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By A. H. C. A. Zimmerman

WE have just heard what must be regarded as a thoughtful, constructive and somewhat painful analysis of the financial function of our industry. While thinking about this, it is interesting to reflect on the conditions which have stunted the growth of the financial side of our affairs. Mining must be regarded as a wealthy business. •while immeasurable grub takes and development budgets have been lost, there can be little argument that a productive ore-body nearly always produces the type of wealth that breeds some extravagance. I recognize that this statement can be attacked from many sides, but an historical comparison with a commercial enterprise involving similar investment will demonstrate what I mean. However, these old times are be-ginning to disappear for a variety of reasons. High amongst these are: ( l) Increased costs of exploration. (2) Remoteness of many new finds. (3) Fixed or declining metal prices (particularly when expressed in constant dollars). ( 4) Constant demands for higher wages.

Jan 1, 1962

By K. C. Marsden, B. Pesic

"Interest in the efficient production and recycling of rare earth elements has increased in recent years along with the prices of these elements. The molten LiCl-KCl eutectic is one ionic solvent which can be utilized for these purposes. The LiCl-KCl eutectic has also been selected as the electrolyte for focused research for advanced pyrochemical recycling processes for used nuclear fuel in several nations. Rare earth elements are fission products with notable neutron absorption characteristics, and thorough understanding of the properties and behavior of these elements is critical to their successful partition from the electrochemically-similar actinide elements. The number of research papers investigating individual rare earth elements has greatly expanded in the approximately 35 years since the last review. These research papers are presented in a variety of languages and technical formats, making data difficult to compare, and are sometimes contradictory. A review and summary of diffusion properties of rare earths in LiCl-KCl eutectic was performed, and the data translated to a common format for evaluation. INTRODUCTIONThe rare earth elements have experienced growing importance in recent decades due to their application in high technology, including optical lenses, lasers, high-temperature superconductors, improved alloys, high energy-density batteries, and powerful magnets for compact electronic devices. Their historic production methods and uses are detailed in several texts (Hampel 1971; Bautista &Jackson 1992; Gupta & Krishnamurthy 2005). A s the p rice o f these e lements has r isen in r ecent years, so has interest in their efficient production and possible recycling options. Rare earth oxides are concentrated through hydrometallurgical techniques, but the high thermochemical stability of their oxides precludes production of rare earth metals in aqueous systems. However, the wide electrochemical window and better control of pO2- in fused salt systems allows the production of these reactive metals from their halides or oxides. The high ionic conductivity and diffusivity of the molten ionic electrolyte allow high currents with limited resistive losses (Fray 1980). Electrolytic methods in fused salts are commonly adopted for the production of bulk rare earths in a variety of molten salt systems. Fluorides are sometimes proposed for oxide electrowinning processes due to ability to dissolve the rare earth oxide, reduced hygroscopic behavior, and the wider electrochemical separation between O2 and halide gas evolution (Mohan Das, Damodaran et al. 1988; Gibilaro, Pivato et al. 2011). However, in most electrolytic production processes, such as that for mischmetal, the rare earth oxides are converted to chloride prior to electrolysis in a chloride bath (Gschneidner Jr. & Eyring 1978; Sharma 1987). Of the chlorides, the LiCl-KCl eutectic is one specific medium in which metal production and production-related investigations have been conducted (Gschneidner J r. & Eyring 1978; Driscoll & Fray 1993). L iCl-KCl eutectic has the advantages o f h igh conductivity, but relatively low viscosity and operating temperature. The low operating temperature allows simpler design, with reduced energy consumption, salt volatility and cell corrosion."

