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By N. Wagner, P. den Hoed, J. D. Steenkamp, S. Soqinase

In pyrometallurgical processes, metal oxides are reduced from molten slag through carbothermic reduction. It is of interest to evaluate the reactivity of the carbonaceous materials towards substances such as slag. Characterization techniques such as coal petrography can provide insight into the influence of feed coal properties and how they potentially dictate reductant performance. This study aimed to compare the petrographically determined organic composition of coal to reductant reactivity. Two South African medium-rank C bituminous coals and one anthracite sample were investigated together with high-carbon ferromanganese industrial slag. The reductant reactivity tests were conducted at 1500°C in a muffle furnace to assess the potential of carbonaceous reductant in reacting with the main slag components. SEM-EDS was applied to understand the extent of MnO (and to a lesser extent, SiO2) reduction from the slag. Coal 2, consisting of a greater proportion of vitrinite (59.5 vol% on a mineral matter-free basis and 54.7 vol% including mineral matter) was the most reactive reductant. The anthracite sample, with the highest inert maceral proportions (71.8 vol% including mineral matter and 76.8 vol% on a mineral matter-free basis), was the least reactive reductant.

Feb 6, 2023

By M. Z. Emad, A. Hassan, M. A. Raza, M. U. Khan, S. A. Saki

Digital modelling of a surface is crucial for Earth science and mining applications for many reasons. These days, high-tech digital representations are used to produce a high-fidelity topographic surface in the form of a digital terrain model (DTM). DTMs are created from 2D data-points collected by a variety of techniques such as traditional ground surveying, image processing, LiDAR, radar, and global positioning systems. At the points for which data is not available, the heights need to be interpolated or extrapolated from the points with measured elevations. There are several interpolation/extrapolation techniques available, which may be categorized based on criteria such as area size, accuracy or exactness of the surface, smoothness, continuity, and preciseness. In this paper we examine these DTM production methods and highlight their distinctive characteristics. Real data from a mine site is used, as a case study, to create DTMs using various interpolation techniques in Surfer® software. The significant variation in the resulting DTMs demonstrates that developing a DTM is not straightforward and it is important to choose the method carefully because the outcomes depend on the interpolation techniques used. In mining instances, where volume estimations are based on the produced DTM, this can have a significant impact. For our data-set, the natural neighbour interpolation method made the best predictions (R2 = 0.969, β = 0.98, P < 0.0001).

Feb 6, 2023

By Neal Lee

Reduced relief horizontally means an increase in energy expended vertically into the rock surrounding the stemming column, and potentially through the stemming column. The vast majority of holes in any surface blasting operation are afforded two horizontal relief faces at the moment of firing, whether by existing relief faces in front of and to one side, or previously blasted hole(s) in front of and to one side of the holes in question. When the energy expended in any hole on the blast pattern has less than two Horizontal Relief Planes or faces (referred to moving forward here as “HRPs”) available to it at the moment of firing, a higher percentage of the available energy is directed vertically. In the analysis of recorded videos by the author, one will note the fact that stemming ejection/flyrock is observed to a much greater degree from the center of almost all patterns when they are timed to “pull out of the middle” (“box cut" timed patterns). This is because the first hole to fire in each row has only one Horizontal Relief Plane, which significantly decreases horizontal avenue for energy release for these holes. This of course results in an increase in the amount of energy expended vertically. This paper proposes a novel methodology to modify the stemming to better use the explosives energy of each hole, while controlling side effects such as flyrock and airblast.

Feb 6, 2023

By David La Rosa, Matthew Craft, Lee Julian

Rules of thumb are ubiquitous in blasting. Typically presented as ratios, they assist with the initial assumptions of blast design and provide guidance for best practice. Examples include the blast hole diameter as a function of bench height, and stemming length as a function of hole diameter. The most common rules of thumb were developed in mid-20th century and it is important for a blaster to know if the rules of thumb are still reliable.

Feb 6, 2023

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 R. Jacob

Mining has been around for a long time, and new deposits are being discovered continually but are becoming more complex for processing and typically sulfide in nature. Most of the large easy deposits with simplified and cheaper to process oxide material have been mined or the deposits are locked up with legal or social issues and may never be mined. It is common to see the mines today being evaluated to mine have little in oxides and have a sulfide component to the deposit. This creates a problem with explosives being selected for the mine because ANFO could cause a reactive ground issue. When evaluating the cost component of mining for future mines, ANFO is the go-to selected bulk explosive because of the cost and effectiveness. More work needs to be done by projects evaluating costs by properly testing the ground and water conditions to match the correct bulk explosive for the ground conditions of the mine. This will prevent a possible safety hazard and the best result for the mine.

