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By C. A. Geffen-Fowler

This report, sponsored by the Bureau of Mines, presents the results of an examination of the safety of the Blind Shaft Borer (BSB) shaft sinking system and an alternative modified BSB design concept in comparison to conventional shaft sinking technology. Detailed study of the two systems was also performed to identify and recommend design changes for optimum safety conditions. A comparison of the BSB systems with conventional shaft sinking was made on the basis of relative risk levels. Risk incorporates both the frequency and the potential consequence of accidents. A safety evaluation of the component operations of the two BSB systems was performed using a Failure Modes and Effects Analysis (FMEA) methodology. The results of this analysis show generally that both BSB systems are safer than conventional shaft sinking. The potential risk of conventional shaft sinking operations could be reduced by over 30%, on the average, with the use of the original BSB system, and by an average of about 10% with the modified BSB. Design change recommendations to further improve the safety of these systems include better fire suppression systems, improved man haulage systems and more compact hydraulics. An operational safety manual was also developed for the modified BSB system.

Jan 1, 1981

By B Mohanty, G Yamin

A number of parameters, aside from blast design and pre-existing rock conditions, can change the performance of the explosives system in actual blasting practice. Sympathetic pressures caused by detonation of preceding holes have been identified as a major contributor to explosive system malfunctions, leading to uneven blasting performance. These effects can occur both within a hole or across several holes. These can consist of high transient pressures related to the shock phase of the explosion or the relatively longer or quasi-static pressures associated with the explosion gas expansion phase. This study presents the findings from an on- going investigation on measurement and analysis of these pressures between donor and receptor holes in a granitic outcrop for representative inter-hole distances and borehole conditions, employing single cartridges of emulsion explosive in 45 mm diameter holes. The results, despite wide scatter in the measured values, show the very short duration pressures to range up to 7 MPa and arriving within a few milliseconds after detonation, whereas the much lower amplitude pressures arrive after tens of milliseconds. Both have the potential to seriously affect the performance of an explosives system.

Jan 1, 2005

?Longhole blast hole drilling? techniques are not new to the mining industry. Appropriate mechanization and improvement of the techniques and application has evolved from the industry requirements. Today safety and economics play a larger role in the excavation of ore passes, ventilation passes, and relatively small inclined excavations in the conventional gold and platinum industry. The application of dropraise drilling from the top or from the bottom is discussed investigating the current techniques available, DTH application, advantages and disadvantages, limiting factors, typical layouts and proposals, the drop raising technique and future applications. Similarly, the application of longhole blast hole drilling in tabular and massive orebodies is discussed with emphasis on the DTH application, advantages and disadvantages, limiting factors, typical layouts, the long hole stoping techniques and future applications.

Jan 1, 2003

By J C. Waters

Pseudoclastic hydrothermal alteration textures occur within quenched coherent dykes forming part of a subaqueous dome complex (~4 Ma) onPonza Island, Italy. These textures are similar to those observed in considerably older (~500 Ma) subaqueous volcanic rocks at a number of localities throughout the Mount Read Volcanics in Tasmania and elsewhere in ancient volcanic sequences of this type in Australia. This is significant because the processes of formation, hydrothermal alteration and secondary mineralisation of ancient volcanic sequences may be better understood if we can make comparisons with modern analogues. Observations at Ponza imply that these pseudoclastic alteration features form synvolcanically or immediately after dyke emplacement and lava extrusion. This is compatible with scenarios presented for their formation in ancient sequences in the Mount Read Volcanics, Tasmania.

Jan 1, 1995

By Elaine T. Bowers

The Sunnyside single-entry project pioneered the use of single entries for longwall development in this country. During the 10-year course of the project, an immense amount of information was gathered. Over three miles of entries were observed primarily through instrument groupings placed in strategically located areas or "rooms." Nearly 1,200 instruments were monitored to gain information on the behavior of coal entries during development stages and through the mining of two longwall panels. This was one of the most extensively documented projects undertaken by the Bureau, The data gathered has a great potential for scientific research especially in the area of longwall mining. This Bureau of Mines report presents the ground control data gathered, in the form of computerized plots. Roof-to-floor deformation and load on cribs and roof bolts make up the bulk of the data, which is presented as load or deformation versus time. The plots are organized, generally, by the three main entries involved and, specifically, by the individual areas or rooms in those entries. No major attempt will be made, in this paper, to analyze the data other than to identify its source arid its history.

Jan 1, 1983

By Y. Nakata, K. Nagata

Plasma is partially ionized gas composed of ions, electrons and activated elements at high temperature. Some flying ash from incinerated municipal waste is melted to become glass by a transfer-type arc plasma furnace. As the glass is ionic silicate, when an electric current passes through anode to cathode, ions in molten slag electrochemically react with electron in plasma at the surface of molten slag. In case of molten Na2O-SiO2, sodium ions in the molten slag carry electric current and SiO2are reduced to evaporate as SiO gas by electron in plasma. The cases of Ag+in NaNO3-KNO3molten salt and Fe2+in FeO-SiO2slag were examined. The amount of cathodic reaction is larger than that of anodic reaction and not apparently according to the Faraday?s law on the electrochemical reactions.

