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By N. B. Aughenbaugh

Compacted, fine-grained soils, often referred to collectively as clays, are used as permeability barriers in many mineral engineering projects such as heap leaching, containment ponds, tailings disposal and earth dams. Source materials for these liners include a variety of sand, silt and clay admixtures. These exhibit dramatically different engineering properties when densified. Therefore, it is imperative to adequately assess and characterize any soils being considered for compacted liners. The permeability and plastic properties of fine-grained soils are reviewed with respect to the state of compaction as the water content varies. Because they are weak in tension, compacted clays are susceptible to cracking when subjected to differential flexural movements. Designs of compacted clay liners also must include an evaluation of their flexibility. That is the ability of a fine-grain soil to bend plastically without cracking. This paper will also discuss the importance of flexibility with respect to soil types, compaction effort, failure mechanism and testing evaluation to the performance of clay liners in preventing seepage of pollutants from a containment site.

Jan 1, 1991

By K. Koizumf, A. A. Cram, K. Whitchurch

The Expert Scheduling is a new, exciting method for scheduling underground and open-cut coal mines. A key feature of the Expert Scheduler is the adoption of an expert or artificial intelligence system. The expert system makes decisions regarding the schedule, such as which area should be mined. With existing scheduling systems these choices are made by the scheduling engineer. Developing one area may be better than another if it offers better quality or lower costs. Information the engineer considers in these decisions could be; • coal tonnage and quality targets, • equipment utilisation, • mining cost, • and other practical constraints. In expert scheduling a number of experts are appointed to make these decisions. A number of mining strategies are examined for each period. Information for each strategy is evaluated by "experts" and the "best" solution adopted. The method is based on the Blackboard Techniques. With this technique information is presented to "knowledge sources” or "experts" by the Blackboard Controller for their "opinions". These "opinions" are examined by the Blackboard Controller to select the best strategy. Engineers can readily add experts to the system, and modify the weighting of experts to suit mining conditions. Using an Expert Scheduler means that many schedule op- tions can be analysed quickly with full repeatability.

Jan 1, 1996

By P. Asadollahi, M. Invernizzi

"This paper describes the innovative full-face conventional tunnel excavation technology, with its advantages in terms of savings and safety. The full-face approach has been developed throughout the experiences gained in tunnel construction. The innovative design approach is focused primarily on the deformation response of the ground acting first and foremost ahead of the face, which is analyzed, predicted and controlled by pre-confinement of the core. The advantage of this method is particularly evident in difficult grounds. This paper will present the outstanding benefits given by the adoption of the full-face approach in two projects, the “Sochi” and the “Visnove” tunnels. THEORY AND DESIGN ASPECTS OF THE FULL-FACE EXCAVATION The main challenges in tunnel and underground construction industry are gathering the design data from the ground that is being excavated and foreseeing the critical stage during construction, where the materials are in its most critical configuration. These challenges shall be addressed during excavation when the lining and the excavation disturbance have not yet reach the equilibrium. The in situ stresses in the ground are redistributed (forming an “arch-effect”) around the opening, with zones of increased stresses around the walls of the excavation (Figure 1). The distribution of the stresses can be close or far from the excavation profile, depending upon having a ground capable of withstanding the deviated stresses well or unable to withstand them, respectively. In the latter case, the ground will plasticize and deform in proportion to the volume of ground involved in the plasticization phenomenon. When the ground completely cannot withstand the stresses redistribution, it will cause the collapse of the excavation. While in the first case, the arch effect occurs naturally, in the second case, it does occur naturally only when the ground is stabilized properly. In the case of collapse, the arch-effect must be produced artificially operating on the ground prior excavation. The design should be based on the understanding of if and how the arch-effect can be mobilized during tunnel excavation and ensure that is formed by calibrating excavation and stabilization operations appropriately. The arch-effect is function of the medium that is being excavated, the action taken to excavate and the reaction expected following the excavation."

Jan 1, 2018

By Greg R. Wheeler

Few members of the general public have a clear understanding of mineral resources. Most people do not know how minerals are mined or why they must be extracted from many diverse locations. Many people acquire knowledge of mineral development from mass media sources with incomplete details or obvious anti-mining bias. The California Mineral Education Foundation was formed in 1991 to provide educational opportunities for the public and industry. There have been major changes in earth science teaching requirements for kindergarten through 12th grade (K-12) curricula since the passage of California Senate Bill 813 in 1983. Model graduation standards, curriculum standards and the state science framework mandate substantial coverage of geoscience topics. The California State Commission on Teacher Credentialing has completed changes in multiple subject and single subject science credentials which will require more geoscience preparation for all teachers. The need for pre-service and in-service education in geoscience is at an all time high. Teachers must have continuing education to maintain their credentials and many are now seeking information in geoscience. The California Mineral Education Foundation designed and conducted the California Mineral Education Conferences held in August 1991 and 1992. The conferences involved lectures and field trips on mining geology, environmental problems and political concerns. Master teachers were employed to share how they get across mineral resource concepts in the classroom. Ninety-six percent of the participants stated that they had changed to a more positive perception of mining after taking the three day course.