Feb 6, 2023

By Jorge Cárdenas, Gustavo Huerta, Regina Rocha Oriundo, Miguel Angel Humpire, Johan Salas Flores

Currently a critical activity for slopes stability and safety in mining is pre-split blasting to reduce damage from trim blast. Most common explosive used are based on packaged explosives, with 1 ½ in diameter cartridges initiated by detonating cord. Traditional loading process requires a significant amount of trained personnel, which in our application context could take up to 20 blasters. When pre-split blast is scheduled, it usually reduces the availability of the blasters on the total loading services at site which are also demanded to have production blasting ready at same 12-hour shift daylight time.

Feb 6, 2023

By Jorge Blázquez, Pablo Ravanal, Paulo Couceiro, Juan Navarro

Blasting performance is influenced by rock mass properties and blast design parameters. From them, the rock is the only variable that cannot be modified, but it can be measured, so that, blast design variables can be adapted to optimize the results. A new methodology to assess rock mass quality from drill-monitoring data from both autonomous and manual rotary drilling modes is described to guide blasting in open pit operations. For that, a thorough normalization process has been developed to minimize external influences induced in the data by the rig system for autonomous mode and by the operator intervention for manual mode. Principal component analysis has been used to combine MWD information. Two rock description indexes are derived directly from Measurement While Drilling (MWD) data collected. The first index is a Structural factor that classifies the rock mass condition in three classes (massive, fractured and heavily fractured). The second index is a Strength factor that classifies the rock according to the strength properties. Both indexes have been combined to obtain an overall drilling rock factor along the hole. This has been named by the authors as the X-Rock model.

Feb 6, 2023

By D. Rudenko, C. T. Aimone-Martin, J. K. Ratliff, I. G. Wong, J. Aiken, R. E. Burnham, T. A. Davidsavor

A small quarry blast was conducted with a maximum of 90 pounds per delay and shortly afterwards, area residents sensed ground motion and building shaking indicative of an earthquake. In addition, seismometers up to 500 miles (800 km) away recorded a magnitude 2.8 earthquake located in the area. Positioned in a seismically inactive area, southern Minnesota is not known for earthquakes. The earthquake was originally described by the USGS to be a surface blast at the quarry. Analysis showed that the earthquake occurred shortly (approximately seven seconds) after the quarry blast some distance away and well below the surface. This paper describes the evaluation of the “seismic events” including the blast, the following earthquake, initial governmental response, and provides the framework for assessing the relationship between the blast and the earthquake. The paper also discusses management of large volume claims from a complex event and presents a claims management strategy with best practices.

Feb 6, 2023

By Matthew Hirsch, Jason Connot, Nathan Rouse, Srivatsan Jayaraman, Akash Adhikari, Brent Meins, Purushotham Tukkaraja

The Deep Underground Neutrino Experiment (DUNE) is a world-class particle physics research project currently being constructed 4,850 ft, 1,478 m underground at the Sanford Underground Research Facility (SURF), former site of the historic Homestake Gold Mine in Lead, SD. Construction for the project involves drill and blast excavation of 800,000 tons of rock to house neutrino detecting cryostats adjacent to on-going particle research and sensitive lab areas. To protect nearby labs during the planned 4 years of blasting operations, project specs required installation of six steel, heavily reinforced blast doors designed to withstand 20 psi blast loads. This research aimed to quantify the pressure reduction across the blast doors and more accurately model underground blast wave propagation. 827 blasts to date have been monitored at eight locations on the 4850 level of SURF with some locations behind blast doors and some in front. Additionally, pressure measurements directly in front of and behind one blast door were taken during 94 blasts.

Feb 6, 2023

By Armin Iravani, Changping Yi, Matthias Wimmer, Daniel Johansson, Santiago Gómez, Håkan Schunnesson

Sublevel caving (SLC) is a mass mining method based upon the utilization of gravity flow of blasted ore and caved waste rock. Drilling and blasting are the initial and the major impact on primary fragmentation and later material flow characteristics. The heterogeneity of rock mass has a great impact on materials’ mechanical properties and plays a significant role in rock fragmentation by blasting. In this work, a numerical model for sublevel caving based on 3D Voronoi tessellations was developed to section rock mass into arbitrarily shaped regions for modelling the heterogeneous rock mass. A coupled finite element and discrete element method was employed to investigate both the fragmentation due to blasting and the gravity flow of ore in a heterogeneous orebody. In the coupled model, the caved waste rock was modelled with loose discrete particles while the orebody to be blasted was simulated with bonded particles. The detonation of explosives was described with a particle blast method and a finite element model was used to model the remaining orebody. The results indicated that the fragmentation at the upper part of the ring is coarse while it is fine at the lower part of the ring. The heterogeneity of rock mass induced some boulders after blasting.