Jan 1, 2012

By W. B. Agocs

"AbstractThe airborne magnetometer data of the Marmora iron ore deposit at Marmora, Ontario, have been used as an example to show the mapped results obtained by the use of line spacings of from 1 mile to 14 mile. The maps are illustrative of the results which could be obtained from such line spacings for any type of geophysical survey, and they show the probability of 'missing' a feature of economic value if the line spacing is too coarse.The probability equations are given for the crossing of randomly oriented features whose maximum dimension is less than the spacing of the control lines for circular, elongate, and rectangular outlines. The equations are P = D/S; P = 2L/S; P = 2(L+W)/,.S; P = A/,.S; P = (2L(S+T)-L2),.ST; and P (D(S+T-,.D)) ST, respectively; where P is the probability; D is the diameter; L is the length; W is the width; and S and T are line spacings.IntroductionTHE EFFECT of station spacing, and the effect of the distance between the plane of observation and the plane of the source of the potential field anomalies, have been studied by geophysicists in the past.The purpose of this paper, however, is to illustrate the effect of line spacing •on the resultant mapped magnetic anomaly for a known magnetite mass, and to present the elementary probability equations for determining the optimum control spacing for detecting a particular type of feature. The effect of line spacing which is illustrated by the magnetic maps presented herewith would be comparable to results which would be obtained by any geophysical survey, since the contours between lines are of necessity interpolated."

Jan 1, 1955

By G. S. Ospanova

The results of complex processing sulphide copper ore and advantages of recovery of copper by vat and heap leaching, sorption, cementation and electrolytic solutions processing and utilization of waste material after heap leaching of copper for production of building materials were investigated. The combined chemical solvents with the additives of oxidizing agents are developed at the KazNTU. The solvents are inorganic or organic chemical reagents, which form complexes of Cu, Au, Ag, Pt, Ni, Sr, Co etc. Recovery of non-ferrous metals from solutions and purification of industrial waste waters is carried out on the base of using new synthetic and natural sorbents (from local raw materials) which are able to bind ions in both cationic and anionic forms depending on type of ligands and external conditions. Optimum parameters of copper sorption were determined. The developed wasteless technologies of copper extraction from sulphide ores with usage of new non-toxic solvents and accessible sorbents with full recycling of water are tested in pilot scale heap leaching, and are recommended as the ecological, economical and practical alternative to traditional methods.

Jan 1, 2007

By L. F. Haven

"The desirable shovel speed-torque curves are described, along with the characteristics of the more important electrical components used to approximate these curves. A particular shovel regulator system combining these components is discussed in detail and some of the advantages and disadvantages of the system are given.INTRODUCTIONIN 1959, STATIC CONTROL was for the first time successfully applied, installed and operated on a mining machine in North America. Since that time, a great deal has been learned about this control by the people maintaining these machines as well as by the de-signers.In 1961, the first SCR (Silicon Controlled Rectifier) or thyristor control system was installed on an excavator. This control differed from the earlier static control in that thyristor excitors supplied the generator fields directly. The development of thyristors of a sufficient rating to supply amounts of phase-controlled power to the generator fields eliminated the bulky Mag. Amp. -Rectifier combination previously used."

Jan 1, 1969

By J. A. Brusset

Introduction I am indebted for most of the information in this paper to Mr. P. S. Lea, Deputy Chief Inspector of Mines of Great Britain, and Mr. A. E. Crook, Engineering Inspector of Mines, Ministry of Fuel and Power. Other coal-mining men in Canada may be as surprised as I was to learn that there are twenty-five Diesel locomotives in service underground in British gassy coal mines. Many more are in use underground in non-gassy coal mines and in metal mines. Approval has been granted for an additional fifty flame-proof locomotives to be used in gassy mines, and these should be in operation by the end of 1946, or as soon as manufacturing facilities permit.

Jan 1, 1946

By D. F. Kidd

Introduction In a companion article, Surveys at Great Bear Lake, 1931, R. C. McDonald has described the general character, topography, and climate of the Great Bear Lake-Coppermine River area and the main means of access (l). The present paper will largely be confined to the geological features of the district. In the last two years, the rocks of the region have received considerable attention, and papers including references to .the geological succession have been written by Knight(2), Duncan(3), Norris( 4), Reid(5), Cameron(6),and Kidd(7). The writer confined his field-work during the 1931 season to the district between LaBine point and Hunter bay and northwest to the head of McTavish arm. Brief trips were made down the Sloan river from McLaren lake, 25 miles northeast of Hunter bay, to that place, to Dowdell (Sixty-six) point, the south point of Echo bay, and to the region north of the Dismal lakes and west of the Coppermine river. The inner part of Echo bay, which is the area discussed by Reid and Cameron, has not been seen by the writer and the geology there will not be discussed.

