Search Documents

By T. Marin, J. E. Seccatore, M. Cardu

The most energy-intensive process in the mining industry is particle size reduction – comminution. The first phase of this process is blasting to fragment the rock from the initial Boussinesq’s halfspace size. Scientific literature demonstrates that the output of a blast in terms of fragment size distribution can be manipulated by varying the specific charge (powder factor) and charge distribution. This study focuses on the influence of blasting on the internal resistance of the blasted fragments; in particular the influence of the spatial distribution of charges. Small-scale blasts were performed on 14 marble blocks using different powder factors and charge distributions. Three control blocks were fragmented by mechanical means for comparison. The results show the correlations between charge distributions and the specific energy of mechanical comminution. Opportunities for adjusting charge diameter and distribution in opencast blasts to improve the performancet of comminution circuits are discussed.

Aug 8, 2024

By AK Chakraborty, AK Raina

Burden of drill hole is third most sensitive parameter effecting the ground vibration in blasting apart from maximum charge per delay and distance. Various types of burdens can be seen in practical bench blasting situations. Burden can be expressed as drilled burden and initiation burden. Drill holes may have various front row burdens (toe burden), which may be different from the designed burden. In order to ascertain the impact of front row burden as well as the initiation burden on intensity of ground vibration and air overpressure experiments were conducted in sandstone overburden benches of an opencast coal mine and limestone quarry. Blast trials were carried out in cognisance of both drill and initiation burden while keeping all other parameters constant. Effect of front row burden was also extensively studied by keeping almost all other parameters constant. The results of the study reveal that there is substantial influence of front row burden on the vibration and air overpressure. The statistical analysis of vibration and air overpressure data with drilled burden and initiation burden gives significant evidence that the level of peak particle velocity of vibration (Vmax)) is reduced by reducing effective burden with modification of initiation. Data analysis carried out for air overpressure versus initiation burden shows that reducing effective burden with modification of initiation results in increasing the level of P. The study reveals a qualitative assessment of the influence of burden on the blast induced vibration and air overpressure. The study also recommends to modify the initiation pattern to reduce the effective burden in order to reduce the vibration, without disturbing the fragmentation.

Jan 1, 2004

By Gilbert Soler

PRODUCERS of alloy steels recognize the importance of chemical composition in rela-tion to the hot-working properties and the typical surface defects found in their prod-uct. Each analysis of steel has its own peculiar characteristics. Under conditions of standard mill practice each analysis is susceptible to certain types of defects. Mill practice must be varied to obtain the best combination of surface and internal quality in the product. Chemical composition influences the cast structure and crystallization character-istics of the ingot. It also determines the rate of heating and cooling, the plastic hot-working range, and the phase structure of the steel at various temperatures as well as the tendency toward scale formation and decarburization, This paper endeavors to emphasize the manner in which chemical composition affects the various properties of steel, and to indicate the relative impor-tance of these factors in relation to the hot-working properties and surface charac-teristics of killed steel. The influence of chemical composition may be outlined as follows: I. Effect on the cast structure of steel, including: A. State of deoxidation, and type of inclusions. B. Gas content of steel. C. Freezing point and melting point of steel.

Jan 1, 1940

By D. D. Schlepp

There is a continuing debate about the influence of circulating load and classifier efficiency on the capacity of the circuit. Specifically, the effects of preferential classification, bypassed fines, and the sharpness of classification will be examined. Horizontal cyclones have also proven to be very successful in a number of operations but their impact on the circuit capacity has not been clearly defined.

