Search Documents

By S. W. Thomas

One of the most difficult tasks associated with placer mining is the sampling of the deposit. More placer projects have failed due to inaccurate assessment of the reserves than to any other reason. Within the realm of placers, those containing valuable minerals with a high unit value .are more difficult to sample than those with larger bulk, lower unit value minerals. Some items to consider when sampling a placer deposit are as follows: A) A relatively large size sample is needed for accurate valuation of the ground being tested. Placers are composed of many sizes of gravel which makes a representative sample difficult to obtain. B) When sampling placers for high unit value minerals such as gold, any error in mineral content of the sample will be magnified in the calculation of reserves.

Jan 1, 1985

By Martin Knights, Geoff Featherstone, John Flanagan, David Lawrence

The proposed paper will address specific transport, engineering, environmental and community related issues concerning the current construction and future operation of Europe’s biggest urban road tunnel project—the US$500m Dublin Port Tunnel. Situated in Ireland’s capital, the three mile long, 40 ft diameter twin tunnel project encounters a range of ground conditions using TBM, Shield, Cut & Cover with diaphragm walling and major slope stabilisation and Multi-jacked pipe techniques. Where possible units of measurement are given in feet and inches.

Jan 1, 2003

By D. G. Foot, J. D. McKay, R. A. Ynchausti

The increasing popularity of column flotation as an efficient and profitable mineral beneficiation technique has resulted in the need to perform a study of basic column operating parameters in order to understand mineral behavior in a column. Variation of column rougher flotation parameters on the Nevada Fish Creek fluorite and Utah Collins manganese ores enabled characterization of four beneficiation zones within a column flotation cell. Although specific mineral behavior in each zone was peculiar to the mineral system involved, particle retention time predominantly affected both manganese and fluorite recoveries in the collection zones of the column while enhancing mineral grades in the cleaning zones. Column parameters such as column length, feed injection location, and tailings recirculation velocity were inherently linked to particle retention time and retention time distribution, both of which affected mineral recovery. Froth depth had a discernible effect on fluorite concentrate grades; as froth depth increased, fluorite grades increased. Wash water additions affected both fluorite and manganese recoveries and fluorite grade. Axial mixing drastically reduced fluorite and manganese recoveries due to short circuiting of some of the feed slurry in the column.

Jan 1, 1988

By Jed H. Mosgrove

One of the most interesting of all the subjects required of persons studying the different facets of coal mining is coal mine gases. Some mine gases have been a real problem since the very beginning of underground mining, and in the early days there was insufficient knowledge to cope with them. The history of mining shows that until about the last 50 years, much work was done primarily by the hand methods which are primitive by today's standards. Miners had to contend with gases without the aid of enclosed lighting, permissible mine machinery, sophisticated testing devices, and high-pressure ventilating fans. In early days the miners were not educated about the different mine gases nor did they have the technical equipment to determine the actual composition of the deadly atmospheres they encountered. They simply applied a descriptive term to each gas or mixture of gases depending on its effect on a person or the surrounding atmosphere. The gases or mixtures of gases were then referred to as "damps," a term which was probably derived from the German word "dampf," meaning vapors or gases. The more common damps encountered were : Blackdamp A condition of the atmosphere in which a miner's light would be extinguished and in which breathing would be difficult, sometimes even resulting in suffocation. An atmosphere deficient in oxygen which could contain a combination of any of the mine gases Firedamp A flammable mixture of methane and air which would either burn or explode when ignited. White Damp A mixture of gases containing carbon monoxide, most often found in mines during fires or after explosions.

Jan 1, 1981

By Marek Niec

Native sulfur deposits in Poland occur in Upper Miocene strata on the northern (platform) border of the Carpathian foredeep. Systematic exploration since 1953 has resulted in the discovery of seven stratifom-stratibound sulfur-bearing limestone deposits that together contain about 0.6 billion tons of demonstrated sulfur reserves and about 0.5 billion tons of inferred and hypothetical resources. One open pit and three Frasch mines are currently in operation; another is under construction and one has been abandoned. Total production is about five million tons per year from ore containing on the average about 25% sulfur. Field, isotope, and micropaleontological data indicate that the sulfur-bearing limestone was formed through the bacterial reduction of gypsum in the presence of methane discharged from source beds and traps in the Carpathian foredeep. Subsequent recrystallization of the sulfur-bearing limestone, tectonic activity, jointing, karstification, and partial leaching of the sulfur has transformed the sulfur deposits and has altered the thickness and content of the sulfur-bearing strata, and their porosity and permeability, affecting the productivity and water consumption of the sulfur wells. Caputerized borehole logging techniques and geostatistical reserve estimates are used in mine planning. Great environmental impact constrains the development of sulfur mines.