Jan 1, 1932

By Andrew Abraham

Continual improvement is the key to success in today?s competitive global arena. You require tools that promote dynamic quality management, deliver cost savings to your bottom line and provide the foundation for process improvement. ISO 9000 and ISO 14001 management systems and OHSAS 18001 are those tools. Since their inception, the benefits of ISO management systems and registration have been touted as the way to achieve better bottom line results. This spurred many companies to embark upon the road to registration with high expectations. The potential benefits of ISO management system implementation and third party registration that are commonly provided by Registrars and consultants are compelling adverts for success. ISO 9001:2000 is promoted as an essential tool for systematic efficient and affective management controls that provide a framework for analyzing errors and improving a company?s internal operational processes. It also allows companies to comply with internal and external customer and regulatory requirements thus continually improving the quality of their products and services and thus enhancing customer satisfaction. This, in turn, leads to greater customer recognition and increased market share. ISO 14001 implementation and registration may assist your company in reducing its litigation risk, raw material and energy consumption, waste disposal costs and possibly non tariff trade barriers. It should also provide continuity of operations, enhanced operational efficiency and consequently a competitive advantage in the market place. Registration of your ISO 14001 management system should also improve your company?s profile and credibility leading to regulatory flexibility and improved community goodwill. All of this will be a catalyst for improved morale and pride by employees and management alike. Likewise, OHSAS 18001, the latest certification specification for Occupational Health and Safety Management Systems supports Occupational Health and Safety legal and regulatory obligations and compliance, manages & controls Occupational Health and Safety risks and improves performance, safety culture and efficiency. OHSAS 18001 is an audit certification, and not a legislative requirement. Suggested benefits of implementation include reduction in accidents, lost time and associated liability and insurance costs and improving reputation and credibility through demonstrated commitment to health and safety. The foregoing increases access to new customers, joint venture partners and financing The skeptics say these are motherhood statements and lack corroborative evidence, i.e., ?Show me the money!?

May 1, 2003

By P. B. Queneau, Peter V. Avotins, Lauch F. Farris

"The Lang Bay germanium property is a carbonaceous sandstone deposit outcropping near the Pacific coast, 100 km north of Vancouver. The germanium-bearing seams are up to 5 m thick. Where one such seam outcrops, it averages 50 to 60 g Ge/tonne. Drill core analyses have shown considerably greater concentrations of germanium at depth. Additional drilling to establish continuity and grade of the germanium-b earing strata is scheduled for 1986. The germanium occurs in association with lignite, which makes up 1 to 2% of the seam. American Cyanamid Company engineers have developed a proprietary flotation reagent effective for concentrating the germanium rich vitrain portion of the Lang Bay lignite. Ongoing laboratory studies are developing procedures for further upgrading and refining of this germanium. This paper outlines progress made by Fargo Oil Corporation on Lang Bay geology, reserve estimation, mine planning, ore dressing, refining, and economic evaluation.IntroductionIn 1871, Mendeleyev specula ted on the properties of a ""missing"" element between silico n and tin on the periodic table. The discovery of germanium fifteen years later proved the Mendeleyev predictions to be remarkably accurate. Almo half a century later, the pioneering work of McCutcheon of Eagle-Picher led to production of germanium dioxide from Oklahoma zinc smelting residues. Demand for the element surged due to development of the Ge02 diode rectifier during World War II, followed by development of the transistor in 1947. The chief commercial sources for germanium during the following two decades were the Cu-Zn mines in the Congo and the Zn-Cu-Pb mines of Tsumeb in Southwest Africa. The germanium was chemically combined in complex Cu-Fe sulphides (germanite and renierite), from which the element was recovered either by leaching the selectively roasted sulphide, or by direct fuming of GeS(I). Although these deposits have reportedly been depleted (2), new deposits of renierite have been discovered in Zaire. Alternative sources of germanium are therefore being sought worldwide for use in infrared optics, semiconductors, fibre optics, and catalysts. One such source is germanium-rich coal (2)."

