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By P. Lozada

The objective currently demanded from controlled blasting techniques is to minimize damage to the remaining rock mass while protecting the integrity of mine walls and ensuring the quality of the fragmented material for easier extraction. Finding this balance represents one of the three main challenges faced by large open-pit mines. They must achieve mine stability by complying with slope designs while also maintaining good results in terms of fragmentation and equipment productivity. The main constraints are related to unfavorable geological conditions, water presence, limited drilling diameters and available explosive products, as well as managing drilling times and blast scheduling, among others. For slope control, in addition to presplitting, blasting designs generally include buffered rows, drilled with smaller diameters, and loaded with fewer kilograms of explosives than production holes. The objective is to reduce the powder factor (kg/t) to minimize the energetic influence on the walls and attenuate damage. However, this often requires using very short charge lengths compared to the bench height (one-third or less) and reducing the pattern geometry, which increases the number of holes per ton and drilling costs. This traditional technique of reducing powder factor in the buffered rows has the main limitation of not being able to distribute the explosive energy throughout the entire column, leading to fragmentation issues mainly in the steaming area. Measurements conducted by Orica in their operations indicate at least a 30% increase in P80 particle size in the buffer zone associated with this condition. To improve energy distribution, techniques such as decking, or vertically decoupled charges can be employed. However, these techniques cannot be applied under wet conditions, and strict control over implementation quality is required to avoid deviations, which increases loading operational times and resource required. In this sense, the use of less energetic and lower-density explosives is a better alternative. On one hand, they allow for complete charge columns in the buffered rows, ensuring homogeneous fragmentation, and on the other hand, they reduce the energetic influence on the slopes, significantly decreasing vibration levels. With less energy per kilogram of explosive (MJ/kg) and less charge per linear meter (kg/m), it becomes possible to handle higher specific charges and longer explosive columns, providing flexibility in drilling and loading design options without compromising slope stability.

Jan 1, 2024

By Tristan Worsey, John Rathbun, Andres Malone

A run of mine, low grade gold heap leaching operation is currently looking to increase ounce recovery by decreasing run of mine fragmentation size. Current blasting practices have resulted in an average fragmentation size of 80% passing 7.05 inches (179 mm). It is estimated that a decrease of 2 inches (51 mm) in the 80% passing fragmentation size has the potential to yield up to a 2.5% increase in the overall life of mine recovery within this ore body. This potential recovery increase could lead to an increase in recoverable ounces which, in turn, would lead to a better profit margin. As this particular deposit is composed of predominantly low grade heap leach the capital investment in a crushing facility was cost prohibitive, it was therefore decided to look into the current blasting practices as a means to improve fragmentation.

Jan 1, 2015

By Jerome H. Stofleth

In June of 1998, the DeBruce Grain Elevator was devastated by an accidental explosion caused by the unintentional ignition of grain dust. The DeBruce grain elevator was the largest ‘single head-house’ grain elevator in the nation. It was comprised of 450 cylindrical grain silos, 30 feet in diameter by 120 feet tall, with a centrally located headhouse. Immediately after the explosion, rescue operations were started for seven missing workers. The Federal Emergency Management Agency (FEMA) had taken over operations of the site by day two. On day three FEMA contacted the Washington DC office of the Department of Energy for explosive expertise, who in turn contacted explosives experts at Sandia National Laboratories (SNL) and Los Alamos National Laboratories (LANL). FEMA was looking for guidance in making the decision to downgrade their operation from a rescue to a recovery operation. Based on some chemical equilibrium calculations, and basic explosive engineering techniques, the SNL/LANL team was able to provide the necessary input to allow the decision to be made for the operational downgrade. At this point, only one worker remained un-recovered.