Jan 1, 2004

By Brett Campbell

The San Vicente to 2nd Aqueduct Pipeline?Tunnel project is a raw water conveyance tunnel linking the San Vicente Reservoir (SVR) to the 2nd Aqueduct Pipeline via Rancho Penasquitos Pressure Control Facility (RPPCF). This 58,230 lf long tunnel will be 8.5? final ID, and has four points of construction access. The job is classified into 6 Reaches of tunnel, identified by the dominant geology within the reach. This paper will focus on Reach 3, specifically the measures necessary to drill and blast a 550 lineal foot section of granitic rock tunnel immediately in front of an open face digger shield.

Jan 1, 2008

By Micheal Mitariten

The recovery of natural gas (primarily methane) from coalbed deposits is an established and growing source for the U.S and accounts for over 7% of its total production. The gas from on-purpose degassing is often pipeline quality and requires only compression and dehydration before being admitted to the pipeline grid. However, the raw gas is sometimes contaminated with nitrogen (N2) and/or carbon dioxide (CO2) that can make the gas inadmissible to the transportation pipeline. In general, the N2 must be 4% or less and the CO2 should be 2% or less. In treating gas produced from virgin coal bed or from degassing operations where CO2 is present, amine systems are traditionally used for its removal. Engelhard’s Molecular Gate® adsorption system offers an attractive alternative due to its skid-mounted equipment, low pressure and unattended operation, cost and high on-stream reliability. Natural gas can also be sourced from the residual coal, after the coal has been mined. This source can be the GOB or gas remaining in abandoned coal mines. This source is almost universally contaminated, often with a combination of CO2 and N2. If the source is from air intrusion, the source can also be contaminated with O2. In treating CO2 / N2 contaminated feeds, the Molecular Gate adsorption system removes both of the impurities along with a level of O2 within a single processing step. To date, ten Molecular Gate units are underway with three systems having been installed for upgrading gas from abandoned coal mines. The technology consists of specialty adsorbents and advanced PSA processes that are jointly offered as fabricated packaged equipment by Engelhard Corporation and Guild Associates, Inc. Upgrading requirements, project challenges and project arrangements are discussed in this paper.

Jan 1, 2005

By M. Valdebenito, J. Rajala

An OCS Expert control system was implemented by Svedala Cisa at the Minera Maricunga Refugio Crush-Leach Operation near Copiapo, Chile. The purpose of the Expert system was to maximize production through the primary and secondary crushing circuits and help balance crusher usage between each stage to maximize total plant production. Interesting aspects of the control strategies are discussed. Benefits of the control were verified through a randomized On/Off test program. Tonnage increases ranged from 5% to approximately 20% at good confidence intervals. Benefits analysis results are discussed. The crushing plant at Refugio is very remote and is located at approximately 15,500 ft. This poses many challenges. The effect of altitude and remote location on plant operation are discussed.

Jan 1, 2002

Importance of Strain to Fragment Strength in Blasting Induced Pre-Conditioning When a rock is blasted, cracks propagate through the rock causing the rock to fracture. This paper focuses on applying the results from a series of small scale blasting tests were designed to show the effect that varying blast variables such as explosive type and explosive energy have on the resulting strength of the post blast fragments. It was shown that the velocity of detonation of the explosive product affects the reduction of fragment strength. This has important implications for the downstream comminution process. The observations from these tests are then explained with reference to the principles of fracture mechanics. A simple but effective prediction of blast induced preconditioning is shown.