Jan 1, 1990

By S Love, M Anderson, M Boland

"The high rate of failure of new mine developments to meet feasibility study expectations has been the subject of many fine technical papers. Yet failure rates remain stubbornly high.Similarly, the common occurrence of disastrous acquisitions resulting from failed due diligence on projects is well known. Yet such mistakes continue to be made.The authors argue that project and due diligence failure are caused at least partly by cognitive biases. These biases pervade decision-making throughout project evaluations.A wider understanding of these biases (and their effects) is necessary. Only then can mitigating actions be taken.The opportunity for this wider understanding exists. A number of best-selling books have been published on the topic in recent years. With wider understanding of key concepts and terms, cognitive biases can be recognised and discussed. They can also be challenged and mitigated.The authors believe that these concepts should be entry-level, required knowledge for anyone evaluating, developing, reviewing or financing mining projects.Perhaps the most prevalent biases in project evaluation failure are the ‘over-optimism’ biases. In particular, the planning fallacy and confirmation bias.The anchoring effect is also pervasive. This bias propagates unrealistic assumptions from scoping and prefeasibility studies through to so-called definitive feasibility studies. Unrecognised anchoring biases also undermine the validity of many ‘independent’ due diligence reviews. They are also prevalent in corporate acquisitions.The availability heuristic refers to a mental shortcut that can lead to a number of biases. One of these is the narrative fallacy. The mind constructs coherent narratives and opinions, regardless of the amount and quality of the information that support them. Narrative fallacy commonly occurs in the evaluation of social and political risk. Another is disaster neglect, which is especially common in the failure to assess risks associated with tailings management.This paper outlines the relevance of these biases to mine project evaluations. It also provides examples where the authors have observed their effects.CITATION:Love, S, Boland, M and Anderson, M, 2016. Influence of cognitive biases on project evaluation, in Proceedings Project Evaluation 2016, pp 226–235 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 8, 2016

By W. R. Reed, D. E. Pollock, T. W. Beck, J. A. Organiscak, J. D. Potts

"In underground continuous mining operations, ventilation, water sprays, and machine-mounted flooded bed scrubbers are the primary means of controlling respirable dust exposures at the working face. Changes in mining arrangements, such as, face ventilation configuration, orientation of crosscuts mined in relation to the section ventilation, and equipment operator positioning, can impact the ability of dust controls to reduce occupational respirable dust exposures. This study reports and analyzes dust concentrations measured by the Office of Mine Safety and Health Research for both remote-controlled continuous mining machine operators and haulage operators at ten U.S. underground mines. Results of these respirable dust surveys show that continuous miner exposures varied little based on depth of cut, but are significantly affected by ventilation configuration. Haulage operators experienced elevated concentrations in blowing face ventilation. The type of cut influenced exposures, with elevated exposures observed for both continuous miner operators and haulage operators when working in crosscuts driven into, or counter to, the section airflow. Individual cuts are highlighted to demonstrate instances of minimal and excessive dust exposure attributable to particular mining configurations. These findings form the basis of recommendations for lowering face worker respirable dust exposures when performing a variety of continuous mining cuts.INTRODUCTION Underground continuous coal mining operations may encounter a wide range of conditions and arrangements during production and development activities. These activities typically produce respirable coal mine dust, putting operators of continuous mining machines and coal haulers at risk for elevated exposures. In order to comply with federal regulations limiting respirable dust exposures for the duration of a working shift, mine operators typically implement ventilation, water sprays, and machine-mounted flooded-bed dust collectors (scrubbers) to dilute and control mine dusts during coal cutting. Nevertheless, changes in operational conditions can limit the ability of these controls to effectively reduce dust exposures. Some examples of conditions that can change during the course of mining include face ventilation configuration, orientation of crosscuts mined in relation to the section ventilation, and operator positioning. Because these arrangements are largely under the control of mine operators, any insight into associated exposures may inform future plans and behaviors, reducing occupational exposures to respirable dust. The objective of this OMSHR study is to evaluate respirable dust exposures associated with a range of continuous mining arrangements by comparing occupational dust concentrations measured during a series of field surveys. These comparisons consider face ventilation configurations, depths of cut, and crosscut mining practices."

