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By J. F. T. Agapito, R. R. Goodrich

Yield pillars have been used for many years to help reduce stresses near mine openings and improve roof and floor stability. A yield pillar is often defined as a pillar that fails but retains residual strength. Stress transfer occurs through the roof and floor after the peak strength of the pillar is reached. High stresses are transferred from around the openings onto abutments that can be barrier pillars or unmined ground. This mechanism, often referred to as pressure arching, is possible as long as the width of yield pillar mining (panel width) is less than the critical width above which stresses cannot be carried by the overburden. Significant stress transfer also can occur due to small amounts of pillar and/or floor yielding before the peak strength is reached. This is accomplished in a quasi-elastic manner with little or no visible roof and pillar fracturing or floor heave. Long-term stability may be achieved when stresses and mechanical properties are favorable to prefailure yielding. This paper gives practical examples where improvements in stability and resource recovery were achieved with this mechanism. Yielding was assessed by comparing measured and calculated vertical pillar stresses. Results indicated that calculated stresses in the pillars were 25% to 40% higher than the measured stresses, demonstrating significant arching load transfer to the abutments. Prefailure yielding is probably often present but unintentional in both development and production areas. Better recognition and use of this mechanism should lead to design improvements, as mines become deeper.

Jan 1, 2003

By J. Craig Green

Companies mining for coal, oil shale, and minerals in the western US must often complete extensive geotechnical studies to satisfy federal and state regulations. The modern mining process is further complicated by the legal problems and liabilities associated with mineral rights and land leasing. Yet the study of water rights-unique to the West is often incomplete or ignored until the latter stages of mine planning. Water rights in the West are not adequately understood by many mining companies and their geotechnical consultants. Some firms, headquartered outside the western US, have not had to contend with the water supply problems of a semi-arid region. Water problems encountered by eastern mining companies, for example, are primarily water quality, drainage, and flood control. Even when water quantity is a problem in these areas, ownership and/or use of it is governed by entirely different legal and administrative concepts than in the West. Both legal and engineering issues have to be considered when studying western water rights. Legal issues, such as existence and title, must be addressed to insure that a particular water right is properly established and maintained. The exercise of a water right, however, often requires engineering analyses that focus on preventing injury to the properly established water rights of others.

Jan 8, 1981

By R. A. Metz, Isaac Vera, Hans Ruge

The El Soldado copper mineralization occurs as relatively high-grade irregular ore bodies with assay contacts and with frequent inclusions of barren rock. The sampling methods must be timely for production grade control purposes, as well as accurate and inexpensive. Sampling techniques evolved from sampling dump cars at the haulage level to sampling Scooptrams at the loading pockets. These methods were abandoned in favor of sampling production blastholes. Several sampling alternatives are discussed. These involve the selection of optimum volumes and sampling frequencies while taking into consideration geological parameters and statistical analyses of sampling data.

Jan 1, 1992

By P. Venkatasubramanian

The aerospace and nuclear industries have been applying systematic techniques for assessing the safety of complex technical systems for many years. These techniques such as fault tree analysis, failure mode, and effect analysis, etc., and more recently "expert systems," were developed to formally evaluate systems safety and to determine how hazards can he reduced. The application of formal methods such as expert systems has the potential for further reduction in both frequency and the consequences of mine accidents. This paper presents a general expert system model of diagnostic reasoning and describes its use as an inference method for analysis and problem identification for accidents due to the presence of an open cycle diesel-powered mine cars in underground coal mines.

Jan 1, 1987

By D. B. Apel

Rock mechanics software plays an important role during the design process of modern underground mines by allowing for verification of the stability of the planned excavations. The paper describes the methodology used to plan and locate the permanent underground openings at McArthur River Mine with the assistance of numerical modeling software.

Jan 1, 2004

By Takahide Wakamatsu, Junji Shibata

Complex polymetallic sulfide ore deposits occur in Tohoku district, northern part of Honshu island, Japan. The ore is locally called "Kuroko” ( black ore ) and is compactly composed of fine grained sulfide minerals of such principal metals as copper, lead, zinc and iron. Currently one of Kuroko mill plants is producing such concentrates as copper, lead, zinc, pyrite, barite, and clay minerals, mainly employing differential flotation techniques. This paper describes briefly the progress of techniques in Kuroko processing over the past thirty years and also the present state of Kuroko processing and its challenges to be studied and overcome in the future.

