepen a plunge pool at the base of a waterfall complex considered to be a partial barrier to migrating sockeye salmon. Drilling and blasting to remove 12 to 15 cubic yards of rock occurred over a two day period.

Jan 1, 2015

By Alastair Torrance, Italo Onederra, Do Sun Kim, Kush Patel, Gary Cavanough

Reactivity of ammonium nitrate-based explosives is associated with the presence of sulphide in the ground reacting with explosive products and in some instances causing spontaneous reactions which can lead to detonation. This paper explains the mechanism of these reactions, the potential cause of spontaneous detonation and how inhibited explosives prevent the reaction

Jan 1, 2019

By Michael S. Wieland

"This report investigates whether it is tractable and thereupon reasonable to remove the boosterinfluences when ranking the toxic fumes of non-cap-sensitive mining explosives. The hazard potential is represented by relative fume toxicity RFT, the resultant influence computed from a formulated rule with a restricted set (tally) of fume components and multiplying constants. The RFT result is compared to the rule criterion that represents the worst case tolerable toxicity stipulated by regulations or otherwise. The typical nonstoichiometric booster composition can render notable unwanted influence on the RFT ranking results. Historically, the remedy was to shoot the booster separately and reduce the trial concentrations by the relevant subtractions. Unreal negative concentration results were noted on rare occasions, revealing the faulty nature of the reduction procedure. With thermodynamic reaction chemistry codes TDRC, on the other hand, the booster ingredients can be retained in or removed from the reactant tabulation, yielding reduction factors taken as the concentration ratios for the two circumstances. The underlying presumption regarding reduction factors is that the ratios of component concentrations with and without the booster ingredients when resolved theoretically ought to equal those rendered experimentally, when tractable. Upon rearranging the presumed relationship, the unadjusted fume concentrations divided by theoretical reduction factors yield the wanted readjusted fume concentrations, thereby removing the booster influence without generating unreal negative concentrations."

Jan 1, 1999

By Dick Green

During the recent troubles in Northern Ireland due to terrorist activities, there have been many buildings demolished or damaged by improvised explosives. This article explains about the Demolition of Churchill House in Belfast, the first controlled use explosives to demolish a high rise office building since the recent troubles started, and a further indication that normality is returning to the lovely city in Ireland.

Jan 1, 2006

By Damien Bretall, William Fourney

Due to the changing face of warfare there is an ever growing need to protect the underside of combat vehicles from mine blasts. This paper presents a new method to better characterize the pressure profiles experienced by a plate as the blast develops. The explosive deformation of a small-scale plate was recorded using synchronized high-speed digital cameras, and then analyzed using 3D Digital Image Correlation software. Time-varying pressure profiles were input into an axisymmetric FEM simulation by fitting curves to data obtained from tests using Kolsky bars to measure pressures. These were then modified to find possible profiles that produce the measured deformations. It was discovered that the final deformation cannot be determined from only total impulse or peak pressures, and that it is very sensitive to the time and spatial decay of the pressures.

Jan 1, 2009

By G. C. Naveen

Punatsangchu Hydroelectric Project Authority is constructing 1020 MW underground hydroelectric project in Bhutan. The project envisages construction of concrete dam, Desilting Chamber, Head Race Tunnel, Power House Complex and Tail Race Tunnel. Tunneling is one of the major activity in any underground projects as they are driven for multiple activities. By and large the tunnels are a major part of connecting networks from surface to caverns/underground working sites. Many tunnels in hydropower project are part of water conducting systems and one such important tunnel is the Tail Race Tunnel in this project and had to be excavated in thinly foliated rockmass conditions by D&B method. The rockmass is traversed by three to four joint sets and few minor shear seams. Rock Class “Q” values were between III and IV. Tunnel was excavated by full face parallel hole drilling blasting method. The adopted blasting method consisted of drilling 45mm (1.77 inch) diameter holes to a depth of 2m and the drilled holes were charged with 40mm (1.57 inch) diameter cartridge explosives and charges were initiated with half second non electric initiators. The perimeter holes were drilled at closer spacing of 30cm (1 feet) and alternate holes were charged using 32mm (1.23 inch) diameter cartridges explosive. Low dipping foliation joints present in the rockmass tend to slab in crown portion and erratic occurrence of intrusive bodies lead to unpredictable behavior of rock mass posing a major challenge for the safe excavation. Stability was a major issue through controlled blasting under constant supervision too could not limit the overbreak in certain weak rockmass conditions thereby exposing cavities of about 2.5m (8.2 feet). The stabilization of these cavities and handling the overbreak due to rockmass condition was time consuming and warranted additional supports. With systematic measurements and controlled blast designs the Horse Shoe Shaped Tail Race Tunnel of 9.1 m (29.85 feet) diameter and 304m (997.37 feet) length to connect with Downstream Surge Gallery of 314m (1030 feet) length, 18m (59 feet) wide and 58.8m (193 feet) height in thinly foliated and jointed biotite gneiss rockmass was successfully excavated.