Jan 1, 1992

By W. G. Pariseau

Regression analysis of calculated on measured displacements were used to assess the influence of fill and fold plunge on shaft pillar mining at the Homestake Mine. These effects were neglected in the original three-dimensional finite element analysis undertaken in 1991. An average fold plunge of 15? and a 24K fill (Young’ modulus of 24,000 psi or 165 Mpa) were used in the reanalysis. Measured displacements were obtained from an array of 36 m (120 ft) multiple-position borehole extensometers installed in June 1994 and read to March 2003. Results indicate the effects of both on calculated displacements and thus on regression parameters are noticeable. However, these neglected effects would not have changed the original inference of Ross Shaft stability during pillar mining.

Jan 1, 2004

By Herbert D. Drechsler

La financiación minera está inter-relacionada con los siguientes aspectos: "determinatión de los recursos totales a utilizar en una empresa minera; adjudicación eficiente de estos recursos a los varios multiples activos de la empresa; y obtención del mejor balance financiero en relación con la situación general de toda la compañia". La primera parte comprende un repaso de los problemas financieros a traves del estudio y análisis del Balance General y Cuenta de Explotación. La parte siguiente es una exposición de la naturaleza de los criterion desarrollados en el estudio de viabilidad. La tercera parte describe las fuentes de financiación del capital, y la parte final describe casos prácticos de financiación minera.

Jan 1, 1982

By Gus H. Goudarzi

The apatite deposits in east-central Bahia, Brazil, are about 50 km east of Serra do Jacobina, between lat. 11° and 12° S. and long. 39°40' and 40° W. Apatite was found and examined at 15 localities in a mineralized belt that strikes about N.25° - 30 W. over a distance of about 100 km, but the size of the deposits has not yet been determined. Rocks of the region consist of a sequence of Precambrian migmatites and quartz feldspar paragneisses containing units of pyroxene-rich rocks, lenses of sillimanite-bearing quartzite, amphibolite zones, and calc-silicate marble lenses. Pegmatites and granites of probable anatectic origin (anatexite) are abundant. Faults are numerous. Clastic sediments of Tertiary and Quaternary ages cover most of the area; thus, outcrops of the Precambrian rocks are sparse. Trenches and pits have exposed mineralized zones as much as 10 m wide at some localities within the region. A layer of apatite at least 1 ½ m thick is exposed in a trench at Lagoa do Mel. At Rio do Peixe, vertical shafts have penetrated a mineralized zone, to a depth of as much as 13 m, of which about 25 percent is apatite. Apatite is massive or forms minute crystals, stringers, and disseminated grains in alkalic host rocks. At Apolinario, euhedral crystals of apatite are as much as 50 cm long and 30 cm in diameter. Associated minerals include vermiculite, biotite, scapolite, opal, chalcedony, epidote, montmorillonite, chlorite, kaolinite, sericite, magnetite, and limonite. Apatite is everywhere intimately associated with pyroxene-rich rocks, alkalic syenite pegmatites, and alkalic granite pegmatites. At Panelas-Retiro, apatite is associated with pegmatites, crystalline calcite (vein calcite), vermiculite, and pyroxene-bearing rocks. Analyses of samples show that the apatite is radioactive and rare-earth-bearing. Traces of vanadium and titanium were detected by spectroscopic analysis. The apatite was probably derived from phosphatic zones in the original Precambrian sedimentary rocks and has been crystallized and some mobilized by high-temperature regional metamorphism (higher amphibolite facies) into veins, pegmatites, and along certain preferred beds and fractures. Radiometric and geophysical surveys, in addition to conventional geological investigations, are planned to further investigate the nature and economic potential of the deposits.

Jan 1, 1972

By D. Elsworth, M. Bai

The influence of mining on the hydro-geo-mechanical environment can be greatly modified by alternating mining geometries. The limiting magnitudes of surface subsidence and groundwater flow over the mining area, as a result of mine geometric changes, can be reasonably predicted through the coupled finite-element model introduced in this paper. The model has been verified using real and conceptual case studies which reveal that changes in strata conductivities are strongly related to the strata deformation induced by mining. The greatest modification of hydraulic conductivities occurs within the caving or severely fractured zones. The study indicates that narrowing the panel face width will substantially reduce both the intensity and extent of mining damage to the overlying strata, limit surface subsidence and constrain the change in hydraulic conductivity to a reduced scale and smaller extent, particularly as mining depth increases.