Sep 13, 2010

A comprehensive review of ore pass records, from ten Quebec underground mines, indicated some of the limitations of available design tools to predict the occurrence of ore pass interlocking hang-ups in metal mines. The Distinct Element Method was used to perform a series of numerical experiments in order to investigate the influence of ore pass geometry, rock fragments shape and size distribution on material flow in an ore pass. Guidelines have been developed to help limit the occurrence of interlocking hang-ups in an ore pass. The proposed guidelines were evaluated with respect to field observations. Ein kompletter Bericht der Erzrollezeichnungen, von 10 Quebec unterirdischen Gruben, hat einige der Beschränkungen der vorhandenen Designwerkzeuge angezeigt, um das Auftreten Erzrolle der blockierenhang-ups in den Metallgruben genau vorauszusagen. Eine Reihe numerische Experimente mit der eindeutigen Element-Methode, wurden aufgenommen, um den Einfluss von Erzrollegeometrie, Partikelform nachzuforschen und Felsenkorngrößenverteilungen auf Materialfluss in ein Erz überschreiten. Dieses hat zu die Entwicklung der Richtlinien geführt deren Implementierung das Auftreten der blockierenhang-ups in eine Erzrolle begrenzen sollte. Die vorgeschlagenen Richtlinien wurden in Bezug auf Labor- und Feldbeobachtungen ausgewertet. Une revue de la performance actuelle des cheminées à minerai dans 10 mines souterraines du Québec a indiqué les limites des outils de conception servant à dimensionner les cheminées pour minimiser le nombre d’accrochages par enchevêtrement rocheux. Des séries de modélisations numériques, utilisant la méthode des éléments distincts, ont été réalisées afin d’évaluer l’influence de la géométrie des cheminées, de la forme des fragments rocheux et de la distribution granulométrique sur l’écoulement du matériel dans les cheminées. Cet exercice a permis de développer des lignes directrices pour le dimensionnement des cheminées afin de limiter l’occurrence d’accrochage par enchevêtrement rocheux. Les lignes directrices proposées ont été évaluées en fonction des observations effectuées sur le terrain.

Jan 1, 2003

By J. M. Goris

"Researchers at the U.S. Bureau of Mines are conducting research on cable-type ground supports to assess their material and support properties and to provide design criteria for implementing cable supports as a workable roof control system under various underground mining conditions. Much of this work involves laboratory assessment of the material and support properties of cable supports using both conventional and birdcage steel cables. Included in this assessment are single and double cables, effects of changes in embedment length on support strengths, water-cement ratios, use of breather tubes, and pumpability and water-bleeding properties of grouts.IntroductionSince cable supports were introduced in the early 1970s, considerable research has been conducted in laboratories and at mine sites to understand their behaviour. The U.S. Bureau of Mines began a laboratory evaluation project in 1985 at the Spokane Research Center (SRC) to study the behaviour of cables supports under uniaxial loads so that the effects of various cable support components, such as grout and breather tubes, could be identified. Other objectives were to compare the behaviour of various types of cables and grouts and to collect meaningful data for numerical analyses. Pull tests were conducted to determine how cables supports reacted under uniaxial loads and how they failed when ultimate loads were exceeded. Such data are essential for the development of numerical models for analyzing rock mass behaviour when the rock is supported with cables.Test ProgramBecause each cable support can be composed of either single or double cables as well as a breather tube, pull tests were designed to include a variety of samples containing these components. A series of samples containing a single conventional cable, a neat cement grout having a water-cement ratio of 0.45, and no chemical additives was selected as a standard (Table I). Then one component in the system, such as the presence of a breather tube, was changed, and results of tests compared to results obtained for the standard samples to determine what influence that component might have on the behaviour of the support system. If significant changes in test data occurred, they could be attributed to that one component. To control the quality of the samples, the physical condition of the cables and tubes were monitored closely, and compressive and tensile strengths as well as flow properties were determined for the grout used in each test series."

Jan 1, 1991

By A H. Clemens, T A. Moore

This paper discusses a number of technical issues related to marketing coal. It outlines how the results of research undertaken in New Zealand and overseas can help producers address a range of technical factors that impact on production costs and marketability. The paper also discusses trends in coal utilisation for power generation and how new technologies may require coal with different characteristics. Research and development into options for CO2 sequestration are discussed including carbon storage in forests, and removal of CO2 from flue or fuel gas in power stations, and its disposal.

Jan 1, 1997

By L. M. Sandoval, R. Kaunda, C. N. Vasquez, S. C. Falcon

Artisanal and small-scale mining (ASM) involves a wide range of practices, from highly informal and minimally mechanized mining operations with predominantly manual work to formal practices carried out by small but high-tech industrial mining operations [1]. ASM may be a traditional practice, with skills passed from one generation to another. It can be an important driver of local economic development, while simultaneously contributing to a complex array of positive and negative socioeconomic and environmental impacts. There are more than 100 million artisanal and small-scale miners in 80 countries worldwide, and they supply around 20% of the worldwide gold production [2]. According to the Peruvian Ministry of Energy and Mining (MINEM), in 2020, 32% of fatal accidents in formal (legal) Peruvian mining operations were caused by groundfall events [3].The lack of resources, knowledge of best practices in health and safety, and insufficient equipment used in ASM make the probability of suffering work accidents very high. Furthermore, groundfall is one of the main causes of accidents and injuries in underground mines around the world [4], and it is also a concerning problem in ASM, where the associated fatality rate is similarly high. Unfortunately, a proper record of accidents in ASM is not kept, so an estimate of the actual number of groundfall accidents cannot be accurately developed [5]. Currently miners rely on empirical and observational tools acquired through previous experience to assess groundfall risks. The risks for artisanal miners can tend to be significantly greater than risks for those from the mining industry. This is due to the lack of regulation of ASM, which tends to operate outside the legal framework and the regulations lack of enforcement in force for occupational health and safety regulations.