By Charles Dowding, Cathrine Aimone-Martin

This article summarizes an investigation of the structural response of a brick façade home in New Mexico. The subject Ricter residence was located some 1100 to 1400 ft away from an aggregate quarry, and was subjected to a maximum peak particle velocity and air blast over pressure of 0.29 ips and 122 dB, respectively. Superstructure (corner) and mid-wall responses to blasting and human induced activities were measured. An existing exterior crack in the brick work was instrumented to measure crack width response to blasting, human induced activities, and environmentally induced changes in temperature and humidity. Crack and structure response data were correlated with ground velocity and airblast excitations. Amplification of ground motions at the upper structure were calculated and compared with values for typical wood frame structures. The natural frequency and damping characteristics of the structure were determined to compare with measured amplification values. Wall strains produced by bending and inplane tension strains were computed from upper corner structure response and compared to failure strains for drywall and brick veneer. Calculated strains were found to be far lower than those required to crack brick and environmentally induced crack response was found to be far greater than that caused by blast induced ground motion or airblast overpressures

Jan 1, 2005

By S. Lim, G. Walsh, V. Romero

The cable television show, Mythbusters, contacted the New Mexico Institute of Mining and Technology requesting a pressure gauge to be used in underwater testing. The requirements for the gauge were: it must be passive (i.e. require no power to function), it must indicate when a certain, pre-determined pressure was reached, and that indication was to be visual. A pressure gauge was developed, using standard, commercially available rupture discs, set to burst at 500 psi. Underwater testing was conducted using a 400 lb Pentolite charge. Test devices were set out at ranges from 50 to 200 feet from the seat of the blast. The rupture discs showed a lethal range up to 100 feet, but not at 150 feet. This result matched well with the behavior predicted through modeling and simple shock physics calculations. Additionally, the geometry between the incoming shock and the pressure gauge did not seem to have a strong effect on gauge performance.

Jan 1, 2009

By Jorge Cárdenas Miranda, Hector Espinoza

Currently in open pit mining in Peru with double bench, it is a challenge to optimize fragmentation in the drill rows near to the slopes to ensure the performance in the loading and haulage operation along with the process in the plant. That is why the present paper addresses a previously unanalyzed variable on the effect of the discontinuity plane on the fragmentation results. From the numerical mathematical models applied through algorithms in advanced computational tools such as Elfen, it was quantified the improvement in fragmentation results as P80 through a correct pre-split plane both in its extension as well as in its width. The first results show an improvement of 30% in the P80 and ensuring the quality of the walls without damage to the matrix of the final wall. The basis developed in this paper is based on the concept of wave reflection in the free face zones where greater efforts are presented for fragmentation, a similar theory is presented in the variation of initiation sequences that seek a greater area of reflective planes in the form of "V". Cases were evaluated with a percentage of compliance of the pre-split planes from 0 to 100% evaluating the impact on the results and correlated with field information explaining the behavior and validating the benefit. From the quantification of the benefits, this work opens the possibility of focusing resources on optimizing the pre-split process to achieve an improvement in the fragmentation results, giving a greater tool in the decision to optimize the blasting process.

Feb 6, 2023