Jan 1, 2015

By W. R. Reed, D. E. Pollock, T. W. Beck, J. A. Organiscak, J. D. Potts

In underground continuous mining operations, ventilation, water sprays and machine-mounted flooded-bed scrubbers are the primary means of controlling respirable dust exposures at the working face. Changes in mining arrangements — such as face ventilation configuration, orientation of crosscuts mined in relation to the section ventilation and equipment operator positioning — can have impacts on the ability of dust controls to reduce occupational respirable dust exposures. This study reports and analyzes dust concentrations measured by the Pittsburgh Mining Research Division for remotecontrolled continuous mining machine operators as well as haulage operators at 10 U.S. underground mines. The results of these respirable dust surveys show that continuous miner exposures varied little with depth of cut but are significantly higher with exhaust ventilation. Haulage operators experienced elevated concentrations with blowing face ventilation. Elevated dust concentrations were observed for both continuous miner operators and haulage operators when working in crosscuts driven into or counter to the section airflow. Individual cuts are highlighted to demonstrate instances of minimal and excessive dust exposures attributable to particular mining configurations. These findings form the basis for recommendations for lowering face worker respirable dust exposures.

Jan 1, 2016

By Peiwei Hu, Min Lu, Tiejun Chen

Based on the analysis of properties of vanadium tailing (VT), the surface modification study was carried out as a polymer filler. The modification effects of the three kinds of coupling agents on VT and the mechanical properties of polypropylene (PP) composites with a modified vanadium tailing (MVT) were compared to determine the suitable surface modification agent and modification processes for VT. The results show that the best one is aluminate coupling agent DL-411. When the content is 1.2 wt% and the temperature was 100 °C, the activity index of modified vanadium tailing (MVT) is 95.53%. FTIR analysis shows that DL-411 has the strongest binding ability on VT. XRD analysis shows that VT has a heterogeneous nucleation on PP to induced b form formation, and DL-411 could enhance this nucleation. So the composites has higher strength and better toughness. When the content of MVT is 10 phr, the tensile strength, impact strength, flexural strength and flexural modulus of the composites are 47.51 MPa, 38.43 kJ/m2, 59.57 and 1654.36 MPa, respectively.

Mar 1, 2018

By Jamal Rostami, Manso Deen Sesay, Sydney Slouka, HUGH MILLER, Anshuman Mohanty, Midhat Sajad, Kun Zhang

The lack of progress in controlling pulmonary diseases such as pneumoconiosis cases in recent years necessitates additional studies on dust generation and the characterization of airborne dust. Studies are underway by a NIOSH-sponsored project to observe the characteristics of the dust generated by pick cutters under various wear levels. This research performed a full-scale linear-cutting-test matrix on eight coal samples with various bit penetrations, spacing, and wear conditions. The specific energy and resulting PSD (particle size distribution) of airborne dust and material left at the cutting surface were measured and analyzed. The dust concentration was determined using the NMAM (NIOSH Manual of Analytical Methods) 0600 method. For fines, the PSD was characterized using Laser Diffraction, measuring percent channel and aerodynamic diameter, while Imagej, a virtual sieving application, was used for larger particles. The results show that for a new bit, as the cutting depth and spacing increase, the specific energy and dust generation decrease. The size and shape of the dust particles have been analyzed, and the observed trends are discussed in this paper.