Jan 1, 2004

By Christodoulos Xiouris, Ali Reza, James Karnesky

A rocket parachute signal flare is often used to signal a maritime emergency. In the general operation of these devices, a solid rocket motor propels a metal body to an altitude of approximately 1000 ft (305 m). At the end of the rocket motor, a propelling charge drives a signal flare and parachute out of the metal body and ignites the flare, which then burns for approximately 40 seconds as it falls to earth. In this paper, we describe an engineering investigation of an accidental ignition of a rocket parachute signal flare, which caused injury to the user. T

Feb 1, 2020

By Pavel A. Torres, Darwin Torres, Sandro Huaman

Given the limited efficiency of blast-induced ground vibrations prediction empirical models, due to the complex geological system from a Peruvian mine. An artificial neural network was built in order to get better results. More accurate and precise predictions allowed the generation of blasting domains for future designs and decision making.

Feb 1, 2020

By Christodoulos Xiouris, Ali Reza, James Karnesky

A rocket parachute signal flare is often used to signal a maritime emergency. In the general operation of these devices, a solid rocket motor propels a metal body to an altitude of approximately 1000 ft(305m).At the end of the rocket motor, a propelling charge drives a signal flare and parachute out of the metal body and ignites the flare, which then burns for approximately 40 seconds as it falls to earth. In this paper, we describe an engineering investigation of an accidental ignition of a rocket parachute signal flare, which caused injury to the user. The components of the flare involved in the accident were inspected via x-ray and microscopic imaging techniques, and compared with those of unfired flares recovered from the same vessel. Chemical analysis of residue on recovered components from the accident flare was also performed. These comparisons were used to determine the likelihood that the actuation mechanism had been deliberately manipulated. In the subject model of the flare, ignition of the rocket motor is accomplished through a percussion cap which is struck by a firing pin. Prior to activation, the firing pin holds down a pre-compressed spring. We present a comparison of the ignition system of the incident flare with those of other rocket parachute flares, which do not incorporate any stored mechanical energy.

By Alan B. Richards, Aleks Todoroski

The undesirable effects of blasting fumes can be controlled by minimising the amount of fume created, and by avoiding the movement of the fume plume to sensitive locations. Substantial progress has been made by the blasting industry to reduce the amount of fume typically created by blasting, but at this time no specific blast can be guaranteed to be ‘fume free’.

Jan 1, 2017

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 Hideaki Kitajima, Daisuke Fukuda, Kazuma Moriya, Katsuya Sasaki, Katsuhiko Kaneko

The purpose of this research is to analyze the fracture process and achieve design optimization of a splitting method for concrete and rocks termed the electric discharge impulse crushing method (EDICM). The EDICM utilizes the cartridges being set in boreholes in the splitting target. The cartridge has a thin metal wire and is filled with nitromethane. By applying the electric discharge to the wire in the cartridge, plasma is caused leading to the vaporization of the wire. Then the deflagration of the nitromethane commences, which generates borehole pressure for splitting the target. Although the required splitting time is roughly several hundred micro-seconds and much slower than ordinary blasting, the fracturing still completes in quite short time and understanding the fracture process of opaque and brittle materials such as rock and concrete in this time scale is of academic importance.

Jan 1, 2011

By J Silva Castro, Braden Lusk

Information management is important in all disciplines. In mining; collection and analysis of information before, during and even after mining is a keystone to performance. During mining, information is useful to optimize the resources and make appropriate decisions. Current technologies allow for collecting information in real time. Records of blasting activity at the mine are common practice in surface coal mining operations. The most common blast information recorded contains the location of the blast, scaled distance, geometry of the blast, weight of explosive used and quantity of blasted rock. Sometimes due to the proximity of protected structures, seismograph evidence of the particle velocity and airblast levels is required. However, in the majority of cases, the seismograph information is not linked to the blast information. Blast related information is recorded separately from the seismograph information and seismograms are little more than an attachment to the blast record. This fact makes simultaneous visualization and analysis of the technical details of the blast with the vibration and airblast information difficult.

