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By Javier Illanes Pizarro, Gustavo Huerta Valer, Jorge Cárdenas Miranda

Bench stability is the basis of sustainability in an open pit mining operation. Taking care of the pit walls while maintaining fragmentation results can prove a challenge. In this study, technical proposals have been developed for extra hard rock mass (UCS>175MPa) with presence of unfavorable structural planes in high copper grade zones. The base case shows low compliance of fragmentation results and a significant loss in berm width, with over size boulders causing low primary crushing rates. Paradigms in current drill and blast design were overcome to improve fragmentation results and achieve objectives.

Feb 6, 2023

By Lazar Kricak, Vladislav Kecojevic, Dragan Bogunovic

In spite of many advantages explosives have, their usage may cause environmental problem such as seismic vibration. One of the solutions to this particular problem may be application of an artificial screen as a barrier to the seismic wave path. This paper presents the results of experimental research on the artificial screen concept, its characteristics and role in attenuation of seismic effects generated by blasting. More than 1,500 laboratory measurements were conducted with different combinations of screen sizes, positions of the screen to blasting source, and intensities of blasting impulses. The results of the study show a significant reduction of generated vibrations by employment of artificial screens.

Jan 1, 2007

By Les Willan, Chris Batten, Matt Sparkes

In late 2008 Xstrata Newlands Coal Mine in Central Queensland and Orica Mining Services engaged in discussion to investigate methodologies to change their current mining practices and overcome the issues in the mining of steeply dipping coal seams, the associated coal loss risk and to assist in improving mining productivity. A strategy was developed and it was determined that through-seam blasting was essential to the success of winning the coal from the Wollombi Pit at Newlands.

Jan 1, 2010

By BruneJurgen F., Richard C. Gilmore, Matthew Schreiner, Ray Johnson

Explosive pockets of methane-air mixtures accumulate in underground coal mines and, when ignited, produce an air-blast wave that can disturb combustible coal dust on the floor, roof, and ribs. To prevent explosions, the coal dust must be continuously diluted through application of inert rock dust, usually powdered limestone. Application of powdered dust process creates a respiratory nuisance downwind, where miners cannot work until the dust settles. Rock dust suppliers have developed wet and foam applied products to reduce the nuisance and limit the interruption to mining during dust application. To test the effectiveness of these alternative dust products, researchers at the Colorado School of Mines (Mines) have constructed a full-scale explosion test drift located at the Mines Edgar Experimental Mine (Edgar) to study the dispersibility of different rock dust applications. This paper examines the use of Pentaerythritol tetranitrate (PETN) detonating cord to produce controlled air-blasts that simulate methane-air explosions. The air blasts are generated with curtains of detonating cord that produce shockwaves with wind speeds between 30 to 70 m/s (100 to 225 fps) depending on the length of 5.3 g/m (25 grain/ft) detonating cord used. These velocities represent the minimum air speeds required to trigger propagating coal dust explosions. Researchers have conducted 40 test blasts with various lengths of detonating cord. Results show the two primary waves and two reflected waves each decaying into airblast waves with overpressures of 14 to 27 kPa (2 to 4 psi). Pressures were recorded with commercial piezoelectric transducers and custom-built, bi-directional probes to record the total and dynamic pressures of the wind generated in the explosion. Researchers were able to generate consistent and repeatable wind speeds and air-blast durations sufficiently similar to a methane-air explosion to study the dispersibility of various rock dust products and application methods

Jan 1, 2019

By Dale S. Preece

A new three dimensional (3D) mechanistic model of fragmentation, called the Fracture Density Model (FDM) is used to simulate full-scale bench blasts at the Bararp dimensional stone quarry in Sweden. The model uses several computational mechanics algorithms to simulate the effect of blasting in different rock types

Feb 1, 2020

By Emily Johnson, Catherine Johnson, Rachel Bauer, Paul Pitzel

Demolition projects involving explosives may incorporate cutting charges to sever columns in collaboration with kicker charges that “move” the columns out of alignment. Traditional kicker charges often involve the use of dynamite secured to the column above the cutting charge. Nitroglycerine, the main component of dynamite, causes medical problems and can be a hazard to workers on site. Dynamite can also cause fragmentation of the column and structures, resulting in potential injuries to people or leading to the possibility of cutoffs in neighboring charges. This study investigates the use of water-cased kicker charges to reduce the amount of dynamite in demolition. Water charges, traditional charges, and detonating cord charges were placed on hanging steel columns and analyzed for the fragmentation of the column and velocity of the column. A W 10 X 22 beam was hung in an underground limestone test area and allowed to swing freely acting as a severed column. Charges were attached to the bottom of the column with tape and initiated using electric detonators. Explosive charges of dynamite or detonating cord were placed in the center of a water container or directly on the column for use as the kicker charge. Tests were recorded with high-speed video and velocity was calculated using Phantom Camera Control software. Velocity and time were then used to calculate force, kinetic energy, impulse, and pressure exerted by the explosive on the column. The water charge transferred energy to the column over a larger area with no direct contact of explosive and the column. Water charges moved the column faster and with more power than traditional charges. After preliminary tests, water charges were also used as the primary kicker charges in a full-scale demolition project as a case study using 118 charges. The kicker charges successfully moved building members without creating fragmentation while using less dynamite than traditional kicker charges. Due to the success, multiple full-scale projects are being designed using water charges to show success and repeatability.

