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By Shi Yuan

Molten copper was deoxidized using a one-end-closed yttria-stabilized zirconia (YSZ) tube. A thin layer of porous Ni-Zr02 cermet electrode was deposited on the inner wall of the YSZ tube. The outer surface of the tube was in contact with the melt and the inner surface with a flowing reducing gas. Without applying external EMF, the melt was deoxidized by short-circuiting the melt with the cermet electrode. The deoxidation process was analyzed and the rate controlling steps were identified. These experiments were also conducted at different temperatures to evaluate the effect of temperature on the deoxidation kinetics.

Jan 1, 1994

By Rodolfo V. de la Cruz

The in-situ deformability of a highly jointed basalt rock mass was determined by two distinctly different methods: one, by the NX- borehole jack method where the displacements of opposing curved platens were related to the applied hydraulic pressures, and; two, by the modified Goodman jack method where the tangential strains on the borehole walls were related to the induced tangential stresses. The modulus obtained by the modified Goodman jack method were much higher than those obtained by the NX- borehole jack method. To explain the discrepancy, the influence of fractures and test variables such as depth, orientation, hole number and applied pressure on the calculated modulus of the rock mass were analyzed by factorial analysis and it was found that the orientations and depths of measurement has statistically significant effects. The in-situ deformability values obtained by non-linear regression analysis were also found comparable with other measurements and empirically predicted values for the basalt rock mass.

Jan 1, 1982

By N M. Rana, A Take, N Ghahramani, S McDougall, S G. Evans

A critical issue associated with mining operations has been the stability of tailings impoundments. Some breach events have produced catastrophic tailings flows that have caused significant economic damage, mass casualties and long-lasting environmental impact in the downstream environment. This paper reports independently estimated values of runout distance, inundation area and fahrboschung of 16 tailings flows. The adopted methodology involves the geospatial analysis of satellite and aerial imagery to classify each tailings flow into a primary impact zone (Zone 1: main overland flow) and a secondary impact zone (Zone 2: along-creek diluted flow) to characterise runout. Only Zone 1 runout values are reported herein given the greater significance in relation to downstream impact. The fahrboschung is calculated using elevation data from global 30 m digital elevation models (DEMs) and source literature. The results show that all the selected tailings flows travelled long distances (2.4 km to 98.5 km) and inundated large areas (0.35 km2 to 27.0 km2) over very low fahrboschung values (0.04° to 4.8°). This indicates very high flow mobility that is largely governed by the high water content sourced from interstitial waters and, in many cases, supernatant ponds. Scatter plots display poor correlations owing to the complexity and variability in travel path characteristics (confinement, slope angle and obstructions) and the inherent properties of the flowing mass. The slope angle of the travel path exerts a strong control over the flow velocity which has implications on kinetic energy and downstream geomorphological impact. Mean tailings flow velocities may range from ~6 m/s on near-flat, open terrain to over 30 m/s in relatively steeper, channelised travel paths, indicating that tailings flows fall within the extremely rapid and high mobility spectrum of global mass movements. The presented work forms an inceptive part of the CanBreach tailings project, a major component of which is to develop a comprehensive database of case histories to examine the role of geotechnics, failure modes and downstream terrains in influencing tailings flow behaviour.

Jul 1, 2021

By C. Sun

Due to unfavorable geological condition, excessive deformation of mine drifts occurred in a large underground copper and nickel mine. In searching for a solution, a comprehensive underground monitoring program was implemented and the opening convergence and the surrounding rock deformation were monitored. A large number of field data were collected and thoroughly analyzed. The convergence and deformation as function of time and depth were determined and a rock stability index was proposed. Based on the deformation-time and deformation-depth relations, critical deformation times and locations were identified and defined as characteristic values to be used for mine opening and support designs. The characteristic values are critical in the application of two-step supporting system, and the determination of support parameters. The application of the method developed in this study has demonstrated that this practical approach in support design and installation is effective. With the two-step supporting system, a long-term drift stability can be achieved in the mine.

Jan 1, 1998

By O Joneydi, J Viljoen, R Funnell

Computational Fluid Dynamics (CFD) modelling is a useful tool that can assist engineers in designing effective ventilation systems for the control of airborne dust generated during mining operations. Thistechnology can save time, effort and the costs associated with re-work or the traditional on-site experimental field trials by running desktop 3D simulations of the various proposed scenarios using state-of-the-art CFD analysis tools. Before implementing a dust management system, an understanding of the behaviour of airborne dust particles in the face zone can be achieved, which can improve the confidence in the secondary ventilation and dust management design. Usingadvanced numerical models, suitable dust extraction strategies can be foreseen, and multiple scenarios can be simulated and investigated quickly. As a case study, dry drilling operations in Kimberlite orebodies produce large quantities of fine dust which poses health and safety risks. An effective dust management system is required to achieve acceptable face conditions. A possible practical solution is a ducted exhaust ventilation system with a force fan in the face zone. This paper demonstrates how CFD analysis can be used as a tool to assist the design engineer with validating and optimising the proposed ventilation design by tracking the trajectories of different size dust particles, to determine the best equipment layout and appropriate flow rates which minimises airborne dust.

