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By Q. F. Wang

Spontaneous combustion hazard of loose coal in the top-coal caving region of entry affects the safety of the entry and top- caving longwall face seriously. In this paper, by combining on- site temperature tests with lab tests and numerical simulation, the characteristics of microcirculation close to the top-coal caving region are analyzed. A model for the temperature fields of the microcirculation in loose coal is presented. Based on this model, the temperature distribution and possible self-ignition region can be predicted. Further, the heat and mass transfers in microcirculation are studied. Finally, the mechanism of oxygenation during the spontaneous combustion of microcirculation in loose coal of the top-coal caving region of entries is put forward. The research results in this papa may provide ideas for the prevention and putting out of the fire caused by spontaneous combustion in the caving zone.

Jan 1, 2004

By R. L. Soderberg

Large open stopes mined by vertical crater retreat or sublevel s are sometimes backfilled with uncemented sand to support the stope walls and alleviate rock bursts. The failure of bulkheads in two different mines prompted a research project at the Bureau of Mines to prevent a recurrence of these failures. A series of laboratory tests with drains and sand filters was conducted to measure the bulk-head pressures when adequate drainage was maintained. Results showed that bulkhead pressure was reduced to near zero while drains were in operation, as compared to full hydrostatic pressure when drains were blocked or drainage was restricted. A relatively simple, free-draining bulkhead was shown to be adequate.

Jan 1, 1985

By ERIK CHARRIER, HUGH MILLER, JOSEF BOURGEOIS

In this study, a unique excavation system was characterized, utilizing waterjet technology as the primary tool for material removal during rehabilitation of reinforced concrete and shotcrete structural liners. Through empiric testing, this research seeks to validate the hypothesis that waterjet removal of these support systems will result in less unintended damage than conventional removal methods. The intent is to develop a viable technology that will reduce the collateral damage caused to surrounding liners during excavation, improve the adhesion between shotcrete and the substrate for longer lasting ground support, and improve overall safety for workers in underground environments. An analysis on the fracture mechanisms and operating parameters of each method was completed. Instrumented shotcrete panels were physically tested and examined through visual inspection and ground penetrating radar (GPR) to compare substrate damage according to each testing method. After testing was completed, the data strongly indicates that waterjet cutting causes less collateral damage to the surrounding intact liner and substrate when compared to that of conventional impact hammers. This research is intended to provide a scientific basis for additional applied research in the rapid excavation and repair of shotcrete support systems.

Sep 23, 2021

By Paul C. Merritt

Samuel Hopkins, an 18th century inventor from Philadelphia, has been little noted nor long remembered by History, but it was he who on July 31, 1790, obtained what no other man can ever achieve -the first patent issued by the Government of the United States. Signed by President George Washington, the patent guaranteed to Hopkins the protection of the American Government for his "improvement, not known or used before, . . . in the making of Potash . . . by a new Apparatus and Process." The patent itself is no longer important, but it serves as a milestone in the development of an industry that is now rapidly moving to fulfill its role as a mineral to feed the world. Potash ranks as one of the oldest products of Man, having been used as a condiment by the habitants of Gaul a thousand years before Athens achieved its Golden Age of culture. By Hopkins' time, the uses of potash had changed considerably, going primarily into glass-making, tanning, soap, and explosives, yet the same sources and techniques of manufacturing potash used during the earlier 2000 years-that is, leaching of plant ashes in iron pots with water, followed by water evaporation and crystallization of the potassium salts-were still being used.