Jan 1, 1986

By Maurice Lauzon

"Aerial surveys of the open pits have been conducted regularly at Lake Asbestos of Quebec, Ltd. -a subsidiary of American Smelting and Re-fining Company -since 1958. Ground controls are supplied by Lake Asbestos, and a topographic map of the pits at a scale of 1 in. to 50 ft., with 2-foot contour intervals, is obtained by aerial photography. The information from the topographic map is then transferred by the Lake Asbestos engineering staff to sections from which the volumes removed are calculated. Considering the size and complexity of the operation, this system has proved to be the cheapest, fastest and most accurate way of determining the quantities of rock and overburden removed. More than 11,000,000 tons of ore and waste are mined each year in three different pits. Further-more, the nature, shape and extent of the orebodies make it necessary to mine on many (up to eight) benches of a pit during a single year. In addition, there are sections of the pits where it is impossible or un-safe to survey the crest of some benches by standard ground methods. For these reasons, the tonnages obtained by truck count are checked and adjusted by aerial survey. These surveys are now taking place every six months. With this system, it is possible for a two-man surveying crew to look after all field work in the mine area."

Jan 1, 1967

By Rita Aiello, Stan Mack, Peter Werth, Joseph McCarney, Jozef Stachulak

"Johnson Matthey has developed the first diesel particulate filter (DPF) for underground mining that controls particulate matter (PM) at the same time as maintaining emissions of NO2 at or below engine baseline levels. DPF technology is critical for controlling PM which is classified as a carcinogen, but passively regenerating systems rely on the use of oxidation catalysts that can potentially increase NO2 emissions. This paper reviews the development of low-NO2 PM control technology and the results from testing this technology underground on diesel mining equipment. KEYWORDS Decomposition catalyst, Diesel particulate filter (DPF), Diesel particulate matter, Mining Continuously Regenerating Trap (CRT®), NO2, SCR INTRODUCTION The introduction of diesel particulate filter (DPF) technology on heavy duty diesel (HDD) engines has been an important step towards addressing the clean air and health concerns for mining companies. Control of diesel particulate matter (PM) emitted from diesel engines is already being implemented for on- and off-road vehicles, and similar legislation is being prepared for mining equipment. In addition to PM, the diesel emission control strategies (DECS) also reduce carbon monoxide (CO) and hydrocarbons (HC). Some DECS control oxides of nitrogen, or NOx, which is composed of NO and NO2. Johnson Matthey has led the development of emission control technologies for diesel engines for almost 30 years. Over the last ten years alone JM has supplied over 3 million Continuously Regenerating Trap (CRT®) DPF systems for on-road vehicles, and over 200,000 systems for off-road vehicles. The patented CRT technology combines a diesel oxidation catalyst (DOC) with a DPF to effectively trap harmful PM from diesel exhaust, while removing CO and HC. The DOC converts part of the engine NOx to NO2, which reacts with the trapped soot to regenerate the filter. As engines become more fuel efficient, less waste heat enters the exhaust. This can be a disadvantage for after-treatment systems as it leads to lower catalyst operating temperatures. The CRT system regenerates passively, without addition of heat, at temperatures that are typical of diesel engine exhaust. JM recently launched the Mining CRT system which integrates CRT technology with NO2 abatement to reduce PM and tailpipe NO2 from underground diesel mining equipment. This is the first technology proven to control both PM and NO2 emissions for a cleaner, healthier working environment. The Mining CRT is also cost-effective compared to other technologies."

Jan 1, 2019

"Developed by CRIRSCO, IRT is a document that draws on the best of the CRIRSCO-style reporting standards. These reporting standards are recognised and adopted world-wide for market-related reporting and financial investment.The IRT is not an international reporting code and does not supersede existing national reporting standards. Rather it is a guideline that encapsulates the content of these standards for the benefit of the international mining industry and its various stakeholders.The template is a 'living document' that is continuously updated and improved as new national laws, rules, codes and guidelines are created or amended.The International Template is advisory only and where national codes already exist, these will take precedence. The International Template is intended to assist those countries that either do not have a reporting code or whose code is outdated, to produce a new code consistent with international best practice. It also provides a consolidated version of national codes that reflects their compatible international components and may thus be used in comparisons with other international reporting systems. The word 'Template' is used advisedly to indicate that this document is a model for code development and does not in itself constitute a 'code' which implies that it has legal or other regulatory force.From this point forward, the Template includes words that imply a mandatory action, such as ""requires"", ""applies"", ""must"" etc. This is to enable the Template to be easily adopted by countries and organisations wishing to do so, and does not imply that the Template itself is a mandatory reporting standard.INTRODUCTION2 In this edition of the International Reporting Template (""The Template""), important terms and their definitions are highlighted in bold text. The guidelines are placed after the respective Template clauses using indented italics. They are intended to provide assistance and guidance to readers for interpreting the application of the clauses in the Template.Indented italics are also used for Appendix 1 — 'Generic Terms and Equivalents"", and Table 1 —'Check List of Assessment and Reporting Criteria' to make it clear that they are also part of the guidelines for the application of the Template.Appendix 1 contains a table of generic terms and their equivalents, designed to avoid unnecessary duplication or ambiguity in the textAppendix 2 provides Rules of Conduct for Mineral Resource and Mineral Reserve estimators that may be considered in addition to the Codes of Ethics or Practice normally applying to members of professional institutions."