Jan 1, 1995

By R. D. Deister

The Buick concentrator represents state-of-the-art technology in automated digital process control operation utilizing a centralized computer. The process control strategies implemented at Buick are no longer new to the industry, but the successful application of these developments is still rather unique in North America. Productivity improvements, determined to be a direct result of the process control developments, are the primary topics of this paper. Emphasis is placed on metallurgical benefits including both lead and zinc recoveries; lead concentrate grade; and reductions realized in reagent consumptions, operating costs, and personnel. A detailed description of the concentrator, along with a history of the process control development and a more in-depth discussion of the control strategies implemented at Buick can be found in the references. (The Buick flowsheet is depicted in Fig. 1).

Jan 1, 1987

By R. M. Damodaran

The flotation performance of Florida phosphate rock was evaluated in terms of the mixing behavior of reagents and particulates during anionic conditioning of phosphate slurries. The various conditioning variables that influence mixing, namely, solids loading, agitation speed and conditioning time, were investigated to determine their effect on reagent coating of the particles. The phosphate recovery was used to monitor the conditioning efficiency. The mixing characteristics of the phosphate feed were evaluated in terms of the ratio of the mixing power (P) to the minimum power (Pm) required to keep the slurry in suspension. It was found that mixing conditions govern the conditioning time required to obtain a high recovery. Reagentization was slower at lower P/Pm ratios. At higher P/Pm ratios, the flotation recovery was optimized, and the agitation speed was found to have no significant effect. Optimum mixing conditions were obtained for a74 wt% slurry at an agitation speed of 450 rpm (47 radians/sec). Under these optimum mixing conditions, the collector dosage required for an improved recovery was lower and the conditioning time was shorter.

Jan 1, 1997

By A. K. Bakshi, Komar S. Kawatra

A plant trial of a new on-line pressure vessel rheometer for slurries, developed at Michigan Technological University, was carried out at a nearby copper concentrator. The rheometer measured the flow curves (shear stress vs. shear rate) of chalcocite slurries. Viscosity of non-Newtonian slurries changes with shear rate and so, for such slurries viscosity measurement at a single shear rate (often seen in the literature for grinding and classification studies) cannot be correlated to process performance. For these slurries, viscosity at various shear rates can be measured from flow curves generated by the pressure vessel rheometer. Other rheological properties, such as flow type and yield stress can be determined by this rheometer to better characterize the slurries. The slurry at the copper concentrator consisted of ground chalcocite ore. The solids content in the slurry varied between 30-60 % by weight. Top size of the particles was 125 micron, and 80% passing size was 34 micron. Measurements by the pressure vessel rheometer showed that most of the slurries had pseudoplastic flow at shear rates below -3000 sec-l, where the viscosity of the slurry decreased with increase in shear rate. Above -3000 sec-l, like a Newtonian fluid, the viscosity of the slurry remained steady. Flow curves and viscosity from the pressure vessel rheometer were verified with a Brookfield viscometer and a vibrating sphere viscometer, and the results were found to be accurate.

Jan 1, 1997

The need for geological control in orebody estimation and modelling is self- evident to geologists and mining engineers engaged in practical day-to-day estimation. It is only fairly recently, however, that attempts have been made to incorporate explicitly such requirements into published accounts of geostatistical estimation; see, for example, Dowd and Scott (1982, 19841, Rendu and Readdy (1982), Dagbert et al. (1984), Dowd (1984), Benest and Winter (1984). In practice, many geological controls in automatic or semi-automatic estimation and modelling are essentially geometrical controls. The aim of this paper is to present two techniques for geological/geometrical control. Whilst the applications are new, neither technique is entirely original and both have been adapted from other fields and sources. Both techniques are, in some sense, types of estimators and/or interpolators of shapes. The first is a method for fitting spline surfaces to control orebody boundary estimation and to unroll orebodies. The second is an application of Minkowski addition to interpolate shapes such as orebody outlines or stope boundaries and to control estimations.