Feb 1, 2025

By E. Ghali, W. Zhang, G. Gabra, N. Sorour, G. Houlachi

The additives polyacrylamide, 1-Butyl-3-methylimidazolium chloride, Tetra-butylammonium bromide, Benzalkonium chloride and chitin are evaluated during zinc electrolysis from synthetic acidic sulphate electrolyte containing Mn2+ ions, in absence and in presence of 0.0055 mg dm-3 of Sb3+ ions. Galvanostatic polarization tests for 2 hours at 50 mA cm-2 and 38oC were carried out to determine the cathodic and anodic potentials, and current efficiency of the deposited zinc. Potentiodynamic polarization and cyclic voltammetry tests have also been employed to study the electrochemical behavior of each additive on the zinc deposit on aluminum electrode. Results showed that, in presence of Sb3+, adding 1 to 3 mg of 1-Butyl-3-methylimidazolium chloride increases the cell voltage by ˜0-7 mV. Current efficiency is increased by ˜4.90-6.40%; power consumption is reduced by ˜147-173 kWh t-1 by adding 1-3 mg, respectively. However, in absence of Sb3+, cell voltage is decreased by ˜7-28 mV, current efficiency is increased by ˜0.70-1.50%; power consumption is reduced by ˜41-47 kWh t-1 by adding 1-3 mg. The effect of the other additives on cell voltage, current efficiency, lead content and morphology of zinc deposit has also been examined. Surface morphology and crystallographic orientation of the deposit was studied using scanning electron microscopic (SEM) and X-ray diffraction (XRD), respectively. The content of lead in the deposit has also been measured using inductively coupled plasma spectroscopy (ICP).

Jan 1, 2015

By Yungang Li, Hui Li, Ramana G. Reddy, Jinglong Liang

High solid corrosion protective coatings were prepared by the dust of the converter with an average particle size of 59.33 μm. The effect of different amount of benzyl alcohol diluent on the performance of high solid anti-corrosion coatings was studied. With the increase of the amount of diluent, the viscosity of high solid anti-corrosion coatings reducing, the film apparent bubble content decreasing, and film resistant to salt water corrosion ability decreased, while acid corrosion capacity enhancement. When the dosage of diluents is 15%, the coating film is more resistant to acid corrosion.

Mar 1, 2017

By Charles E. Glass

A steadily growing body of evidence indicates that earthquake ground motions can cause failure of rock slopes that are otherwise stable under static loading conditions. As a result, the economic optimum working slope angle is reduced when earthquake shaking is considered in surface mine design, especially in regions of high seismicity. When designing surface mine slopes to withstand seismic motion it is as important to consider the probability of experiencing various levels of ground shaking as it is to consider the characteristics of the ground motion. For most slope designs, simple probabilistic techniques such as extreme value or maximum likelihood techniques are appropriate. These techniques, however, should be applied in such a way that a probability value is assigned to characteristic ground motion parameters at the mine rather than to nearby earthquake magnitudes. Several techniques have been developed to analyze rock slopes subjected to dynamic loads. Most of these techniques do not adequately account for the ground motion parameters of concern. The best technique appears to be one that utilizes actual earthquake time histories. A simple technique that calculates block displacement for any input accelerogram, using a linear acceleration approximation between time steps, has been developed that accurately accounts for rock block response. Results using this technique indicate that the following factors are important for assessing rock slope stability in earthquake regions:

Jan 1, 1983

By Joshua Hoffman, William Chad Wedding, Braden Lusk

The University of Kentucky employs an explosively driven shock tube in the course of experimentation. A good deal of the work completed relates to the verification of blast mitigation products and strategies. The work is dependent upon reliably reproducing specific pressure time histories called out by the test in question. The facilities are located in the workings of an underground limestone quarry in Georgetown Kentucky. As such, the temperature maintains fairly consistent 60°F (15.6°C), making it a comfortable work environment year round. Unfortunately, the relative humidity follows the prevailing weather conditions allowing a wide variation, especially between the winter and summer seasons. A study was undertaken to gauge the influence of relative humidity on shock wave generation, including the positive and negative phases of the wave.

Jan 1, 2011

By W. G. Miller, J. D. Scott, D. C. Sego

ABSTRACT The influence of using different extraction processes (caustic versus non-caustic) on thethixotropic strength of oil sands fine tailings is examined, as is the influence of adding a coagulant tocaustic fine tailings. The thixotropic strength of fine tailings at large void ratios manifests itself as a bonding or gel strength that has been widely noted both in the laboratory and in the field. This gel strength has a significant influence on preventing the initial consolidation or settlement of fine tailings. Differences between the fine tailings’ thixotropic strength development are explained based on their physical and chemical characteristics.