Jan 1, 2003

By W. K. Smith, V. P. Krueger, D. C. Mulder

"AbstractThis paper describes the geological procedures used to evaluate two mineable high-volatile C bituminous coal seams at Coal Valley , located in the outer foothills belt of the Rocky Mountain Eastern Slopes in west-central Alberta. Lexco Testing Ltd., the exploration arm of Luscos: Ltd., owns and operates an all -weather geophysical logging system which provides gamma, focused density , single-point resistance and caliper logs in a single pass. A mathematical analysis for a theoretical interpretation of the single-point resistance log confirms empirical research that bed boundaries are located at a point 10% from the bottom of the curve. A unique and efficient triple-tube, wireline rotary coring system cuts an undisturbed 0.076m- diameter core in a plastic liner at recoveries exceeding 90% . Although only 10% of the total footage is cored, it provides vital analytical and geotechnical data, and, when integrated with the geophysical logs, improves the quality and extends the usefulness of interpreting both sets of data. All data are programmed to produce computerized structure contour, isopach, isoratio and isoquality maps, and volume calculations.General IntroductionTHE COAL VALLEY AREA is located in the outer foothills belt of the Rocky Mountain Eastern Slopes, 60 miles (96 km) by road southwest of Edson, Alberta. Luscar Ltd. holds leases which total 49,000 acres (19,830 ha) , of which 18,300 acres (7,410 ha) have been assigned to the Coal Valley mine area (Fig. 1 ) . There are two Paleocene high-volatile C bituminous coal seams initially developed for mining within a total stratigraphic interval of 750 feet (230 m ) (Fig. 2 ). These seams strike generally NW, and in the undisturbed areas generally dip westerly from 10 to 30 degrees."

Jan 1, 1977

By J. Desroches, J. Burghardt, B. Lecampion, A. P. Bunger

"We present detailed comparisons between theoretical predictions and experiments for the initiation of radial hydraulic fractures transverse to a wellbore. Most of these experiments provide a measure of the time evolution of pressure, length, opening and flux entering the fracture during the test. We compare all these measurements simultaneously to our theoretical predictions, thoroughly testing hydraulic fracture initiation theory, which is shown to be predictive. These comparisons notably emphasize the difference between the initiation pressure (the wellbore pressure for which the fracture initiates) and the breakdown pressure (a misnomer which simply corresponds to the maximum pressure recorded during the test). INTRODUCTION In this paper, we will compare hydraulic fracturing laboratory experiments performed in different tight materials (PMMA, cement, shale) with the predictions from a numerical solution of the governing equations of hydraulic fracture mechanics (e.g. Geerstma & de Klerk, 1969; Detournay & Peirce, 2014). We focus on transverse radial hydraulic fractures initiating from a radial notch at the wellbore wall (see Figure 1). In particular, we will clarify the difference between the initiation pressure (the wellbore pressure at which the fracture initiates) and the breakdown pressure (a misnomer which simply corresponds to the maximum pressure recorded during a test, usually carried out at constant pump rate). This difference stems from the strong viscous effects at play during wellbore pressurization, fracture initiation and early propagation (i.e. fluid entrance in the newly created fracture). It has been observed on a number of experiments (e.g. Weijers, 1995; Zhao et al., 1996) and has a strong practical application, first because the maximum pressure is the most obvious value to report and second because that maximum value is necessary to specify injection systems."