Jan 1, 1986

By A. de Ferran

Is the Brazilian gold rush over? Judging from the situation in Brazil over the past few decades, the answer is almost certainly yes. The picture of swarms of Brazilian prospectors or "Garimpeiros" crowding or, more correctly, overcrowding the gold regions of the Amazon jungle using the time-aged empirical approach to gold exploration has finally run its course. There are two fallacies that have lead to a reduction in the discovery of new gold fields in Brazil. The first fallacy is that "Brazil's geology is largely unknown." The extreme depth of weathering and the general lack of understanding of the shield deposits are at the origin of this misconception. The second fallacy is that "Brazilian prospectors ("garimpeiros") are very naive, have very little technical knowledge and can only produce gold at very low recovery rates." This is more of a result of wishful thinking for the purpose of justifying limiting exploration programs than it is a real consideration. In this paper, the author takes a methodical heuristic approach to gold exploration in Brazil and offers this as an alternative to the empirical approach of the garimpeiros.

Jan 1, 1998

By S. Subbarayan, S. Chander, M. S. Klima

A laboratory study was conducted to investigate the potential for recovering anthracite from coal preparation-plant tailings. The study included washability analyses, cyclone simulations and froth flotation testing Samples were collected from either the tailings streams or the slurry ponds of five anthracite-cleaning plants. From each sample, a washability analysis was conducted on the 28x100 and 100x200-mesh fractions. Using the above data, along with published partition data, simulations were performed with various cyclone-staging arrangements for both water-only and dense-medium cyclones treating the 28x200-mesh fractions. Separate froth -flotation tests were conducted on the 28x100- and 100x200-mesh fractions from three of the plant samples. The washability, simulation and flotation results are presented as grade-yield curves.

Jan 1, 1996

By M. J. McPherson, P. Mousset-Jones, G. Danko

Ventilation and refrigeration fortune climate modification contributes significantly to the operating costs of a deep hot mine. Mine climate simulation programs can he used to minimize the impact of these costs. There are several computer codes available to assist in this work. Whichever simulation program is used, it is the mine ventilation engineer who must supply the input data. This paper raises and answers the following question, namely, what accuracy is required of the basic input parameters, in order for a certain precision to he obtained in the predicted air temperatures? In the first part of the paper a new approach is described to estimate the dry and wet bulb temperature of the airflow, either in a dry or wet roadway. The calculation procedure allows an arbitrary temperature change with time, using Duhamel's superposition solution. Matrix-vector representation is applied to simplify the computational structure. In the second part of the paper the sensitivities of the dry and wet bulb air temperatures are analyzed, to the changes of the rock thernrophysical properties, the heat transfer coefficient, and the wetness factor.

Jan 1, 1987

By A. Wright

Gold Fields Mining Corporation is presently evaluating gold mineralization beneath thick, wet alluvium at the Chimney Creek Project, Nevada. Contamination of reverse circulation samples has been visually apparent since drilling began in the area. Tests have shown that, while contamination can affect assays, reverse circulation holes appear to define mineralized zones almost as well as the diamond drill holes. To improve reverse circulation sample integrity several techniques were tried including a stiff-mud injection system but with limited success. Diamond core drilling continues to be used in conjunction with reverse circulation drilling to further delineate the mineralization.

Jan 1, 1991

By R. Latifovic

Assessment of the possible impact of existing and future mining projects located in remote areas may be difficult and costly. This may have an adverse effect on the process of issuing mine permits and development of new mines. A remote sensing based land cover change assessment methodology presented in this paper is a promising avenue to render this process more meaningful, precise and affordable. It has been applied to a case study of the Oil Sands Mining Development in the north-east of the Canadian province of Alberta. Recently, the Athabasca Oil Sands Region (AOSR) is a place of unprecedented growth of open-pit mining operations. This study was focused on the primary impact onto the landscape and vegetation resulting from exploration and, mining development. This impact was assessed using an information extraction method applied to two LANDSAT scenes. The analysis based on derived land cover maps shows a 8.64% decrease of natural vegetation in the study area (715,094 ha) in 2001 relative to 1992. It is demonstrated that the methodology presented here provides reliable results and is fully applicable for the assessment of the environmental impact of large scale mining operations.

Jan 1, 2006

By S. Donges, P. L. Dunstan, B. J. Huls

The commissioning of a distributed digital control system for the grinding circuit at Cuajone was completed by mid-August 1985. Development of a successful strategy, excellent operator acceptability, and the visual aspects offered by the display of the central console improved mill through- put significantly. The inherent features of a digital system enhanced the flexibility in grinding control and allowed the milk and classifiers to be operated at maximum capacity. This paper discusses the strategy development and the production restrictions encountered, and evaluates the overall performance of the digital control system.