Oct 12, 2022

By A. Saramak

"The paper focuses on problems of atmospheric pollution by the dusts, produced during the course of crushing and grinding processes, and the main objective of investigative programme is an assessment of emission of particulate pollutants for following crushing devices operated in plant scale: impactors, cone and jaw crushers. All crushers operate in aggregate production plants in Poland. In the first stage of investigations there were determined dust emission levels and supporting characteristics for all crushers under investigation. Then there were introduced indices that allow for comparative analysis in terms of dust emission, for devices with different energy consumptions and comminution ratio. It appeared that crushers with high the overall dust emission do not always achieved unfavorable dust emission per comminution ratio or energy consumption. The introduced indices proved their usefulness, because they helped to carry out a comparative analysis among crushers, operating under different technological conditions. It is also easier to assess environmental impact of individual crushing devices, under analysis. Results of investigations also show that environmental impact of different types of crushers is diverse and it is difficult to compare dust emissions of various types of crushers without taking into account technological aspects (like throughput, comminution ratio, energy consumption, and others) of their operations.INTRODUCTION Mineral processing of raw material is a complex process, involving in general operations of size reductions and separation. Depending on the type of specific raw material, the technological circuit may include operations of comminution and size classification. This is a typical circuit for aggregate production. In ore treatment industry the process in much more complicated and include also a metallurgical treatment of ore concentrate – the final product from processing plant stage.In general, regardless the type of raw material, operations of size reduction are present in each technological circuit of mineral processing. Operations of crushing and grinding are an integral part of processing technology, because they play a crucial role in effective treatment of mineral raw materials (Gawenda 2013). Their duty is to liberate the useful minerals from the gangue in ore treatment industry, or to produce the material with the required particle size in case of aggregate processing. Crushing and grinding operations are of a high negative impact on environment and humans. They consume great amounts of energy, what indirectly contributes to higher emission of carbon dioxide CO2. Apart from energy, crushing and grinding device consume significant amount of steel and other metals and alloys due to high wear of working parts and grinding media. This is also of negative environmental impact due to emissions of additional amounts of CO2 in production of steel and other metals required as spare parts for comminution devices."

Jan 1, 2018

By Ming-yi Zhang, Zhong-nian Yang, Xiao-ming Guan, Quan-wei Liu

"In slurry balanced shield tunneling, how to ensure the safety of construction and to reduce the influence on the environment has arisen wide attention of scholars both at home and abroad. But now it is still in the stage of experience as to the instability mechanism of the slurry shield tunneling excavation and its stability analysis. Based on the large-diameter model tests and FLAC 3D, the effect of the different waterhead (non-water, 0.9m and 1.1m) on stability of excavation face of slurry balanced shield is investigated, and the stability mechanics is proposed. The results show that: waterhead heights play an important role on excavation face instability features of slurry balanced shield in sandy stratum, Regarding the different waterhead heights, the development mode of the excavation face instability features can be divided into non-water mode, lower-waterhead mode and higher-waterhead mode; soil arching is existed in the process of excavation face instability, the settlement of ground lags behind excavation face failure, the soil arching will block or eliminate the effects of ground settlement; excess pore water pressure need to be considered besides earth pressure and hydrostatic pressure when the supporting force is calculated. INTRODUCTION With the development of the society, for the cities all over the world, the exploitation of underground space has become an important measure to solve the problems about population, resources and environment and an important way to heal the city syndrome and implement the sustainable development strategy of city. Constructing shield tunnel with large diameter is the major trend for development of tunnel construction (Yin, 1999). Instability of excavation face caused by relief of shield soil stress is still one problem that needs to be solved (Xiang, 2001). How to reduce the effects of construction on surrounding environment? How to accurately determine the instability of shield excavation face and to effectively and reasonably select the supporting force? These are the crucial problems which need to be solved during shield construction."

