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By Jeffrey W. Lin, Jonathan D. Abbott, Patrick R. Bowden, Tyson J. Plitt

Pentolite is a class of high explosives containing trinitrotoluene (TNT) and pentaerythritol tetranitrate (PETN) with PETN content typically ranging from 40 to 60 wt%. Manufacture involves melting TNT, 80 °C, followed by addition of PETN and trace ingredients to form a homogeneous mixture. Once a mix is ready to be poured, several factors can influence the behavior of the finished product including how long the mix has been at temperature and cooling rate. After the manufacturing process has been completed, storage conditions combined with manufacturing conditions may cause physical changes. Two such changes explored were exudation, liquid exuding from solid boosters, and ratchet growth, irreversible volumetric expansion. Exudation is principally caused by excess water in the process. Ratchet growth is a common phenomenon of nitroaromatic compounds such as TNT where time and temperature fluctuations can cause materials to increase volume, simultaneously decreasing density. Although neither phenomenon affects common attributes such as sensitivity, performance, and shelf-life, both can cause issues in storage and handling. In this study pentolite was cast into various forms under different manufacturing conditions and evaluated over several months of controlled storage conditions including ambient, temperature cycling and elevated isothermal. Subjective and objective measurements were made throughout the evaluation period with the aim to determine the preferred storage methodology.

Jan 21, 2025

By Robert Hopler

SECTION 9.---BORING AND BLASTING.*155. Blasting is the operation of bringing down and detaching from its bed or position masses of material by means of explosives.

Jan 1, 2011

By Bonifacio Digay

Stawell Gold Mines (SGM) is an underground mining operation located in Victoria, Australia.The mining method employed is long hole retreat stoping, utilising up and downholes and artificial concrete pillars. Stawell is currently mining the Golden Gift and Magdala orebodies.

Jan 1, 2012

By Art Frye, Lee Pratt, Gaichang Zhao, Greg Newman

This paper will discuss the Wight Pit wall slash at the Mount Polley open-pit copper-gold mine that scavenged a high grade block of ore from two double-benches of the pit wall. The Wight Pit orebody, discovered in 2003, is located in the Northeast of the property with the southeast pit wall approximately 50m (165ft) from the edge of Polley Lake. In early 2009, the Wight Pit was nearing completion while an estimated 150,000 tonnes (165,000 tons) of ore averaging a grade of 1.4% copper remained just inside the southeast pit wall. The ore block started 24m (78ft) above the pit floor and extended up another 48m (157ft) with a 70o plane defining the back of the block.

Jan 1, 2011

By Gour Sen, Peter Bellairs

Blasting conducted in rock temperatures greater than or equal to 55°C (13 1 “F) and / or in rock containing sulphide minerals and their oxidation products can result in unplanned detonations. Blasting practices involving the identification of the affected areas together with the use of speciality explosive products and rigorous attention to quality control are required to safely blast in these types of environments. Sulphide dust explosions occur in some underground mines where the primary blast results in a secondary explosion of the sulphide rock dust which propagates some distance from the primary blast area. This phenomena results in considerable damage and the generation of significant volumes of toxic gasses delaying re-entry to the affected area of the mine thereby increasing both costs and safety concerns. The exothermic reaction between ammonium nitrate based explosives and rock types containing partially oxidised sulphides have resulted in numerous high risk blasting incidents. These reactions can occur at ambient temperatures and often result in premature detonations / deflagrations causing a great deal of consternation at the affected minesite resulting in lost production and considerable expenditure to solve the problem. Rock masses at elevated temperatures can also result in unplanned detonations unless appropriate precautions are taken. This paper discusses each of these hazards, cites some case studies and details appropriate generic safe and efficient blasting techniques for each of the above applications using appropriately formulated explosive products.

Jan 1, 2000

By Charles Clark, Mark Mukhija, Jaime Klein

Comminution – the reduction in size of solid materials – is the most energy intensive component of the mining process (Bauer, 2015). It is estimated that comminution consumes around three percent of all electricity generated in the world (Ceecthefuture.org, 2017). On an energy equivalent basis, downstream processing consumes six times more energy than drilling and blasting (Kanchibotla, Sarma et al., 2014).