Jan 1, 1989

By D. A. Knight, V. G. Medina

Kidston's 14 000 t/d mine and mill complex in Queensland, Australia, started operation in January 1985. During its first 18 months of operation, the mine produced over 7000 kg (225,000 oz) of gold, making it the largest gold producer in Australia. This paper describes the planning, logistics, flowsheet, and process for the Kidston project, and some of the problems encountered during startup and the measures taken to correct these problems.

Jan 1, 1987

By Richard R. Klimpel

This paper reviews the use of sulfide mineral collectors in industrial flotation practice. The approach of the paper is to characterize sulfide mineral collectors in a number of ways, including by chemical structure, by influences with different classes of mineralogy, by interactions with particle size, and by interactions with frother type.

Jan 1, 1999

By Michel Grenier, Gopal Kunchur, Stephen Hardcastle

This paper presents the findings of a dust study in a typical fluorspar processing plant. The primary purpose of this study was to identify employees and occupational groups exposed to high dust levels and determine compliance with personnel regulations for regular and extended work shifts. The range of airborne concentration of respirable silica and fluoride compounds in specific areas and on personnel was determined. State of the art dust monitoring equipment and tracer gas techniques were used to measure dust concentration, pinpoint dust sources and map major airflow trends in the mill. Results of the survey indicated silica dust concentrations in excess of permissible limits being produced mainly by crushers at the south end of the building. Tracer gas releases and gas chromatographic analysis further showed that prevailing south to north air currents tended to carry and spread dust produced by the crushing operations throughout the process plant. Airborne concentrations of fluoride compounds measured during the study were always well below the prescribed threshold limit value (TLV) for the contaminant. Recommendations, including a mechanical exhaust ventilation system on crushers and transfer points, scheduled preventive maintenance on existing bar sprays and wearing of personal protective equipment were made which significantly improved the work environment. Further testing conducted after Installation of the dust extraction system revealed significant improvements in most areas of the mill.

Jan 1, 1991

By J. M. Dean, R. L. Grayson, N. P. Reddy, Y. J. Wang

This 1988 survey provided a cross section of computer software use by the US coal industry. From 1250 mailed questionnaires, 171 responses were received, representing a 4.9% sampling of the 3496 US coal mines. Since the distribution of responses by regional stratum matched well with the distribution of mines by stratum, the survey was given statistical validity. A statistical description details the computer use by region, mining type, organizational size, the level of application within the organization, the type of software application used, the variety of computers on which the software was used and the percent of users within engineering, management and general applications categories. Overall, 63.5% of the respondents use computers at some level in their organizations. All of the mines producing more than 454 kt/a (500,000 stpy) used computers. However, for those producing more than 9 kt/a (10,000 stpy) but less than 91 kt/a (100,000stpy), only 44% used computers. Generally, the software applications were still data-processing oriented. The application sophistication grew with increasing mine size. Computer system models and configurations for different sized organizations are recommended based on the configurations used in the industry at the time of the survey.

Jan 1, 1994

By T. H. Combs, G. T. Lineberry

Increased productivity in the US underground coal industry has taxed pre-existing conveyor belt haulage systems. The usual remedies are costly and can disrupt production. A reduction in the belt feeder discharge rate on shuttle car sections results in more uniform loading and reduces spillage vulnerability. An investigation was made to determine the effect, if any, on shuttle car discharge time arising from lower feeder discharge rates. A five-section, underground mine is modeled, and belt spillage is introduced. The sectional feeder discharge rate is progressively lowered until spillage is precluded. At each level, the simulated spillage is measured and compared to the loss in face production. Methods for predicting the loss in face production from lower feeder discharge rates were investigated.

Jan 1, 1995

By J. A. Chermak, D. D. Runnells

Sulfide-bearing waste rock, ore and tailings have the potential for generating acid rock drainage (ARD) when exposed to an oxidizing environment. The possibility exists of utilizing the acid produced to react with lime and/or limestone to form a self-sealing cap on the reactive waste rock and tailings. Laboratory column experiments were conducted using acid-generating waste rock with a surface amendment of limestone and/or lime. Artificial rainwater was introduced and allowed to drain through the columns. Results demonstrated that the limestone and lime reacted with the acidic rock, resulting in the precipitation of a hardpan layer of gypsum and amorphous iron oxyhydroxide at the surface. The hardpan layer significantly reduced the effective permeability of the column. Based on the results of this study, it should be possible to create hardpan layers as chemical caps to significantly reduce the infiltration of rainwater and snowmelt into acidic waste rock or tailings material in the field. Unlike traditional capping methods, e.g., clay and high-density polyethylene (HDPE) covers, chemical caps should be self-healing.