Jan 1, 2016

By A. J. Makoka, B. C. Qi

Reliable monitoring of corrosion is vitally important in the combat against corrosion and over the last two decades the interpretation of electrochemical noise has received considerable attention as a means to discriminate between different types of corrosion. To this end, many different analytical methods have been proposed, such as power spectral density analysis and analysis via various other stochastic criteria. However, although many corrosion systems are nonlinear and therefore not readily interpretable by the abovementioned analytical approaches, few studies in the analysis of electrochemical noise to date have exploited advances made in the analysis of nonlinear systems. In this paper, the use of phase space methods to analyze and detect change in corrosion systems via electrochemical noise is considered. In particular, the electrochemical noise data are used to reconstruct trajectories in the so-called phase space of the system and changes in the topology of these trajectories or attractors as represented by correlation dimension curves are consequently interpreted as an indication of change in the dynamics of the system.

Jan 1, 2005

By M. Heger, V. Lund, P. Mongeon, D. Bogunovic, V. Kecojevic

The U.S. coal mining industry consumes a significant amount of energy, primarily diesel fuel and electricity. The continuous global increase in energy demand, high energy prices and environmental issues related to carbon dioxide emission represent a substantial challenge for the mining industry. This paper presents the result of research on development of an integrated data environment system for analysis of energy consumption in a surface coal mine. A case study on an operating surface coal mine is carried out to demonstrate the practical application of the developed system. The research work presented here may be used by mining professionals to help provide the answers to the crucial questions of when, where and how much energy is being used. This developed system represents a framework for efficient management of energy consumption.

Jan 1, 2009

By Cynthia K. Belt

Improved energy efficiency has grown in importance within industry as energy costs have escalated. The analysis of trends and changes to a process is critical in making the best business decision in energy management. Frequently, energy use per day (Kilowatt-Hour or British Thermal Units) is used to track energy efficiency. Sometimes, the somewhat more complex method of energy per processed weight (Kilowatt-Hour per Metric Ton or BTU per Pound) is used to make this evaluation. Yet both methods ignore the effects due to throughput and weather. In this paper, different thermal processes and systems will be evaluated using statistical methods to highlight alternative methods to evaluate energy efficiency. Examples and potential problems will be discussed for both a single process and a collection of processes within a plant or corporation.

Jan 1, 2008

By Jisheng Han

Interaction effect exists when two or more neighboring seams are mined. The mining activity in one seam causes stress redistribution and strata movement in both the roof and floor. When the thickness of interburden between two neighboring seams is small, some hazardous situations like roof cutters, roof falls, floor heave and rib spalling in one seam may be encountered due to the effect of the mining activity in the other seam. An investigation about roof cutters, roof falls and floor heave was conducted in a West Virginia mine to study the interaction of multi-seam mining. The mine is mining the Sewickley Seam, which is about 90 ft above the Pittsburgh Seam which was mined in the 1960's using room and pillar method. The roof falls and other stability anomalies of entries observed underground in the Sewickley Seam were found closely related to the location of barrier pillars and gas well pillars left in the Pittsburgh Seam. Then numerical modeling was carried out to check the interaction between these two seams of mining. It was found through the modeling results that in the areas where pillaring operation was conducted in the Pittsburgh Seam, the stress concentrated less in the Sewickley Seam while near the edge of the gas well pillars and barrier pillars, high stress concentration was observed. It was concluded that under the geological conditions of the study mine, the entries stability would be affected by the lower seam mining activity, especially above or around the edges of pillars.

Jan 1, 2005

By Ali Kahriman, Abdulkadir Karadogan, Alper Celtikci, Ahmet Varol, Ertugrul Kaya, Turgay Ozat

This paper presents analysis of environmental effects induced by cautious blasting during the construction of the Istanbul Subway 4 Levent - Ayazaga Darulsafaka Metro Tunnel Project carried out by the contractor, located at Northern Istanbul in Turkey. Within the scope of the study, for the prediction of the peak particle velocity and to determine the slope of the attenuation curves together with the maximum charge per delay for the S6-7-8 shafts of this tunnel route, ground vibration components were measured carefully by using five vibration monitors during the construction of the tunnels which required blasting. The particle velocities and frequency values of all blast events are evaluated according to the United States Bureau of Mines (USBM) and German DIN 4150 Norms in order to predict, and compare the influence grades to the neighboring buildings, and structures. Also, data pairs of scaled distance and peak particle velocity obtained from 107 records belong to 51 shots were analyzed statistically. Empirical relationships with correlation at the 95 % confidence interval were established for these tunnel excavations and suggested for the test sites in order to estimate particle velocity of the ground vibrations. As a result of the studies, some practical charts are created in order to minimize the psychological effects of the shots, and simplify the authorities of shots’ job. And last but not least, make sure that the shots will be done in a controlled way.