Jan 1, 1995

By George F. Klernrnick

The Pokorny sulfur deposit is located in the northwest comer of the Delaware basin in the Rustler Springs sulfur district of west Texas. To date, 57 sulfur test wells have been drilled by Addwest Minerals delineating a resource of greater than one million long tons (It) of native sulfur. The deposit, hosted by the Permian Ochoan Castile Formation evaporite sequence, is a sulfur-bearing bioepigenetic limestone replacement of banded bituminous anhydrite. Three distinct mineralized horizons are present that correlate with zones of halite dissolution in the Castile. Sulfur mineralization occurs as hydrocarbon-poor disseminated grains, and as crystalline linings of discontinuous planar voids and large vugs.

Jan 1, 1992

By Peijian Zhang, Yansheng Liu, Yuusaku Tominaga

The directions for ventilation control are often given in linguistic styles such as "if the airflow rate measured is small, a high value of rotation on a local fan should be chosen." In order to control the underground climate using a computer instead of a human being, both the reliability of data values measured underground and the application of human recognition of data values are required. The efficiency of data transmission is dependent on a method of checking a signal which is changed by mixing noises resulting from cases of electrical and mechanical damage to cables. In the study, fuzzy reasoning is adopted to choose a checking method for underground conditions from a normally operating state to an emergency. Fuzzy reasoning is applied to control airflow rate under the linguistic control rules given. It is shown that an effective series of linguistic control rules derived by fuzzy-sets theory is available in ventilation control when used in conjunction with an air velocity sensor, a computer and a local fan with thyristor control. Moreover, a system to make an optimum series of linguistic control rules for ventilation control is introduced.

Jan 1, 1987

By F. Calizaya, I. Duckworth

An ore-pass is an underground conduit used to transfer ore from one level of a mine to another. This method of transportation depends on the elevation energy only; therefore, it has very low operating cost. However, two inherent problems may hamper this process: (1) hang-ups of interlocked pieces and (2) a sudden release of trapped air from the ore-pass (belching). These events can create unsafe conditions with the potential for catastrophic consequences. This paper presents a summary of CFD modeling studies that were formulated to investigate the pressure build-up and belching of dust and rock particles from long ore-passes. The models were calibrated against field data collected from an actual ore-pass system and used to predict the airflow-pressure distributions in the mine for various ore feed rates and ore-pass geometries. P.T. Freeport Indonesia’s Grasberg ore-pass system (240,000 tpd capacity) was used for this purpose. This system comprises of four active ore-passes, with each being more than 600 m in vertical length.

Jan 1, 2004

By G. M. (Frits) Swinkels

The Apex property, mined in the early Twentieth Century for direct shipping copper, also contains gallium and germanium in iron oxide minerals. In 1982, Musto Explorations Limited began an exploration program to define reserves. A metallurgical process was developed, and a production decision was reached in late 1983. This text describes the process development and design. The Apex mine, located near St. George in Southwestern Utah is owned by St. George Mining Corporation, a subsidiary of Musto Explorations of Vancouver, B.C. Musto acquired the property in early 1982. A pilot plant was operated by Hazen Research, Inc., Golden, CO later in 1982. In late 1983 sufficient information had been developed for St. George to proceed with the project. The final process design was prepared by G. M. Swinkels of Vancouver, consultant to Musto, and Hazen Research. Process engineering was done by Hazen Research, and St. George acted as its own contractor. Commissioning of the plant began in October 1985.

Jan 1, 1986

By E. Woodburn, R. P. King, R. Putman

Flotation plant simulation, a relatively recent methodology in mineral processing, is defined and corresponding uses are discussed. Typical simulation structures are compared. Current problem areas exist although these are not insurmountable. Following a brief state of the art discussion, the N. I. M. simulation program is reviewed. In general, digital plant simulation is expected to be of substantial benefit in the near future.

Jan 1, 1976

By J. A. Ryder

Compressed air is a relatively inefficient yet very convenient vehicle for transmitting mechanical energy. It is inefficient when compared to, say, hydraulic or electric energy systems since compressor and pneumatic machine efficiencies are quite low (in the range 20-65%) and reticulation losses can be quite high unless adequate pipe diameters are used to minimize friction drops. It is convenient in that capital and maintenance costs of pipes and machines are exceptionally low, the equipment is flexible and lightweight, the technological level is simple, the form of the energy supply is intrinsic- ally safe, and as an additional minor but psychologically important benefit, it provides a ready source of cooling and air supply for emergency use in deep hot mines. It is for these reasons that compressed air is a premier source of energy for many forms of underground equipment, in particular hand or rig-mounted rockdrills, some forms of rock- handling equipment, and a host of minor applications including agitators, small-lift pumps and temporary f am installations. In a typical S. African deep-level gold or platinum mine, compressed air generation accounts for 15% of the total mine electrical energy bill - more than is used for hoisting. In these mines it is not uncommon for over 100 km of underground compressed air piping to be installed, primarily to supply handheld rockdrills.