Jan 1, 2015

By Imane Benhamed, Jaouher Diouani, Laurent Cassayre, Florent Bourgeois, Carine Julcour-Lebigue, Université de Carthage

The attrition-leaching process aims at improving leaching performance when formation of passivation layers at the surface of leached particles is a severe limiting factor, as discussed recently by Julcour and coworkers (Julcour et al., 2015). This paper proposes a geochemistry-based modelling scheme for deriving the window of possible operating conditions for the attrition-leaching process to match the properties of the processed ore. The rationale is that the attrition-leaching process maintains the surface of reacting particles in an unpassivated state by continuous mechanical removal of surface leach layers, so that the process reactions can be modelled from thermodynamic equilibria throughout the duration of the process. The strength of the proposed modelling approach is that it bridges the gap between the properties of the ore and the process operating conditions. The present paper exemplifies the proposed process modelling route for derivation of the attrition-leaching process operating conditions in the context of the leaching of silicate ores, matching model predictions against controlled laboratory experiments. It is shown how thermodynamic modelling, when used in conjunction with a solid knowledge of the phases present in the system, can assist with deciding upon suitable process operating conditions. As an example, this firstprinciple modelling approach predicted that steel grinding medium would be converted into siderite (FeCO3) under a wide range of operating conditions, which led to questioning this initial choice of grinding medium for the attrition-leaching process under mineral carbonation conditions. It is emphasised that the same approach could be applied to ores of greater economic significance.

Jan 1, 2016

By L. Vu, V. Popov, J. Beland, R. Darling

"The Ferderber gold deposit is of Archean age. It consists of a series of gold-bearing quartz lenses within a shear zone that crosscuts the central part of the quartz dioritic Bourlamaque batholith. On average, this zone strikes N70E and dips 65SE. The Ferderber shear zone, which hosts the ore lenses, has been affected by a succession of tectonic events. A possible early period of brittle shear, accompanied by the formation of quartz lenses, resulted from strike slip movement along the zone. These early quartz veins were subsequently folded and boudinaged during reverse movement that accompanied a prolonged period of ductile shear. More quartz veins were emplaced in the shear zone at this time; these were also deformed by the thrusting. The latest tectonic event to affect the shear zone was a period of brittle fracture.Early dextral strike-slip movement on the shear zone is suggested by the local occurrence of Riedel shears, the preferred association of ore with east-northeast oriented segments of the zone, and by the apparent en echelon arrangement of some ore lenses. The most important event, a reverse movement, is indicatedby the attitudesoffoliation, folds, boudins, COS tectonites and slip planes. The late brittle fracturing formed narrow gouge filled faults, locally flanked by brecciazones, whichrun generally within and parallel to the shear zone, and also conjugate fractures that crosscut the zone.The Ferderber and six other adjacent gold deposits were formed in a structural regime dominated by a generally horizontal north-south regional compression. The Y axis of the strain ellipsoid is east-west and varies from horizontal to a plunge of 25 0 w."

Jan 1, 1987

By B. R. Johnston, K. D. Streeter

"ABSTRACTCoal Mountain Operations is the newest of Fording Coal’s operations although it is the oldest in terms of its historical production. In October, 1994, Fording purchased the former Corbin Creek/Byron Creek Mine. The mine is located in southeastern British Columbia, approximately 150 air kilometers from Calgary, Alberta. It was first developed in 1905 and has gone through a variety of owners in its 90-year history.This paper will deal with the remobilization strategy and the mining plans for the operation which are being implemented to make this operation competitive in the world export coal market. IntroductionIn October 1994, following a due diligence process, Fording Coal Limited purchased Coal Mountain Operations from Corbin Creek Resources, an employee group which had previously owned the mine. The purchase awarded Fording Coal Limited with 100% of the assets, and control of all the coal leases at Coal Mountain.The mine is located in southeastern British Columbia, southeast of Sparwood at the hamlet of Corbin, (Fig. 1).Rehiring of laid-off employees started in November 1994, with mining activities also recommencing in November. The coal preparation plant was restarted in December with one shift, went to two shifts in January 1995, and had four-shift, full-time operation in April 1996."