Jan 1, 2011

By B. A. Slaker, T. Miller, M. M. Murphy

An underground limestone mine in eastern Ohio was experiencing significant floor heave and roof falls, attributed to high horizontal stresses. Areas of the mine showing floor heave were monitored with roof-to-floor extensometers and photogrammetry surveys to determine the rate and magnitude of heave. Extensometer data were recorded hourly at four locations across adjacent entries while photogrammetry surveys of the floor were performed at the same locations every two to five weeks. A final survey was performed using an I-Site 8200 laser scanner. Following instrumentation, floor heave up to 10.1 cm (4 in.) was measured by the extensometers, photogrammetric reconstructions and laser scanner over a six-month period. The extensometers were biased by the location where they were placed, failing to consistently capture the location and extent of floor heave and cracking. The photogrammetry surveys were not precise enough to capture small magnitude movements. Mining in the area was halted and within several months the floor movement and incidence of roof falls were significantly lessened.

Jan 1, 2018

By K. Heasley, A. Yassien, A. Khair, S. Peng

There are three major components of a fully grouted roof bolt which primarily determine its ability to develop and sustain load: the steel rebar, the resin annulus, and the rock/grout interface. The untensioned, fully grouted roof bolt is subjected to loading only when the surrounding rock deforms. Vertical rock deformation is generally a result of strata sagging and bedding plane separation, whereas horizontal deformation is typically a result of bedding plane sliding. These two types of deformation create different types of internal loads with-in the roof bolt, tensile stress for vertical rock deformations and shear stress for horizontal rock deformations. Also, as a result of the mutual load transfer between the rock and bolt, shear stress will be developed along the grout/rock interface. According to the exact bolt loading conditions, different failure modes may occur: bolt axial failure, bolt shear failure, and shear failure along the grout/rock interface. Understanding these possible failure modes and their root causes is the key to eliminating roof failures in underground mines employing fully grouted resin bolts. Using ABAQUS 5.8, a finite element model was developed to simulate the components of the fully grouted bolt and its interaction with the surrounding roof strata. Several models were conducted to investigate how load transfer occurs between the rock and the bolt under different geological and mining conditions. The effects of bed-ding plane location and properties, and strata sequence on bolt stability were studied. Also, the effects of hole roughness on bolt stability were discussed. Bolt axial failure was not observed within the range of the studied parameters; however, a combination of high overburden depth, a bedding plane located at 2 to 3 ft from the roofline or a low coefficient of friction along the bedding plane caused strata sliding and shears failure in the bolt. Also, in the case of a weak immediate roof, the shear stress at the grout/rock interface could exceed its ultimate capacity lead to slippage.

Jan 1, 2004

By Mahiyar Nasarwanji, Jonathan K. Hrica, Jonisha P. Pollard, Lydia M. Kocher, Brianna M. Eiter

Within the metal/nonmetal mining sector, fall-related incidents account for a large proportion of fatal and nonfatal injuries that occur in mining in the United States. However, the events and contributing factors leading up to these incidents have not been fully investigated. To help provide a clearer picture of these factors, an analysis of imminent danger orders issued by the U.S. Mine Safety and Health Administration (MSHA) from 2010 through 2017 at both surface and underground metal/nonmetal mine sites revealed that most orders are associated with fall risks. Of these cases, 84 percent involved the workers not using fall protection, fall protection not being provided or the improper use of fall protection. Fall risks for workers most frequently occurred when standing on mobile equipment, performing maintenance and repairs on plant equipment or working near highwalls. In most cases, a single, basic, corrective action — such as using fall protection — would have allowed workers to perform the task safely. Overall, these findings suggest that a systematic approach is needed to identify, eliminate and prevent imminent danger situations. Furthermore, to protect mineworkers from falls from height, frequently performed tasks requiring fall protection should be redesigned to eliminate the reliance on personal fall protection.

By Mahiyar Nasarwanji, Jonathan K. Hrica, Jonisha P. Pollard, Lydia M. Kocher, Brianna M. Eiter

Within the metal/nonmetal mining sector, fall-related incidents account for a large proportion of fatal and non-fatal injuries. However, the events and contributing factors leading up to these incidents have not been fully investigated. To help provide a clearer picture of these factors, an analysis of imminent danger orders issued by the Mine Safety and Health Administration (MSHA) between 2010 and 2017 at both surface and underground metal/nonmetal mine sites revealed that most orders are associated with fall risks. Of these cases, 84% involved the workers not using fall protection, fall protection not being provided, or the improper use of fall protection. Fall risks for workers most frequently occurred when standing on mobile equipment, performing maintenance and repairs on plant equipment, or working near highwalls. In most cases, a single, basic, corrective action (e.g., using fall protection) would have allowed workers to perform the task safely. Overall, these findings suggest that a systematic approach is needed to identify, eliminate, and prevent imminent danger situations. Furthermore, to protect mineworkers from falls from height, frequently performed tasks requiring fall protection should be redesigned to eliminate the reliance on personal fall protection.