Jan 1, 2012

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 Fred Baldassare, Marcia Harris, Kenneth K. Eltschlager

Surface mine blasting was recently investigated as a potential source of high concentrations of stray gases found in nearby residences of western Pennsylvania. In one incident carbon monoxide was detected in a home and in the other, high concentrations of carbon dioxide were found in a home. Both carbon monoxide and carbon dioxide are by-products of blasting. However, other potential sources of these gases may also exist in a residential setting. In each case, gas chromatography (GC) and carbon isotopic analyses were used to define atmospheric concentrations inside the homes, and to determine the source of a stray gas. Molecular and isotopic analyses provide geochemical evidence as to the origin and source of the stray gas. This paper discusses elements of a stray gas investigation and the analyses necessary to identify the source of a stray gas.

Jan 1, 2004

By Thierry Bernard

Since the signature hole method principle has been described in the 80's, there has always been a lot of controversy about it. The theory is easy to understand but when it comes to apply it for predicting vibration level, optimizing timing to reduce PPV or shifting frequencies, it’s not always working as expected. Simulations show waveforms that don't make any sense or predictions that are far away from actual results.

Jan 1, 2012

By Francisco Leite, Tomi Kouvonen, Bianca Saraiva, Vinicius Miranda, Auã Oliveira

One of the main challenges facing mining engineers is to draw up a plan that can be implemented in a timely manner, taking into account the operational variability of the mine’s production processes. These plans are often drawn up based on deterministic modelling (provided there are a set of known inputs that will result in a single set of outputs), when in truth we are talking about stochastic events (the cycles involved behave like random variables and their nature may be studied and reproduced). The result of using this kind of methodology can lead to non-optimized intuitive choices, which may harm the long-term targets defined by the planning team. Based on this principle, this document investigates the simulation of the rock fragmentation process in an open pit mine to assess the stochastic behavior of the loading and haulage operating cycles. The data assessed by the simulation process were the total costs of these operations in function of the powder factor. Based on a sample set data items, it was possible to check the probability distribution of the event as a Poisson distribution, applied to the loading and haulage cycles. The simulation consists of the repeated sequenced reproduction of these events (Monte Carlo simulation), in order to find the configuration that best fits the loading and haulage operations. By integrating these systems, it was possible to better understand the influence of the blasting in these operations, and as such to reduce the associated costs.

Feb 6, 2023

By B. Corrêa, M. Cavalcante

A large open pit iron ore mine in Brazil, which has a heterogeneous lithology, faces a challenge in defining drill and blast patterns to achieve the expected results. The mine needed to obtain an automated representation of the fragmentation curves and correlate them to the respective blasts, lithologies and quality parameters, seeking the continuous optimization of the fragmentation process and its benefits to the subsequent comminution processes. Trials were carried out for 5 months to demonstrate the functionality of an autonomous fragmentation monitoring system that analyzes the granulometric curve of the material throughout the muckpile and makes the results available online and in real time. The system, which contains a binocular camera, a processing unit and an antenna, was installed in a shovel, to evaluate the following KPI's: monitoring failures, monitoring capacity, physical availability and reportability of oversized boulders. The system analyzed 33,060 samples, with an average capacity of 285 photos every 24 hours, 127 during the day and 158 at night, all measured, analyzed, stored, and made available on its online platform, reporting 223 alerts of P80 above 400mm (15.7 in) and 38 particle sizes above 900mm (35.4 in). The inactive and operational hours of the monitoring system corresponded, respectively, to the idle and worked hours of the shovel, according to dispatch data. There were no camera or processor failures, and rain, dust or poor internet conditions did not impact sampling and fragmentation analysis, indicating 100% physical availability of the system. The autonomous monitoring analyzed 139 times more samples compared to the currently used manual method. In addition to increasing sampling representativeness and automating the process, it increases the safety, quality, and productivity of granulometric analysis, eliminating the exposure of people in the mine and human bias in the analyses. Additional analyses were performed by correlating digitally centralized drill and blast data, data from autonomous drills and fragmentation results. Automated obtention of granulometric curves favors quick decision-making and optimization of blasts to achieve better results in productivity and cost reduction in the plant and mine operation. The autonomous fragmentation monitoring system met the need presented by the mine, proving to be a key tool in continuous improvement projects, including Mine to Plant.