Jan 1, 1979

By H. Para, A. Aguirre, G. Artadi

Mining is a very important economical activity in Peru which has been recently developed without considering environmental aspects. Here, we show an experience at the Milpo mine, situated 4,200 meters above sea level; a mining company that has the value of being one of few from the last decade that is engaged in consolidating a model of environmental protection. The model includes aspects of contamination prevention and control, with bioindicators such as pasture cultivation, vegetables, forests, and hydrobiological species breeding. Socially, through means of development programs in natural areas, forestation and support to rural agriculture, together with environmental education, it is being demonstrated that it is possible to ensure tangible results in environmental conservation and the well-being of the populations around the mine.

Jan 1, 1998

By C. J. Hall

An investigation of multi-shaft airflow problems by the author in 1976 (1) was presented in the hope of arousing considerable written comment, but in fact-. only one contribution (2) was forthcoming. The investigation in this paper is taken several stages fur¬ther, because the matter is of major importance in many American hard rock mines with complex networks extending over thousands of meters vertically. The examples used have all been generated thermodynamical¬ly and checked by motive column (denisty) calculations. Dry air has been used to reduce the amount of time spent on the rather complex calculations, but it has been shown (3) that the principals developed apply equally well to air/vapor/water mixtures. Initially the subject is investigated using both thermodynamic and motive column analyses. The latter part of the paper concentrates on a motive column presentation. Both methods are, of course, equally valid and give identical answers to any situation when correctly applied, as is shown in the worked examples.

Jan 1, 1980

By K. H. McDaniel, K. G. Wallace

This paper describes the development of a Windows-based interactive mine ventilation simulation software program at the Waste Isolation Pilot Plant (WIPP). To enhance the operation of the underground ventilation system, Westinghouse Electric Corp. developed a program called WIPPVENT. While WIPPVENT includes most of the functions of the commercially available simulation program VNETPC from Mine Ven- tilation Services Inc. and uses the same subroutine to calculate airflow distributions, the user interface was completely rewritten as a Windows application with screen grap-hics. WIPPVENT is designed to interact with WIPP ventilation-monitoring systems through the sitewide central monitoring system. Data (e.g., air quantity and differential pressure) can be continuously collected from the underground ventilation remote-monitoring and control system and from the mine's weather stations (psychrometric data). Furthermore, WIPPVENT incorporates regulator characteristic curves specific to the site. The program utilizes this data to create and continuously update a real-time ventilation model. This paper discusses the design, the key features and the interactive capabilities of WIPPVENT.

Jan 1, 1998

By S. Ostap

INTRODUCTION Paradoxically, it has been found that the people who are the most aware of the origin, mineralogy and composition of bauxite are also the people who are the least aware of how bauxite composition affects its treatment by the Bayer process. These people are the exploration and mining geologists normally associated with aluminum producing companies. The purpose of this paper is to give some idea of how the concentration and physical nature of the different minerals found in bauxites affect the operation of the Bayer process used to extract their alumina content. The bauxites we will consider here will be only the tropical bauxites such as occurring in Jamaica, various countries in South America i.e. Guyana, Surinam, Brazil, African bauxites, Malaysia and in Australia. When we speak of the Bayer process, it will be the North American version of the Bayer process using low caustic concentrations and bauxite digestion temperatures varying between 130° to 250°C. TABLE 1 shows the minerals and elements of interest occurring in tropical bauxites. The minerals and elements listed in the table do not by any means represent all of those identified in bauxites. Using mass spectrographic analysis on six bauxites from different geographic locations, we managed to identify between 50-60 different elements. Fortunately, only about 13-14 of these elements possess the necessary chemical properties to be able to accumulate in caustic Bayer solutions. The remainder are either not attacked, or form insoluble reaction products with some main liquor component, i.e., hydroxide, aluminate or carbonate, or reprecipitate with alumina trihydrate during the precipitation stage.

Jan 1, 1984

By J. Peshel

This paper presents a regulatory perspective of the design and construction of the Exploratory Shaft Facility which may become part of the future high-level waste repository. Site characterization concerns and long-term waste isolation concerns require the consideration of various shaft design and construction aspects quite different from that of conventional shaft sinking.

Jan 1, 1989