By Mahiyar Nasarwanji, Jonathan K. Hrica, Jonisha P. Pollard, Lydia M. Kocher, Brianna M. Eiter

Within the metal/nonmetal mining sector, fall-related incidents account for a large proportion of fatal and non-fatal injuries. However, the events and contributing factors leading up to these incidents have not been fully investigated. To help provide a clearer picture of these factors, an analysis of imminent danger orders issued by the Mine Safety and Health Administration (MSHA) between 2010 and 2017 at both surface and underground metal/nonmetal mine sites revealed that most orders are associated with fall risks. Of these cases, 84% involved the workers not using fall protection, fall protection not being provided, or the improper use of fall protection. Fall risks for workers most frequently occurred when standing on mobile equipment, performing maintenance and repairs on plant equipment, or working near highwalls. In most cases, a single, basic, corrective action (e.g., using fall protection) would have allowed workers to perform the task safely. Overall, these findings suggest that a systematic approach is needed to identify, eliminate, and prevent imminent danger situations. Furthermore, to protect mineworkers from falls from height, frequently performed tasks requiring fall protection should be redesigned to eliminate the reliance on personal fall protection.

By S. S. Peng

To prevent mine floor heave, the mechanisms of floor heave must be fully understood. Based on the field study, the mechanisms of two types of floor heaves are analyzed in this paper. The mechanical models for the two types of floor heaves are developed. The floor heave can be predicted by the developed mechanical models and the control measures are recommended.

Jan 1, 1995

The Coke Ovens Laboratory at Australian Iron & Steel, Port Kembla has been involved in the analysis of seam gases and mine airs for approximately twenty (20) years. This period has seen many developments and changes in the techniques used to the point when the current techniques are equal to other labora- tories involved in similar analyses. The laboratory has NATA registration for the analysis of mine airs and gases. Apart from routine testing of seam gases, ventilation airs and gases emmitted from coal bore cores a number of projects have been undertaken. These have served a twofold purpose, one to provide information to the customer, generally Collieries Research and Technology and secondly in developing the skills and capabilities of the Coke Ovens Laboratory. This paper discusses the development and services available at the Coke Ovens Laboratory for the analysis of gases and airs from collieries.

Jan 1, 1983

By David F. Gearhart, Mark Van Dyke, Heather Dougherty, Ted Klemetti, Gabriel S. Esterhuizen

"Coal mine longwall gateroads are subject to changing loading conditions induced by the advancing longwall face. The ground response and support requirements are closely related to the magnitude and orientation of the stress changes, as well as the local geology. This paper presents the monitoring results of gateroad response and support performance at two longwall mines at a 600-ft and 2,000-ft depth of cover. At the first mine, a three-entry gateroad layout was used. The second mine used a four-entry, yield-abutment-yield gateroad pillar system. Local ground deformation and support response were monitored at both sites. The monitoring period started during the development stage and continued during first panel retreat and up to second panel retreat. The two data sets were used to compare the response of the entries in two very different geotechnical settings and different gateroad layouts. The monitoring results were used to validate numerical models that simulate the loading conditions and entry response for these widely differing conditions. The validated models were used to compare the load path and ground response at the two mines. This paper demonstrates the potential for numerical models to assist mine engineers in optimizing longwall layouts and gateroad support systems.INTRODUCTIONThe need for roof stability in coal mine longwall gateroads places significant demands on the gateroad ground support system. The variable loading conditions associated with the approaching longwall face can cause excessive ground deformations that need to be accommodated by the support system. In coal mines in the United States several different types of supports are used to maintain the stability of gateroads. The supports may include grouted roof bolts, cable bolts, and roof trusses as intrinsic support. Standing supports include timber cribs, engineered timber props, and various types of cement-based cribs. The intensity of support is governed by the expected geologic conditions and the expected stress changes that will occur during longwall mining. At present, the design of ground support for gateroads is largely based on local experience. In-mine trials are usually conducted when new support technologies become available or ground conditions dictate a change in the support system. The research reported in this paper has the objective to assist mining engineers in evaluating alternative gateroad supports and to design suitable support systems for the local ground conditions."

Jan 1, 2018