Jan 1, 2010

By A. Bakalarz, M. Duchnowska

"The copper sulfide ore from the Legnica-Glogow Copper Basin in Poland, which is processed by KGHM Polska Miedz S.A., consists of three lithological fractions: dolomitic, sandstone and shale. The copper ore, depending on the mining area, contains all fractions in different ratios. The lithological fractions differ in the particle-size distributions of their useful minerals. In the dolomitic part of the ore, most of the metal sulfide particles are 50-200 microns in size, while those in the sandstone and carbonaceous shale are 30-200 and 5-40 microns in size, respectively. This complex composition results in different mineralization, physicochemical properties and, in particular, upgrading selectivity. Due to the specific nature of the examined copper ore, two of the crucial parameters determining the beneficiation efficiency are size and liberation of sulfide particles. We analyzed the influence of grain size of feed on scavenging selectivity in one of the KGHM flotation plants and performed evaluation and analysis of the upgrading results of industrial beneficiation of the ore, containing mostly dolomite and shale. The upgrading efficiency was estimated using a selectivity indicator obtained by means of the Fuerstenau upgrading curve, which was then correlated with the particle-size distribution of the flotation feed.IntroductionFroth flotation is used extensively in commercial ore treatment flotation plants to separate minerals from gangue and to separate minerals from each other. The floatability of ores and their benefication selectivity are determined by many factors. One of them is particle size. The effect of particle size on flotation performance has been widely studied by many authors (Gaudin et al., 1931; Trahar, 1976; Trahar and Warren, 1976; Lynch et al., 1981; Pease et al., 2004). Particle size also plays a critical role in the probability of particle collision and attachment to bubbles (Solari and Gochin, 1992; Schulze, 1993), kinetic flotation (Taggart, 1956; Ahmed and Jameson, 1985; Debacher, 2002; Brozek and Mlynarczykowska, 2007; Potulska 2008), collector consumption (Sutherland and Wark, 1955; Vianna et al., 2003) and mechanical entrainment (Lynch et al., 1981; George et al., 2004; Konopacka, 2005). Most of the results have shown that there is an optimum particle size range for a given flotation system and that the simultaneous optimization of the recovery and concentrate grade of these particles in conventional flotation equipment is extremely difficult."

Jan 1, 2015

By Dao-Wu Yang, Ju-Lan Zeng, Li-Xian Sun, Yan Yao

"The hydration heat of the pure cement, the fly ash single-dopped cement, as well as the fly ash and fluorgypsum co-dopped cement were investigated by means of micro-calorimety with an eight-channel micro-calorimeter (TAM Air). The results showed that the hydration heat and the hydration rate could be reduced significantly by fly ash and fluorgypsum. However, the reduction was not proportional to the loading of dopant. The exothermic peak of the fly ash and fluorgypsum co-doped cement was appeared earlier than the fly ash single-doped cement. As the temperature decreased, the hydration heat and the hydration rate of the doped cement were reduced, and the exothermic peak appeared later. The effects of fly ash and fluorgypsum on the compressive strength of cement were also investigated. The results revealed that the early compressive strength of concrete made up of the co-doped cement was largely higher than that of the fly ash single-doped cement. Based on the experiment results obtained in this paper, we could conclude that fluorgypsum is a suitable additive for fly ash-doped cement.IntroductionFly ash and fluorgypsum are industrial waste. In 2008, nearly 400 million tons of fly ash has been produced by coal-burning power plants in China. And it is estimated that this number would exceed 500 million at the year of 2015. Besides, every year the fluoride salt factories in China discharge more than 100 million tons of fluorgypsum. Tremendous of fly ash and fluorgypsum occupy considerable land and contaminate air and water sources [1]. As a result, comprehensive utilization of this two industrial waste has draw great attention from all over the world.Cement is the most-used construction material on earth. But the production of cement consumes huge energy and destroys the environment. This problem might can be partly solved by applying fly ash and fluorgypsum as additive for cement [2-4]. During the last decade, some papers that focused on applying fly ash and fluorgypsum as additive for cement have been published [5, 6]. However, to the best of our knowledge, none of these papers investigated the hydration heat of the fly ash and fluorgypsum co-doped cement.The hydration of cement is an exothermic reaction, which can result in serious problem for mass concrete: The interior of the concrete could reach very high temperature as the hydration proceeded [7-9]. As a result, the great temperature difference between the interior and the outer of the concrete would exist and cause serious thermal stresses. Thus, the concrete would be destroyed by the cracks which in tum are resulted from the thermal stresses [10, 11]. The heat released by the cement hydration and the hydration rate is commonly regulated by adding mixed materials or transferring additive such as fly ash and fluorgypsum [12-14]."