Jan 10, 1966

By A. C. Apling, N. B. Barrett

Roadstone production requires the generation of non-flaky material, as outlined in British Standard 812 section 105.1; with respect to this criterion, a mathematical model of a cone crusher must be able to predict the flakiness index of a particular size range as determined by the relationship between thickness and nominal size. The Whiten cone crusher model utilises breakage and classification functions to predict a product particle size distribution only, so a shape function has been proposed that is based on a phenomenological approach, taking into account the transfer between flaky and non-flaky material at each stage of breakage. The results of laboratory tests to determine material breakage characteristics and of examination of pilot-scale test products illustrate the method's potential

Apr 1, 1995

By G. Harper

"AbstractThe Suetut. Copper deposit, 230 miles northwest of Prince George, B.C., was discovered in August of 1971. Subsequent exploration has included 56,417 feet of surface diamond drilling in 139 holes. The deposit occur in gently dipping volcanic rocks of the Upper Triassic Takla Group, which out crops as rugged mountains.The general Mesozoic sequence comprises some 20,000 feet of green and red basaltic to andesitic rocks. The Lower Formation is characterized by subaqueous basalt, andesite and augite porphyry flows with interbedded breccias. They were rapidly deposited in tectonic depressions of limited extent and steep gradients. Facies changes are abundant. The Middle Formation. consists of volcaniclastic rocks made up of fragments from the underlying formation. Two cycles are discernible , both with basal turbiditic, tuffaceous sandstone and shale units overlain by massive, volcanic conglomerates exhibiting graded and cross bedding. A broader, shallower-water basin is indicated. The top of the uppermost unit was subaerially deposited. The Upper Formation is a variable sequence of volcanic sedimentary rocks. Detritus was supplied from a wide source area and included multiple reworked fragments of the lower formations and material from other rock groups known in the region. Zeolite facies metamorphism is recognized throughout: the entire sequence. Epidote is particularly abundant in the Middle Formation, demonstrating the results of metasomatism.The mineralized zone is approximately concordant with the strata over 100-200 feet of the Middle Formation succession . It lies just below the zone of transition from subaqueous to subaerial deposition in the top unit. Hematite, chalcocite, pyrite, bornite, chalcopyrite and native copper are disseminated throughout all sizes of lithic fragments and matrix. Concentration into the specific zone is believed to be due to upward leaching of copper during lowgrade metamorphic and metasomatic reaction. Precipitation occurred in the zone of hydration characterized by prehnite-pumpellyite below the oxidized subaerial rocks."

Jan 1, 1977

By D. J. Reddish

An understanding of the mechanisms that cause large seismic events in a deep mine provides a foundation for designing effective measures to reduce the incidence of these events, as well as reduce the potential for damage arising from these events. The work described in this paper focuses analytical efforts on major recognizable and controllable factors that influence mining-induced seismicity and serves to screen out many of the more random aspects of individual events. Information used in this study was developed in the course of a long-standing rock burst research program conducted by the U. S. Bureau of Mines in cooperation with mines in the Coeur d'Alene Mining District and regional universities. Information was collected on 39 seismic events having local magnitudes greater than 2.5 that occurred between 1989 and 1994. Five major types of events were developed from these data that describe all but two of the 39 large events. The characteristic mechanisms, tint-motion pattern, damage pattern, and relationships to mining and major geologic structures were defined for each type of event. This information provides a foundation for assessing whether or not changes in mining activity aimed at reducing one type of rock burst will increase the incidence of other types.