Jan 1, 2018

By David Flores, Benjamin Cebrian

This paper describes extensive engineering approaches to achieve both dilution control while not hurting fragmentation in the very hard, massive ore sections of a mine case study. Ore Tracker microchips are used to correlate performance of these designs at the SAG mill (bottleneck of this specific operation). Another gold mine uses the same technology to detect when and where operational dilution is happening. The system tells where flagging of the different ore bodies has been followed in order to detect which operators pass the excavation limits beyond ore control flagging.

Feb 1, 2020

By Carl E. Jones

This presentation discusses the properties of the two-component explosive, KinePak, and how it is used by the utility industry.

Jan 1, 1978

By Thomas Barkley

Mining tradition holds that a parallel round underground can not be any deeper than it’s smallest face dimension. ln other words, a mine using a 12’ (3.7 m) high by 24’ (7.3 m) wide room and pillar mine, the deepest pull that can be achieved is plus or minus 12’ (3.7 m). After experience with decking of rounds in a 12’ (3.7 m) diameter shaft to achieve more than 12’ (3.7 m) advance per round, the concept of deepening the pull on horizontal parallel rounds seemed to be a feasible concept. Tests were conducted in a conventional room and pillar metal mine with a round size of 12’ (3.7 m) high by 24’(7.3 m) wide. Standard rounds were drilled with a 16’ (4.9 m) steel as parallel rounds to an average depth of 14.5’ (4.4 m). The average depth of pull on these rounds was about 13’ (4.0 m). Using the available drilling equipment, 20’ (6.1 m) drill steel was used to drill holes to an average depth of 18’ (5.5 m). Five rounds were drilled and shot with a resulting aven$e pull of 16.2’ (4.9 m) or 90 % of drilled depth. Rounds were designed with decked bum cuts to maximize depth of pull in the cut area An innovative method of de&mining drilling accuraq was used to estimate it’s effect on depth of pull in the rounds. This method used a standard automatic 35-mm camera and scaling to determine the average drill deviation for many of the holes in the rounds.

Jan 1, 2000

By L. O. Souza, J. F. Gewher, M. P. Scussiatto, C. S. Mendonca, R. A. McClure, B. T. Kuckartz, J. Kloeckner

Blasting is the most effective and economical tool available to fragment and move rock for most applications. If properly executed, it can improve down-stream operations such as loading, hauling and crushing. It is not possible, however, to have full control over the energy released by the explosives when a poorly designed blast pattern is used. A poorly designed blast can produce serious damage to equipment and create a potentially hazardous condition to people. Advanced mining technology has been developed to address these potential hazards and optimize the blast pattern. This profiling technology can assist with blast planning and provide quick, precise data about the condition of the rock structure to be blasted. The 3G BlastMetrix system presented here uses three-dimensional (3D) stereo photogrammetry to model the rock mass in a fast, practical and safe manner. Through the image overlapping method, a 3D model is created with thousands of points that provide a significant amount of data regarding geology, geometry and topography conditions. The blasting plan can then be made in a way to optimize the rock fragmentation and avoid areas that could create flyrock. This paper is a case study concerning usage of stereo photogrammic surveying and borehole survey systems in a blasting operation at the Brazilian Quarry, Incopel. One 3D image of a drilled bench was generated using photogrammetry survey technology and the borehole survey data collected using the rodded Boretrak borehole survey system. Utilizing the minimum burden profile reports, explosive loading could be done accurately, resulting in an optimized blast with good heave and fragmentation as well as increased safety.

Jan 1, 2013

By Harry Verakis, Thomas Lobb

This paper summarizes the course of mine blasting safety, particularly in underground coal mining, in the USA for over a century of mining operations. During the late 1800's and especially in the first decade of the 1900's, a large number of mine explosions occurred in which blasting played a significant role. A contributor to the large number of mine explosions during this time period was the use of black blasting powder to extract coal and other minerals. A review is made of some of the more significant underground coal mine explosions that resulted from blasting operations during this time period up to the present day. The safety measures that were adopted and required by a series of laws as a result of mine explosion disasters in which blasting was one of the factors are examined. The time line of historical improvements in blasting safety and the tremendous reduction in fatalities and injuries over a century is illustrated and discussed. The improvements, which included the elimination of black powder and dynamite and the introduction of safer explosives termed "permissibles" occurred slowly over time and culminated from the occurrence of many coal mine explosion disasters. The blasting accident history over the past decade is discussed to show the great gains made when compared to the first decade of the 1900's. The most recent blasting accident fatality that occurred in October 2006 at a U.S. underground coal mine is also discussed. Although the blasting accident record is significantly improved from over a century ago, continual improvement is needed to reach the goal of zero fatalities.