Jan 1, 2024

Existing geological structures such as faults or shear zones can greatly influence the interpretations of amplitude or energy attenuations of measured blasting vibrations along both affected and unaffected orientations. Mineralisation in conjunction with large faults or shears is commonplace in the geology of steeply dipping metalliferous deposits, such as those found in the goldfields of Western Australia. Better understanding of the influence of faults or shear zones on blast-induced seismic waves can lead to more effective blast vibration monitoring programs and interpretation of the results measured along affected orientations.

Jan 1, 2011

By Eric C. Gerst

"In this current era of soft commodity and coal prices the mining industry is turning towards optimizingall levels of production to reduce operating costs. Part of this trend includes the automation of miningmachines. As the first tier of the mining process blast hole drill automation offers benefits through the entire value stream from drill bench to material processing."

Jan 1, 2017

By R. Narendrula, S. P. Singh

The productivity of a loading machine is affected by several factors. One of the most significant is the characteristic of the muck being loaded. A study was conducted to examine the effects of the looseness, angle of repose, size distribution and moisture content of the blasted material on the efficiency of the loading machine. The study was conducted in the following stages: (a) controlled experiments in the lab, (b) tests with loader simulator and (c) field work in an operating mine. It was found that looseness (%void) in the muck increases with the increase in the value of the mean particle size and index of uniformity of the fragmented rock. Looseness and angle of repose affect the fill factor and the digging cycle time of a loader and in turn the productivity of the equipment. Moisture content affects the angle of repose as well as the stickiness of the material to the loader’s bucket. It was observed that the angle of repose increased with the increase in the mean particle size and the moisture content of the muck. It was also found that the bucket full factor and rate of scooping decrease with the increase in the values of mean particle size and index of uniformity. This was also conformed during fieldwork that bucket fill factor decreases with the increase in the mean particle size as well as the index of uniformity.

Jan 1, 2005

By Braden Lusk

This paper includes results from analysis of recorded Acoustic Responses of Structures to Blasting. The analysis was performed to determine specific characteristics of sounds experienced inside homes during blast events. Data was collected in a typical house within the Boone North No.2 Coal Surface Mine in Ashford, WV which was instrumented for several blast vibration and acoustic responses. The instrumentation consists of four acoustic microphones distributed throughout the internal areas of the house and three geophones buried near the house. Two additional channels collect the trigger signal and Air Blast information. For each blast event recorded by the system, the mine blast reports were used to obtain major blast characteristics such as distance from the blast to the instrumented house, weight of explosive used, number of boreholes, delays, and other important parameters. This information allowed study the relationship between the acoustic response and the blast design. From a database of 43 records, five records were chosen for complete analysis. These records were chosen based on distance from the blast to the house, and specific blast parameters. This paper presents the result of the relationship between the frequencies and amplitudes for the entire trace of acoustic records, the response due to ground vibration (GV), and the response due to air-blast (AB). Frequency content was obtained through Fast Fourier Transforms (FFT), using D-Plot software. The records have a typical shape that permits cutting and analyzing each part of the signal with respect to GV and AB separately. Some conclusions are reported concerning the relationship between blast parameters and acoustic response of structures.

Jan 1, 2009

By Nolan Eckroade

The demand for blast optimization within the quarrying industry calls for more effective, faster and safer methods of quantification of blast performance. Drones provide the ability to safely and quickly capture high resolution imagery of a muckpile for use in fragmentation photo analysis. Oversize material within a muckpile is an expensive and universal problem affecting quarries, especially in situations where cap rock is present. Although the amount of oversize material in a blast is a key indicator of blast performance, it is difficult, hazardous and slow to measure across an entire muckpile using traditional methods. By piloting a drone using an automated flight plan with set amount of overlap across images, the images can be processed into a single, high resolution orthomosaic image for use in fragmentation photo analysis software.

Jan 1, 2018