Jan 1, 2011

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 S. A. Jacob

Magnesium sheet is notoriously difficult to form at low temperatures without initiating failure, In the present work cold rolling and annealing conditions are varied to produce samples of AZ3lB sheet with a range of grain sizes. The formability of these samples is investigated using tensile testing and forming limit diagrams (FLD's), The results are discussed in terms of twin types and frequencies.

Jan 1, 2005

By R. J. Durrheim, B. Manzunzu, V. Midzi

Selecting ground motion prediction models (GMPM) is crucial in assessing seismic hazard levels in a specific region. This study investigates the influence of ground motion model (GMM) selection on seismic hazard assessment in Johannesburg, South Africa. Most seismic events affecting Johannesburg are related to mining activities and water ingress into the underground mine voids. The most seismically active regions in South Africa include areas around Klerksdorp, Welkom, and Carletonville. These regions experience a significant number of earthquakes, with mining activities being a major factor contributing to seismic events. Ten ground motion prediction equations were selected from regions of similar tectonics setting and were assessed to see if they correspond to the available local data. Six of these were also compared to the ground motions produced by the earthquake of 14 August 2014, which occurred in the Orkney area, one of the mining areas in South Africa. Sensitivity analyses were also carried out to assess the influence of ground motion prediction equations (GMPE) on the seismic hazard of Johannesburg. The results indicate that the choice of GMPM significantly affects the estimation of seismic hazard levels in Johannesburg. Different GMM can lead to varying ground shaking intensity predictions, impacting risk assessments and engineering design considerations. The findings highlight the importance of carefully selecting appropriate GMM tailored to Johannesburg’s specific geological and tectonic characteristics. Understanding how different models perform in this region is essential for accurate seismic risk mitigation strategies.

Jan 12, 2025

By Jeff R. Reinson

The Diavik Diamond Mine is producing diamonds from two orebodies, the A154 South and A154 North kimberlite pipes, discovered beneath the waters of Lac de Gras. Innovative dike technology with appropriate water collection and treatment systems allowed Diavik to start open pit mining of the ore bodies in 2002. To allow planning, engineering, and implementation of sufficient water handling infrastructure, reasonably accurate estimates of groundwater inflow quality and quantity over the life of mine are required. Prior to mining, a numerical model using the continuum approach was developed for regional and site wide water management. After approximately two years of mining, groundwater inflows to the pit were found to exceed those predicted by the base case hydrogeologic model. The most likely explanation was flow through Dewey?s Fault zone. As this fault was not explicitly accounted for in the model, a detailed hydrogeologic investigation was conducted to evaluate its geometry and hydraulic properties. A multi-disciplined approach was used and involved core logging, fluid logging, geophysical logging, packer testing, a pumping test, and water quality sample collection. The results of the field investigation were used to update the conceptual and numerical models and to develop a Discrete Fracture Network (DFN) model to address small scale problems such as flow into future underground drifts. The updated numerical hydrogeologic models predict that up to 70 per cent of the groundwater inflow to the A154 N/S open pit is through the relatively narrow fractured rock zone associated with Dewey?s Fault. Consistent with the continuum model, the DFN model predicts that inflow to a drift excavated in Dewey?s Fault will be approximately 10 times the inflow to a drift excavated in competent rock. The DFN model provides a better understanding of the distribution of these inflows on a local scale over the length of the drift.

May 1, 2006