Feb 6, 2023

By Roland Alford

The ballistic pendulum is a well-established piece of test equipment originally developed for estimating the velocity of bullets and projectiles. When trying to understand the effects of different tamping methods on explosive performance, the ballistic pendulum is an excellent tool allowing calculation of explosive charge impulse. Most ballistic pendula for this application are limited to narrow impulse ranges as the pendulum mass determines the angle of swing; and a mass capable of being moved by a small charge would be far too small for a larger charge. This paper describes a modular design (the Alford Modular Ballistic Pendulum) which overcomes this problem.

Feb 6, 2023

By Simón Díaz‑Quezada, Ernesto Arancibia, HUMBERTO ESTAY, Tomás Vargas

In situ leaching (ISL) is an attractive technique that enables copper recovery from copper oxide ores that are either low-grade or located at depths too great to be economically exploited through conventional methods. At present, in situ leaching (ISL) has been applied to intact copper oxide ores, in particular, those which (i) present a good natural permeability and (ii) do not require preconditioning. Many copper oxide ores present low natural permeability. These are located above the water table and need preconditioning for the ISL application. The present work shows an economic assessment of the application of ISL to this type of copper ores. The preconditioning technique considered here involves the application of partial mining by sublevel stoping by removing a small fraction of the ore. This technique results in forming an ore bed with good permeability and good solution collection at the stope base. The economic assessment of this approach suggests that it can be implemented with positive net present values to copper oxide ores located at depths in the 100–300 m range, with copper grades above 0.4%. The maximum acid consumption values are below 52.5 kg/t, with blasting procedures designed to produce an ore bed with an average particle size below 6″. The breakdown of operational costs indicates that the mining cost is still very high, accounting for up to 60% of the total operating costs. Therefore, optimizing mining procedures is still necessary for improving the economic outlook of this approach and thus expanding the application field of ISL.

Feb 4, 2023

By Manoj Khandelwal, Jian Zhou, Yingui Qiu, Peixi Yang, Pingan Peng

Rockburst prediction is crucial in deep hard rock mines and tunnels to make safer working conditions. Due to the complex interaction of many factors involved in rockburst prediction, such as multi-variable and multi-interference factors, three hybrid support vector machine (SVM) models optimized by particle swarm optimization (PSO), Harris hawk optimization (HHO), and moth flame optimization (MFO) are proposed to predict rockburst hazard level (RHL). The RHL is determined according to four kinds of microseismic characteristic parameters including angular frequency ratio, total energy, apparent stress, and convexity radius. Then, six types of microseismic characteristic parameters are taken as input variables in 343 sets of data, including angular frequency ratio and total energy, etc.. And the RHL is taken as the output target of rockburst prediction. The classification performance of PSO-SVM, HHO-SVM, and MFO-SVM hybrid models is evaluated by accuracy (ACC), precision (PRE), and kappa coefficient. Findings reveal that the MFO-SVM model performs best in terms of accuracy, with ACC, PRE, and kappa coefficients reaching 0.9559, 0.9063, and 0.9094 respectively, while PSO-SVM and HHO-SVM have similar performances. However, the PSO-SVM, HHO-SVM, and MFO-SVM all perform better than the unoptimized SVM model. This confirms that the three optimization algorithms significantly enhance the rockburst prediction capacity of the SVM model to help mine practitioners apply machine learning methods to rockburst prediction problems appropriately.

Feb 3, 2023

By Anastasia Xenaki, Edmundo Laporte, Antonio Nieto, Jesus Castillo Gomez, Oscar Velasquez

It is particularly challenging for the mining industry to create and implement an efficient and adaptable mining innovation model to secure the continuous improvement of processes and products via technology. Human resource departments must play a vital role in shifting the mining culture, enabling these new classes of digitally skilled professionals to manage the mining operations of the future. This paper proposes the implementation of a concept based on the 5S mining innovation model ((a) Nieto, 2019), in a coal mining project in Central Asia, Mongolia. Practical and empirical evidence suggests that the model could serve as a roadmap to developing technologies and methods for the mines of the future.

Feb 1, 2023

By W. G. Pariseau

Joints may be taken into account when using numerical modeling as an aid to mine design by embedding joints in the model. When using the popular finite element method, say UT3PC, a pre-analysis step is necessary, Step 0. This step is for the computation of equivalent properties of a representative elementary volume of jointed rock (REV) in the model. This Step 0 is taken before Steps 1, 2 and 3 for specification of a rock properties file, generation of the mesh, and model analysis are taken. A brief explanation of equivalent properties and several examples aid in explaining the details of Step 0. Focus is on procedures, input files, and output to show ease of computation. Theoretical details are relegated to references (e.g. Pariseau 2022). Comparisons of safety factor distributions about example mine excavations with direct scaling from mine observations then offer some insights concerning equivalent properties, especially strengths.