Mar 2, 2022

Beneficiation of Iron Ore - Washing with Surface-Active Agent The stability of the dispersed phase in 10 wt per cent slurry of iron ore slime and fines was studied at pH 5 and different concentrations of surface-active agents. The behaviour of the dispersed phase of iron ore slime and fines is different for different surface-active agents. The improvement of iron value of slime and fines in the presence of surface-active agent is best realized at pH 8, where the Al2O3/Fe and Al2O3/SiO2 ratios in the concentrates are appreciably reduced. The polar functional group like -COO- interacts with hematite surfaces and forms outer- and inner-sphere surface complexes depending on the suspension pH and adsorbate.

Sep 13, 2010

By M. F. Dunn

During a mine fire or other emergency, it may be desirable to reverse the airflow in order to provide an escapeway or to isolate a fire. Also, in colder areas, the airflow may be reversed to prevent ice buildup. When reversing main mine fans, the mine operator usually does not know what operating characteristics of flow and pressure to expect. Laboratory and field tests of vane axial main mine fans in the 7- to 9-ft diameter size range were conducted to establish forward and reverse performance characteristics under controlled conditions and at typical mine installations. The data obtained suggest that reverse performance characteristics are dependent upon the blade angle and the hub to tip ratio. There is also evidence that reverse performance can be predicted for a family of blade angles and a given hub to tip ratio. Generally, quantity of air is 30 to 65% less in reverse than when operating in the normal forward mode.

Jan 1, 1983

By E. Kapilashrami, S. Seetharaman

Refractory/metal interactions and associated reactions are significant during casting as they can lead to inclusion formation. High-temperature interactions between aluminosilicate refractories and molten steel were studied in the present investigation using the sessile drop method. The changes in the contact angles between molten iron with well-defined oxygen levels and substrates of silica, mullite (3Al2O3?2SiO2) as well as commercial refractories were measured in the dynamic mode. In all cases, the reaction led to slag formation. The experiments were performed under isothermal conditions at 1823 and 1873 K. A known and constant oxygen partial pressure was imposed above the iron drop, through appropriate CO-CO2-Ar mixtures. For all substrates, the contact angles started decreasing due to the lowering of the surface tension of iron, as oxygen was imposed on to the system. When a critical level of oxygen was reached, slag started forming at the drop/substrate interface and at this stage, the contact angle dropped suddenly. Subsequent behaviour of silica and mullite was observed to be different, with SiO2showing a non-wetting behaviour. In the case of SiO2substrate, there were also deep erosions along the periphery of the drops and there was slag accumulation at the sides of the metal drop, probably due to Marangoni flow and/or SiO(g) formation. SEM and EDS analysis of the substrates revealed that the formed slag was fayalite. The thermodynamic criteria for slag formation and possible mechanisms of the reaction are discussed in the light of the experiments. Key words: silica, mullite, fayalite, corundum, slag formation, sessile drop.

Jan 1, 2004

By J. D. Miller, C. L. Lin

In the processing industries, it is well known that particle shape is an important factor which determines the behavior of particulate systems. For example, system properties of technological significance including rheology, suspension stability, agglomeration, packing, permeability…etc, are affected by particle shape. In this regard, characterization and analysis of particle shape is essential for more detailed understanding and improved development of particulate processes. In general, it is clear that the behavior of these systems depends on the statistical characteristics of particle shape. Remarkably few techniques exist to predict the mechanical and hydrodynamic behavior of an irregularly shaped particle or a population of irregularly shaped particles for that matter. The lack of models and correlations can be attributed to the wide variety and complexity of particle shapes, the difficulty of defining shape descriptors suitable for modeling, the limitations of measuring shape, and the lack of classifying techniques to characterize particle shape. In this paper, we present information on how 3D particle shape can be measured, characterized, and analyzed using cone-beam X-ray microtomography (XMT).

Jan 1, 2005

By Hugh Douglas

In the past two years recent increases in silver prices over levels that prevailed for many years have changed supply/demand patterns. On the supply side, a silver mining boom is in progress in the United States and elsewhere. On the demand side, traditional uses of silver by individuals are dropping while industry is conserving. These changes will alter the supply/demand balance and bring about more moderate rises in silver prices, which in turn will impact the mining industry.

Jan 1, 1981

By Hyung-woo Kim, Sup Hong, Sung-Soo Kim, Chang-Ho Lee

A deep-seabed integrated mining system, which consists of four subsystems such as riser pipe, buffer, flexible riser, and tracked vehicles, is presented in Figure 1. In order to collect more manganese nodules, multiple tracked vehicle systems should be used in a deep-seabed integrated mining system.

Sep 1, 2014