Jan 1, 1996

By M. Fig, J. Brune, C. Strebinger, G. Bogin

"A fundamental understanding of flame propagation characteristics through and around obstacles is needed to accurately model methane driven longwall coal mine explosions originating or propagating in the gob. Experimental investigations of methane flames in horizontal cylindrical reactors with simulated gob (i.e. rock piles) were carried out alongside coupled Computational Fluid Dynamics (CFD) and combustion simulations. Stoichiometric methane-air mixtures were ignited in semi-open reactor vessels of 5cm, 9.5cm and 71cm diameter, all with a fixed length to diameter (L/D) ratio of 8.6. This was done both with empty reactors and also with a rock pile placed at the open end of the reactor. The rock pile length to reactor length ratio was fixed at 0.3, and the rock pile height to reactor diameter ratio was fixed at 0.33 for all reactors. The smaller two reactor experiments were modeled with ANSYS Fluent in 2D. Experimental results indicate that for this geometry a similar acceleration mode occurs across scales: that the flame speeds up an average of 40% as it passes over a rock pile with this profile. The model is able to capture several important features of the experimental results, including the significant increase in velocity, the speedup ahead of the rock pile, and the leveling off of the empty tube flame front propagation velocity. INTRODUCTION Explosions in underground coal mines are among the largest industrial explosions, known to result in the rapid combustion of 20m3 of fuel gas or more [1,2] Coal beds hold methane gas under pressure, and when the pressure is relieved through mining activity some of this methane is released. The methane then mixes with ventilation air and, if not sufficiently diluted, may form a combustible mixture, which may result in an explosion. Several large coal mine explosions have occurred around the world recently. These include the 2014 Soma Mine disaster in Turkey that killed 301 people [3], and the 2009 Heilongjiang Mine explosion in China that killed 108 [4]. Other recent mine explosions, including the 2010 disaster at the Upper Big Branch mine that caused 29 fatalities [5], have demonstrated that explosive gases can accumulate and ignite within and around the gob area of a longwall coal mine and then expand into the active mining face and nearby areas, endangering workers and equipment. If enough combustible gas is involved, the initial flame can accelerate, eventually transitioning from deflagration to detonation [6]. Researchers are developing a fundamental understanding of the evolution of the explosion process from the laminar kernel to the fully turbulent regime, and its propagation through obstacles such as those found in the gob. Researchers also studied the initial development of methane flames and the potential for the development of a detonation."

Jan 1, 2018

Productivity in underground metal and nonmetal mines is contingent upon work methods, mine layout, and ore handling techniques. One of the most important factors impacting productivity is the efficient movement of men, materials and supplies from the surface into and throughout the mine. Various transportation systems such as man-trains, service shafts, rubber-tired diesel equipment, etc. are currently used to transport men and supplies in underground mines. In many underground mines, it is not uncommon for a worker to spend 25% of his eight-hour working day traveling from the surface to his work area and returning to the surface.

Jan 1, 1975

By Colin Lawrence, Michael S. Schultz

Due to the planned deepening of the NY Harbor, NYCEDC/NYCDEP is planning to replace two existing water lines between Brooklyn and Staten Island with one deeper water pipe. The crossing, just north of the Verrazanno Bridge is 1.75 miles long. The new pipeline will be tunneled using gasketed concreted segmented liners. Apressurized face machine will be used through the soft ground. This will be the first subaqueous application using this technology in New York City. This paper discusses the planning, design and risk issues associated with the crossing and the challenging soil conditions that resulted in the decision to use a pressurized face machine.

Jan 1, 2007

By W. J. Theron

The purpose of the paper is to give an introduction to the concept of fatigue and its causes in the mining industry. By knowing the fundamental role it plays, together with its dynamics, can positively contribute to a mine?s safety management system. The difference between physical and psychological fatigue will be addressed with a possible range of causes that could trigger fatigue. There are two main sources of fatigue: firstly, work-related fatigue which is associated with activities at the workplace; and secondly non-work-related fatigue. The shared responsibility between the employer and employee is also discussed as it involves factors that occur both in and outside the workplace. Employers have the responsibility to manage fatigue through using a risk management approach. Employees have the responsibility to ensure they get enough sleep, take sufficient and regular nutrition, are healthy and physically fit and come to work fresh and alert. The impact of the implementation of a fatigue management plan and procedures has the potential to eliminate employee fatigue or its causes, reduce the likelihood of fatigue occurring in the workplace, and counteract the effects of fatigue when it occurs. Factors considered when implementing a fatigue management system include: extended hours of work, shift work, time of day and work design. Fatigue is one of the major role players (either causal or contributory) when it comes to causes of fatalities in the mining industry. Our main challenge in identifying whether fatigue played a role is the fact that it cannot be tested in post-mortems like drug or alcohol abuse. It is an aspect worth understanding and getting an organization sensitive to managing it properly to benefit both organizational as well as employee needs. Keywords Signs of fatigue: Causes of fatigue, circadian rhythms, the fatigue equation, fatigue management, fatigue affecting safety, fatigue fighting tips, lifestyle suggestions.