Feb 6, 2023

By Jarrod Bonsmann, Zachary T. Plitt

"A surge in mine related deaths in Middle Eastern conflicts over the past few years has prompted research into the mitigation of the impact on a blast loaded vehicle. In past military conflicts, it has been observed that blast loading can cause injury to the brain but the exact cause is unknown [1]. The recent rise in deaths due to Improvised Explosive Devices (IEDs) has led to research that has speculated that the high acceleration experienced by soldiers on a blast loaded vehicle leads to Traumatic Brain Injury (TBI) [2]. This research aims to investigate vehicle designs that can reducethe peak acceleration for passengers on board the vehicle, in the event that the vehicle is blast loaded by an IED."

Jan 1, 2016

By Felix Degold, Mark Ganster

Achieving a customer optimized fragmentation by using robust data from new technologies e.g. GPS positions of boreholes, fragmentation analysis to calibrate the geology and fragmentation prediction models. The inclusion of the collected data into the blast’s design makes it possible to accomplish a desired particle size distribution.

Feb 1, 2020

By Randy Martin, Jessie Bonner, Peter Boyd, Mark Leidig, Timothy Rath

We conducted the Vermont Damage Experiment in central Vermont during July 2008. Five single-hole explosions with yields ranging from 60.8 kg (134 lbs) to 122.5 kg (270 lbs) were detonated in homogeneous, low fracture density granite. The goal of the experiment was to quantify the different levels of rock damage around the source and then relate the seismic wave generation to the degree and distribution of damage and fragmentation. In addition, explosives with different velocities of detonation (VOD), including black powder (0.53 km/sec; 1737 ft/sec), heavy ANFO (4.8 km/sec; 15734 ft/sec), and COMP B (8.1 km/sec; 26574 ft/sec) were detonated to relate the VOD to seismic wave generation and extent of damage zones in the source region. Over 120 seismic stations were deployed to record the explosions at distances between 5 m and 30 km (15 ft to 19 miles).

Jan 1, 2010

By H. Mullani

We have in southeast Kansas a variety of soils underneath which are a variety of subsoils compressed into what is commonly called “ hard pan.” These soils are of six types, ranging from a clay to a sandy loam. The surface soil in Cherokee County and Crawford County, of whatever quality or type is, generally speaking, from 6 to 12 inches in depth. The so-called “hard pan” ranges from the native grass roots to a depth of from 2 to 12 feet, and in some places even deeper than that.

Jan 1, 2010

By Ayman Tawadrous

Cave mining offers a flexible technique to exploit large, low grade, deep ore bodies with low operating costs. It is typically done in either a top down approach; i.e. sublevel caving, or in a bottom up approach; i.e. block or panel caving, to extract ore bodies that may have been previously considered unfeasible to mine. Sublevel Cave (SLC) mining, in particular, is a cave mining method based upon the utilization of gravity of blasted ore while the overlying host rock fractures and caves under induced stresses and gravity. Thereby the caved waste originating from the overlying rock mass fills the temporary void created by ore extraction to achieve a controlled collapse of the roof.

Jan 1, 2015

By R. Hazael, R. Alford, R. Critchley

The ability to compare explosives is fundamental. Numerous methods are used and while simple conversion factors are often used, the use of TNT Equivalency (TNTe) is not a simple subject as explosives exhibit very different equivalencies depending on whether the pressure or impulse are being considered as well as other conditions. The scaled distance has been found to have a significant effect on the TNTe but due to the difficulty of taking measurements at very close ranges, no TNTe have been quoted for charges in direct contact (Z=0). This paper describes the use of a ballistic pendulum to measure the impulse from contact charges and presents some surprising results that require a two-stage propulsion, as originally described by Backofen, to be explained.

Jan 1, 2024

By Clarence Hall, Charles E. Monroe

Squibs, Fuse, and Detonators It has been made clear in the discussion of combustion and explosion and the description of various explosives that they can be caused to explode by various means. All of them can, under some circumstances, be made to explode by fire. Some of them can be caused to undergo a detonating explosion by setting off a detonator in contact with them. In blasting use is made of both these means for setting off explosives, the means used being determined by circumstances.