Jan 1, 2009

By James Ludwiczak

This paper consists of the conduct of a forensic criminal investigation of the components, construction, use, and functioning of two suicide bombs. As the title states, the task was to form professional opinions as to whether the bombs would work, would cause property damage, and would injure or kill. The bombs were created and installed by a defendant in a Federal death penalty case where the defendant’s daughter was killed in a shootout with the West Virginia State Police. The two black powder bombs were placed under the front seats of the defendant’s automobile and were designed to function by the use of a toggle switch connected to the automobile’s cigarette lighter. The forensic work first consisted of an inspection of the remains of the wiring system and bombs at the Bureau of Alcohol, Tobacco, and Firearms Laboratory, in Ammendale, MD. This was necessary to determine and detail the wire diameter and lengths, the lengths and size of the wire used, the type of toggle switch used, the type of containers, the type of rocket motors used to initiate the black powder, the manufacturer and amount of black powder used in each bomb, and the type, wraps, and amount of duct tape used for the construction of each bomb. Using this data, tests were conducted by duplicating the wiring system and the two bombs to insure that the system functioned properly. Each bomb was duplicated and initiated to observe the violence produced when initiated in the open air. Duplicate bombs were placed under the seats of a similar type of automobile and initiated. The purposes of the tests were to duplicate the bombs, to observe the violence of the initiation, and to observe the damages to the automobile produced by the initiation.

Jan 1, 2007

By Fumihiko Sumiya, Yuji Ogata, Masahiro Seto, Yukio Kato, Yuji Wada, Kunihisa Utsuyama, Yoshikazu Hirosaki

It is well known that emulsion explosives can be dead-pressed especially in underground blasting. Voids in emulsion explosives will affect such malfunction of explosives. To clarify the factors that affect the dead-pressing phenomena, the characteristics of the pressure wave propagation in emulsion explosives were investigated. Three types of microballoons .or microbubbles, glass microballoons(GMB), resin microballoons(RMB) and chemical gas bubbles, were used as sensitizers for emulsion explosives. The pressure profiles inside the explosives were measured to determine the effects of the microballoons or microbubbles contained. The underwater explosion test and the large-scale drop hammer test were carried out to load the explosives with a dynamic pressure and a quasi-dynamic pressure respectively. In the underwater explosion test, the pressure profiles in the emulsion explosives were measured by a piezo-electric pressure gauge inserted to the center of the explosive cartridge which had a diameter of 30mm. In the large-scale drop hammer test, the same type of pressure gauge was placed at the bottom of the explosives. From these experiments, the following results were obtained ; A) The pressure profiles in the sample explosives sensitized by RMB or chemical gases were sharp, while in the sample explosives sensitized by GMB the profile was broad. B) The peak pressure levels in the sample explosives sensitized by RMB or chemical gases were twice as high as that in the sample explosives sensitized by GMB in the underwater explosion test. However in the large-scale drop hammer test, the amplification of the peak pressure is low compared with in the underwater explosion test. C) The impulse value was independent of the types of the microballoons or microbubbles in both tests. It was concluded that the type of the microballoons or microbubbles significantly influenced the characteristics of the pressure wave propagation in emulsion explosives.

Jan 1, 2001

By Michael Weaver, Dale L. Ramsey

The Pinkerton Tunnel open cut project is part of the National Gateway Clearance Initiative improvement project to achieve a minimum of 21 feet of vertical clearance along CSX Transportation rail corridor so that double-stacked intermodal railcars can be transported between mid-Atlantic states and their ports to midwest markets in the U.S. This project involved drilling and blasting of 1.2 million bank cubic yards of rock over a 14 month period while maintaining rail traffic of two passenger and 38 freight trains daily. See story and photos, page 6.

Jan 1, 2015

By W Russell

The Hercudet Non-Electric Delay Blasting Cap System provides a means of achieving greater flexibility in the use of delays, using totally enclosed gas detonation circuits which eliminate the concussive effects of detonating cord trunklines in the confinement of access tunnels beneath pillars of ore. This is an account of one such pillar blast.

Jan 1, 1985