Jan 1, 2011

By O. R. Bell

In Australia's remote North West are located the operations of Cliffs Robe River, one of the world's largest iron ore projects. Initial project cost was $US300 million and required the construction of a deepwater port, two toms for 3000 people, a 105 Mw power station and 170 km of railroad, all in harsh, arid country over 1300 km from the nearest industrial centre. The ore occurs as goethite cappings on scattered mesas and averages 57 percent iron. All aspects of the project are reviewed from pre-operational research, through project construction to current operation.

Jan 1, 1979

By K. Hanna

This U.S. Bureau of Mines report describes a rock mechanics instrumentation program conducted in a shallow underground coal mine in central Illinois. This research program was designed to provide a basic understanding of the structural behavior of entry intersections. A wide variety of instruments and measurement techniques including hydraulic borehole pressure cells, multiple-point borehole extensometers, roof bolt compression pads, and overcoring were employed to monitor roof stresses, pillar loading, strata movement, floor heave, and bolt loading before, during, and after intersection development. A summary of intersection design theories, failure modes, and support techniques is included and instrumentation installation procedures and analysis methods are presented. The study identified two critical parameters that affect intersection stability: in situ horizontal stresses and geological discontinuities. Important design parameters for improving intersection stability are roof span and intersection geometry.

Jan 1, 1991

By S. Averill, B. Schreiner, V. Sopuck

The La Ronge. Kisseynew, Glennie Lake and Flin Flon domains. the main focu for gold exploration in the southeast part of the Saskatchewan Shield, were subject to continental glacial ice advances from the northeast during the Quaternary. Based on forty-four auger hole along with surficial mapping, the general Quaternary stratigraphy in this area is observed to be composed of a lower till unit , an overlying stratified unit of glaciofluvial sand and gravel and/or a glaciolacustrine silt-clay unit. an upper till. and an upper tratified unit. The lower till is commonly found throughout the geological domains except where it has been eroded in glaciofluvial or fluvial channels. Glacial Lake Agassiz fo rmerly covered most of these prospective domains. The lacustrine deposits associated with the lake impede surficial geochemical surveys including soil. lake sediment. and biogeochemical surveys. The approximate extent of clay cover can be predicted from beach elevations. For instance. in the Waddy Lake area. clay i not known to occur above about 1,400 feet (425 m) elevation. Exploration techniques are hampered by clay in at least one third of the volcanic belt. Thi s influence is indicated by the fact that nearly all gold prospect found to date are located above 1,400 feet (425 m) while the area of clay cover is vi rtually unexplored. The upper till i related to a minor ice readvance. This till is the medium often sampled during soil surveys in the area . lts value as a geochemical ampling medium is dependent on the extent of erosional contact with bedrock highs on the lower till. Those areas which are relatively free of lacustrine and fluvial deposits are those where surface geochemical methods work best. In the Waddy Lake volcanic belt approximately 25-50% of the area may be suitable for surficial surveys. The area of the Star Lake prospect occurs above the 1,500 foot (460 m) elevation and was not covered by Lake Agas iz. The effectivene of till sampling as a surface sampling medium was tested in those areas above the clay level. Till orientat ion surveys were carried out at the Star Lake property and the Tower Lake prospect (Waddy Lake area) within the La Ronge Domain . Gold grain counts and analy es of heavy mineral concent rate from 7 kg surface ti ll samples were used to delineate dispersion trains down-ice from mineralization. In addition, the clay fraction and a 30 g (-80 mesh) subsample from the same till sample, were analyzed for gold . In the Star Lake area, ice direction is subparallel to the strike of several narrow northeast trending auriferous structures. arrow dispersion trains down-ice from known