Jan 1, 1998

By Haydn H. Murray

A hydrothermal bentonite located in the high Sierras in Nevada is being mined and processed for use as a natural dietary supplement. Because hydrothermal clay deposits are normally zoned and not uniform in composition, a special stockpile was constructed to assure uniformity of processed products. The stockpile of clay was layered and rectangular in shape. Channel samples were taken from 10 locations around the stockpile and were mixed and quartered to provide representative samples. The samples were then chemically and mineralogically analyzed. The results showed excellent uniformity. The mineralogy and chemical analyses will be discussed in the paper.

Jan 1, 2005

By Kal V. S. Sastry

Modeling and simulation are two major tools available to a mineral process engineer for a consistent and systematic process analysis. The application of these tools to the analysis of specific mineral processing unit operations is well documented in the literature; nevertheless, they are used only to a limited extent in the industry. This is because the fundamental principles of modeling and simulation in the context of mineral processing context are not available. This paper represents the first in a series of papers planned to meet this need. General principles of process modeling and a unified mineral process model development methodology are presented. A simple example of model development using the flotation unit operation is given. A discussion of the practical significance, challenges and opportunities associated with mineral process modeling is included.

Jan 1, 1990

By Dennis A. Beiter, William J. Francart

Barometric pressure changes have been an important consideration in the sealing of mines, especially in the case of mine fires. These changes are caused by storm fronts and regularly, on a daily basis, by atmospheric heating and cooling. In many cases, anticipation of these fluctuations in a mine sealing operation or recovery can be an important consideration when scheduling activities. The barometric pressure changes create pressure differentials across sealed areas, inducing airflows which may create explosive mixtures of mine gasses, cause intensification of fires, and create irrespirable atmospheres outby seals. These effects of barometric pressure fluctuations on mine fire sealing and recovery operations are discussed. Data available from the National Weather Service is also discussed as a tool for predicting barometric pressure changes.

Jan 1, 1997

By E. H. Ahrens

This paper deals with the responsibilities of an operating geologists and the relationship of operations to exploration. It should be of interest to those soon to enter the profession, those new to pining geology and as a review to more experienced geologists. Subjects discussed include detailed geologic mapping, sampling, core logging, assaying, selection of proper map scale, posting geological and assay data, section preparation, identification of ore controls, delineation of development drill targets and geologic hazards, models and the very important topic of salesmanship. Methods and ideas, proven valid in vein, pyrometasomatic replacement and porphyry copper deposits are presented. Hopefully, these will smooth the path for new members of our profession.

Jan 1, 1992

By J. M. King, C. J. Boggs

Acquisitions of mineral properties and companies can saddle the acquirer with unexpected and substantial liabilities and obligations incurred by the acquired or selling company that are not readily apparent from review of the company's books or files. This paper will address selected areas of concern, such as environmental and reclamation liabilities, problems of foreign ownership by the buyer or seller, pension obligations, plant closing laws, effective title review, land use and zoning.

Jan 1, 1992

By R. W. Smith, A. Raichur, M. Misra, I. A. H. Schneider

The concept of microorganisms as chemical reagents (flocculants, flotation modifiers and flotation collectors) is quite new. Potential uses for microorganisms include their use in place of certain conventional flotation reagents and as flocculating agents in minerals engineering processes. In addition, in some studies micro-organisms have been used to modify mineral surfaces and, thus, the flotation or flocculation of the minerals.

Jan 1, 1995

By M. G. Karfakis, K. P. Chong

Determination of fracture toughness using the semi-circular specimen, the chevron edge notch round specimen, the short rod specimen and the cylindrical burst specimen, are critically reviewed. These methods, among all, are the most applicable for fracture toughness determination of rocks. They require minimum machining. Samples are small, and testing procedures are simple. They have a sound analytical basis and allow the fracture toughness to be determined without measurement of fracture length.

Jan 1, 1986

By R. Poulin, R. C. Pakalnis

Approximately 51 % of all ore production in Canadian underground metal mines is derived directly from open-stope operations. This method requires that large excavations remain open until the ore is extracted with a minimum acceptable level of dilution. A survey of underground mines in 1988 reported that a major factor in their closure was uncontrolled dilution. It has been reported that 40% of openstope operations were experiencing dilution in excess of 20%. This level of dilution has significant implications on the economic viability of a project, especially when one considers that a rate of return on a positive project is generally between 10% and 20%. This paper reports on the various definitions of dilution, on the methods of stope design that are presently used with the objective of reducing dilution and on a recently available survey technique that enables dilution to be quantified.

Jan 1, 1996