Jan 1, 1988

By P. F. Hara, O&apos

Stratabound Proterozoic precious metal mineralization in central Arizona is associated with felsic and adnesitic to mafic volcanic rocks and sediments derived from these rocks. Hydrothermal fluids associated with felsic volcanism form gold mineralization within hotspring vent complexes or within asymetric basins, which flank the vent complexes and are filled with tuffaceous sediments. Massive to semi-massive sulfide copper-zinc systems associated with felsic volcanism may locally contain small gold occurances either laterally or vertically zoned from the ore. In andesitio to mafic rocks, zinc-lead-gold-silver-copper bearing mineralization and gold mineralization are both associated with feruginous sulfide bearing cherts. The partitioning of gold into these specific geologic environments may be related to variations in temperature and composition of the hydrothermal fluid and the depth of the seawater-sediment interface below sea level during the mineralization event.

Jan 1, 1988

In the screening process, used to prepare particles for many applications, shape is known to have a significant effect. The degree of flakiness of construction aggregates has been considered particularly important. The objective of this research was to find values of operating parameters that optimize the separation of flaky from non-flaky particles by slotted screens. Thus an investigation was conducted to experimentally determine the influence of the particle size and thickness on the screening process. The Response surface method was employed for modelling and analysis of the data. Experiments employing a central composite design were performed on a pilot-scale, rectangular-aperture, vibrating screen to examine the effects of the screening variables the mass recovery of flaky and non-flaky particles to the oversize product. The SAS statistics package was used to fit a second-order model to each response and to analyze the fitted surface to determine the optimum levels. The optimization associated with a dual response system was then considered. The results of this study should provide a basis for optimizing screening conditions to obtain maximum recovery of non-flaky particles to the screen oversize while minimizing the recovery of flaky particles, which should be of interest to the aggregate industries.

Jan 1, 1999

By J. Pang, S. Chander

The mechanisms of chalcopyrite oxidation in alkaline solutions have been studied using cyclic voltammetry and impedance spectroscopy techniques. The cyclic voltammetry was used to elucidate oxidation/reduction reactions, whereas impedance spectroscopy was used for in-situ characterization of the interface. To analyze the impedance spectra, equivalent circuit models were constructed based on a layer- wise growth of reaction products. Parameters of the equivalent circuit were calculated by comparing the experimental spectrum with that expected on the basis of equivalent circuit. From the value of equivalent circuit parameters, properties of the surface layers were inferred. These properties change substantially with the change in oxygen and/or collector concentration in solution. From such changes the effect of oxygen and collector concentration on the contact angle and flotation behavior of chalcopyrite were interpreted.

Jan 1, 1991

By Terry Ritzel

Predictive maintenance technologies include vibration analysis, tribology, infrared thermography, ultrasonic detection and electrical measurements. These technologies have been applied to large electric mining shovels at the Cyprus Sierrita Mine outside of Tucson, AZ. The predictive maintenance program was initiated on the P&H models 2300 and 4100 electric shovels during August 1996. Results of these technologies have shown the potential for improving electric min- ing shovel availability and minimizing maintenance costs. Predictive technologies provide the tools to assess machinery condition. Availability is enhanced by the condition-based planning of component replacement. Maintenance costs are minimized by focusing resources through condition-based prioritization.

Jan 1, 1997

By Ing. E. h. Martin Herrenknecht

The paper will describe a number of developments and innovations now in use in microtunnelling machines. These include the use of fuzzy logic steering systems, the proven ability to successfully undertake complex curved microtunnel drives, the ability to complete ultra long drives using microtunnelling techniques, and machines with access to the face of the machine from inside the machine. The ability to tunnel in relatively hard rock utilizing a rock head with back loaded cutters changeable from inside the microtunnel machine and the ability to utilize microtunnel machines in multi modes, such as hard rock mode, “open” mode, EPB mode, and slurry mode with the same base machine again with access to the face of the machine will be described. In addition, the latest computer technology gives the operator “full visualization” of machine functions together with the ability to data log machine operating parameters. Reference will be made to a number of projects worldwide recently completed or under way where these innovations have successfully been utilized.

Jan 1, 1999

By Timothy J. Napier-Munn, David M. Weedon

A model of mineral liberation was developed using back calculation techniques to determine breakage/liberation parameters in a similar manner to the way breakage parameters are determined in the Population Balance Model (PBM). Comminution and liberation data was collected from grinding mills operating at Pasminco lead/zinc mine Broken Hill, and Mt. Isa Mines copper concentrator, Mt Isa, Australia. Laboratory scale single particle breakage tests on ore samples from these sites were undertaken using a twin pendulum breakage device. Break- age/liberation parameters were then determined for several mills using back calculation techniques. The liberation/breakage parameters were then used to simulate mill liberation performance under varying conditions.

Jan 1, 1996