Jan 1, 1986

By T Rohde, P Defferrard

In 2010 a store and release cover (the cover) was constructed on the south waste rock dump (SWRD) at Century mine. This also included aerial seeding of province native trees and shrub seeds. The purpose of the cover is to reduce percolation into the potentially acid-forming (PAF) waste rock by maintaining a compacted reduced permeability layer (RPL) at near-saturated conditions. This is achieved by overlaying the RPL with a 1.5 to 2 m thickness of soil-mulch. The soil-mulch has a hummocky final surface that captures rainfall, so it does not runoff, allowing it in part to infiltrate, with excess water removed by evaporation and transpiration. The RPL is the trafficked surface of the SWRD.The unsaturated behaviour of the cover is being monitored by instrumentation including volumetric water content and matric suction sensors and a weather station capable of estimating evapotranspiration. The instrumentation allows for direct measurement of infiltration into the cover, storage of rainfall, percolation through the base of the cover and in situ soil water characteristic curves (SWCC).The key functions used to describe the unsaturated behaviour of the cover materials is the SWCC and the unsaturated hydraulic conductivity function. The SWCC is a plot of soil water versus soil suction. It provides the loci of moisture states of a soil from the saturated to the dry state.The paper presents the results of five years of monitoring. It shows that total infiltration into the top of the SWRD was about 1.6 – 3.7% of cumulative rainfall over five years, with most of the infiltration going into storage within the cover. Runoff from the top of the dump is not allowed therefore, the remaining 95% of the total rainfall was lost to evaporation or as lateral flow when infiltration reached the RPL. The paper presents some simple analyses of the wetting by rainfall infiltration of the cover, leading to breakthrough at the base. Field data are used to support the analyses.Presentation of the SWRD water balance is also included in the paper using SVFLUX™GE which is a finite element model that simulates water transport through a saturated or unsaturated medium.CITATION:Defferrard, P and Rohde, T, 2018. Five years of cover performance monitoring and modelling for a store and release cover at Century Mine, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 179–189 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By Wayne Green

The Regional Municipality of York, located north of the City of Toronto in Ontario, Canada, has experienced unprecedented growth during the past decade, with new home construction averaging 15,000 units per year. This rate of growth is planned to continue well into the future with a projected growth of more than 500,000 new residents by 2031, combined with a tar-get of more than 300,000 new jobs to provide a sustainable economic base for the region. It should be noted that York region has been designated as one of the key growth centers by the province of Ontario, aimed in part to meet the housing and employment needs of Canada?s growing population. York Region is a mix of urban and rural areas and is one of the most desirable areas to live in Southern Ontario. York region offers an attractive lifestyle, with its nine municipalities and the amenities created by the many rivers, streams and protected greenbelt areas that encompass more than 69 per cent of the region?s area.

Jan 1, 2010

By B. E. Blair

"This report presents the physical properties and related geological and petrographic data of some 84 rock types from operating mines, quarries, or blasting research test sites. These fundamental rock data were collected as a quantitative approach to underground mining problems, blasting research, or other related studies; however, the data are equally applicable to any problem wherein rock characteristics are important factors. Stress-strain curves are given where available, and the standardized procedure for determining elastic constants from static tension tests is described. Computed (laboratory) and measured (field) free-medium velocities are compared in those instances where such data are available. A chart is given showing both the optimum and minimum number of test specimens for the various core sizes employed in the Bureau of Mines standardized physical-property tests. Rock-type, geographical, and geological indexes are included to aid the reader in locating physical-property data in this and previously published Bureau of Mines physical-property reports.INTROD'OCTI ONThis report presents the physical properties of 84 rock types tested from 16 different projects (sections 37-52). Two previous physical-property reports 2-3 / (hereinafter referred to as parts I and II) presented data on 160 rock types from 36 different projects (part I, sections 1-25 and part II, sections 26-36).The physical-property data were originally obtained to supplement structural mining problems, seismic studies, or related investigations; however, they should be equally applicable in all fields of studies where the strength, hardness, or other properties of rock are important factors. The properties, determined from laboratory tests performed on diamond-drill core, include the following:"