Jan 1, 1997

By Paul Guliov

Coal-bearing Tertiary sediments of the Ravenscrag Formation in southern Saskatchewan host numerous deposits of clinker resulting from in situ coal combustion. Clinker deposits form when sediments of relatively low temperature firing properties overlie coal seams which are undergoing prolonged spontaneous combustion. The resulting fired material is useful for decorative landscaping aggregate, rock gardens, driveways, mud control and others. Predicting the occurrence of clinker deposits requires a knowledge of the spatial distribution of coal seams and the nature ofoverlying sediments. Knowledge ofpaleotopography at the time of coal combustion can assist in locating more highly-fused material which can yield greater block sizes. Coal data bases can be used as a predictive tool by outlining areas where coal is or was at or near surface and therefore may have been susceptible to spontaneous combustion.

Jan 1, 2001

By X. Cao, A. Birur, R. R. Chromik, J. Cuddy, P. Wanjara, J. Gholipour Baradari, T. Shariff

In this study, 3.1 mm thick Ti-5553 (Ti-5Al-5V-5Mo-3Cr) butt joints were autogenously welded using a 4 kW continuous wave Nd:YAG laser. The effect of welding speed and defocusing distance on the weld quality was investigated in terms of the surface morphology, welding defects, microstructure and hardness. Welds with full penetration were achieved at a defocusing distance ranging from -1 mm to 0 mm and welding speeds from 2.25 to 6.0 m/min. Underfill and porosity were the two main defects most frequently observed but within the optimum process window these defects could be maintained to meet aerospace specification tolerances. The fusion zone (FZ) consisted entirely of retained beta with a refined dendritic morphology. Compared to the bimodal alpha (a) + beta (ß) microstructure of the base metal (BM), the dissolution of the a phase was observed in the heat affected zone (HAZ), which led to an 11 % decrease in hardness from the BM to the FZ. To determine the tensile properties of the welded samples, an automated 3D deformation measurement system was used to measure the local strain in the weld region. The yield strength (YS) and ultimate tensile strength (UTS) increased with increasing welding speed with a highest joint efficiency of 75 % being achieved, albeit with a concomitant reduction in the ductility.

Jan 1, 2010

By Omkar N. S. Beruar

Extraction of sill pillars has always been problematic because of high risk of seismicity and rockburst. Depending on a number of factors, a sill pillar can undergo different failure modes and cause problems in the mine. Of these, sudden and uncontrolled failure of part(s) of the pillar leading to highenergy seismic events and rockbursts is a main concern because it is not possible to predict the location and time of a rockburst apart from its potential to cause extensive damage to the mine structures. To date, a comprehensive technique for sill pillar design and recovery does not exist. Conventional methods of pillar design, such as the pillar stability graph method, are utilized to design stiff sill pillars. In these design approaches, the post-peak response of the pillar-rock system is not considered. This is in part due to a lack of clear and comprehensive understanding of the post-peak behaviour and failure mechanism of sill pillars. In general, the strength of a rockmass is described using a failure criterion. When stresses reach the strength of the rockmass, the rockmass does not necessarily become unstable and knowledge of the loads alone is not enough to assess the instability conditions accurately. In fact, it is not possible to predict instability of rockmass based on the strength/stress ratio alone because instability depends not only on this ratio but also on the loading condition and loading system characteristics. The loading system can dictate whether the sill pillar will go through a stable or unstable failure process. This paper examines the influence of various parameters such as the pillar width to height ratio, the extraction rate, and placement of backfill on the Loading System Stiffness (LSS) and the Pillar Stiffness (PSS). The ultimate goal is to design yielding sill pillars that would yield in a stable manner and will reduce the risk of pillar rockburst. Plane strain finite element analysis is conducted using the generalized Hoek-Brown failure criterion with elastic-brittle-plastic parameters. Examples are given to demonstrate how to calculate these stiffness values and assess the stability condition of sill pillars. It is found that increasing the rate of extraction increases the likelihood of unstable yielding of the pillar as has been found in other studies. Placement of backfill in a timely fashion in the stopes above and below the sill pillars increases the stiffness of the loading system. This indicates that backfilling of stopes while creating the sill pillar increases the likelihood of stable yielding of the sill pillar.

Aug 1, 2013