Feb 1, 2023

By U. Schoepf

Economic and at the same time environmentally acceptable mining of small vertical ore bodies and veins to great depths has always been a challenge for miners. The Bauer cutter system, widely used in civil engineering, has been further developed for applications in exploration and mining, to a sustainable system for selective mining with a focus on small vertical ore bodies and veins, as well as residual ore in open pit operations. Current situation of conventional mining of small ore bodies and vertical veins Small ore bodies and vertical or near-vertical ore veins often pose a challenge to the mining industry. The relatively small size of the ore deposit over great depths or lengths, with only limited exposure to the surface makes economical mining difficult. Open pit mining of such ore bodies must either be terminated early because of the high stripping ratio and the enormous environmental impact or is unprofitable from the very beginning. The required massive stripping of waste rock leads to high material hauling times and costs, intensive roadway and bench construction and maintenance, possible safety hazards due to heavy vehicle movement, pit wall stability risks, intensive surface water management and massive waste dump requirements. In addition, it can be assumed that increasingly extensive rehabilitation measures will be required in the future after mine closure. Particularly in vertically oriented magmatic and hydrothermal deposits the technical, economic and environmental limits for further pushbacks, to extend the open pit depth, can lead to an early end of mine life even if a significant quantity of residual ore is left behind. Going underground is only a viable option in a limited number of mines with very high ore values and volumes. The high development cost of an underground mine, as well as the higher underground mining costs, often prevent further mining to greater depths.

Feb 1, 2023

By J. B. Offei, K. Awuah-Offei

Mining companies registered with the SEC were required to comply with Regulation S-K 1300 for their annual report covering the first fiscal year ending on or after January 1, 2021. Consequently, most mining registrants filed their first S-K 1300 compliant disclosures in 2022. The US Securities & Exchange Commission (SEC), as part of its disclosure review program, has been issuing comment letters in response to these filings. This paper presents an overview of the trends in these comment letters. The authors reviewed comment letters retrieved from the SEC’s EDGAR database based on Standard Industrial Classification (SIC) Codes that cover mining, the content of the comment letter (whether it references S-K 1300 or not), the names of SEC staff listed in the comment letters, and other criteria. The analysis shows the SEC staff's reviews have been comprehensive covering the breadth of S-K 1300 and eliciting compliance with the rule. The staff through their comments are eliciting all the disclosures required by S-K 1300 and are not allowing registrants to substitute disclosures based on other standards for S-K 1300 disclosures. It is important, however, not to over generalize as the comments are based on the particular context.

Feb 1, 2023

By T. A. de Almeida, M. de Paiva Bueno, M. Powell

The mining industry is one of the foundations of modern society, providing not only the raw materials needed to maintain a contemporary lifestyle, but also serving as a basis for the development of future technologies. From the most basic components of an appliance to the materials needed to design an electric car or a space rocket, each raw material has gone through a painstaking procedure of extraction and processing, and ways to make this process more efficient will be of great help to meet an ever-increasing demand for minerals. One of the biggest challenges when extracting mineral resources is to measure the variability of the mineral body prior to processing. Comminution is the most power-demanding stage, and the lack of geometallurgical testing, often for financial reasons, may result in an inefficient operation. The Geopyörä Rock Breakage test was developed with the objective of making mineral variability data more accessible by providing both standard comminution parameters and rock mechanical properties at low cost, and with a modest sample size, allowing a larger number of samples to be tested to reduce uncertainties and assure productivity. The objective of this paper is to present the results of an extensive validation of this new rock breakage method against two of the main tests currently in use, namely the SMC® and Bond ball mill work index tests. More than 100 samples have been tested and the results compared, showing that the new method can accurately estimate the parameters of the traditional tests. This confirms that the new test is a reliable tool for comminution and geometallurgical tests.

Feb 1, 2023

By C. Sunderman, G. Feagan, C. Stazick

Galvanic corrosion between dissimilar materials, such as steel and graphite, leads to safety concerns for many industries, including mining. In this study, researchers from the National Institute for Occupational Safety and Health (NIOSH) analyzed rock samples from two mines in the United States that exhibit electrochemical properties similar to graphite through laboratory measurements to investigate their observed in-situ influence on underground metal support. Uniform corrosion rates of mild steel coupons, inflatable bolt coupons, and friction bolt coupons galvanically coupled to rock samples were obtained using both potentiodynamic polarization and zero resistance ammetry. Increased uniform corrosion rates were witnessed between the coupled rock and steel system, over those of just the steel alone. Surface analysis of the metal samples showed the presence of pitting corrosion, reflective of bolt samples removed from partner mines. Corrosion pitting of ground support structures in contact with graphitic rock in underground mines poses safety concerns for mine workers by increasing the rate of corrosion and decreasing bolt strength over time and will be further investigated for intervention strategies.

Feb 1, 2023