Jun 1, 1955

By C. Birch

"A mineral resource royalty is payment to the holder of mineral rights for the utilization of the mineral resource. In South Africa, this payment is made to the State as holder of the mineral rights (The Mineral and Petroleum Resources Royalty Act of 2008). The principle purpose of this research paper is to identify if the State is benefitting from the mineral resource royalty by considering its impact on seven individual Witwatersrand gold mines.For this study, a simple financial optimiser model was created in Microsoft Excel that links the ore flow, block listing and the cash flow (excluding or including the cost of the mineral resource royalty). Mixed integer linear programing (the Excel Solver function) is utilised to optimise either profit or NPV (at 9% and 12%) by adjusting the cut-off grade.The impact on each of the seven mines mine was different but overall R7.9 billion is estimated to be paid in mineral resource royalty over their expected remaining lives. Due to the cost of the mineral resource royalty and increasing the cut-off grades, the total revenue decreases by R10 billion. A significant portion of this lost revenue would have been paid to the State in the forms of other taxation including company income tax which decreases by R2.8 billion. It is recommended that an industry wide investigation be conducted to determine if the resource royalty is adding to the State’s revenue, or destroying value including premature job losses. IntroductionTaxation of mining companies has become a very topical subject in the context of the postapartheid South African economy. There have been increasing calls for equitable re-distribution of mineral asset wealth for the benefit of all South African citizens and not just to an elite few. As part of the Mineral and Petroleum Resources Development Act (MRDPA) of 2002, the Mineral and Petroleum Resources Royalty Act of 2008 was introduced and came into effect in 2010 (South African Revenue Services, 2008). A mineral royalty is payment to the holder of mineral rights for the utilization of the mineral resource. In the case where the holder of the mineral right is the State, then this payment is made to the State (Cawood, 1999). Studies on the potential impact of the mineral resource royalty on the minerals industry have been conducted during the formulation of the Act and subesquently. These include Cawood and Macfarlane (2003), who suggested a cap of no more than 3% (Cawood and Macfarlane, 2003), as well as Cawood (2011), who predicted rising cut-off grades and thus reducing mineral reserves. In 2013, Grobler completed a Masters in the Faculty of Economic and Management Sciences at the University of Pretoria and concluded that the impact of the mineral resource royalty on the economy is positive. She stated that the royalty has caused operating expenses to increase, but this does not appear to be significant. Furthermore, she stated that the royalty has not affected the way the mining industry operates (Grobler, 2014)."

Jan 1, 2016

The maximum current density at which conventional copper electrowinning plants will result in satisfactory, adherent, and dendrite·free cathodes is determined by the thickness of the diffusion boundary layer. A decrease in the value of that thickness will permit an increase in the current density. This fact is utilized to develop a high current density cell in which the reduction of the boundary layer thickness is accomplished by means of a specially designed electrolyte circulation system. The high current density cell is used to determine the effect of current density on such process parameters as current efficiency, cell voltage, power consumption, and cathode purity. A number of empirical equations are developed for the purpose of estimating the magnitude of these effects.

Jan 1, 1972

By Scott Turner

The present rapid growth of coal stripping in the United States is a curious reversal of the tendency of mining to proceed from outcrop to depth. A combination of technical and economic factors bas stimulated the use of stripping methods until today many million tons of coal We being recovered by open cuts from sites that an earlier generation of engineers would have passed by as not commercially mineable or, if workable at all, only by underground methods. The total quantity of bituminous coal and lignite mined in the United States by stripping in 1928, the latest year for which detailed figures are available, was 19,789,000 short tons. Of this, 71,000 tons came from small workings not equipped with power shovels and 587,000 tons from properties in which stripping and underground work were carried on at the same mine; but as neither of these types is representative of modern stripping practice, they will be omitted in the discussion that follows. The total from strip pits proper in 1928 was 19,131,000 tons, produced by 176 pits employing 385 steam or electric shovels.3 Figures by States are given in Table 1. Detailed statistics will be found in Economics of Strip Coal Mining; a study by O. E. Kiessling, to be published by the United States Bureau of Mines.

Jan 1, 1930