Jan 1, 2010

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 Neal Lee, Braden T. Lusk, Brendan McCray

"Selection of a blasting agent for optimum performance is based on many variables. Often, a decision is made with regard to product cost and field testing. Defining optimum performance can be difficult, since downstream effects of fragmentation on loading, haulage, processing, and energy consumption are not immediately clear. Many operations are beginning to optimize their blasting programs “on the bench,” by utilizing information generated downstream at the loader and/or crusher. During the evaluation of a blasting agent, factors such as velocity of detonation, gas production, and sensitivity are typicallyconsidered. Alternatively, brisance (“the shattering power of an explosive material distinguished from its total work capacity”1) is not. Brisance affects the immediate area surrounding a borehole. Fractures produced here during the shock phase of detonation are believed to have an important effect on rock movement and fragmentation. "

Jan 1, 2017

By Andreas Bienz

The safety of persons from accidental explosions and fires during manufacture, storage, transport etc. of explosives, pyrotechnics, propellants, firework and ammunition is most commonly assessed according to prescriptive rule-based approach: Safety is given when all requirements which are listed in numerous regulations and directives (such as e.g. safety distances, limited quantities, protective installations etc.) are complied with. Such a deterministic prescriptive rule-based approach is quite easy to apply but has got disadvantages, however: The actual state of safety in a specific case is not explicitly and quantitatively expressed, and it is not distinguished between the endangered individuals and the whole group. As a result, the effects of the safety measures cannot be measured. This is why uneconomical and in the worst case useless safety precautions cannot be avoided. In addition, waivers are difficult to negotiate, meaningful and sound arguments for pro and con being lacking.

Jan 1, 2007

By Tyler Acorn

In December of 2009 an estimated one million ton slope failure activated a 10 million ton mass impacting use of the main ramp system in the Newmont Gold Quarry pit. The failure left behind a 400 foot (122 meters), vertical to sub vertical scarp feature and shut down production in the lower benches of the pit.

Jan 1, 2011

By Gordon C. Petersen, Gary A. Almeraris

This paper describes the controlled blasting techniques required to mine a rock tunnel section of a main interceptor located in the Boston Metropolitan area. The 3m (10 ft) x 2.8m (9.25 ft) horseshoe shaped tunnel was driven 490m (1600 ft) by conventional drill and blast methods. The geology varied round by round and consisted of five highly faulted and jointed igneous rock types. The tunnel intersected numerous slickenslides and open mud seams which hampered both drilling and loading operations. Smooth blasting wee critical in order to keep overbreak tc a minimum in this extremely hard but blocky ground.

Jan 1, 1991

By Khushaal Popli, Vanessa Roeland, Brian Hall, Carl Diederichs

Highland Valley Copper (HVC) has embraced an integrated Mine to Mill approach to comminution since the late 1990s. Previous blasting optimization was carried out through adjustments to blast pattern geometry (i.e., reduction of burden and spacing). This approach proved very effective and HVC reduced the burden and spacing of high energy ore blast patterns to what was considered the practical limit that still allowed for efficient drilling and bulk truck loading operations. While mining in the bottom of the Valley pit near the end of the previous pushback, HVC encountered high static groundwater conditions which enabled the transmission of elevated inter-blasthole pressures that had the potential to exceed safe operating limits for initiation products. This risk was mitigated through an expansion of burden and spacing for the high energy ore patterns, reducing the application of blasting energy and increasing the average particle size in Mill feed.

Feb 6, 2023

By Nadya Michel, Daniel Gros-Jean

This is a true story. Names have been changed to illustrate the importance and impact of carbon monoxide risk management in explosive blast projects and the community « Honey I’m not feeling good…” “What is going on Michael?” – – Michael was not answering so Julia, who was on the third level of the magnificent house, hurried down the stairs to check up on him in the basement. Today was day 2 of the construction work of the bathroom, yesterday they had excavated all the space for the shower. She started to breathe heavily as she was approaching the bathroom and saw Michael unconscious on the floor. “Michael!” – Julia immediately dialed 911. She opened a window since the air was heavy and went by Michael to hear him breathe and take his pulse. The paramedics took Michael on a stretcher and rushed him to the hospital. “I’m feeling dizzy” she thought to herself a couple of hours after the incident, and heard Matthew say: “Mom, I’m feeling sick”. Suddenly, she felt like she would pass out and felt in danger but couldn’t move. She desperately searched for her cellphone and dialed 911 but couldn’t speak. The dispatcher sent the firefighters and paramedics to the GPS location that was appearing on the screen and the emergency team was alerted that it was a second call in hours at the same address. When the firefighters arrived, they had to force the door to enter and found Julia in her bedroom on the third floor and Anette and Matthew also unconscious in their bedroom, lying on their respective bed. There was no smoke but on their multigas meter, carbon monoxide (CO) peaked at 1500 ppm on every level of the house, which is abnormally high.

Feb 6, 2023